Administers the Consolidated Army Correspondence Course Program (ACCP), Which Provides High- Quality, Economical Training to Its Users

PREFACE

The Army Institute for Professional Development (AIPD) administers the consolidated Army Correspondence Course Program (ACCP), which provides high- quality, economical training to its users. The AIPD is accredited by the Accrediting Commission of the Distance Education and Training Council (DETC), the nationally recognized accrediting agency for correspondence institutions.

Accreditation is a process that gives public recognition to educational institutions which meet published standards of quality. The DETC has developed a thorough and careful evaluation system to assure that institutions meet standards of academic and administrative excellence before it awards accreditation.

The many TRADOC service schools and DOD agencies that produce the ACCP materials administered by the AIPD develop them to the DETC standards.

The AIPD is also a charter member of the Interservice Correspondence Exchange (ICE). The ICE brings together representatives from the Army, Navy, Air Force, Marine Corps, and Coast Guard to meet and share ideas on improving distance education.

This publication was printed on recycled paper.

COMBAT ENGINEER

PART I

CORRESPONDENCE COURSE U.S. ARMY ENGINEER SCHOOL

This reprint includes Lesson Change #1 dtd 19 Jan 75

MOS: 12B20

INTRODUCTION

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This is one of a series of subcourses intended to assist enlisted personnel of the Army to improve their proficiency in engineer MOS job requirements. This study should increase your job knowledge and your chances of qualifying for proficiency pay and/or pro- motion.

This subcourse and one entitled Combat Engineer--Part II are oriented toward assisting the student already qualified as a Pioneer, MOS 12A10, to qualify as a Combat Engineer, MOS 12B20. The lessons compris- ing Part I are concerned mainly with activities which facilitate operations of friendly combat forces; those in Part II cover activities which, for the most part, impede the enemy.

This subcourse consists of nine lessons and an examination as follows:

LESSON NO. LESSON TITLE REFERENCES

1 2 Reconnaissance and Intelligence S/C 54, FM 5-30, FM 5-36 3 Handtools and Rigging S/C 34, TM 5-461, TM 5-725 4 Engineer Equipment S/C 66, TM 5-331A, C, D 5 Construction Planning S/C 67, TM 5-333 6 Soils in Construction S/C 53, TM S-330 7 Roads and Culverts S/C 64, TM 5-330, FM 5-34 8 Bridges S/C 59, TM 5-277, TM 5-312 9 Expedient Stream Crossings FM 6-34, TM 5-210

Examination.

Twenty-six hours are accredited for this subcourse.

The information in the attached memo- randums accompanying the lessons should be sufficient for you to answer the questions at the ends of the lessons and those in the examination. If you need additional information, you should use the references listed above.

You will not be limited as to the number of hours you may spend on any lesson or the examination.

* * * IMPORTANT NOTICE * * *

THE PASSING SCORE FOR ALL ACCP MATERIAL IS NOW 70%.

PLEASE DISREGARD ALL REFERENCES TO THE 75% REQUIREMENT. LESSON 1 MAP READING

CREDIT HOURS ______

TEXT ASSIGNMENT ______

MATERIALS REQUIRED ______

LESSON OBJECTIVE ______

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LESSON CHANGE NO. 1

Engineer Subcourse 0501-1, Combat Engineer I, Edition 1, is changed as follows:

Introduction: Delete all references to Lesson 1, Map Reading

Lesson 1: Delete in its entirety. This lesson contains outdated material that is no longer available for distribution. Information on map reading may be obtained by enrolling in EN 5320-2, Map and Aerial Photograph Reading I.

1-1 LESSON 2 INTELLIGENCE AND RECONNAISSANCE

CREDIT HOURS ______2 TEXT ASSIGNMENT ______Attached memorandum. MATERIALS REQUIRED ______None. LESSON OBJECTIVE______To increase your knowledge of engineer intelligence and reconnaissance.

______

ATTACHED MEMORANDUM

1. DEFINITIONS

Tactical intelligence is evaluated information and conclusions about the enemy including capabilities and vulnerabilities, the weather, and geographic features of the terrain.

Terrain intelligence is concerned with natural and manmade terrain features, weather and climate of a particular area or region.

Technical intelligence pertains to design, operation, nomenclature, physical characteristics, performance, operational capabilities, and limitations of foreign material and facilities used by or for the support of military forces.

2. THE INTELLIGENCE CYCLE

Step 1. Planning the collection effort and preparing orders.

Step 2. Collecting the information.

Step 3. Processing the collected information.

Step 4. Disseminating and using the resulting intelligence.

Note: Steps 1, 3, and 4 are accomplished by the commander and the intelligence officer.

3. SOURCES OF INFORMATION

Ground reconnaissance.

Aerial reconnaissance.

Maps. Captured enemy documents.

Aerial and ground photography or other imagery.

Other documents, including texts, periodicals, and technical papers.

Captured enemy material.

Captured enemy installations.

Prisoners of war.

Local civilians.

Refugees and military returnees.

Published intelligence and terrain studies.

Note: In fast moving situations, ground and short-range aerial reconnaissance, reports from front line troops and prisoners of war may be the only sources used by a division since the information is more immediate, detailed and local.

4. SALUTE

Reported enemy information should include the following:

Size of unit or installation observed.

Activity that occurred during observation.

2-1 Location of activity (direction of movement, also).

Unit designation.

Time of observation.

Equipment used or on hand, including weapons and vehicles.

5. TACTICAL RECONNAISSANCE

For offensive operations, collection of information is continuous and detailed prior to the advance, during the advance, and during the attack. Emphasis: conditions of route of advance, alternate routes, air-landing facilities, enemy obstacles, local engineer materials, river crossing sites and hydrology, and possible water points.

For defensive operations, collection is continuous and detailed and is intensified immediately upon the decision to occupy a position. Emphasis: terrain studies, lines of communication for counterattack forces, location of obstacles, and demolition sites, and natural cover.

For retrograde operations, collection em- phasizes roads, bridges, terrain, installation, and natural resources in the territory through which the move will occur.

For fortified areas, emphasis is placed on obstacles in front and on the flanks of the enemy position, minefields, location of de- fending weapons, and contaminated areas.

6. ENGINEER RECONNAISSANCE REPORT (Fig. 1 through 5)

Heading: Designation of officer who or- dered the reconnaissance and commander of unit performing the reconnaissance; name, rank, and organization of reconnaissance party leader; time and place reconnaissance was made; maps used; delivery address for report.

Body: contains the following:

Key: serial or critical point number (also used on overlay).

Object: conventional symbol or brief written description of object.

Time: time object observed.

Work estimate?: "yes" if included on back of report; otherwise, "no."

Additional remarks and sketch: grid co- ordinates of object; explanation; calculations; sketch as necessary.

Signature block: commander of unit performing the mission.

Work estimate: reverse side of form used to indicate amount and type of effort required for construction or repair.

7. ROAD RECONNAISSANCE REPORT (Fig. 6 and 7)

Heading: As shown in blocks.

Section I: As shown in blocks; item 6 indicates the lower and upper limits of the traveled way width.

Section II: As shown in blocks; when this data varies for different sections of the road, differences are indicated on the mileage chart by placing the "road classification formula" (to be covered later) by the appropriate portion of the road.

Section III: Obstructions; serial numbers are also used on overlay and on mileage chart.

Mileage chart is on the reverse side of the form.

8. ROAD CLASSIFICATION FORMULA

Prefix: The formula is prefixed by the letter "A" if there are NO LIMITING CHAR- ACTERISTICS. The letter "B" is the prefix if there are ANY LIMITING CHARACTER- ISTICS.

Limiting Characteristics Symbol

Curves (radius 30 m or less) c

Gradients (7% or more) g

Drainage (inadequate) d

Foundation (unstable) f

Surface condition (rough) s

Camber or superelevation (excessive) j

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2-3 2-4

2-5

2-6

An unknown or undetermined characteristic is represented by a question mark following the symbol of the feature to which it refers, both enclosed in parentheses, e.g., (d?).

Width: Width of the traveled way expressed in meters or feet followed by a slash and the combined width of the traveled way and the shoulders, e.g. 14/16 m.

Road Surface Material: Road surface material is expressed by a letter symbol as follows:

Symbol Material

k Concrete

kb Bituminous or asphaltic concrete (bituminous plant mix)

p Paving brick or stone

rb Bitumen-penetrated macadam waterbound macadam with super- ficial asphalt or tar cover

r Waterbound macadam, crushed rock, or coral

l Gravel or lightly metaled surface nb Bituminous surface treatment on natural earth, stabilized soil, sand-clay or other select material

b Used when type of bituminous construction cannot be determined

n Natural earth, stabilized soil, sand- clay, shell cinders, disintegrated granite, or other select material

v Various other types not mentioned above (indicate length when this symbol is used)

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2-9 Length: Length of road in km or miles may or may not be shown. If shown, place in parentheses, e.g., (7.2 km).

Obstructions: Expressed as (Ob) when existing on road, e.g., overhead clearances less than 4.25 m, reduction in the traveled way widths below the standards of table 3 below, gradients of 7% or greater, curves with radii less than or equal to 30 m (100 ft), and fords.

Special Conditions: Snow blockage (T) and flooding (W) are used when the condition is regular, recurrent, and serious.

Example 1: A 5.4/6.2m k; road has no limiting characteristics with 5.4 m traveled way, combined width of 6.2 m traveled way and shoulder, and a concrete surface.

Example 2: Bcgs 14/16 ft 1 (2.4 km) (Ob): Road has limiting characteristics of sharp curves, steep grades, and a rough surface condition; 14 ft of clear traveled way, 16 ft combined with shoulders; a graveled or lightly metaled surface; 2.4 km length; obstructions are present.

Example 3: Bcgd (f?)s 3.2/4.8 m nb (4.3 km) (Ob) (T): Road has limiting characteristics of sharp curves, steep grades, bad drainage, unknown foundation condition, and rough surface; 3.2 m wide traveled way, 4.8 m wide with shoulder; a bituminous surface treatment; 4.3 km long, and it contains obstructions. The road is subject to snow blockage.

Note: The formula is used on the mileage chart of the Road Reconnaissance Report.

9. CRITICAL DIMENSIONS

Clearance, width, and trafficability criteria are shown in tables 1 through 4.

Measuring width of roadway and horizontal and vertical clearances for tunnels, underpasses, and through truss bridges:

10. DETERMINING RADIUS OF CURVES AND GRADIENTS

RADIUS:

R = Cý/8m + m/2

R = radius of curve (circle)

C = length of cord

m = perpendicular distance from center of cord to centerline (CL) of road

Example 4: If the length of the cord is 58 feet and the perpendicular distance from the cord to the centerline of the road is 5 feet, what is the radius of the curve?

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2-11 Vertical distance percent of slope = ------x 100 Horizontal distance

Example 5: If the horizontal distance between points A and B is 200 meters and point A is 18 meters higher than point B, what is the gradient from point A to point B?

Vertical distance Gradient = ------x 100 Horizontal distance

-18 = --- x 100 200

= -.09 x 100

= -9% (minus means it is down- hill from A to B)

An instrument for directly measuring percent of slope is known as a clinometer.

An expedient method of estimating percent of slope is based on the line of sight of a man and the measurement of ground distance by use of the pace. The eye level of the average man is 1.75 meters (5 ft, 7 in) above the ground. The pace of the average man is .75 meter (30 in).

Note: These measurements should be accurately determined for each member of a reconnaissance team.

To determine percent of slope, the individual, who stands at the bottom of the slope and keeps his head and eyes level, sights on a spot up the slope. This spot should be easily identifiable or, if not, another member of the team may be sent forward to mark the location. The individual making the sighting then walks forward to the marked spot recording the number of paces. This procedure is repeated until the top of the slope is reached-- fractions of an eye level height must be estimated. Vertical distance is then computed by multiplying the number of sightings by the eye level height. Horizontal distance is computed by totaling the number of paces and converting to meters by multiplying by the factor, .75. Percent of slope can then be calculated by substituting the values into the percent of slope formula (see example 5a).

2-12 Because this method considers horizontal ground distance and incline distance as equal, reasonable accuracy may be obtained for slopes only less than 30 degrees. Moreover, this method requires considerable practice to achieve acceptable accuracy.

11. BRIDGE RECONNAISSANCE REPORT (Fig. 8 and 9)

Heading: As shown in blocks.

Essential Information: Serial number, location, horizontal clearance, underbridge clearance, number and description of each span (new line on report for each different span). In column 8 place an "X" beside the span length if the span is not useable because of damage and a "W" beside the span length if the span is over water. Symbols for use in column 7 (type of construction material) are as follows:

Steel or other metal a

Concrete k

Reinforced concrete ak

Prestressed concrete kk

Stone or brick p

Wood n

See paragraph 12 for column 6 (type of construction).

Additional Information: Military load class, overall length, roadway width, vertical clearance, bridge bypass, description of approaches to bridge, characteristics of features spanned by bridge, abutments, intermediate supports, and bridge structural data. Other remarks as appropriate.

Sketches: As indicated, reverse side.

Computation of Bridge Class: Utilize Bridge Design and Classification Card (GTA 5-7-5).

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2-14

2-15

2-16 2-17

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2-19 2-20 12. TYPES OF BRIDGE CONSTRUCTION

The numbers shown below are used in column 6 (Bridge Reconnaissance Report) to indicate type of construction:

Use (9) and a written description for all other type span construction, such as swing, lift, cantilever, bascule.

13. TUNNEL RECONNAISSANCE REPORT (Fig. 10 and 11)

All blocks are self-explanatory. See paragraph 9 for blocks 14 and 15, and paragraph 10 for block 16. Sketches are self-explanatory.

14. FORD RECONNAISSANCE REPORT (Fig. 12 and 13)

All blocks are self-explanatory. Show direction of flow in sketch. Include a photograph when possible which includes approaches and shows military vehicle fording the stream.

A ford is a location in a water barrier where the physical characteristics of the current, bottom, and approaches permit the passage

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2-22 of personnel and/or vehicles and other equipment which will remain in contact with the bottom.

15. FERRY RECONNAISSANCE REPORT (Fig. 14 and 15)

All blocks are self-explanatory. Item 12 should indicate seasons or dates when ferry is inoperable.

16. OVERLAY (Fig. 16)

It contains critical dimensions and measurements needed by the commander to evalu- ate the road net. The route classification and significant features are indicated by standard military symbols. A title block, grid reference marks and magnetic north arrow are included.

17. MILITARY SYMBOLS

Note: The left and right bank of a stream are determined by looking in the direction of the current downstream. Special attention must be paid when recording approach conditions on the symbol; in the following symbol the wavy line indicates the approach on the left shore is easy, while on the right shore it is difficult:

Any overhead clearance of a bridge less than the standards of table 1 is underlined. Any width of a one-lane or two-lane bridge which is less than the standards of table 2 is underlined. The two-way class of any two-lane bridge is downgraded if the width of the bridge is less than the standards of table 2.

The width of the traveled way of tunnels or underpasses which is less than that of the outside route is underlined.

Engineer resources symbols as shown be low are also included on the overlay:

2-23 18. ROUTE CLASSIFICATION

Width of the route refers to the width of the narrowest road on the route (in meters or feet).

Type is the least desirable type road on the route (X, Y, or Z).

X - hard-surface all-weather.

Y - light- or loose-surface, limited all- weather (crushed rock, waterbound macadam, gravel, lightly metalled surface).

Z - light- or loose-surface, fair-weather (natural or stabilized soil, sand- clay, shell, cinder, disintegrated granite).

Military Load Classification is the maximum class of vehicle which can use the route (normally the one way classification of the weakest bridge).

Obstructions are factors which limit the traffic capacity (Ob, par 8).

Route Classification Formula utilizes the four factors in sequence.

Example 6: 20 ft Y 50 = 20 ft minimum width, limited all-weather type, maximum load class 50, no obstructions.

Example 7: 10.5 m X 70 = 10.5 meters minimum width, all-weather type, class 70.

Example 8: 20 ft Y 50 (Ob) = 20 ft minimum width, limited all-weather type, class 50 with an obstruction (one or more). In addition to (Ob), (T) for snow blockage or (W) for flooding may be used.

Note: See figure 16 for use of classification on overlay.

EXERCISES

First requirement. Multiple-choice exercises 1 and 2 deal with the intelligence cycle and sources of information.

1. What are the four steps of the intelligence cycle?

a. production, evaluation, dissemination, and use

b. planning, collection, processing, and dissemination

c. collection, evaluation, production, and dissemination

d. planning, evaluation, processing, and use

2. In fast moving situations, immediate, detailed and local information is needed. What sources may be the only ones used by a division?

a. captured enemy documents and installations, local civilians and long- range aerial reconnaissance

b. short-range aerial reconnaissance, texts, periodicals and technical papers

c. prisoners of war, reports from front line troops, and ground and short- range aerial reconnaissance

d. ground reconnaissance, local civilians, refugees and military returnees, captured enemy material

Second requirement. Multiple-choice exercises 3 and 4 enable you to show your understanding of reporting procedures and reconnaissance in tactical situations.

3. You have been appointed squad leader and are responsible for insuring that your men know how to report information. What items would they include when reporting information?

a. size, activity, location, unit, time, and equipment

2-24 b. size, secure, search, silence, segre- gate

c. what, when, why, how, who

d. shape, activity, location, unit, time, and equipment

4. During offensive operations, how often do the engineer battalions collect information?

a. when specific requirements for information arise

b. infrequently

c. during lulls in combat or movement

d. continuously

Third requirement. Multiple-choice exercises 5 through 18 emphasize the reconnaissance report forms and overlays.

5. You are evaluating your squad©s Engineer Reconnaissance Report. Re- ferring to figures 1 through 5, Engineer Reconnaissance Report, where would be a possible water point location?

a. UT 509686 c. UT 557963

b. UT 512692 d. UT 558680

6. Your squad has been given the mission of removing the log post obstacle blocking route 132. Referring to figures 1 through 5, Engineer Reconais- sance Report, how long will it take in hours for one squad to remove the obstacle?

a. 0.5 c. 9.0

b. 2.0 d. 24.0

7. You are evaluating your squad©s Road Reconnaissance Report. Refer- ring to figures 6 and 7, what obstruction is located at UT 109879?

a. road crater

b. narrow bridge

c. ford d. underpass

8. Refer to figures 6 and 7, Road Reconnaissance Report. What critical feature could you expect to find approximately 4.4 miles from Fort Belvoir? a. turn off with deciduous tree concealment b. underpass c. turn off with coniferous tree concealment d. narrow bridge

9. You are reviewing the information on a Bridge Reconnaissance Report. Your platoon sergeant wants to know how the bridge is constructed. Refer- ring to figures 8 and 9, what type of construction is the bridge? a. beam c. girder c. slab d. arch

10. Refer to figures 8 and 9, Bridge Reconnaissance Report. Pohick Creek flows in which direction under the bridge? a. southwest c. northwest b. north d. south

11. You have just completed a Tun- nel Reconnaissance Report. Referring to figures 10 and 11, what entry did you make for the length of the tunnel (in meters)? a. 60 c. 100 b. 75 d. 150

12. Refer to figures 10 and 11, Tun- nel Reconnaissance Report. is this tunnel an obstacle and why? a. no, the gradient is greater than 7% b. yes, overhead clearance less than 4.25 m c. no, meets obstruction criteria d. yes, traveled way width below standards, table 3

2-25 13. You are evaluating your squad©s Ford Reconnaissance Report. Refer- ring to figures 12 and 13, what is the low water level depth (in meters)? a. 0.3 c. 6.1 b. 0.5 d. 7.3

14. Refer to figures 12 and 13, Ford Reconnaissance Report. What must be done to improve the ford to enable it to carry loads over 10 tons? a. construct a causeway b. repair stream bottom c. attach cable anchorage to vehicles d. attach floats to reduce weight

15. Your squad has been given the mission of ferrying troops. Referring to figures 14 and 15, Ferry Reconnais- sance Report, how many passengers can the ferry carry? a. 8 c. 85 b. 40 d. 200

16. Refer to figures 14 and 15, Ferry Reconnaissance Report. The asphalt highway approach classification exceeds the ferry classification by how much? a. 5 c. 37 b. 15 d. 40

17. Refer to figure 16, Overlay. What type of route is VA 617? a. all-weather b. limited all-weather c. hard surfaced, most-weather d. fair-weather

18. Refer to figure 16, Overlay. What is the length of the ford (in meters)?

a. 8.2 c. 18.0

b. 17.3 d. 40.0

Fourth requirement. Multiple-choice exercise 19 concerns road classification.

19. You are performing a road reconnaissance. The road is 20 feet wide of paving stone surface, bumpy, with a combined width of traveled way and shoulders of 32 feet, steep gradients, and subject to snow blockage. What is the road classification formula?

a. Bgs 20/32 ft p(T)

b. Bgp 32/20 ft (T)

c. Bsg 20/32 ft p(Ob)

d. Bgp 20/32 ft s(T)

Fifth requirement. Multiple-choice exercises 20 and 21 provide an opportunity for you to calculate radius of a curve and gradient.

20. One of your men requests that you check his calculations for radius of a curve. The length of cord = 71 ft; perpendicular distance from cord to centerline of road = 6 ft. What is the radius of the curve (in feet)?

a. 6 c. 74

b. 60 d. 108

21. You have measured the horizontal distance between point A and point B and determined that it is 150 meters. Point A is 12 meters higher than point B. What is the gradient from point B to point A (in percent)?

a. 8 c. 16

b. 12 d. 20

Sixth requirement. Multiple-choice exercise 22 enables you to show your understanding of route classification.

22. You are determining a route classification. Limiting factors on different sections of the route are: gravel surface, two lane, 6 meters wide, a military load classification of 50, and under deep snow cover. What is the route classification?

a. 6mZ50 (S) c. 50Y6 (Ob)

b. 6mY50 (T) d. 6mZ50 (T)

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LESSON 3 HANDTOOLS AND RIGGING

CREDIT HOURS ______4 TEXT ASSIGNMENT ______Attached memorandum. MATERIALS REQUIRED ______None. LESSON OBJECTIVE ______To increase your knowledge of the care and use of handtools; and wire and manila rope.

______

ATTACHED MEMORANDUM

Section I. GENERAL RIGGING

1. CHARACTERISTICS OF FIBER ROPE

Fiber rope sizes are designated by inches of diameter up to 5/8 inch, then they are designated by circumference.

The weight of rope varies with use, weather conditions, and added preservatives.

Table 1 lists some of the properties of manila and sisal rope, including strength. The table shows that the minimum breaking strength is considerably greater than the safe working capacity. The difference is caused by the application of a safety factor. A safety factor is always used because the breaking strength of rope becomes reduced after use and exposure to weather conditions. In addition, a safety factor is required because of shock loading, knots, sharp bends and other stresses which the rope may have to withstand during its use.

If tables are not available, the rule of thumb for safe working capacity is used. This is that the safe working capacity in tons for fiber rope is equal to the square of the rope diameter in inches (SWC = Dý). For example, the safe working capacity for a 1/2-inch diameter fiber rope would be 1/2 squared or 1/4, ton. No attempt should be made to load a rope to its breaking strength.

2. CARE AND HANDLING OF FIBER ROPE

Fiber rope should be dry when stored and should be stored in a cool, dry place.

It should be coiled on a spool or hung from pegs in a way that will allow circulation of air.

Avoid dragging the rope through sand or dirt, or pulling the rope over sharp edges Sand or grit between the fibers of the rope will cut the fibers and reduce its strength.

Slacken taut lines before they are exposed to rain or dampness because a wet rope shrinks and may break.

A frozen rope should not be used until it is completely thawed; otherwise the frozen fibers will be broken as they resist bending.

Avoid exposure of fiber rope to excessive heat and fumes of chemicals.

When handling new rope the protective burlap covering should not be removed until the rope is to be used to protect the rope and prevent tangling (fig. 1). The end of the rope must be pulled through the center of the coil from the bottom when uncoiling the rope.

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3. INSPECTING THE FIBER ROPE

The outside condition of the rope will not show internal deterioration. For this reason it is necessary to untwist the strands slightly to inspect the inside of the rope.

Since any weak point in the rope weakens the entire rope, it is necessary to examine it in a number of places.

If the rope appears to be satisfactory, pull out a couple of fibers and attempt to break them. These fibers should offer considerable resistance to breakage.

When any unsatisfactory conditions are found, destroy the rope or cut it into short pieces.

4. WHIPPING FIBER ROPE

Whipping the ends of the fiber rope prevents the ends from untwisting. (This can also be accomplished by knotting.)

A rope is whipped by wrapping the end tightly with a small cord as shown in figure 2.

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5. CHARACTERISTICS OF WIRE ROPE

The size of wire rope is designated by its diameter.

The weight of wire rope varies with the size and the type of construction. Approxi- mate weights and breaking strengths for certain sizes are given in table 2.

The strength of a wire rope is determined by its size, grade, and method of fabrication. The individual wires may be made of various materials.

The ultimate or maximum strength of a wire rope is referred to as the breaking strength. Since a suitable margin of safety must be provided when applying a load to a wire rope, the breaking strength is divided by an appropriate safety factor (table 3).

As a rule of thumb, the diameter of wire rope in inches can be squared and multiplied by 8 to obtain the safe working capacity n tons.

The proper safety factor depends not only on the loads applied, but also on the speed of operation; the type of fittings used for securing the rope ends; the acceleration and deceleration; the length of rope; the number, size, and location of sheaves and drums, the factors causing abrasion and corrosion.

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6. CARE AND PROPER HANDLING INCREASE THE LIFE OF THE WIRE ROPE

At the time of fabrication, a lubricant is applied to wire rope. To renew the lubricant, a good grade oil or grease can be used.

Used wire rope should be carefully cleaned of any accumulation of dirt, grit, or other foreign material. Scraping or steaming will remove most of the dirt, grit, or rust.

Wire rope should be coiled on a spool for storage and should be properly tagged as to size and length.

It should be stored in a dry place to reduce corrosion, and kept away from harmful chemicals and fumes.

When loose wire rope is handled, small loops frequently form in the slack portion of the rope. If tension is applied to the rope while these loops are in position, they will not straighten out but will form sharp kinks. All of these loops should be straightened out of the rope prior to applying a load.

After a kink has formed in a wire rope, it is impossible to remove it and the strength of the rope is seriously damaged at the point where the kink occurs. Such a kinked portion should be cut out of the rope before it is used.

Small loops or twists will form if the rope is being wound into the coil direction opposite to the lay of the rope. Left lay wire rope should be coiled in a counterclockwise direction and right lay wire rope should be coiled in a clockwise direction.

When removing wire rope from a reel or coil, it is imperative that the reel or coil rotate as the rope unwinds.

7. CLASSIFICATION OF WIRE ROPE

Wire and strand combinations (fig. 3) vary according to the purpose for which the rope is intended. The smaller and more numerous the wires the more flexible the rope but the less resistant to external abrasion. Rope made up of a smaller number of larger wires is more resistant to external abrasion but is less flexible.

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Lay (fig.4) refers to the direction of wind- ing of the wires in the strands and of the strands in the rope. Both may be wound in the same direction, or they may be wound in opposite directions. There are three types of rope lays:

The most common lay in wire rope is the right regular lay. Left regular lay is used where the untwisting rotation of the rope will counteract the unscrewing forces in the supported load.

Because of the greater length of exposed wires, the lang lay assures longer abrasion resistance of the wires, less radial pressure on small diameter sheaves or drums by the ropes, and less bending stresses in wire. One disadvantage of the lang lay is a tendency to kink.

Reverse lay applies to ropes in which the strands are alternately regular. The use of reverse lay rope is usually limited to certain types of conveyors.

8. SEIZING WIRE ROPE

Seizing is the most satisfactory method of binding the end of a wire rope, although welding will also hold the ends together satisfactorily. The seizing will last longer and there is no danger of weakening the wire through the application of heat. (Wire rope is seized as shown in figure 5.)

The method for determining the number of seizings, lengths, and space between is as follows:

The number of seizings to be applied to each end equals approximately three times the diameter of the rope (No. seizing = 3D).

Example: 3 x 3/4 (dia) = 2 1/4. Use 3 seizings.

Each seizing should be 1 to 1 1/2 times as long as the diameter of the rope (length of seizing = 1 1/2D).

Example: 1 1/2 x 3/4 (dia) = 1 1/8. Use 2-inch seizings.

The seizings should be spaced a distance apart equal to twice the diameter (spacing = 2D).

Example: 2 x 3/4 (dia) = 1 1/2. Use 2-inch spaces.

Note: Always change fraction to next larger whole number.

9. CUTTING

Wire rope may be cut with a wire rope cutter, a cold chisel, a hacksaw, bolt clippers 3-5 or an oxyacetylene cutting torch. Before cutting, the strands must be tightly bound to prevent unlaying of the rope. Seizing or welding will secure the ends that are to be cut.

10. KNOTS

The choice of the best knot, bend, or hitch to use depends on the job it has to do. The following definitions will aid in understanding the methods of knotting.

Rope--A rope is a large, stout cord made of strands of fiber or wire twisted or braided together.

Line--A line is a thread, string, cord, or rope; especially a comparatively slender and strong cord.

Running end--The running end is the free or working end of a rope.

Standing part--The standing part is the rest of the rope, excluding the running end.

Bight--A bight is a bend or u-shaped curve in a rope.

Loop--A loop is formed by crossing the running end over or under the standing part forming a circle in the rope.

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Turn--A turn is placing of a loop around a specific object such as a post, rail, or ring with the running end continuing in a direction opposite to the standing part.

Round turn--A round turn is a modified turn, but with the running end leaving the circle in the same general direction of the standing part.

Overhand turn or loop--An overhand turn or loop is made when the running end passes over the standing part.

Underhand turn or loop--An underhand turn or loop is made when the running end passes under the standing part.

Knot--A knot is an interlacement of the parts of one or more flexible bodies, as cordage rope, forming a lump known as a knot; any tie or fastening formed with a rope, including bends, hitches, and splices.

Bend--A bend is used to fasten two ropes together or to fasten a rope to a ring or loop.

Hitch--A hitch is used to tie a rope around a timber, pipe, or post so that it will hold temporarily but can be readily undone.

11. KNOTS AT THE END OF A ROPE

An overhand knot may be used to prevent the end of a rope from untwisting, to form a knot at the end of a rope or to serve as a part of another knot (fig. 6).

The figure eight knot is used to form a knot at the end of a rope. The figure eight knot

is used in the end of a rope to prevent the end from slipping through a fastening or loop in another rope (fig. 7).

The wall knot (fig. 8) with crown is used to prevent the end of a rope from untwisting when an enlarged end is not objectionable.

The wall knot will prevent the rope from untwisting, but to make a neat round knob, it should be crowned (fig. 9).

12. KNOTS FOR JOINING TWO ROPES

The square knot (fig. 10) is used for tying two ropes of equal size together so they will not slip. The square knot will not hold if the ropes are wet or if they are of different sizes

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A single sheet bend (fig. 11) has two major uses: (1) tying together two ropes of unequal size and (2) tying a rope to an eye. This knot will draw tight but will loosen or slip when the lines are slackened. The single sheet bend is stronger and more easily untied than the square knot.

The double sheet bend (fig. 12) has a greater holding power than the single sheet bend for joining ropes of equal or unequal diameter, joining wet ropes, or tying a rope to an eye. It will not slip or draw tight under heavy loads. This knot is more secure than the single sheet bend when used in a spliced eye.

The carrick bend (fig.13) is used for heavy loads and for joining large hawsers or heavy rope. It will not draw tight under a heavy load and is easily untied if the ends are seized to their own standing part.

13. KNOTS FOR MAKING LOOPS

The bowline (fig. 14) is one of the most common knots and has a variety of uses, one

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of which is the lowering of men and material. It is the best knot for forming a single loop that will not tighten or slip under strain, and is easily untied if each running end is seized to its own standing part. The bowline forms a loop which may be of any length.

The double bowline (fig.15) forms 3 nonslipping loops. This knot can be used for slinging a man. As he sits in the sling, one loop is used to support his back and the remaining two loops support his legs; a notched board passed through the two loops makes a comfortable seat known as a boatswains chair.

The running bowline (fig.16) forms a strong running loop. It is a convenient form of running an eye. The running bowline provides a sling of the choker type at the end of a single line. It is used when a handling is to be tied around an object at a point that cannot be safely reached, such as the end of a limb.

A bowline on a bight (fig. 17) forms two nonslipping loops. The bowline on a bight can be used for the same purpose as a boatswain©s chair. It is used when a greater strength than that given by a single bowline is necessary, when it is desirable to form a loop at some point in a rope other than at the end, or when the end of a rope is not accessible. The bowline on a bight is easily untied, and can be tied at the end of a rope by doubling the rope for a short section.

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A Spanish bowline (fig. 18) can be tied at any point in a rope, either at a place where the line is double or at an end which has been doubled back. The Spanish bowline is used in rescue work or to give a two-fold grip for lifting a pipe or other round objects in a sling.

The French bowline (fig. 19) is sometimes used as a sling for lifting injured men. When used for this purpose, one loop is used as a seat and the other loop is put around the body under the arms. The weight of the injured man keeps the two loops tight so that he cannot fall out. It is particularly useful as a sling for an insensible man. The French bowline may also be used where a man is working alone and needs both hands free. The two loops of this knot can be adjusted to the size required.

A speir knot (fig. 20) is used when a fixed loop, a nonslip knot, and a quick release are required. It can be tied quickly and released by a pull on the running end.

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A figure eight with an extra turn (fig. 21) can be used to tighten a rope. This knot is especially well suited for tightening a one- rope bridge across a small stream.

A catspaw (fig. 22) can be used for fastening an endless sling to a hook, or it can be made at the end of a rope for fastening the rope to a hook.

14. HITCHES

The halt hitch (A, fig. 23) is used to tie a rope to a timber or to a larger rope. It will

3-13 hold against a steady pull on the standing part of the rope, but is not a secure hitch. It is frequently used for securing the free end of a rope, and is an aid and the foundation of many knots.

Two half hitches (B, fig. 23) are especially useful for securing the running end of a rope to the standing part. If the two hitches are slid together along the standing part to form a single knot, the knot becomes a clove hitch.

The hitch used for fastening a rope to a pole, timber, or spar is the round turn and two half hitches (fig. 24).

The timber hitch (fig. 25) is used for moving timber or poles. This hitch is excellent for securing a piece of lumber or similar object.

A timber hitch and half hitch (fig. 26) are combined to hold heavy timber or poles when they are being dragged.

The clove hitch (fig. 27) is one of the most widely used knots. It is used to fasten a rope to a timber, pipe, or post. It is also used for making other knots. This knot puts very little strain on the fibers when the rope is put around an object in one continuous direction. The clove hitch can be tied at any point in a rope. If there isn©t constant tension on the rope, another loop (round of the rope around the object and under the center of the clove hitch) will permit a tightening and slacken- ing motion of the rope.

The rolling hitch (fig. 28) is used to a secure a rope to another rope, or fasten it to a pole or pipe so that the rope will not slip. This knot grips tightly, but is easily moved along a rope or pole when strain is relieved.

The telegraph hitch (fig. 29) is a very useful and secure hitch which is used to hoist or haul posts and poles.

The scaffold hitch (fig. 30) is used to support the end of a scaffold plank with a single rope. It prevents the plank from tilting.

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The blackwall hitch (fig. 31) is used for fastening a rope to a hook. It is generally used to attach a rope temporarily to a hook or similar object in derrick work. Human life and breakable equipment should never be en- trusted to the blackwall hitch.

The girth hitch (fig. 32) is used in tying suspender ropes to hand ropes in the construction of expedient foot bridges.

A sheepshank (fig. 33) is a method of shortening a rope, but it also may be used to take the load off a weak spot in the rope. It

3-15 is only a temporary knot unless eyes are fastened to the standing part on each end.

The fisherman©s bend (fig. 34) is an excellent knot for attaching a rope to a light anchor, a ring, or a rectangular piece of stone. It can be used to fasten a rope or cable to a ring or post or where there will be slacken- ing and tightening motion in the rope.

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The harness hitch (fig. 35) forms a nonslipping loop in a rope. It is often employed by putting an arm through the loop, then placing the loop on the shoulder and pulling the object attached to the rope. The hitch is tied only in the middle of a rope. It will slip if only one end of the rope is pulled.

15. KNOTS FOR TIGHTENING ROPE

The butterfly knot (fig. 36) is used to pull taut a high line, handline, tread rope for foot bridges, or similar installations. Use of this knot will provide the capability to tighten a fixed rope when mechanical means are not available. (The harness hitch (fig. 35) can also be used for this purpose.)

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The baker bowline (fig. 37) may be used for the same purpose as the butterfly knot (fig. 36) and for lashing cargo. When used to lash cargo, secure one end with two half hitches, pass the rope over the cargo and tie a baker bowline (fig. 37), then secure the lashing with a slippery half hitch. To release the rope, simply pull on the running end.

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16. LASHINGS

The square lashing (fig. 38) is used to lash two spars together at right angles to each other. To tie a square lashing, begin with a clove hitch on one spar and make a minimum of 4 complete turns around both members. Continue with two frapping turns between the vertical and the horizontal spar to tighten the lashing. Tie off the running end to the opposite spar from which you started with another clove hitch to finish the square lashing.

The shears lashing (fig. 39) is used to lash 2 spars together at one end to form an expedient device called a shears. This is done by laying 2 spars side by side, spaced approximately 1/3 the diameter of a spar apart, with the butt ends together. The shears lashing is started a short distance in from the top of one of the spars by tying the end of the rope to it with a clove hitch. Then 8 tight turns are made around both spars above the clove hitch. The lashing is tightened with a minimum of 2 frapping turns around the 8 turns. The shears lashing is finished by tying the end of the rope to the opposite spar from which you started with another clove hitch.

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Block lashing (fig. 40) is used to tie a tackle block to a spar. First, 3 right turns of the rope are made around the spar where the tackle block is to be attached. The next 2 turns of the rope are passed through the mouth of the hook or shackle of the tackle block and drawn tightly. Then 3 additional taut turns of the rope are put around the spar above the hook or shackle. The block lashing is completed by tying the 2 ends of the rope together with a square knot. When a sling is supported by a block lashing, the sling is passed through the center 4 turns.

17. KNOTS FOR WIRE ROPE

Under special circumstances when wire rope fittings are not available and it is necessary to fasten wire rope by some other manner, certain knots can be used. In all knots made with wire rope, the running end of the rope should be fastened to the standing part after the knot is tied.

The fisherman©s bend, clove hitch, and carrick bend can be used for fastening wire rope.

3-23 18. SPLICES

Splices are used to join fiber rope or wire rope. The splices are as strong as the rope itself. There are four general types of splices in fiber rope--long, back, short, and eye splices. The methods of making all four types of splices are similar. They generally consist of three basic steps--unlaying the strands of the rope, placing the rope ends together, and interweaving the strands and tucking them into the rope. Table 4 shows the length of rope to be unlaid on each of the two ends of the ropes, and the amount of rope required for the tuck.

The short and long splices are very similar. The short splice (fig. 41) causes an increase in the diameter of the rope for a short distance and can be used only where this increase in diameter will not affect operations. However, the long splice (fig. 42) does not increase the diameter and a skillfully made long splice will run through sheaves. Both splices are as strong as the rope itself.

Eye or side splice (fig. 43) is used for making a permanent loop in the end of a rope. This splice is also used to splice one rope into the side of another.

The end of a rope is back spliced to prevent unlaying. If a slight enlargement of the end is not objectionable, a crown splice (fig. 44) should be used.

19. ATTACHMENTS FOR WIRE ROPES

Most attachments give maximum strength when the rope is connected with another rope, hook, or ring (fig. 45).

End fittings may be placed directly on the wire rope (fig. 46). There are three types of end fittings which may be easily changed.

Clips (fig. 47) are reliable and durable. They are used for making eyes in ropes. The clips should be placed about six rope diameters apart for best service. The number of clips to be installed is equal to three times the diameter plus one.

Clamps (fig. 48) can be used with or without a thimble to make an eye. The clamp has 90% the strength of the rope.

A wedge socket (fig. 49) end fitting is used when it may be necessary to change the fitting at frequent intervals. The fitting is about two-thirds as strong as the rope itself.

20. SLINGS

Slings may be made up of fiber rope, wire rope, or chain. Fiber rope makes good sling material because of its flexibility, but it is more easily damaged by any sharp edges on the material hoisted. Wire rope is widely used because of its strength and flexibility. Chain slings are used for lifting very hot items or items with sharp metal edges.

There are three basic types of slings.

The endless sling (fig. 50) is made by splicing the ends of a wire rope together, or by inserting a cold shut link in a chain.

A single sling (fig. 51) can be made by forming an eye in each end of a piece of fiber rope or wire rope. In some instances the ends of a wire rope are spliced into eyes around thimbles and one eye is fastened to a hook with a shackle.

Combination slings (fig. 52). Single slings can be combined into bridle slings, bas- ket slings, and choker slings to lift virtually any type of load. Either two or four single slings can be used in a given combination. Where greater length is required, two of the single slings can be combined into a longer single sling. 3-24

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It is very important that slings strong enough to lift the load be selected. Tables 5 and 6 list the safe working loads of manila and wire rope slings under various lift conditions.

Slings should be inspected regularly to prevent injury to personnel or damage to equipment.

21. BLOCKS AND TACKLE

A block is essentially a wood or metal frame containing one or more rotating pul- leys called sheaves.

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Tackle is an assembly of ropes and blocks used to gain the desired mechanical advantage. Simple tackle is one or more blocks reeved with a single rope (fig. 53). Com- pound tackle is two or more blocks reeved with one or more ropes (fig. 54)

22. ANCHORS

When heavy loads are handled with tackle, it is necessary to have some means of anchorage. Wherever possible, natural anchorages should be used for speed and economy. Tem- porary anchorages include pickets, rock anchors, holdfasts (fig. 55), and deadmen (fig. 56). Permanent anchorages may be made up of steel anchors set in concrete or fastened to permanent structures.

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23. GUYLINES

Guylines should always be fastened to anchorages at a point as near to the ground as possible. The angle at which the guyline pulls on an anchor should be as nearly parallel to the ground as possible to avoid pulling the anchorage out of the ground. It is better to

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3-31 link two or more anchors together in an anchorage than to use a single anchor, because the multiple anchors spread the load against the ground. In linking anchors together, a point high on one anchor should be secured to a point near the ground on the anchor behind it.

(Figure 54 on page 3-33)

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Section II. LIFTING AND MOVING LOADS

With an elementary knowledge of rigging, rope, tackle, and timber, devices can be made in the field to assist greatly in lifting or moving heavy loads. There are a variety of devices you can use. The four most commonly used are the gin pole, tripod, shears, and boom.

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24. GIN POLE

The gin pole (fig. 57) consists of an upright spar which is guyed at the top to maintain it in vertical or nearly vertical position, and equipped with suitable hoisting tackle.

The proper method for rigging a gin pole is as follows: Lay out the pole with the base at the spot where it is to be erected. In order to make provisions for the guylines and tackle blocks, place the gin pole on cribbing for ease of lashing (fig. 58). The procedure is as follows:

Make a tight lashing of eight turns of fiber rope about 1 foot from the top of the pole, with two of the center turns engaging the hook of the upper block of the tackle. Secure the ends of the lashing with a square knot. Nail wooden cleats (boards) to the pole flush with the lower and upper sides of the lashing to prevent the lashing from slipping.

Lay out two guy ropes, one for the side guylines and one for the fore and back guylines. Each rope should be four times the length of the gin pole.

In the center of each guy rope, form a clove hitch over the top of the pole next to the tackle lashing to form two guys, and be sure the guylines are alined in the direction of their anchors.

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Lash a block to the gin pole about 2 feet from the base of the pole, the same as was done for the tackle lashing at the top, and place a cleat above the lashing to prevent slipping. This block serves as a leading block on the fall line which allows a directional change of pull from the vertical to the horizontal. A snatch block is the most convenient type to use for this purpose.

Reeve the hoisting tackle and use the block lashed to the top of the pole so that the fall line can be passed through the leading block at the base of the gin pole.

Drive a stake about 3 feet from the base of the gin pole. Tie a rope from the stake to the base of the pole below the lashing on the leading block and near the bottom

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of the pole. This is to prevent the pole from skidding while it is being erected.

Check all lines to be sure that they are not snarled. Check all lashings to see that they are made up properly, and see that all knots are tight. Check the hooks on the blocks to see that they are moused properly. The gin pole is now ready to be erected.

The proper procedure for erecting a gin pole is as follows: A gin pole 40 feet long may be raised easily by hand, but longer poles must be raised by supplementary rigging or power equipment. The number of men needed depends on the weight of the pole. The procedure is as follows:

Dig a hole about 2 feet deep for the base of the gin pole.

String out the guys to their respective anchorages and assign a man to each anchorage to control the slack in the guyline with a round turn around the anchorage as the pole is raised. If it has not been done already, install an anchorage for the base of the pole.

If necessary, the tackle system utilized to raise and lower the load may be used to assist in raising the gin pole, but the attaching of an additional tackle system to the rear guyline is preferable. Attach the running block of the rear guyline tackle system to the rear guyline the end of which is, at this point of erection, near the base of the gin pole. The fixed or stationary block is then secured to the rear anchor. The fall line should come out of the running block to give greater mechanical advantage to the tackle system. The tackle system is stretched to the base of the pole before it is erected to prevent the choking of the tackle blocks during the erection of the gin pole.

Keep a slight tension on the rear guyline and on each of the side guylines, and then haul in on the fall line of the tackle system while eight men (more for larger poles) raise the top of the pole by hand until the tackle system can take control.

The rear guyline must be kept under tension to prevent the pole from swinging and throwing all of its weight on one of the side guys.

When the pole is in its final position, approximately vertical or inclined as desired, make all guys fast to their anchorages with the round turn and two half hitches. It frequently is desirable to double the portion of rope used for the half hitches.

Open the leading block at the base of the gin pole and place the fall line from the tackle system through it. When the leading block is closed the gin pole is ready for use. If it is necessary to move (drift) the top of the pole without moving the base, it should be done when there is no load on the pole, unless the guys are equipped with tackle.

25. TRIPOD

The tripod (fig. 59) consists of three legs lashed at the top. Its advantage over other devices is its stability. Its disadvantage is that the load can only be moved up and down. The proper method for lashing a tripod is as follows (fig. 60):

The material used for lashing can be fiber rope, wire rope, or chain. Metal rings joined with short chain sections and large enough to slip over the top of the tripod legs also can be used. The method described below is for fiber rope 1 inch in diameter or smaller. Since the strength of the tripod is affected directly by the strength of the rope and the lashing used, more turns than described below should be used for extra heavy loads and fewer turns can be used for light loads.

Select three spars of approximately equal size and place a mark near the top of each spar to indicate the center of the lashing.

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Lay two of the spars parallel with their tops resting on a skid or block and a third spar between the first two, with the butt in the opposite direction and the lashing marks on all three in line. The spacing between spars should be about one-half the diameter of the spars. Leave the space between the spars so that the lashing will not be drawn too tight when the tripod is erected.

With a 1-inch rope, make a clove hitch around one of the outside spars about 4 inches above the lashing mark and take eight turns of the line around the three spars. Be sure to maintain the space between the spars while making the turns.

Finish the lashing by taking two close frapping turns around the lashing between each pair of spars. Secure the end of the rope with a clove hitch on the center spar just above the lashing. Frap- ping turns should not be drawn too tight.

The proper procedures for erecting a tripod as follows:

The legs of a tripod in its final position should be spread so that each leg is equidistant from the others. This spread should not be less than one-half nor more than two-thirds of the length of the

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legs. Chain, rope, or boards should be used to hold the legs in this position. A leading block for the fall line of the tackle may be lashed to one of the legs.

Raise the tops of the spars about 4 feet, keeping the base of the legs on the ground.

Cross the two outer legs. The third or center leg then rests on top of the cross. With the legs in this position, pass a sling over the cross so that it passes over the top or center leg and around the other two.

Hook the upper block of a tackle to the sling and mouse the hook.

Continue raising the tripod by pushing in on the legs as they are lifted at the center. Eight men should be able to raise an ordinary tripod into position.

When the tripod legs are in their final position, place a rope or chain lashing between the legs to hold them from shift- ing.

26. SHEARS

Shears (fig. 61) are easily assembled and require only two guys. The shear legs may be round poles, timbers, heavy planks, or steel bars, depending on the material at hand and the purpose of the shears. They are adaptable to working at an inclination from the vertical. In addition to their hoisting and lifting capabilities, shears are used extensively as towers for cableways and in floating bridge operations.

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The procedure for lashing the shears is as follows:

The spread of the legs should equal about one-half the height of the shears. The maximum allowable drift (inclination) is 45ù. Tackle blocks and guys for shears are essential. The guy ropes can be secured to firm posts or trees with a turn of the rope so that the length of the guys can be adjusted easily.

Lay two timbers together on the ground in line with the guys, with the butt ends pointing toward the back guy and close to the point of erection.

Place a large block under the tops of the legs just below the point of lashing, and insert a small spacer block between the tops at the same point. The separation between the legs at this point should be equal to one-third the diameter of one leg, to make handling of the lashing easier.

With sufficient 1-inch rope for 14 turns around both legs, make a clove hitch around one spar, and take 8 turns around both legs above the clove hitch. Wrap the turns tightly so that the lashing is made smooth and without kinks.

Finish the lashing by taking two frapping turns around the lashing between the legs and securing the end of the rope to the other leg just below the lashing. For handling heavy loads, the number of lashing turns is increased.

The proper procedure for the erecting of shears is as follows:

Holes should be dug at the points where the legs of the shears are to stand. In case of placement on rocky ground, the base for the shears should be level. The legs of the shears should be crossed and the butts placed at the edges of the holes. With a short length of rope, make two turns over the cross at the top of the shears and tie the rope together to form a sling. Be sure to have the sling bearing against the spars and not on the shears lashing entirely.

Reeve a set of blocks and place the hook of the upper block through the sling. Secure the sling in the hook by mousing. Fasten the lower block to one of the legs near the butt, so that it will be in a convenient position when the shears have been raised, but will be out of the way during erection.

If the shears are to be used on heavy lifts, another tackle is rigged in the back guy near its anchorage. The two guys should be secured to the top of the shears with clove hitches to legs opposite their anchorages above the lashing.

Several men (depending on the size of the shears) should lift the top end of the shear legs and "walk" them up by hand until the tackle on the rear guyline can take effect. After this, the shear legs can be raised into final position by haul- ing in on the tackle. Secure the front guyline to its anchorage before raising the shear legs and keep a slight tension on this line to control movement.

The legs should be kept from spreading by connecting them with rope, chain, or boards. It may be necessary, under some conditions, to anchor each leg of the shears during erection to keep the legs from sliding in the wrong direction.

27. BOOM DERRICK

Booms (fig. 62) are used on gin poles to lift loads where a long horizontal reach is required. For medium loads, the boom can swing about the gin pole.

The methods of rigging and erecting the boom derrick is as follows:

Rig a gin pole as described previously, but lash another block about 2 feet below the tackle lashing at the top of the pole. Reeve the tackle so that the fall line comes from the traveling block to the end of the boom after the mast is erected.

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Erect the mast in the manner described previously, but pass the fall line of the tackle through the extra block at the top of the pole before erection to increase the mechanical advantage of the tackle system.

Select a boom with the same diameter and not more than two-thirds as long as the mast. Spike two boards to the butt end of the boom and lash them with rope, making a fork. The lashing should be made with a minimum of sixteen turns and tied off with a square knot. Drive wedges under the lashing next to the cleats to help make the fork more secure.

Spike cleats to the mast about 4 feet above the resting place of the boom and place another block lashing just above these cleats. This block lashing will support the butt of the boom. If a separate tackle system is ripped up to support the butt of the boom, an additional block lashing should be placed on the boom just below the larger lashing to secure the running block of the tackle system.

If the boom is light enough, manpower may be used to lift the boom in place on the mast through the sling which will support it. The sling consists of 2 turns of rope with the ends tied together with a square knot. The sling should pass through the center 4 turns of the block lashing on the mast and should cradle the boom. On heavier booms, the tackle system on the top of the mast can be used to raise the butt of the boom to the desired position onto the mast.

Lash the traveling block of the mast tackle to the top end of the boom and lash the standing block of the boom tackle at the same point. Reeve the boom tackle so that the fall line comes from the standing block and passes through the block at the base of the mast. The use of the leading block on this fall line is optional, but when handling heavy loads, more power may be applied to a horizontal line leading from the block with less strain on the boom and guys.

Section III. ENGINEER HANDTOOLS

28. PIONEER TOOLS

The single bit ax is a chopping tool used to fell or prune trees, to cut or trim logs and heavy brush, and to split and cut wood. The head has a flat face on one end. A blade, called a "bit", with a slightly fanshaped cutting edge, is at the other end. Before using the ax, always clear the work area of material that might deflect the ax blade. While using the ax, the user©s body weight should be distributed evenly on both legs, with knees set but not tense. The feet should be spread apart at a comfortable distance to retain balance, while the body should be relaxed and free to swing and bend at the waist.

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The brush hook is used where it is not practical to use the ax, for cutting under brush, shrubs, and branches. To use the brush hook on a tree branch lift the curve of the hook above the branch and make short, chopping strokes downward against the surface of the branch. In cutting small brush, the brush hook is swung horizontally like a scythe, with the hooked portion used to keep the brush from bouncing away from the cutting edge.

The adz is a chopping tool used for hewing and smoothing lumber or logs, where a great deal of wood or bark is to be removed. The adz is a form of ax on which the edge of the blade is at a right angle to the handle. At one end of the adz©s curved head is a flat surface and the eye. At the other end is the cutting blade. The cutting edge of the blade is 3 1/2 to 4 1/2 inches wide, and is beveled on the inside of the curve only. To use the adz, first clear the work area of branches and debris, and while using it do not let wood chips pile up on the work surface. Block the timber to be worked on so it cannot slip, slide, or roll. Straddle the timber and grip the adz handle with both hands. The left hand should be near the handle©s end and the right hand held on the handle from 12 to 15 inches below, while keeping the hands in approximately the same position on the handle. When using the adz, the right hand does not slide toward the left hand as in swinging the ax, because the right hand must be in a position to keep control of the adz head at all times. Since the tool©s cutting edge operates close to the feet and legs of the adz user, sliding the right hand to the end of the handle would leave the adz blade free to be deflected toward the user, possibly causing injury.

Large crosscut saws are used for heavy work such as felling trees, cutting large trees into logs, and sawing heavy timbers. The large crosscut saws have a high grade steel blade with two types of teeth, known as cutters and rakers. The cutters can be the crosscut or ripping type of tooth, and are slightly longer than the rakers. The cutters do the cutting and the rakers chisel out and remove chips from the kerf.

The one-man crosscut saw is operated like the handsaw, except that the left hand helps to guide and pull the blade with the handle attached to the saw back, at the saw©s heel end.

The two-man crosscut saw must be operated by two men. It is moved across the wood by pulling action only. One man pulls the blade toward himself as far as it will go, while the other man guides the saw. Then the procedure is reversed, with the first man doing the guiding and the second man pulling the saw toward himself.

The stillson pipe wrench is designed for use on round objects like pipe, shafting, and rods, where a smooth surface requires a wrench that can take a bite on the work to turn it.

In using this wrench, the grip on the work is increased by pressing the wrench handle downward in the direction of the jaw opening. To use the pipe wrench, turn the adjusting nut so the jaw opening is slightly larger than the object to be gripped. Place the work as far back into the jaw as possible, and tighten the adjusting nut so the movable jaw fits snugly on the object to be turned. Apply force to the back of the handle so the wrench is turning in the direction of the jaw opening. Applying pressure to the opposite direction, toward the adjusting nut, will loosen this wrench©s grip. Never use the pipe wrench on nuts or bolts, because the wrench©s hard teeth will make nuts or bolts unusable by chewing them up.

Bars are heavy steel tools used to lift and move heavy objects, and to pry where lever- age is needed.

In moving heavy objects or prying with a bar, it should be used in a position where the weight of the user©s body is exerted downward on the long section of the lever. When possible, use a block or other object as a fulcrum behind the bar, near the spot where the bar©s point is wedged under the object to be moved. In ripping or tearing apart

3-41 roughly with a bar, wedge it under the object to be ripped off, and jerk the hand end up and down to loosen the object. When using a bar for prying, always be sure the point is securely set under the object being worked on, so the bar will not slip and damage the work or cause injury.

The wrecking bar is used to pull nails or spikes, to open heavy crates, and to do demolition or wrecking work. The wrecking bar is a shaft of tough steel with a gooseneck claw end for removing large nails and spikes and for prying. The other end is called the pinch point and is tapered down to resemble a chisel. The pinch point can be straight, slightly angled, or offset. The size of the bars found in the carpenter sets averages from 30 to 48 inches, with a diameter of 1/2 to 1 1/8 inches.

The crowbar is used for heavy prying (lifting) and for moving heavy timbers and other large objects for short distances. It can also be used for loosening rock formations, as a lever for moving rails, and for breaking up hard earth when digging. The crowbar that is issued with pioneer tool sets is a steel bar, about 5 feet long, tapered to a rounded point at the end where it is usually held. There is a pinch point with a chisel-like, squared-off wedge, at the other end. Some crowbars have the pinch point set at a slight angle.

The pinchbar is used in light ripping and prying jobs. The one issued with pioneer sets is a steel bar, from 26 to 36 inches long, with a tapered point at one end and a chisel-like pinch point at the other. The pinch point is sometimes bent slightly. Some pinchbars have a short claw at the tapered end. This bar ranges from 1/2 to 1 inch in diameter.

Jacks are used to raise or lower work or heavy loads short distances. Jacks are also used to lift the side or the end of a vehicle. Jacks are metal tools that are operated through a rack bar or screw or operated hydraulically. They are available to handle loads of from 1 1/2 to 100 tons. The jack issued with pioneer tool sets are both the screw type and the hydraulically operated type and have a lifting capacity of 12 tons.

Climbing tools are used for scaling poles and trees when erecting power lines and gin poles, for clearing and topping trees, and for similar operations.

The climbing tools consist of a safety belt, a safety strap, and the leg iron set with spurs or gaffs. The safety belt is an adjustable leather belt that has loops in which to carry tools. It also has two D-rings fastened to it for holding the safety strap. The safety strap is a leather strap with metal snaphooks on each end, for hooking into the D-rings of the safety belt. The leg irons are called the tree and pole climbers and consist of flattened metal bars that are curved at one end to fit under the foot arch, with the straight portion continuing along the inside of the lower leg. Leather straps secure these climbers to the leg and ankle. On the leg iron, pointing downward at the arch, is a spur (gaff) which sticks into the surface of the tree or pole and carries the weight of the wearer©s body when climbing. In some climber sets, this metal gaff is detachable and two sets of gaffs are included.

29. CARPENTER©S TOOLS

Handsaws are tools with thin, flat steel blades that have a row of spaced notches called "teeth" along one edge and are made of special steel that is hardened, tapered, tempered, and ground. The blade is fastened to some type of handle. Saws are available in different types and sizes. Each type of material that can be sawed demands a special type of saw for best results. Factors to be considered in selecting the correct saw for a job include type and hardness of the material to be cut, its grain or composition, how long a cut will be, whether it will be an inside or outside cut, and specific physical properties of the material (as green, wet, new, or used lumber).

The crosscut saw is designed to cut across the grain of the wood. Its teeth are constructed so they have bevels and resemble a row of small triangular knives. On a crosscut saw each side of the tooth is filed to cutting edge like a knife. Crosscut saws and ripsaws have the same general appearance, except that their teeth differ in shape and bevel.

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The ripsaw is designed to cut with the grain of the wood. On a ripsaw, each tooth is filed straight across to a sharp square edge like a little chisel. The teeth of the ripsaw are a series of little chisels set in two parallel rows that overlap each other for cutting with the grain of the wood.

The nested saws are used to cut along curved lines, to start cuts for larger saws, and to make cuts inside a board or partition where sawing must start from a drilled hole or small opening. The nested saws consist of a wooden handle to which three different blades can be attached for making up the three saws known as the keyhole, compass, and plumber©s saws. A slotted end at the heel of each blade slips into the pistol-grip type handle, where a thumbnut fastens the blade in place.

The hacksaw is designed to cut almost any size or shape of metal object. Hacksaws come in sizes from 8 to 12 inches in length, with blades from 14 to 32 points to the inch. Two types of hacksaw blades are made: hard and flexible. All of the metal in a hard blade is tempered, while the flexible blade is hardened or tempered only along the tooth edge. The 18-point flexible blade, which is issued with pioneer tool sets, is considered best for general use.

Planes are smoothing tools used to true the edges or surfaces of wood, where a finished surface or close-fitting joints are required. Planes are made to do specific jobs and are found in many forms.

Block planes are the smallest type, aver- aging 6 inches in length, and are generally operated with one hand. They are used primarily to make small cuts, where the cut must be made across the grain of the wood, and to square edges. The cutting edge bevel of the block plane is used with its bevel up, away from the work.

Bench planes are normally used to cut with the grain of the wood. Common types are the smoothing plane (5 1/2 to 10 inches) with a straight cutting edge used for finishing purposes, the jack plane (11 to 15 inches) for all-purpose planing and the jointer plane (20 to 24 inches) for truing finished surfaces.

The chalkline is used to lay out a straight line between two points that are too far apart to permit use of a square or straightedge for drawing a line. It can be used for such jobs as staking out foundations; laying brick; alining walls, forms, and posts; and marking long boards for sawing. To use the chalkline, first mark the spots between which a straight line is desired, by stakes, nails, or other objects. Tie the chalkline to the object marking the spot, or have a man hold it there. Hold the chalk in the palm of the hand, then draw the chalkline over the chalk while moving toward the other layout point. Fasten the chalkline, now coated with chalk, to the other layout point, or hand it to the man stationed there, and make sure the line is stretched tightly between the points. Grasp the line midway between both points and pull it away from the work surface at a right angle to the work surface. Release the line from the fingers so it will snap downward to deposit chalk on the work surface in a straight line.

The carpenter©s level is used to determine whether a surface is truly horizontal or vertical. It is a long, rectangular body of wood or metal that is cut away on its side and near the end to hold small glass tubes. These glass tubes are almost entirely filled with a non- freezing liquid which leaves a small bubble free to move as the level is moved. All sides of this level are true-surface edges. The glass tubes have hairline marks at equal distances from the middle of the tube to mark the upper position of the bubble when the surface on which the tool rests is level. To test the levelness of a surface, place the carpenter©s level on the work surface. Check the glass tube that is horizontal with the surface being tested, to see if the bubble is centered evenly between the hairline guides on the tube. If the bubble is not centered, lower or raise one side of the work surface enough to center the bubble. Then turn the level around, end to end, and doublecheck the reading to be sure the level is accurate. To plumb an object, hold the level flat against the vertical surface to be plumbed and follow the same steps used

3-43 for testing levelness, using the glass tube that is horizontal.

The line level is used to check the level of a line between two points, as in checking the floor of an excavation, or to check a line that is to be an elevation guide. It is a short level with a hook at each end for hanging onto a line.

To use the line level, stretch a cord tautly between the two points so the cord is at the exact elevation and lies along the desired working line. Hang the level by its hooks about midway between the two end points and adjust the line at each end so the bubble in the glass tube lies between the hairlines.

A plumb bob is used to obtain a true vertical line for checking whether uprights or walls are truly vertical.

To use the plumb bob, fasten it to a cord that is long enough to extend the tool from the checking point to the spot where a reading must be made. Fasten the cord to the top checking point and let the plumb bob hang freely on the cord. The spot above which the plumb bob©s point stops is the true vertical with the spot at the other end of the cord. If breezes or other air circulation keep the plumb moving, it may be necessary to shield it with the body or a board to get an accurate reading.

The carpenter©s square (fig. 63) is used to measure and mark lumber, to test the squareness and flatness of wood, and to make calculations with the aid of its graduations and tables. This square, sometimes called a framing square because it is especially useful in structure framing, is an L-shaped, flat piece of steel. The longer portion is called the body or blade and is 24 inches long. The shorter portion is 16 inches long and is called the tongue. Graduations in inches and fractions of inches are found on both sides and on the inside and outside edges of this square. Several scales and tables are on the square, for figuring lengths of lumber and laying out work to dimension.

Place the square blade on the board with the heel at the end of the board, and the 24- inch body lying along the length of the board. Mark the spot where the body ends, then move the heel end over to this spot and mark the next 24-inch segment at the end of the body. Continue moving the square along the length of the board, making a mark every 24 inches until the measurement is completed. Measuring the distance for setting studs at the normally used 16- or 24-inch centers is particularly easy with the square, because the lengths of its body and tongue are designed for this purpose.

To mark a board at a right angle to its edge, place the inner edge of the square©s body along the edge of the board. The tongue will be at a right angle to the edge of the board and the line can be drawn along the tongue edge.

To test a board for squareness, place the inner edge of the body along the edge of the board, with the edge of the tongue at the end of the board. If the board is square, there will be no light showing through between the inner edges of the square and the edges of the board.

To test whether a board is warped (not flat), set the outer edge of the body or tongue along both diagonals of the board. If the board is not flat, the edge of the square will not touch the board along its entire length.

Along the outer edges of both sides of this square©s body and tongue are inch markings which are divided into graduations of 1/32, 1/16, 1/12, 1/10, 1/8, and 1/4. These graduations are used in measuring and in laying out work.

The tables and scales on the carpenter©s steel square (essex table, hundredths scale, rafter or framing table, brace table, octagon scale) are used to make quick calculations.

Combination square (fig. 63) combines the equivalent of many tools such as the straightedge, plumb, level, outside try square, inside try square, marking gage, depth gage, and miter square. It is a foot-long steel blade with a metal head which can be moved and clamped to any desired position along the

3-44 blade. The head has machined edges at 45- and 90-degree angles with the blade and is fitted with a vial or tube in the carpenter©s level and a steel scriber or awl. To set the head of this square to any position on the blade, loosen the knurled nut and move the head to the desired position, then tighten the nut.

The combination square is used to lay out and mark angles, as a depth gage, and for plumbing and squaring purposes.

The try square (fig. 63) has many uses. It will serve as a guide for marking lines at right angles to an edge or surface; to test straight- ness and squareness of edges, faces, and ends of small boards; to check an edge or surface to determine whether it is the same width or thickness throughout its length; to serve as a scale for laying out work on small pieces of lumber when cutting and framing; and to test inside or outside angles of 45 and 90 degrees. To use the try square most effectively, be sure to press the beam or stock of the

3-45 tool firmly against the edge of the board or other material being checked or marked.

The sliding T-bevel (fig. 63) is similar to the try square, but its blade is adjustable to any angle. It is used for laying out angles other than right angles, for testing bevels, and for repeating or transferring angles from one piece of lumber to another. To set the sliding T-bevel, loosen the thumbscrew at the rounded edge of the handle just enough to permit the blade to slide along its slot and to rotate with slight friction. Place the T-bevel handle against one side of the required angle, and the blade against the other side of the angle. Tighten the thumbscrew so the blade fits firmly against the handle.

30. PORTABLE ELECTRIC TOOLS

The portable electric tool outfit is designed for a variety of uses including construction, intrenching, timber cutting, bridging, and clearing to reduce manual effort and increase production.

The generator in the electric tool trailer is a standard 3 KW, 60-cycle, 115-volt skid- mounted unit.

All power tools should be grounded to preclude electric shock. The cord generally has a three-prong type plug. If the plug is the two- prong type, it will be necessary to ground the tool. This is done by connecting the post or clip that extends from the third wire on the cord to an electric conduit, a pipe, or a metal rod driven into the ground. Safety goggles should be worn when using power tools.

The portable electric drill can be used with a wide variety of bits and attachments for drilling holes, buffing, sawing, and driving screws. It is essentially an electric motor in a metal housing fitted with a chuck into which a bit or other attachment can be fastened. It has a spade handle or pistol-grip type handle. Some drills have another attached "steadying" handle and a bar that can be attached for use as an auxiliary handle. To insert the drill bit into the electric drill chuck, fit the chuck key into the teeth of the chuck. Turn the key counterclockwise until the chuck opens enough to admit the shank of the bit. Insert the bit and tighten the chuck jaws securely by turning the key clockwise. Re- move the key from the chuck and store the key where it will not get lost.

The work to be drilled must be stationary or firmly secured. Make a slight dent in the spot to be drilled, by use of a center marker or punch, so the drill bit will not bounce or slide away from the place where the hole is desired. Turn the drill switch on, hold the drill in position, and place the revolving drill bit on the marked spot. In drilling, exert enough firm, even pressure to keep the bit cutting, but do not use great pressure since this can dull or break the bit. Keep the drill at the required angle to the work, without rocking the bit or changing its angle.

While drilling, withdraw the bit frequently from the work to clear the chips from the bit flutes and to allow the bit to cool so it will not lose its tempering or break. If the bit binds, this is an indication that its flutes are jammed with shavings. Always keep the bit turning with power on while withdrawing it from the hole.

The portable electric hammer can be used for beveling, caulking, beading, drilling in masonry, driving nails, digging in clay, breaking light concrete, and performing other similar jobs. The portable electric hammer consists of a metal housing on a spade type or pistol- grip handle. Inside the housing, a strong spring moves a steel piston back and forth in a pounding manner when the power switch is on. The housing©s nozzle is designed to hold a variety of bits such as chisels, diggers and tampers. The forward stroke of the piston activates the bit. A removable tool-retaining spring clip is located at the housing nozzle. In using the electric hammer, the bit to be used is slid into the nozzle so it snaps into place and is held securely. The handle of the electric hammer is held firmly with one hand while the other hand steadies and guides the tool. Operations performed with this hammer require the use of safety goggles to protect the eyes.

3-46 The electric impact wrench is used primarily for installing and removing nuts, bolts, and screws. It can also be used with proper accessories to drill and tap a variety of materials, to drive studs, and to drive or remove socket-head or self-tapping screws.

It consists of a pistol-grip handle on a metal housing containing the motor that activates the socket-retainer/driving-anvil inside the muzzle of the housing. Attach- ments used with this wrench are fastened to the driving anvil by snapping them onto the socket retainer. A ratchet switch makes it possible to reverse the action of the tool for loosening or tightening work.

Before using the electric wrench, check that the wrench and its reversible features are functioning correctly. Do this by connecting its cord to a suitable power source, depressing the on-off switch, and allowing the wrench to operate a few seconds while noting the direction of the rotation. Stop the wrench, adjust the ratchet switch so the direction is reversed, and start the wrench again.

Some of the most common uses of the portable electric circular saw are cutting studding to length, cutting off the ends of subfloors or sheathing, ripping boards and planks, and preparing inside and outside trim. The pioneer electric tool set©s saw has a 10- inch blade. The blades are available with teeth specifically designed for crosscutting or ripping. There is also a blade with a combination of cutting and raker teeth, for ripping, crosscutting, or mitering.

To use, set the saw©s guide to the correct angle and depth of cut. Be sure the material to be sawed is steadied by its own weight or is secured firmly by clamping or wedging. Press the switch trigger in the handle to start the saw. The saw blade must be revolving at full speed before it contacts the material to be cut. When cutting, apply firm pressure but do not force the saw. To attach a new blade make certain that the teeth are in the proper cutting direction (pointing upward toward front of saw) and tighten the flange and clamp-screw with the wrench.

Electric disk sanders can be used for heavy- duty sanding, grinding, wire brushing, and planning. Before using the sander, secure the proper attachment to the spindle, and be sure the work is stationary or make it so by weights or clamps. Switch on the sander so the attachment is turning before placing it on the work surface. Grasp the sander firmly with one hand on each handle, and begin sweeping the machine back and forth over approximately an 18-inch span, using light pressure.

Chain saws are used in cutting logs and timber. They are used horizontally in felling trees and vertically in cutting logs. The gasoline driven chain saw, a component of the portable electric tool set, is a portable one- man saw with the teeth arranged on a flexible steel chain-like belt that rotates so the teeth cut only in one direction, toward the power end of the saw. It has a pistol-grip handle and a sturdy bar frame above the engine for holding and guiding. Before using the chain saw, make sure the teeth on the chain have been positioned correctly, so the saw cuts toward the end of the saw where the motor or engine is attached. Also be sure the teeth are sharp and undamaged. In sawing, hold the chain saw against the tree, pile, or timber to be cut, and apply light pressure in guiding the saw through the work. When cutting felled logs, the weight of the saw furnishes enough pressure and the saw user simply guides the saw.

In the care of portable power tools, keep them, and especially their housing intake and exhaust holes, clean and free of dust and dirt at all time. Wipe these tools with a soft cloth and use compressed air to blow sawdust and other particles from areas that cannot be reached with a cloth. Examine the tool©s cord for exposed or loose wires and for damaged insulation. Wipe the cord clean often to prevent deterioration from oil or grease. Check the cord©s ground wire connection to make sure it is not loose, and check the plug for loose prongs or cracked casing. Do not hold or drag the electric tool by its cord at any time. Store power tools in containers designated for this purpose or in the tool trailer,

3-47 after coating any rustable metal with oil. An experienced technician should make a periodic check of all electric tools to include an examination of motor parts, cleaning, brushes, wiring and commutator.

31. STORAGE

Emphasis should be placed on easy access to those tools used most frequently.

Handtools issued in a special box, case, or other receptable should be placed in that receptable when stored. A list of tools that belong in each toolbox should be part of the toolbox, for inventory purposes and to aid in replacing each tool where it belongs.

32. TOOL MAINTENANCE INSURES MAXIMUM LIFE TO TOOLS

To prevent rust on metal parts of handtools, wipe those parts with a soft cloth that has light oil on it. It is not necessary to coat aluminum, galvanized metal, or other non- rusting materials with oil.

Rub linseed oil into the wooden parts of handtools when they feel slightly dry on the surface, to preserve the wood and keep it from drying out completely.

Painting handtools is another means of pre- venting rust. Before painting a handtool, it should be examined for cracks or breaks. The cutting edges and serrated jaws or sections should not be painted. Do not allow several layers of paint to accumulate on, or paint to run into, scored or knurled places on a tool, where the scored places serve as a handhold. Be careful to keep paint away from the tool©s swivels, slides, pivots, and other moving parts.

All edged tools should be kept sharp and in top condition. There are three methods of keeping tools sharp.

Whetting or honing--When an edged tool begins to show a slight dullness, whet its cutting edge with an oilstone or a combination carborundum stone. These whetting or honing stones come in a variety of shapes and sizes to fit all types of tools.

Filing--When an oilstone cannot be used satisfactorily to whet a cutting edge, a touchup with the proper size and shape of file will help keep a keen cutting edge.

Grinding--When a tool©s keen cutting edge cannot be restored by whetting or filing, an abrasive stone in the form of a grinding wheel either hand operated or power driven is used. The main point to remember in grinding handtools, is to avoid overheating the tool by prolonged grinding. When grinding handtools, always wear goggles or some other approved shield to avoid injury from flying particles. Keep control of the tool being ground by steadying the hand against the grinder©s tool rest.

33. SAFETY

Constant attention to safety measures at all levels within the unit is necessary to minimize injury to personnel and damage to prop- erty.

Before using any handtool, inspect it for defects.

Store handtools in suitable storage space, so that the tools do not injure persons who are storing, removing, or working with them in the toolroom.

Be sure handtools are not dirty, oily, or greasy.

Do not carry sharp-edged or pointed tools in pockets or where they could protrude and cause injury.

Do not use metal or power tools in locations where source of ignition may cause a fire or explosion.

Wear safety goggles or other approved safety type face and eye protectors when performing operations that might result in flying particles.

Do not toss tools from one location to another. When handtools must be passed between personnel and handing them over is

3-48 impossible or impractical, use suitable containers or rope.

Do not work on electrical circuits while cir- cuit is on.

Do not wear loose or torn clothing that may cause injury by becoming entangled with hand or power tools.

Do not swing a chopping or chipping tool until certain that no one in the vicinity will be endangered by the back swing.

Use each handtool for the purpose for which it was intended.

Never leave power tools running unat- tended.

EXERCISES

First requirement. Solve multiple-choice exercises 1 through 8 to show that you understand the characteristics of rope and cable as they apply to practical situations.

1. A coil of approximately 200 feet of 1-inch diameter manila rope has been made available to your squad. What is the maximum safe load weight in pounds that is within the capacity of the rope?

a. 2,250 c. 2,350

b. 2,300 d. 2,400

2. Your squad has received a coil of new 3/4" rope with a protective burlap covering. After removing the burlap, where on the coil would you look for the end of the rope to uncoil it?

a. top c. bottom

b. side d. outside

3. Your squad leader wants to verify his proposed use of 1-inch diameter mild plow steel (mps) wire rope, for use as a sling. What is the safe working capacity (swc) or safe working load of this cable? (Round off to nearest thousand pounds.) a. 8,000 c. 32,000 b. 16,000 d. 64,000

4. A wire rope which is being used in hoisting operations is noticeably kinked. What action should you take? a. reeve the hoist with a new cable b. run the hoist without a load to work the kink out c. smooth out or cut off the frayed ends d. cut out the kinked portion before use

5. The size of wire in wire rope gives the rope various qualities. If a rope has a small number of large wires making up the strands, what properties would the rope have? a. very flexible and very resistant to external abrasion b. not very flexible but very resistant to external abrasion c. not very flexible and not very resistant to external abrasion d. very flexible but not very resistant to external abrasion

6. Your squad has been given a mission to cut and seize a 200-foot 7/8- inch diameter wire rope into 100-foot sections. How many seizings would be necessary for each side of the cut? a. 3 c. 4 b. 3 d. 5

7. In addition to selecting the correct number of seizings, spacing of the seizings is also important. About

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how far apart in inches should the seizings in exercise 6 be?

a. 1 c. 3

b. 2 d. 6

8. The proper length of the individual seizing is also important. In exercise 6, we determined the proper number. In exercise 7 we determined the spacing between seizings. What is the length of the individual seizings for exercise 6?

a. 1/2 to 1 inch

b. 1 to 2 inches

c. 1 1/2 to 2 1/2 inches

d. 3 to 4 inches

Second requirement. Multiple-choice exercises 9 through 19 will provide an opportunity for you to test your knowledge of knots, splices, attachment, anchorages, and slings.

9. What knot would you use to prevent the end of a rope from slipping through a fastening or loop in another rope?

a. butterfly knot

b. carrick bend

c. square knot

d. figure eight knot

10. Each knot, bend, or hitch serves a particular function or is best suited for a particular purpose. Which knot is used for heavy loads and for joining large hawsers or heavy rope?

a. square knot

b. figure eight knot

c. butterfly knot

d. carrick bend

11. You have been given the task of joining two ropes of unequal size. What knot would give you the greatest holding power? a. square knot b. single sheet bend c. double sheet bend d. overhand knot

12. There are a variety of knots that are suited for various jobs. What knot is used to make a boatswains chair? a. single sheet bend b. double bowline c. catspaw d. two half hitches

13. Some knots are especially suited for use in rescue work. What knot would you use to lift an unconscious man? a. catspaw b. French bowline c. Spanish bowline d. bowline on a bight

14. You are preparing to splice two fiber ropes. How many turns must you unlay on the end of each rope to form a short splice? a. 7 c. 9 b. 8 d. 10

15. There are three types of end fittings which may be placed directly on wire rope and are easily changed. What are these three types? a. open socket, wedge socket, and closed socket

b. wedge socket, open socket, and clips

c. clips, clamps, and open socket

d. wedge socket, clips, and clamps

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16. You have been issued a roll of 1/2-inch fiber rope to be used for slings in hoisting and removing operations. What is the safe vertical lift capacity in pounds of these slings when used singly?

a. 275 c. 418

b. 390 d. 475

17. What is the safe working capacity in pounds of a single wire rope sling of improved plow steel with a 1/2-inch diameter?

a. 1,690 c. 4,320

b. 3,560 d. 5,460

18. When using slings, care must be exercised not to exceed their lift capacity. What is the vertical lift capacity in pounds of a single sling made from 3/4-inch new improved plow steel (ips) wire rope?

a. 4,320 c. 16,800

b. 9,480 d. 21,000

19. In all three types of anchorages, the pull exerted on the anchorage by the guyline should be at what angle to minimize the possibility of pulling the anchorage out of the ground?

a. as perpendicular to the ground as possible

b. at 45ù angle to the ground

c. as nearly parallel to the ground as possible

d. at 30ù angle from the vertical

Third requirement. Multiple-choice exercises 20 through 28 provide an opportunity for you to show that you understand guylines and various devices used to lift and move loads.

20. You are a member of a crew erecting a gin pole. Lashings for attaching the tackle are usually made before guidelines are attached. How many inches below the top of the gin pole should the lashing be attached? a. 12 c. 18 b. 15 d. 24

21. In making the guylines for a gin pole, you use one rope to form two guylines. How many times longer than the gin pole should you cut this rope? a. 2 c. 4 b. 3 d. 5

22. How many feet up from the bottom of the gin pole should you attach the snatch block? a. 2 c. 6 b. 4 d. 8

23. How many feet deep should you dig the hole in the ground for the base of a 40-foot gin pole? a. 1 c. 3 b. 2 d. 4

24. You have been assigned the task of constructing a tripod in which the middle pole is pointed in the opposite direction from the other two while the spars are being lashed together. How much space do you leave between spars at the place that they are lashed together? a. diameter of spars b. half the diameter of the spars c. twice the diameter of rope used d. width of diameter of rope used

25. The legs of a tripod in its final position should be spread so that each leg is equidistant from the others. How far should this spread be? a. not less than one-half and not more than two-thirds the length of the legs

3-51

b. not less than two-thirds and not more than the length of the legs

c. one-fourth the length of the legs

d. not less than one-fourth and not more than three-fourths the length of the legs

26. You have two 12-inch diameter poles 25 feet long with which to construct a set of shears. How many inches of space should you have between the poles at the place you lash them together?

a. 1 c. 4

b. 2 d. 6

27. If the height of the shears is 20 feet, what distance in feet should the spread of the legs be?

a. 4 c. 8

b. 6 d. 10

28. You are constructing a boom derrick to lift loads where a long horizontal reach is necessary. The mast of the boom derrick is constructed in the same manner as a gin pole. The length of the boom should not exceed what fraction of the length of the mast?

Fourth requirement. Multiple-choice exercises 29 through 32 will require you to apply your knowledge of pioneer tools issued to the engineer platoon.

29. An adz, when used properly, can be a valuable tool, but it can be dangerous if used improperly. How would you position yourself while smoothing a log with this tool? (As- sume the log has been blocked so it will not slip.)

a. straddle the log

b. hold the log with either the right or left foot

c. kneel on one knee to be closer to the work

d. hold the work in one hand while chopping with the other

30. In widening a road, a crew has felled several large trees. Pending repair of the chain saw, what type of saw would be used to cut them up?

a. crosscut handsaw

b. rip saw

c. hack saw

d. two-man crosscut

31. If you had to remove a coupling from a piece of pipe, what type of wrench would be appropriate?

a. open-end nonadjustable

b. crescent

c. monkey

d. stillson

32. A building, weighing approximately 10 tons, must be raised in order to level it by placing shims on top of the footings. Which of the following tools would you use for this purpose?

a. pinch bar c. jack

b. wrecking bar d. crowbar

Fifth requirement. Solve multiple choice exercises 33 through 37 to test your understanding of the purpose and use of selected carpenter tools found in the engineer platoon.

33. You notice that one of your fellow soldiers who is trying to saw a board parallel to the grain is having difficulty. What type saw should be used under these conditions?

a. ripsaw

b. large crosscut saw

c. crosscut handsaw

d. hacksaw

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34. Which of the following tasks would you normally perform using a chalkline? a. checking the squareness of construction timber b. measuring the distance between batterboards c. marking a road centerline d. staking out foundations

35. In framing a building the studs or vertical members are placed either 16 or 24 inches apart. What tool is particularly adapted to establishing center-to-center spacing between studs? a. carpenter©s level b. combination square c. carpenter©s square d. carpenter©s rule

36. You have been given the task to determine if a taut string line between two batter boards is horizontal. What tool would you normally use to check this? a. line level b. plumb bob c. combination square d. sliding T-bevel

37. What is the principal difference between a combination square and a T-bevel? a. the combination square has a bubble for leveling purposes b. the combination square is not adjustable c. the sliding T-bevel is not adjustable

d. the sliding T-bevel is graduated in inches

Sixth requirement. Solve multiple-choice exercises 38 through 43 as a means of dem- onstrating your knowledge of the portable electric tool outfit issued to the engineer platoon.

38. What precautions should you take when using an electric power drill?

a. ground to preclude electric shock

b. run the drill before inserting the bit

c. avoid pressure on the drill

d. run the tool slowly to avoid overheating

39. If you have to drill several small holes in concrete or masonry, which tool from the portable electric tool outfit would you use?

a. electric drill

b. impact wrench

c. electric hammer

d. electric spud

40. What before-operations check should you make when preparing to use the electric impact wrench?

a. sharpness of drill components

b. oil level in tank

c. pressure required for operation

d. reversible features

41. The portable circular saw is a widely used tool. It is important that the saw blade be installed properly for safe operation. Some blades are stamped "this side out". If the blade is not stamped, how should you install it?

a. with the teeth pointing upward at the front of the saw b. with the teeth pointing downward at the front of the saw c. with the teeth on the bottom pointing backwards d. with the manufacturer©s name on the outside

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42. Power to operate electric power tools is provided by the generator. Which major component of the portable electric tool outfit is independently gasoline-powered?

a. drill c. chain saw

b. sander d. hammer

43. What power tools can be found in the portable electric tool outfit?

a. impact wrench, drill, circular saw, and paving breaker

b. electric hammer, machinist©s lathe, gasoline saw and sander

c. electric drill, impact wrench, electric hammer and circular saw

d. circular saw, sander, electric hammer, and pneumatic rock drill

Seventh requirement. Solve multiple-choice exercises 44 through 48 to test your understanding of care, maintenance, and safety procedures involving handtools.

44. Experience has shown that tool storage is an extension of good house- keeping practice. In arrangement of storage space for engineer tools, what would you emphasize particularly?

a. avoidance of damage to tools

b. easy access to tools used frequently

c. avoidance of moisture

d. security

45. Unless tools are kept properly sharpened their effectiveness will be seriously reduced. How should edged tools that receive normal use and no abuse, be sharpened?

a. buffing c. grinding

b. filing d. whetting

46. If you find it necessary to sharpen an ax on a power-driven grinder in order to remove deep nicks, what precaution should you observe to avoid further damage to the tool? a. avoid prolonged grinding b. have grinder turn away from tool c. run the grinder at half speed d. use oil on the grinding wheel

47. Efficient use of handtools includes safe handling of tools to avoid injury to the operators, helpers, and others in the work area. What protective device should be used when grinding, striking metal with metal, drilling, chipping, etc? a. gloves c. goggles b. hardhat d. safety shoes

48. If you were using a carpenter©s level on a roof 12 feet from the ground and it was needed by someone else working on the ground, what is the safest way you would get it down? a. drop it carefully over soft ground so it could be caught b. slide it down on a board c. let it down on a handline d. carry it down personally

LESSON 4 ENGINEER EQUIPMENT

CREDIT HOURS ______2 TEXT ASSIGNMENT ______Attached memorandum. MATERIALS REQUIRED ______None. LESSON OBJECTIVE ______To increase your knowledge of engineer construction equipment and tools, and concrete operations.

______

ATTACHED MEMORANDUM

Section 1. EARTHMOVING EQUIPMENT

1. TRUCK, DUMP

The truck, dump (dump truck) is designed for use over all types of roads, highways, and cross-country terrain, and in all types of weather. It will ford a hard-bottom stream to a depth of 30 inches. It is used to haul and dump earth, sand, gravel, coal, and the like. It can also be used as a transport for general cargo.

The dump truck is equipped with--

a five-speed transmission

a two-speed transfer case

air-actuated, hydraulic type service brakes

a pintle hook at the rear to permit towing of a trailer.

To protect the operator, the cab is enclosed with a removable canvas tarpaulin.

The dump body includes a cab protector, combination side racks, and troop seats. It has a capacity of 5 cubic yards and a uni- versal type tailgate which may be opened at either the top or the bottom.

2. TRACTOR, FULL TRACKED

Tractors, full tracked (crawler tractors) serve many purposes, such as prime movers for pulling or pushing loads, power units for winches and hoists, and moving mounts for dozer blades, side booms, and scoop loaders.

The three major assemblies are a center section and two side sections.

The center section contains the power source and the operator©s controls.

The side sections consist of track frames which mount tracks extending approximately the full length of the tractor.

Crawler tractors are classified according to weight and minimum and maximum drawbar pounds pull. This means light, medium, and heavy class tractors; for example, a D6S is in the light class, D7E and HD16M are in the medium class, and D8 and TD24 are in the heavy class. These tractors are equipped with diesel engines with rating from 85 to 202 brake horsepower, and either 4 or 6 cylinders depending on make and model. They attain much of their all-type-terrain versa- tility from their low ground bearing pressure at the track, which varies from about 6 to 9 pounds per square inch, depending on the particular model.

Dozer blades consist of a moldboard, cutting edges, side bits, and blade arms connecting the blade to the tractor. The cutting edges and side bits are replaceable and made of hardened steel.

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Blade design allows either edge to be raised or lowered from the horizontal position. The top of the blade can be pitched forward or backward, and the blade can be angled from the direction of travel. Gen- erally, at least two of these features are incorporated in a single blade type.

Blades vary in size and are designed to perform different earthmoving functions.

The straight blade is mounted in a fixed position perpendicular to the line of travel of the tractor. It can be tilted laterally approximately 12 inches, and the blade top can be pitched either forward or backward within a 10ù arc.

The angle blade is designed so the blade can be set at angles up to approximately 25ù to the direction of travel of the tractor. It also can be set at right angles to the tractor and used as a straight blade. When angled, the blade can be tilted up to approximately 12 inches but cannot be pitched.

Blades having a tilting characteristic are used for cutting ditches and breaking through crusted material. The tilting ability permits the concentration of the tractor power upon a small segment of the blade. The pitching characteristic will permit a variance in ground pressure of the blade; thus, penetration will be increased or decreased accordingly. Chang- ing the blade pitch will provide a cutting or dragging action, whichever is desirable.

Angle blades are most effective when used to sidecast materials during a backfilling operation or in making a sidehill cut. In addition, they have been successfully used for rough grading operations and for spreading piles or windrows of material.

Back rippers mounted on drawbar tractors provide a means of breaking up hard surfaces (pavements and so on) not easily penetrated by dozer blades. They generally consist of four curved shanks with lock-on teeth which can penetrate depths up to 9 inches.

3. GRADER

The grader can be employed for leveling and crowning, mixing and spreading, ditching and bank sloping, and sidecasting material. It may also be used for maintaining haul roads and for light stripping operations, but it is not intended for heavy excavation.

When ditches deeper than 3 feet are to be constructed, it is more economical to utilize some other type of equipment.

The grader consists of a scarifier, moldboard or blade, and circle mounted on draw- bars which are pivotally connected to the front of the main frame.

Controls for starting and operating the vehicle are located in the operator©s compart- ment.

Section II. LIFTING AND LOADING EQUIPMENT

4. CRANE-SHOVEL, TRUCK MOUNTED

The basic crane-shovel unit consists of a carrier, truck mounting, and revolving superstructure or upper revolving frame. This unit is supplied with a crane boom for lifting, and designed for use with shovel, clamshell, dragline, backhoe, or piledriver attachments.

The superstructure upon which are mounted the engine, upper machinery, and gantry re- volves on a bearing mono-race.

Except for two outriggers on each side to improve stability, the carrier is equipped like the dump truck.

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Note: The following warning is placed on the inside of the crane-shovel and must be observed at all times.

______WARNING______

OPERATIONS ADJACENT TO OVERHEAD LINES IS PROHIBITED UNLESS ONE OF THE FOLLOWING CONDITIONS IS SATISFIED

POWER HAS BEEN SHUT OFF AND POSITIVE MEANS TAKEN TO PREVENT 1 LINES FROM BEING ENERGIZED.

REQUIRED POSITION AND BLOCK EQUIP- VOLTAGE CLEARANCE MENT INSURING NO PARTS, UNDER 69 KV ______10 FEET 2 INCLUDING CABLE, CAN COME 69 KV ______12 FEET WITHIN THE FOLLOWING 115-161 KV ______15 FEET CLEARANCES: 230-285 KV ______20 FEET 345 KV ______25 FEET 500 KV ______35 FEET

IF EQUIPMENT MUST BE OPERATED CLOSER THAN CLEARANCE SPEC- IFIED IN 2 ABOVE, AN INSULATING CAGE AND AN INSULATING LINK 3 SHALL BE PROVIDED TO PROTECT AGAINST LINE VOLTAGE AT WORK AREA.

5. CRANE BOOM

The crane boom is usually made in two sections fastened approximately in the center by one of two methods: bolted butt plate (flange) connection or pin and clevis connection.

The upper section with the boom head and a system of sheaves is usually but not necessarily the same length as the lower section.

The crane boom is also the basis for the clamshell, dragline, and piledriving operations.

Basic crane equipment includes hoist drums, hook block to provide the required parts of line (reeving), and the boom suspension and hoist wire ropes.

Cranes are units used primarily for lifting an object or load, transferring it to a new location by swinging or traveling, and then placing the load in the new location.

The types of loads that can be handled are determined by the types of accessories that are available for use on the hook. These accessories include, but are not limited to, slings, concrete buckets, and magnets.

6. SHOVEL

The shovel attachment includes the shovel boom; dipper stick; bucket; mechanism for crowding, retracting, and dumping the bucket; and necessary wire ropes. The shovel is designed to operate against a face or bank which it displaces as it moves forward.

7. CLAMSHELL

The clamshell equipment consists of a crane boom, hoist drum laggings, clamshell bucket, tagline, and the necessary wire ropes --boom, holding, closing, and tagline. Like the crane, the clamshell is a vertically operated attachment capable of working at, above, and below ground level, but equipped with a bucket instead of a hook block.

The clamshell is capable of digging loose to medium type soils in all zones as well as dumping in any of the three zones.

The height that can be reached by the clamshell is dependent on the length of boom used.

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The depth reached by the clamshell is limited by the length of wire rope that the cable drums will accommodate.

8. DRAGLINE

The dragline components consist of the lat- tice type boom, dragline bucket, and fairlead assembly.

It can be employed on dredging operations where the material handled is wet and sticky.

It can dig trenches, strip overburden, clean and dig roadside ditches, and slope embankments.

When handling mud the dragline is the most practical attachment to use as its reach enables it to handle a wide area from one position, and the sliding action of the bucket offsets the suction effects.

9. BACKHOE

The backhoe attachment consists of five major components: dipper, dipper handle, box type boom, auxiliary A-frame, and a grooved drum lagging that is installed on the front drum for the dipper pull rope. It is most suited for trench excavating as it is capable of digging well below the tracks of the unit, and capable also of digging soft to hard material because the weight of the boom plus the positive pull on the dipper is used to force the dipper into the material.

10. PILEDRIVER

The piledriver attachment consists of a crane boom, adapter plates, leads, catwalk, hammer, pile cap, and the necessary wire ropes. It is used to drive various types of wood and concrete piles, and sheet-steel piling for foundations, sheathing, cofferdam work, and the like.

11. SCOOP LOADER

The scoop loader like the crane-shovel is a lifting and loading item. It can be utilized in all zones of operation and can dig at ground level, above ground level, and below ground level. The loader can travel from one construction site to another under its own power.

Typical uses of the scoop loaders are stock- piling materials, digging gun emplacements, backfilling ditches, loading trucks, lifting and moving construction materials, and when equipped with rock type tread tires they can operate efficiently in and around rock quar- ries.

Section III. AIR COMPRESSORS

12. AIR COMPRESSORS

An air compressor is a machine for com- pressing air from an initial intake pressure to a higher exhaust pressure through reduction in volume.

It consists of a driving unit, a compressor unit, and their accessories.

The driving unit provides power to operate the compressor and may be a gasoline or diesel engine.

The compressor is governed by a pressure control system which is adjusted to compress air to a minimum pressure of 100 pounds per square inch (psi). The compressor may be of reciprocating or rotary design.

Air compressors should always be as level as possible and never tilted more than 15ù from a level plane.

The accessories include such items as an aftercooler, intercooler, air receiver tank, and a pressure control system.

13. AFTERCOOLER

The presence of water or moisture in an air transmission line is not desirable. The

4-4 most satisfactory means of minimizing these conditions is to remove the moisture from the air immediately after compression and before the air enters the distribution systems. This can be accomplished very efficiently through the use of an aftercooler, which is an air radiator that transfers heat from compressed air to the atmosphere.

The aftercooler reduces the temperature of compressed air to the condensation point where most of the moisture is removed.

Cooling the air eliminates the difficulties which moisture causes, not only at points where air is used, but also throughout the distribution system.

14. INTERCOOLER

If air is compressed to 100-pound gage pressure without heat loss, the final temperature would be about 485ùF. This increase in temperature raises the pressure of the air under compression, thus necessitating an increase in work to compress the air.

After the air is discharged into the receiver tank and lines, the temperature rapidly falls to near that of the sur- rounding atmosphere, thus losing part of the energy generated during compression.

The ideal compressor would compress the air at a constant temperature but this is impossible in present-day compressors.

In some compressors the work of compres- sing is divided between two or more stages, depending upon the final discharge pressure required. An intercooler is employed between the different stages to reduce the temperature of the compressed air between stages.

The amount of cooling surface required is dependent upon the quantity of free air compressed per minute and the final discharge pressure.

Theoretically, the cooler should have a sufficient amount of cooling surface to reduce the temperature between stages to that of the low pressure cylinder intake.

15. AIR RECEIVER TANK

The receiver tank is of welded steel construction and acts as a surge tank and condensation trap. It stores enough air during operation to actuate the pressure control system and is usually fitted with at least one service valve, one drain valve, and a safety valve.

16. PRESSURE CONTROL SYSTEM

Every compressor is governed by a pressure control unit. In a reciprocating compressor, when the pressure reaches a set maximum, the pressure control unit causes the engine to idle and the suction valves of the compressor to remain open; on a rotary compressor the valve in the intake manifold is closed and the engine idles. Therefore, in both, no air is compressed. When the pressure drops below the set minimum, the pressure control unit causes the engine to increase speed and the suction valves to close; therefore, air will be compressed.

Section IV. PNEUMATIC TOOLS

17. GENERAL

To operate pneumatic tools, two requirements are demanded from the air compressor, a specific volume of air (expressed in cubic feet per minute (cfm) and a specific pressure (psi). The number of tools that may be operated from an air compressor depends on the total air requirement of the tools.

Example: A certain tool requires 95 cfm at 80 psi.

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A 210 cfm compressor could supply air to operate two such tools. This would require 190 cfm.

If another tool were added, this would overload the compressor and cause excessive wear.

When the pressure and volume to a pneumatic tool are reduced 10 percent below the set minimum, the efficiency of the tool is reduced 41 percent.

The advantages of pneumatic tools are as follows:

Ease of maintenance--a pneumatic tool has the advantage of simplicity of design over similar gasoline or electric powered tools, and requires less maintenance.

There are few wearing parts in pneumatic tools whereas gasoline tools have many.

An electric tool has only a few parts, but few operators possess the technical ability or the equipment to repair them in the field.

Ease of operation--pneumatic tools are simpler to operate than gasoline or electric powered tools.

Little specialized training is required, and even an unskilled soldier can be taught the basic principles of operation in a short time.

Durability--pneumatic tools are much more rugged than gasoline or electric powered tools.

Minimal special care is required while being transported or in storage.

Climatic conditions--pneumatic tools are not affected by wet weather operations. In fact they can be operated under water without any ill effects.

However, extreme cold or high humidity can present problems. As the air is ex- hausted from the exhaust port the expansion results in supercooling, causing ice to form around the exhaust port which eventually will stop the tool©s operations. This can be corrected by using nonpermanent antifreeze or alcohol solution in the air line oiler to prevent the moisture from freezing.

Safety--pneumatic tools with nonspark- ing attachments can be operated around petroleum and explosive material without presenting a fire hazard.

Overloading--pneumatic tools will not be damaged in case too great a load is placed on the working device, providing it is used properly.

The disadvantages of pneumatic tools are as follows:

The radius of operation for a pneumatic tool is limited by the length and size of air hose to which it must be attached.

If the tool is moved too far from the source of power (200 feet maximum with 3/4-inch diameter hose), friction line loss will hinder the operation of tools.

Failure of power source--if the compressor fails, all tools being operated from the compressor become useless.

Cumbersomeness--a pneumatic tool is frequently difficult to handle because of its attachment to the air hose. This is particularly true in rough terrain where the hose has a tendency to hang on rocks or brush.

18. CHAIN SAW

The chain saw is a heavy duty saw intended primarily for cutting trees and large timbers up to 24 inches in diameter. It weighs 45 pounds and has an air requirement of 90 cfm and a recommended air pressure of 80-100 psi.

The saw is a portable two-man saw with the teeth arranged on a flexible steel chain- like belt that rotates so the teeth cut only in one direction, toward the power end of the saw.

During operation, hold the chain saw against the object to be cut and apply light pressure on both ends, guiding the saw through the work.

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Failure to maintain proper blade tension causes the biggest maintenance problem on the chain saw.

The blade should be adjusted to maintain 1/2-inch slack when pulled up at the center. More slack than this will allow it to jump out of the saw guide, causing the blade to bend or break.

If the blade is too tight, it will bend and cause sprocket damage.

Safety precautions include--

Wear safety goggles.

Maintain the proper blade tension.

Maintain a firm grip and good footing at all times.

Never force the saw into the wood; allow it to cut at its own speed.

Be sure the bumper spikes are held securely against the work before starting the saw.

Be careful that the saw is not twisted or bound in the cut.

Always keep the work position clear of material that has been cut.

19. CIRCULAR SAW

The circular saw is used for crosscutting or ripsawing timber for construction purposes. The saw weighs 25 to 32 1/2 pounds according to make and model, has an air requirement from 55 to 75 cfm, and a recommended air pressure of 80-100 psi.

The circular saw at 45 degrees can cut to a depth of 3-5/16 inches. At 90 degrees it can cut to a depth of 4 3/8 inches.

To operate, set the saw to the correct angle and depth of cut. Two V notches on the front of the foot simplify cutting to a line.

Be sure the material to be sawed is steadied by its own weight or is secured firmly by clamping or wedging.

Depress the switch trigger in the handle to start the saw.

The saw blade must be revolving at full speed before it contacts the material©s cutting surface.

When cutting, apply firm pressure but do not force the saw.

In many cases, the pneumatic circular saw is inverted and used as a table saw. When this is done, the exhaust port is exposed to the wood cuttings. An accumulation of these cuttings will clog up the air motor and make the saw useless.

For best performance--

The two grease fittings that lubricate the rotor shaft bearing and governor should be lubricated weekly according to lubrication orders.

The gearcase should be checked every 8 hours to insure that lubricant just covers the worm gear.

To operate the saw safely--

Never tighten, loosen, or change the blade while the saw is connected to the air line.

Never operate the saw with a defective telescopic guard or with the guard held in an open position.

Check all wood for nails and metal before making a cut.

Never pull the blade backwards or withdraw it from the cut while the blade is rotating.

Adjust foot to minimum depth required for cut.

Keep hand away from moving blade, and shut off air when the tool is not in use.

20. NAIL DRIVER

The pneumatic nail driver and rivet buster is a long-stroke piston type riveting hammer with nail-driving attachments for holding 1/2- inch and 3/4-inch diameter nailheads. It is used primarily for driving large nails, spikes, and driftpins into heavy or large timbers, or for cutting the heads off rivets. The hammer weighs 25 pounds, has an air requirement for

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32 cfm, and a recommended air pressure of 90 psi.

Before operation insure that an air line oiler is in place to lubricate the nailer.

Start all nails or spikes with a hand hammer.

Aline nail set to angle of nail or spike and always keep the attachment in contact with the object being driven.

Attempts to countersink a nail with the nail driver will result in a broken retainer spring.

As part of the nail driver maintenance, lubrication of the driver is done through an air line oiler (par 27). Retainer housings on nail drivers often break because operators fail to keep the nail set against the work.

As safety measures--

Keep air connections tight.

Keep exhaust away from the body.

Never make adjustments or attempt to change attachments without bleeding the tool and disconnecting the hose.

21. WOOD BORER

The pneumatic reversible wood borer drill is a heavy duty low speed machine designed to drive ship auger type drills. It is used extensively in trestle bridge and other timber construction work where it is necessary to drill holes for bolts or pins. The drill weighs 30 pounds, has an air requirement of 60 cfm, and a recommended air pressure of 80-100 psi. Drill bits are issued in 12- and 36-inch lengths and in diameter sizes of 7/16-inch, 3/4-inch, and 2-inch.

To operate, always start the drill slowly until the screw is well set.

When using the small diameter bits, always start the hole with the 12-inch length and then use the 36-inch length.

Hold the drill firmly but do not force it.

Exert enough effort to counteract the tendency of the tool to rotate, and be prepared to resist the torque in case the bit becomes stuck.

During boring and withdrawing of the auger, keep it in line with the hole.

As preventive maintenance, check the oil reservoir after every 4 hours of operation. When required, refill with OE 10 below 32 degrees, and OE 30 above 32 degrees.

Lubricate the grease fittings after 64 hours of operation.

As a safety precaution--

Hold the tool firmly but do not apply too much pressure as this could cause the bit to overheat and possibly break.

Disconnect tool before making adjustments.

22. BACKFILL TAMPER

The backfill tamper is a percussion or piston type manually controlled tool. It is used to compact loose earth in small or confined areas that are not accessible to other types of compaction equipment. The tamper weighs 34 pounds, has an air requirement of 24-27 cfm, and a recommended pressure of 80-90 psi.

To operate, allow the tamper to work at its own speed, but keep it moving across the fill and do not let it rest in one position.

When tamping loose earth, better results can often be obtained by wrapping the tamping head with burlap or similar material. However, when tamping gravel, leave the head unwrapped.

Tamp in 2- or 3-inch lifts in small areas, moving the tamper continuously.

As a part of the maintenance requirement, lubricate with OE 10 all year.

Overlubrication causes failure of the packing gland and seal.

For the non-self-lubricating tamper, there is a lubricating button. To lubricate this model, depress the button for 10 seconds while tool is on after every 2 hours of operation.

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Do not operate the tamper so that the tamper butt hits the material at an angle; this causes the piston to break where it attaches to the tamping butt.

For safe operation--

Keep tool away from feet and head.

Wear goggles when compacting hard materials, gravel, and the like.

23. PAVING BREAKER, 80-LB

The paving breaker, 80-lb is a heavy duty reciprocating-percussion type tool. It is used for heavy duty demolition work on concrete, brick, asphalt, macadam, and the like. It is also used for the demolition of walls, columns, piers, and foundations, and for general rock breaking. The breaker weighs 75-90 pounds, has an air requirement of 60-65 cfm, and a recommended air pressure of 80-90 psi.

The four attachments issued with this paving breaker are: moil point, chisel point, tamper, and sheeting driver.

The moil point is a 20-inch long piece of 1 1/4-inch hexagonal tool steel, pointed at one end and having a retainer collar 6 inches from the opposite end. It should be used when breaking through concrete, stone, or material of a similar high abrasive and density character.

The chisel point is similar to the moil point except that it has a 3-inch wide working edge that is used to cut macadam, frozen ground, or extremely hard earth, but is not for breaking concrete.

The tamper is a 5- to 7-inch diameter steel pad mounted on a piece of 1 1/4-inch hexagonal tool steel.

The sheeting driver is made of two steel angles and an impact pad that transmits the blow to the wood or metal sheeting that is being driven. It is used for driving wood or metal sheeting up to 2 inches thick.

To operate--

Hold the paving breaker down while it is in operation, but use only sufficient pressure to guide the tool and keep it in place.

For optimum output, breakers should be used in tandem.

Leaning heavily on the tool results in less work, and slows the output of the tool. That is, it shortens the stroke of the tool.

Only small cuts (4 to 8 inches) should be taken.

When working in nonreinforced concrete with a moil point, based on 6- to 8-inch depths, production will range from 50 square feet per hour in large areas to 12 square feet per hour in narrow cuts. In reinforced concrete, production may drop to 50 square feet per 8-hour shift.

The operating technique for the tamper is the same as the operation of the backfill tamper described in paragraph 22, except that this tamper (paving breaker attachment) can compact up to 8-inch lifts of earth.

Observation of the following maintenance indicators will aid in keeping the paving breaker operable.

Do not attempt to drill holes with the moil point. The moil point is a breaking device.

Attempts to drill holes with it will result in breakage of the point.

Use correct size shanked tools; improper shank sizes will reduce the effectiveness of the blow and will cause damage to the paving breaker.

If a moil point becomes stuck, take the paving breaker off and by using another point break the stuck point free.

Shut off the tool when the moil point breaks through the material. This will prevent the front head from bouncing on the concrete and thus eliminate breakage of the retainer bolt.

Use the chisel point for its designed use only.

If the chisel point is used for breaking concrete, etc., the point will be damaged beyond repair.

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Keep all nuts tight.

Check the airhose to paving breaker connections to assure that no air is es- caping.

For safe operation--

Hold the paving breaker firmly and plant feet firmly while operating.

Always bleed the airhose when stopping operations for any length of time.

Wear goggles when operating the paving breaker to protect eyes from pavement chips and dust.

Keep the work area clear of broken material.

24. PAVING BREAKER, 25-LB

The paving breaker, 25-lb is a medium- weight pneumatic tool designed for spading, trimming, cutting, or picking clay, hardpan, or frozen ground too hard for the use of a manual digging tool such as the ordinary hand spade or pick.

The breaker weighs 18-25 pounds, has an air requirement of 35 cfm, and a recommended air pressure of 80-90 psi.

Three attachments are normally issued with this 25-pound paving breaker--the moil point, pick, and spade. In some cases, a metal drum ripping tool may be issued for opening 55-gallon drums.

The moil point consists of a 15-inch straight length of 1-inch diameter tool steel pointed on one end, with a collar and a 7/8-inch hexagonal shank 2 3/4-inches long. It is used as a light demolition tool on masonry, brick, concrete, or other material.

The moil point can often be used in narrow, awkward places where there is insufficient room to swing a hand pick.

The pick has a blade 3 inches wide by 8 inches long with a pointed cutting end. It is used for digging into frozen ground, cemented gravel, or other materials too hard to be penetrated by the clay spade.

The spade, commonly called the clay spade, is shaped like a garden spade, and is 5 1/2 inches wide by 8 inches long. It is used for digging trenches, preparing footings or foundations, digging caissons, driving tunnels, or doing any general digging too difficult and slow for an ordinary hand spade.

The metal drum ripping tool has a cutting blade 1 inch wide, topped by an extended snubnose 5/8-inch thick. There are two types:

Type I is used to cut heads from metal drums. To do this, the nose of the ripping tool is curved to allow it to more easily follow the curvature of the head on the drum.

Type II is used to split metal drums lengthwise, so it has a straight instead of a curved nose.

The operation of the paving breaker, 25- pound and attachments is essentially the same as that for like items used with the paving breaker, 80-pound.

Preventive maintenance regarding the breaker consists basically of the care of the tool retainer.

Two flat surfaces ground on the hammer permit the repeated blasts of air to clean foreign matter out of the cylinder and tool retainer.

The front head group is the tool retainer. It includes the tool retainer body which is bolted to the cylinder body; the rubber bumper which absorbs shock; and the collar and attachment retainer.

Particular attention should be given to the tool retainer assembly. Dirt and other abrasive materials get into the bottom of the retainer and cause excessive wear. The major portion of this wear can be prevented if the operator does not allow the tool to penetrate above the wide portion of the clay spade.

To operate safely--

Keep the airhose connections tight.

Keep exhaust away from the body.

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25. ROCK DRILL

The rock drill is a handheld, piston-rotary- type unit primarily designed as a hard rock drill; however, it is equally efficient in soft and medium formations as well. It is used primarily for vertical drilling. If, however, large numbers of horizontal holes are required, some mechanical means must be de- vised for holding the drill in place. The drill weighs 57 pounds, has an air requirement of 95 cfm, and a recommended air pressure of 80-100 psi. Hollow steel drill rods are issued in 2-, 4-, 6-, 8-, and 10-foot lengths.

Drill bits are issued in diameter sizes of 1 5/8, 1 3/4 and 2 inches.

To operate--

Place bit between heels of boots and lean tool slightly forward.

Start drill at a slow speed, half throttle, until the hole is approximately 1 inch deep.

Step back from drill and hold tool in vertical position, then push the throttle lever down to full throttle.

Blow out the hole periodically by engaging exhaust valve.

Bent steels should not be used. They not only cause damage to the drill, but usually result in a stuck bit and lost production.

Preventive maintenance requires that OE 10 below 32 degrees, and OE 30 above 32 degrees be used in the oil reservoir; and that oil be checked every 2 to 3 hours of continued operation.

For safe operation, never straddle hose.

Check air connections before and during Á operations.

Wear goggles.

26. SUMP PUMP

The sump pump is a small capacity pump that is handy for use on small jobs where an air compressor is available. It can be run completely submerged when an exhaust line is used. The pump may be rated at 175 gallons per minute against a 25-foot head or up to 150 gallons per minute against a 150 foot head. It may be either a class 1 pump for transferring sewage and sludge, or a class 2 pump for transferring petroleum products. The pump weighs 50 pounds, has an air requirement of 100 cfm, and a recommended pressure of 80-90 psi.

During operation, keep the sump pump inlet strainer clean and free of debris.

Keep the pump away from mud bottoms and clean it as often as necessary to assure maximum efficiency.

Keep the exhaust line outlet above the water level.

There are no maintenance problems inherent with the sump pump; however--

If silt and dirt are left in the pump after use, it will cause the impeller to stick and will require disassembly and cleaning before it can be used again.

If water is allowed to get into the pump through the exhaust port, it will cause failure of the grease seals.

When idle, the pump should be drained of water.

Use only water pump grease in the fittings on the sump pump.

To be safe, shut off the exhaust pressure from the line before disconnecting the line from the tool.

Never kink the hose to stop the air flow.

Keep the clamps on the hose tight.

Be sure the airhose is suitable to withstand the pressure required for the tool.

27. AIR LINE OILER

The air line oiler is a reservoir of either a pint or a quart capacity which is placed in the air line directly in front of the air tool for the purpose of lubricating the tool. As the air passes through the oiler it picks up the oil which is carried into the tool. The amount of oil entering the air stream is

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controlled by an adjustable needle. Oilers occur in both directional and nondirectional types. The arrow should be pointed in the direction of air flow when connected in the line.

NOTE: Use the air line oiler or the tool oil reservoir for lubrication but never use both at the same time.

28. MAINTENANCE OF PNEUMATIC TOOLS

Two items are important in the maintenance of a pneumatic tool. These are lubrication and air pressure.

To check for proper lubrication of a pneumatic tool, pass a piece of paper in front of the tool exhaust port. If a thin film of oil accumulates on the paper, the tool is being properly lubricated. If drops of oil appear on the paper or if oil is foaming around the exhaust port, this indicates overlubrication. If no oil appears, the lubrication device should be checked immediately.

Each tool requires a specified volume of air at a specified pressure. If volume and pressure are allowed to drop excessively, considerable damage will be done to the tool. When a pneumatic tool job is being inspected, check for air leaks in hose or around air connections and listen to and observe the tool in operation. If a tool appears to be operating sluggishly or appears to be surging (detected by er- ratic operation), it indicates either too much or too little pressure. The tools should never be operated with less than 70 or over 100 pounds per square inch at the tool. Check the air pressure gage on the air compressor and if it continual- ly remains below 70 pounds per square inch this indicates overloading of the unit (too little pressure at the tool), and should be corrected.

Section V. MIXING, PLACING, CURING, AND FINISHING OF CONCRETE

29. MIXING

Mixing is generally done by machine but some hand mixing is invariably necessary. A clean surface is required for this purpose. Ordinarily a wooden platform with close joints, to prevent loss of mortar, is used. The platform should be leveled before mixing is started. A clean, even paved surface will also serve the purpose of a mixing platform.

The measured quantity of sand is placed on the bottom, the cement is spread over the sand, and then the coarse aggregate is spread on top.

Either a hoe or a square pointed D-handle shovel can be used to mix the materials. The dry materials should be turned at least three times until the color of the mixture is uniform.

Water is added slowly while the mixture is turned again at least three times.

Water is gradually added until the proper consistency is obtained.

When two men are mixing, they should face each other, working their way through the pile and keeping the shovels close to the surface of the platform while turning the materials.

One man can mix 1 cubic yard of concrete by hand in about an hour, but this is not an economical method of mixing concrete in batches of over 1 cubic yard.

Power concrete mixers are available in several sizes and types. A mixer will normally produce a batch about every 3 minutes, including charging and discharging.

The 16S concrete mixer is a self-contained unit capable of producing 16 cubic feet of concrete, plus a 10 percent overload, per batch. The hourly production capacity will vary between 10 and 15 cubic yards depending

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on the efficiency of the personnel, support equipment available, and the correct utilization of charging and discharging methods. It can handle aggregates up to 3 inches without damage.

Methods used to obtain maximum output from the 16S mixer are--

Sand, gravel, and cement stockpiles should be located as close to the mixer as practicable.

The mixer should be level. Leveling may be accomplished by digging in the wheels, if necessary.

The skip of the mixer may be dug in to facilitate loading, particularly when wheelbarrows are to be used.

When wheelbarrows are used in charging the mixer or in placing the mixed concrete, plank runways should be used. Such runways accelerate materials handling.

In charging the skip, gravel or rock should be loaded first, the cement second, then enough sand to cover the entire batch. The gravel scours the skip bottom and carries the entire load into the mixing drum. The sand cover prevents excessive loss of cement dust as the batch enters the drum.

Water should begin to enter the drum about 3 seconds before the dry materials are charged into the drum. The early addition of water aids in cleaning the drum and results in a faster, more ho- mogeneous mix. When all aggregate and water have been added, the batch should be mixed for a minimum of 1 minute.

The mixer should be kept clean. At the beginning of each day©s operations the machine should be coated with form oil to prevent cement or mix from sticking to the paint or bare metal. Each time the mixer is shut down, a half batch of gravel or of stone and water should be run through the machine for approximately 5 minutes in order to loosen any concrete caked in the drum. The entire machine should be washed, cleaned, and reoiled after each day©s operation and after the termination of a project. Never pound the skip bottom or the drum to loosen materials, because pounding may cause dents and bumps around which cement or mix may form.

During cold weather, the water tank, pump, and lines must be drained each time the mixer is shut down to prevent possible damage from freezing.

Note: The designation 16SM for some 16-cubic foot capacity mixers refers to a mortar mixing capability in addition to a concrete capability.

Measuring the mix materials may be by weight or volume.

Measurement by weight is the most reliable method, since the accuracy of volume measurement depends on the accuracy of an estimate of the amount of bulking which varies according to the moisture in the sand. However, measurement by volume is more practical under expedient conditions. On comparatively small jobs the aggregate can be weighed on platform scales. The scales should be set on the ground and runways constructed so that a wheelbarrow can be run onto one side of the scale and off the other. With practice it is possible to fill a wheelbarrow so accurately that it is seldom necessary to add or remove material to obtain the correct weight. The amount of aggregate placed on each wheelbarrow should be the same and the quantity per batch should be supplied by an even number of wheelbarrow loads. Hence, the wheelbarrow may not be loaded to capacity each time.

Measuring by volume can be done by means of a 1-cubic foot measuring box built on the job. The inside of the box should be marked off in tenths of a cubic foot. The GI bucket can also be used as a measuring device; it contains 0.467 cubic foot which may be considered one- half cubic foot.

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If wheelbarrows are to be used to carry the aggregate from the storage pile to the mixer, the following procedure, based on a 3-cubic foot wheelbarrow, should be used.

Assume that the proportions by volume are 1:2:3 and each batch is to contain three sacks of cement. Use the 1-cubic foot measuring box to load 2.0 cubic feet of sand in the wheelbarrow. Draw a line around the inside of the wheelbarrow at the level of the sand. Three wheelbarrows filled to this level will then be used per batch. The coarse aggregate can be measured directly from the wheelbarrow.

Water for mixing must be accurately measured for each batch. When using the mixer, hook up the water supply at the hose coupling on the mixer.

Set the water check drum, then set the water tank for desired amount of water.

If the mixer is not equipped with an automatic measuring device, a pail, marked for gallons and fractions, may be used to measure the water. In any event, mixing water should be measured carefully.

There are two ways of charging concrete mixers, by hand and with the mechanical skip. The 16S mixer is equipped with a mechanical skip. The cement, sand, and gravel are placed in the skip and then dumped into the mixer together while the water runs into the mixing drum on the side opposite the skip. The mixing water is measured from a storage tank on top of the mixer a few seconds before the skip is dumped to wash the mixer between batches. The coarse aggregate is placed in the skip first, the cement next and the sand is placed on top to prevent excessive loss of cement as the batch enters the mixer.

When the material is ready for discharge from the mixer, the discharge chute is moved into place to receive the concrete from the drum of the mixer. In some cases, dry concrete has a tendency to carry up to the top of the drum and not drop down in time to be deposited on the chute. Very wet concrete may not carry up high enough to be caught by the chute. This condition can be corrected by adjusting the speed of the mixer. For very wet concrete, the speed of the drum should be increased and for dry concrete, it should be slowed down.

The mixing time is determined from the time the water is added to the mixture. All mixing water should be added in the first quarter of the mixing period. The minimum mixing time per batch of concrete is 1 minute unless the batch exceeds 1 cubic yard. An additional 15 seconds of mixing time is required for each additional 1/2 cubic yard of concrete or fraction thereof.

The consistency of concrete is measured by the slump test. The aim in controlling the slump is to control directly the consistency and workability necessary for proper placement.

30. PLACING

Concrete should be deposited in even horizontal layers and should not be puddled or vibrated into place. Each layer should be soft when a new layer is placed upon it. The layers should be from 6 to 24 inches in depth depending on the type of construction. To prevent honeycombing or avoid spaces in the concrete, the concrete should be vibrated or spaded. Vibration periods of 5 to 15 seconds with the immersion-type vibrator for each penetration is usually sufficient. When over- vibration occurs, the surface concrete not only appears wet, but it actually consists of a layer of mortar containing practically no coarse aggregate.

On large pours, to avoid excess pressure on forms, the rate of filling should not exceed 4 feet per hour measured vertically, except for columns. In order to avoid cracking during settlement, an interval of at least 4 hours, preferably 24 hours, should elapse between completion of columns and walls and the placing of slabs, beams, or girders supported by them.

31. CURING

The water content of fresh concrete is considerably more than enough for hydration of 4-14

the cement. However, an appreciable loss of this water, by evaporation or otherwise, after initial set has taken place will delay or prevent complete hydration. The object of curing is to prevent or replenish the loss of necessary moisture during the early, relatively rapid stage of hydration.

The usual procedure for accomplishing this is to keep the exposed surface continuously moist by spraying or ponding, or by covering with earth, sand, or burlap maintained in a moist condition.

Early drying must be prevented or the concrete will not reach its full potential quality. In warm, dry, windy weather, corners, edges, and surfaces become dry more readily. If these portions are prevented from drying, and fully develop their hardness and quality, interior portions of the concrete will have been adequately cured.

32. FINISHING OF CONCRETE

After a floor slab, sidewalk, or pavement has been placed, the top surface is rarely at the exact elevation desired. The process of striking off the excess concrete in order to bring the surface to the right elevation is called screeding. Other finishing operations include floating, troweling, brooming, and rubbing. Screeding operation can begin as soon as the concrete has been placed.

Prior to screeding the concrete should be vibrated to lower larger sized aggregate to avoid interference with the screed.

A templet with a straight lower edge if a flat surface is required, or curved if a curved surface is required, is moved back and forth across the concrete with a sawing motion. The templet rides on wood or metal strips that have been established as guides. There should be a surplus of concrete against the front face of the templet which will be forced into the low spots as the templet is moved forward. If there is a tendency for the templet to tear the surface, the rate of forward movement of the templet should be reduced or the bottom edge should be covered with metal. In most cases, this will stop the tearing action. Such procedures are necessary when air-entrained concrete is used because of the sticky nature of this type of concrete.

It is possible to hand screed surfaces up to 30 feet in width but for efficient screeding it is best not to go beyond 10 feet.

Three men, excluding a vibrator operator, can screed approximately 200 square feet of concrete per hour. Two men operate the screed and the third man pulls excess concrete from the front of the screed.

Sometimes, it is necessary to screed the surface twice to remove the surge of excess concrete caused by the first screeding.

If a smoother surface is required than the one obtained by screeding, the surface should be worked sparingly with a wood or metal float or finishing machine.

This process should take place shortly after screeding and while the concrete is still plastic and workable.

High spots are eliminated, low spots filled in, and enough mortar is brought (floated) to the surface to produce the desired finish.

The concrete must not be overworked while it is still plastic, to avoid bringing an excess of water and mortar to the surface. Such material will form a thin weak layer that will scale or wear off under usage.

Where a coarse texture is desired as the final finish, it is usually necessary to float the surface a second time after it has partially hardened so that the required surface will be obtained.

In slab construction long-handled wood floats are used.

The steel float is used the same way as the wood float but it gives the finished

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concrete a much smoother surface. Steel floating should begin when the water sheen disappears from the concrete surface, to avoid cracking and dusting of the finished concrete. Cement or water should not be used to aid in finishing the surface.

If a dense, smooth finish is desired, floating must be followed by steel troweling at some time after the moisture film or sheen disappears from the floated surface and when the concrete has hardened enough to prevent fine material and water from being worked to the surface. This step should be delayed as long as possible. Excessive troweling too early tends to produce crazing and lack of durability; too long a delay in troweling results in a surface too hard to finish properly. The usual tendency is to start to trowel too soon.

Troweling should leave the surface smooth, even, and free of marks and ripples.

Spreading dry cement on a wet surface to take up excess water is not good practice where a wear-resistant and durable surface is required.

Wet spots must be avoided if possible; when they do occur, finishing operations should not be resumed until the water has been absorbed, has evaporated, or has been mopped up.

A surface that is fine-textured but not slippery may be obtained by troweling lightly over the surface with a circular motion immediately after the first regular troweling. In this process, the trowel is kept flat on the surface of the concrete.

Where a "hard steel-troweled finish" is required, the first regular troweling is followed by a second troweling after the concrete has become hard enough so that no mortar ad- heres to the trowel and a ringing sound is produced as the trowel passes over the surface. During this final troweling, the trowel should be tilted slightly and heavy pressure exerted to thoroughly compact the surface.

Hair cracks are usually due to a concentration of water and fines at the surface resulting from overworking the concrete during finishing operations. Such cracking is aggravated by too rapid drying or cooling. Checks that develop before troweling usually can be closed by pounding the concrete with a hand float.

A nonskid surface can be produced by brooming the concrete before it has thoroughly hardened. Brooming is carried out after the floating operation.

For some floors and sidewalks where severe scoring is not desirable, the broomed finish can be produced with a hairbrush after the surface has been troweled to a smooth finish once.

Where rough scoring is required, a stiff broom made of steel wire or coarse fiber should be used. Brooming should be done in such a way that the direction of the scoring is at right angles to the direction of the traffic.

A rubbed finish is required when a uniform and attractive surface must be obtained, although it is possible to produce a surface of satisfactory appearance without rubbing if plywood or lined forms are used.

The first rubbing should be done with coarse carborundum stones as soon as the concrete has hardened so that the aggregate is not pulled out.

The concrete should then be cured until final rubbing.

Finer carborundum stones are used for the final rubbing. The concrete should be kept damp while being rubbed. Any mortar used to aid in this process and left on the surface should be kept damp for 1 to 2 days after it sets in order to cure properly. The mortar layer should be kept to the minimum as it is likely to scale off and mar the appearance of the surface.

33. MACHINE FINISHING

Machine finishing is carried out at such time as the concrete takes its initial set. The concrete must, however, be in workable condition at the time of the finishing operation. The screeds and vibrator on the machine finisher are set to give the proper surface 4-16

elevation and produce a dense concrete. In most cases, there should be a sufficiently thick layer of mortar ahead of the screed to insure that all low spots will be filled. The vibrator follows the front screed and the rear screed is last. The rear screed should be adjusted to carry enough grout ahead of it to insure continuous contact between screed and pavement. If forms have been set in good alinement and firmly supported, and if the concrete has the right workability, no more than two passes of the machine should be required to produce a satisfactory surface.

34. HAND FINISHING

Sometimes hand finishing behind the finishing machine is necessary.

It is sometimes necessary also to use a longitudinal float to decrease longitudinal variations in the surface.

Such a float is made of wood, 6 to 10 inches wide and 12 to 18 feet long, fitted with a handle at each end and operated by two men on form-riding bridges. The float is oscillated longitudinally as it is moved transversely. A 10-foot straightedge pulled from the center of the pavement to the form will remove any minor surface irregularities and laitance.

Unless considerable care is exercised as the straightedge or float approaches the form, it will ride up on the concrete resulting in a hump in the surface, especially where construction and expansion joints occur. The surface should have no coating of weak mortar or scum that will later scale off.

35. FINAL FINISHING

After the water sheen disappears, the final surface finish is applied by dragging a clean piece of burlap longitudinally along the pavement strip. This is known as belting and is done by two men, one on each side of the forms.

A nonskid surface is obtained by stroking with bassine brooms having fibers about 4 1/2 inches long. The grooves cut by the broom should not be over 3/16 inch deep. All corners of the paving should be rounded with an edging tool.

Expansion joints must be cleaned out and prepared for filling.

EXERCISES

First requirement. Multiple-choice exercises 1 through 6 are designed primarily to enable you to show what you have learned about earthmoving equipment.

1. Your squad has one dump truck with which to haul earth from a small excavation project. What is the rated capacity of the truck©s dump body?

a. 1 1/2 cubic yards

b. 3 tons

c. 5 cubic yards

d. 9 tons

2. Dozer blades vary in size and are designed to perform different earthmoving functions. What two adjustments can be performed on the straight blade on a crawler tractor?

a. tilt and pitch

b. angle and pitch

c. tilt and curve

d. curve and angle

3. The moldboard of the grader is fastened to the circle. It consists of the cutting edges and end bib. By rotating the circle the moldboard may be placed at any angle within a complete circle. Considering this capability, which of the following tasks would you say the grader can perform?

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a. ditching up to 5 feet deep b. making sidehill cuts e. mixing and spreading d. loading or digging

4. The crane-shovel with its variety of front end attachments is the most common type of lifting and loading equipment. Which of the following are a part of the basic crane-shovel? a. truck mounting and shovel front attachment b. truck mounting and revolving superstructure e. revolving superstructure and shovel front d. carrier and one of the basic attachments

5. A major task in any construction operation is the handling of construction supplies and excavating. Which of the following items of lifting and loading equipment would you consider as most effective for outloading aggregate into dump trucks from several stockpiles, approximately 150 feet apart? a. crawler mounted shovel b. crawler mounted backhoe e. truck mounted clamshell d. wheel mounted scooploader

6. The standard length boom for a truck-mounted crane is 30 feet. When raised for operation, what is the minimum safe working distance (in ft) from 69 KV lines for any part of boom equipment? a. 5 c. 25 b. 12 d. 40 Second requirement. Multiple-choice exercises 7 through 14 deal with utilization of air compressor tools.

7. Compressed air is used to inflate rubber equipment, to spray paint, to operate pneumatic tools, to power the guidance systems of certain mis- siles, to clean equipments to perform various jobs around maintenance shops, and to furnish air for underwater divers. What two requirements are demanded from an air compressor to operate pneumatic tools?

a. specified volume of air (cfm) and an air receiver tank

b. pressure control system and air pressure of 80-100 psi

c. specified volume of air (cfm) at a specific pressure (psi)

d. specific pressure (psi) and an intercooler

8. Your squad has been assigned the task of clearing a grove of trees. What is the maximum diameter in inches you can normally cut with the standard pneumatic chain saw?

a. 12 c. 24

b. 18 d. 36

9. What are the lengths, in inches, of auger bits used with the wood borer?

a. 6 and 8 c. 12 and 36

b. 12 and 14 d. 24 and 36

10. The head of the backfill tamper is attached to the end of the piston shank which is tapered to fit the socket in the head. The large flat area of the head provides the tamping surface. For best results, which of the following materials requires that you wrap the tamper head with burlap?

a. gravel c. asphalt

b. loose earth d. silt

11. The need for patching oil bituminous pavements occurs because of base or surface failures which are re- flected in the surface of the pavement.

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Your squad has the mission of patching pavement. The method is to cut back well beyond the apparent limits of the broken area. Which of the following tools would you use to cut back the macadam? a. crowbar b. paving breaker c. clay digger d. posthole auger

12. The work output of the men on the job is materially affected by the way the job is organized and super- vised. To receive optimum output from the paving breakers, how should they be used? a. in close areas b. singly c. in tandem d. horizontally

13. Holes are drilled for various purposes, such as to receive charges of explosives, for exploration, the injec- tion of grout, or stabilizing bolts and cables. Within practical limits the equipment which will produce the best overall efficiency should be used. Which of the following tools would be best for drilling a 1 5/8-inch, 5-foot hole in quarry rock? a. 80-lb paving breaker with moil point b. 25-lb paving breaker with moil point c. 25-lb paving breaker with 6-foot drill steel d. rock drill with 6-foot steel drill rod

14. Two items are important in the maintenance of a pneumatic tool. These are lubrication and air pressure. In order to check a pneumatic tool for proper lubrication, what should you see on a piece of paper after you pass it in front of the exhaust port?

a. a thin film of oil

b. drops of oil

c. no oil mark

d. a burn

Third requirement. Multiple-choice exercises 15 through 20 provide an opportunity for you to show that you understand mixing, placing, curing, and finishing of concrete.

15. Established and well-defined concrete mixing procedures must be followed if the finished concrete is to be of good quality. During operation of a 16S mixer, when would you introduce water into the mixing drum?

a. before the dry materials

b. at the same time as the dry materials

c. intermittently with dry materials

d. after the dry materials

16. Overmixing is objectionable because the grinding action increases fines, which require more water to maintain consistency of concrete. Also, overmixing may drive out entrained air. What is the minimum mixing time for the 16S mixer when the batch does not exceed one cubic yard?

a. 30 seconds c. 1 minute

b. 45 seconds d. 1 1/2 minutes

17. Good concrete placing and compacting techniques produce a tight bond between mortar and coarse aggregate and assure complete filling of the forms. Which of the following practices should be used to produce good concrete?

a. each layer should be hard before placing a new layer upon it

b. each layer should be soft when a new layer is placed upon it c. concrete for large pours should be placed at a rate of at least 6 feet per hour

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d. one or two hours should elapse between completion of columns and walls and the placing of slabs, beams, or girders supported by them

18. Concrete exposed to dry air from the time it is placed is about 50 percent as strong at 6 months as concrete moist cured 14 days before being exposed to dry air. What is a conse- quence of concrete drying too early? a. it is not smooth b. it does not reach its full potential quality c. volume is increased approximately 15 percent d. volume is decreased approximately 15 percent

19. From an economic standpoint, the top surface of a structure or portion of a structure can be finished to serve as a floor surface. Which of the following would you use to produce the smoothest surface? a. screed b. wood or metal float c. broom d. burlap drag

20. Hand finishing with floats behind the finishing machine is often more harmful than beneficial. Which of the following is a result of floating behind the machine? a. finish is too smooth b. too many ridges are left c. scaling is possible d. it tends to leave too many surface irregularities

LESSON 5 CONSTRUCTION PLANNING

CREDIT HOURS ______2 TEXT ASSIGNMENT ______Attached memorandum. MATERIALS REQUIRED______None. LESSON OBJECTIVE ______To teach you the fundamentals of construction drawings, symbols, sketches, bills of materials, specifications and materials takeoff.

______

ATTACHED MEMORANDUM

Section I. CONSTRUCTION DRAWINGS

1. DRAWINGS

Drawings are graphic representations of buildings, structures, or areas that give most of the information necessary for proposed construction.

Architectural drawings represent factors such as overall size, appearance, arrangement of internal space, and number, size, and kind of doors, windows, and fittings.

Engineer (structural) drawings reflect the mechanical systems of a building such as plumbing, lighting, heating, ventilating, and air conditioning. They also reflect the strength of the supporting members.

Utility drawings show the details of construction for the following service facilities outside buildings:

Electrical distribution systems.

Water supply and distribution systems.

Sewage systems and disposal plants.

Liquid fuel systems.

Construction drawings are obtained by combining both architectural drawings and engineer drawings into a set for a particular structure.

Production drawings describe equipment, parts, or articles that are suitable for production in quantity.

2. LINE CONVENTIONS

In order to include all the necessary information on a drawing in a meaningful manner, different types and weights of lines are used to represent the features of an object. The meaning of a line with certain characteristics has been standardized, and will be the same on any drawing. The line conventions most encountered in construction drawings are described below and shown in figure 1. Ap- plication of these line conventions is demon- strated in figure 2.

Visible lines are heavyweight unbroken lines used for the primary feature of a drawing. For drawings of objects, this line convention represents the edges, the intersection of two surfaces, or the surface limit that is visible from the viewing angle of the drawing. This line is often called the outline.

Hidden lines are medium weight lines of evenly spaced short dashes used to represent an edge, the intersection of two surfaces, or the surface limit which is not visible from the viewing angle of the drawing.

A thin (light) line composed of alternate long and short dashes of consistent length is called a center line. It is used to signify the center of a circle or arc and to divide an object into equal or symmetrical parts.

5-1 5-2 5-3

Dimension lines are solid continuous lines terminating in arrowheads at each end. Di- mension lines are broken only to permit writing in the dimensions. On construction drawings the dimension lines are unbroken. The points of the arrowheads touch the extension lines which mark the limits of the dimension. The dimension is expressed in feet and inches on architectural drawings and in feet and decimal fraction of a foot on engineering drawings.

An extension line is a thin (light) unbroken line that is used to indicate the extent of the dimension lines. The extension line extends the visible lines of an object when it is not convenient to draw a dimension line directly between the visible lines. There is always a small space between the extension line and the visible line.

A leader is a thin (light) line terminated with an arrowhead or dot that is used to indicate the part or feature to which a number or other information refers.

A medium weight line made of long dashes broken by two short dashes is called a pan- tom or datum line and indicates one of three things: the relative position of an absent part, an alternative position of a part, or repeated detail which is not drawn.

Stitch lines are medium lines made of short dashes evenly spaced and labeled used to indicate stitching or sewing.

Break lines are thin (light) lines inter- rupted by a Z-shaped symbol. The break line indicates that the object has been shortened to save space on the drawing. The true length is indicated by the dimension specified. The short break line convention varies with shape and material and indicates that part of the object has been cut away to show section detail or hidden features.

Cutting plane lines are a pair of short, heavy lines with arrowheads projected at 90ù used to indicate the cutting plane when a drawing includes a section view. Letters (AA, BB, etc.) are usually placed at the arrowheads to identify the section view. The arrowheads show the viewing direction of the section view. Where necessary, the section lines may be connected by a line of short, heavy dashes indicating the exact path of the cutting plane.

When a drawing includes a section, the surface or surfaces which are in the cutting plane are indicated by section lines. When the object sectioned is all one material, the section lines are usually closely spaced parallel lines of medium thickness. Where

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different materials are involved, different section conventions are used to distinguish between them.

3. SYMBOLS

Just as there are different types of lines on drawings, so also there are different symbols for different materials. The symbols shown in figure 3 are the conventional, symbols used to represent the more common types of materials.

4. PROJECTIONS

An object can be viewed and therefore drawn from an infinite number of positions. Some views are easier to draw and interpret than others.

An orthographic projection is commonly used to present an object on a drawing.

In this projection, the object is presented as if it were viewed through a trans- parent box (fig. 4).

The projections of the object on the sides of the box are the views seen by looking straight at the object through each side.

If the outlines are scribed on each surface, and the box is opened and laid flat, the result is a six-view, orthographic projection drawing.

As a general rule most drawings are presented in three views. The most common three-view drawing (fig. 5) arrangement shows the front, top, and right side view of an object.

In a three-view drawing, the front view shows the most characteristic feature of the object.

Note in figure 5 that the right side or end view is projected to the right of the front.

All the horizontal outlines of the front view are extended horizontally to make up the side view and all the vertical outlines of the front view are extended vertically to make up the top view.

Note: By studying the drawing you should obtain the following information about the object: the shape of the object, its overall length (2 1/8 inches), its width (1 1/2 inches), and its height (1 3/8 inches). It is notched 1 1/8 inches from the right side and 7/8 inch from the bottom.

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After having studied each view of the object, you should be able to visualize the object as it appears in figure 6.

If a hole is drilled in the notched portion of the object, the drawing would appear as in figure 7. The position of the hole is indicated by hidden lines in the front and side view and as a circle in the top view. The location of the center of the drilled hole is indicated by a center line.

Note: Two views can sometimes be used- to sufficiently describe a simple object.

Isometric projection is a three dimensional representation of an object. In figure 6, the notched box formed by the combination of the three orthographic projections forms an isometric projection.

5. FUNDAMENTALS OF INTERPRETATION

The objects used for illustrations thus far have been simple, and interpretation of the drawings nearly obvious. More complex or irregular drawings may require more effort to interpret. The principles introduced here will enable you to interpret most properly prepared drawings.

The orthographic projection principles are fundamental to all fields and a thorough understanding of them is necessary if you are to read any type of physical print.

The fundamental step in interpreting a drawing is relating the different views. If you pick a point on a front view, the same point on the right side view will be directly to the right of it. Similarly, the same point on the top view will be directly above the point on the front view.

These relationships are illustrated in 1 , figure 8, by the horizontal and vertical datum lines between the views. The same relationship exists between the top and right side views but is not obvious because they are not hinged together.

If the outside edges of both views are extended horizontally or vertically until they cross, as in 2 , figure 8, and a line is drawn connecting these points of intersection, the relationship can be seen. The line connecting the points of intersection will be at a 45ù angle with the horizontal. All other points in the views can be related by bending their project line at this 45ù line. If the same point appears on three views, the three occurrences will be related as shown by point 1 in 2 , figure 8. On complex drawings it is often helpful to draw this 45ù line to

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be sure you are looking at the same point on all three views when interpreting the drawing.

Example 1: Figure 9 is a three-view drawing (orthographic projection) of an object, along with an isometric outline of a box with the same overall dimensions of the object. You are to develop the isometric projection of this object by interpreting the three views and completing the basic outline given.

Solution: To develop the actual shape of the object proceed as follows:

First note that point h in the front view, point e in the side view, and point g in the top view correspond to point n on the isometric.

Point a is common to all three views and is shown as a on the isometric.

Point b in the front view, c in the top view and d in the side view correspond to isometric point q.

Point f in the top view corresponds to m of the isometric.

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Point l in the side view and j in the front view correspond to point p in the isometric.

Finally, k in the side view corresponds to r in the isometric.

Once the points of each view are related to points of an isometric, interpretation becomes a simple matter of connecting the similar points on the isometric that are connected in the views. In the front view notice that j and h are connected by a line. Also, in the isometric, n and p are similarly connected.

Trace the isometric on a sheet of paper. Proceeding as above, the following lines can now be drawn on the isometric:

from a to r (a to k in side view)

from a to q (a to b, front view; a to c, top; a to d, side)

from a to p ( a to j, front; a to l, side)

from a to n (a to h, front; a to g, top; a to e, side)

from q to r (d to k, side)

from q to n (b to h, front; c to g, top; d to e, side)

The tracing of the isometric should now look like that shown in figure 10.

6. SECTIONS

Section views are used to give a clear view of the interior or hidden features of object which normally cannot be clearly observed in conventional outside views.

A section view is obtained by cutting away part of an object to show the shape and construction at the cutting plane. The most common position of the cutting plane is through the longest dimension, or main longitudinal axis and parallel to the front view as shown in figure 11.

The part that is cut by the cutting plane is marked with closely spaced, parallel (section) lines.

The section lines indicate the surfaces which were created by the cutting plane and which do not exit on the uncut object.

When two or more parts are cut in one view, a different slant or style of section line is used for each part.

Notice how the cutting plane is shown on a drawing as illustrated in 1 figure 11.

The cutting plane in 2 illustrates where the imaginary cut is made. The object as it would look if it were cut in half is shown in 3 . The section view as it would appear on a drawing is shown in 4 .

When the cutting plane is a single continuous plane passing entirely through the object, the resulting view is called a full- section view ( 1 fig. 12). The cutting plane is usually taken straight through on the main axis or center line.

The cutting plane will not always be taken completely through the object. 2 figure 12 shows a half-section. The cutting plane passes only half-way through the object. This is common practice for symmetrical objects. The half-section permits both the internal and external features to be shown and their relationship to one another.

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7. DIMENSIONS

The item you will be most concerned with when reading prints is the dimensions.

As previously stated, dimensions on architectural drawings are usually given in feet, inches, and fractions of an inch.

Engineering drawings often give dimensions in feet and decimal fractions of a foot.

Metric dimensions are used on drawings of European origin, most drawings related to optical equipment, and a growing percentage of American machine drawings.

Note: During construction, you should use measuring instruments cali- brated in the same system as used on the construction prints to eliminate the chance of error in con- version.

5-10 There are two general types of dimensions --those indicating size and those indicating location.

The overall dimensions of an object indicate its size. Dimensions giving the size of a component, the diameter of a circle, the depth of a groove, or the width of a keyway are size dimensions.

Location dimensions show the relative position of two components or the extreme limits of travel of a moving part. They are given from center to center, from center to surface, or from surface to surface.

The placement of dimensions on a drawing is not arbitrary. They are placed to indicate which dimensions are specified in the design of the object. Measurements for construction should always be made from the points indicated by the dimension lines on the print.

Sample Exercises. Figure 13 is a drawing of a jig block. As a test of your ability to visualize and interpret three-view drawings, answer the following questions pertaining to this figure. The answers are given at the end of this lesson.

1. What kind of lines are J, O, W, X, Y, and V?

2. What type of lines are Q and Z ?

3. What kind of lines are P and S?

4. What letter or letters denote(s) extension line(s)?

5. What letters in the top view denote outlines or visible lines?

6. What surface in the top view represents surface A in the isometric?

7. Surface N in the front view represents what surface in the isometric?

8. Surface B is represented by what surface in the front view?

9. Surface C is represented by what surface in the top view?

10. Surface B is represented by what letter in the top view?

11. What is the overall height of the jig block?

12. What is the overall width of the jig block?

13. What is the overall length of the jig block?

14. What is the dimension of Z in the side view?

15. What is the dimension of Q in the side view?

16. What is the width of surface H?

17. What is the length of surface N?

18. What is the length of line W?

8. DRAWING FORMATS

A drawing not only provides information about the size and shape of the object being represented but also provides information

5-11 that enables the drawing to be identified, processed, and filed methodically.

The systematic arrangement of the drawing sheet to provide a consistent location for this information is known as the format of a drawing.

A typical title block as illustrated in figure 14 shows:

A -- The name and address of the preparing agency

B -- The title of the drawing

C -- The drafting record

D -- The approval block

E -- The scale and specification number

F -- The drawing number and sheet number

The scale block will indicate the scale on the drawing either as a ratio (for example: 1/4 or 1:4 meaning 1 inch on the drawing equals 4 inches on the object, or 12" = 1" meaning 12 inches on the drawing equals 1 inch on the object) or as a graphic scale as shown in figure 15.

Where the same scale is not used on all parts of a drawing, the scale block may be marked "as noted" or left blank, and the scale noted underneath each part of the drawing.

If graphic scales are used, several scales may be shown with number (fig. 15) and the appropriate scale number noted alongside each part of the drawing.

Note: When reading drawings, always follow the dimensions specified on the drawing first, and use the scale on the drawing only where no dimension is given.

The drawing number©s purpose is to permit quick identification. 5-12

If a drawing has more than one sheet this information is included in the number block indicating the sheet number and number of sheets.

The notes may list allowable substitutions, special provisions for certain locations, addi- tonal reference material, and so forth. The notes must always be read before beginning construction.

Notations on drawings or prints explaining materials or construction methods which cannot be indicated by symbols are called specifications. Such specifications provide a means of control of the quality of the materials and workmanship. The emphasis should be on the performance rather than on detailed methods of manufacture.

It is usually necessary only to specify the quality required, rather than to specify the manner in which quality will be obtained. In specifying structural steel it is necessary only to specify the type of steel with reference to the standard specifications which control its manufacture. Type and grading of lumber should be specified; and in the case of concrete, the desired ultimate compressive strength at 28 days after placing should be specified.

Section II. CONSTRUCTION ESTIMATES

9. MATERIAL ESTIMATES

A bill of materials (BOM) is a tabulated statement of requirements for a given project showing piece number, name, description, quantity, material, stock size and number, and sometimes the weight of each piece.

Bills of materials for facilities of the Engi- neer Functional Component System (EFCS) are contained in TM 5-303, and some drawings in TM 5-302 are accompanied by a simplified bill of materials. In such cases, the estimator should check the bill against the drawing and specifications for any discrepancies. If al- terations or modifications of the plans are necessary, which is often the case for facilities of the EFCS, the estimator will have to make the required additions and/or deletions to the accompanying bills.

When drawings and specifications for a project are not accompanied by a bill of materials, the estimator must do a materials takeoff from the drawings and prepare the bill of materials.

10. MATERIALS TAKEOFF

The first step in the preparation of a BOM is the tabulation of a materials takeoff. The takeoff usually is an actual tally and check- off of the items shown, noted, or specified on the construction drawings and specifications.

Both architectural and engineering plane provide the means by which names of the various items can be listed in order to make up the materials takeoff.

Indicated or scaled dimensions of buildings, structures, or utilities layouts are used to determine material unit dimensions.

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The materials takeoff tabulation should include column headings for each of the following:

Item number.

Part--Description of the item.

Number of pieces--Total number of pieces of the item in the complete object.

Nominal size--Taken from the notes and specifications on the drawing.

Length in place--Taken from the dimensions (or scale) of the drawing.

Standard length--Length of material available that will be used for the particular item.

Number of pieces per standard length-- Number of pieces of the item that can be obtained from the standard length used.

Number of standard lengths--Number of standard lengths needed to obtain the total number of pieces of the item.

Note: Parts are not combined unless size and nomenclature are identical.

Development of the materials takeoff begins with an examination of the plans to determine what is needed. Each part is listed and described in detail (Col 1 thru 5). This data is taken directly from the drawing.

The next phase of a takeoff list is indicating the standard lengths of lumber to use for each wooden part (Col 6 thru 8).

For columns 6 and 7, it is necessary to determine the standard length of material from which the parts can be cut and how many can be cut from the length selected.

8-, 10-, 12-, 14-, 16-, 18-, and 20-foot lengths of lumber are the standard lengths.

The selected standard length is entered in column 6.

The number per standard length (Col 7) is developed by dividing the standard length (Col 6) by the length in place (Col 5).

The number of standard lengths (Col 8) is obtained by dividing the number of pieces (Col 3) by Column 7.

Example 2: Figure 16 is the construction detail for a timber box culvert. Develop the materials takeoff for this culvert.

Solution: After studying the plans, each part must be listed. In the front view, begin your tabulation from the top to the bottom, left to right (or in any orderly fashion so that no part is omitted). Beginning with the cap, notice that it is 3 x 12 lumber (front view) 4©-0" long (side view). This entry is: ______

(1) (2) (3) (4) (5) Item Part Number Nominal Length of pieces size in place ______

1 Cap 10 3 X 12 4©-0" ______

Next, look at the collar. 2" x 10" material is needed for this part. However, two different sizes are needed for this item; therefore, two separate entries are needed. The short collar is 18" long and the long collar is 4©-4" long (side view). These entries are: ______

(1) (2) (3) (4) (5) Item Part Number Nominal Length of pieces size in place ______

2 Collar (short) 4 2" x 10" 1©-6"

3 Collar (long) 4 2" x 10" 4©-4" ______

Proceeding in the same manner for the stringer, scab, and sill, the first five column entries for the takeoff are: ______

(1) (2) (3) (4) (5) Item Part Number Nominal Length of pieces size in place ______

1 Cap 10 3 x 12 4©-0" 2 Collar (short) 4 2 x 10 1©-6" 3 Collar (long) 4 2 x 10 4©-4" 4 Stringer 2 2 x 12 12©-0" 5 Scabbing 2 2 x 10 1©-6" 6 Sill 10 3 x 12 4©-0" ______

The last three entries required some calculations. In column 6 the shortest standard length supplying the most pieces with the least waste is normally chosen.

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Continuing the example of the timber box culvert let us proceed to finalize the takeoff list. In completing the cap (item 1) note that 10 pieces, 4©-0" long are required. Choos- ing an 8-foot standard length and converting to inches proceed as follows:

8©-0" = 8 x 12 = 96 inches

4©-0" = 4 x 12 = 48 inches

Then:

96 --- = 2 pieces with no waste. 48

Since this is the most economical selection we can make, column 6 will read 8©-0" and column 7 will read 2.

Developing column 8, divide the number of pieces listed in column 3 by the pieces per standard length listed in column 7. This gives:

10 --- = 5 standard lengths. 2

Thus, the completed takeoff for item 1 would be:

______(7) (1) (2) (3) (5) (6) Number of (8) Item Part Number Length Standard pieces per Number of of pieces in place length standard standard length lengths ______

1 Cap 10 4©-0" 8©-0" 2 5 ______

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Note: In this example column 4 is omitted since it is not used in the calculations.

For the short collar (item 2) we need 4 pieces 1©-6" long. Again using an 8-foot standard length and proceeding as above:

8©-0" = 96 inches

1©-6" = 12 + 6 = 18 inches

Then:

96 --- = 5 pieces with 6 inches of waste. 18

Since only 4 pieces are needed we will have 1 extra piece 18 inches long, plus 5 inches of waste, giving a total waste of 23 inches. But since the shortest standard length is 8 feet, this is the most economical.

Column 8 is developed as above:

4 pieces required ------= 5 pieces/standard length

0.8 standard length

Note: For any part of a standard length, a full standard length must be used.

______(7) (1) (2) (3) (5) (6) Number of (8) Item Part Number Length Standard pieces per Number of of pieces in place length standard standard length lengths ______

2 Collar (short) 4 1©-6" 8©-0" 5 1 ______

Note: Although only 4 pieces are required, column 7 reads 5 pieces since this is the number obtainable.

For the long collar (item 3) 4 pieces, 4©-4" long are required. Trying an 8-foot standard length:

8©-0" = 96 inches 4©-4" (4 x 12) + 4 = 48 + 4 = 52 inches

Then:

96 --- = 1 piece with a waste of 44 inches 52

Next try a 10-foot standard length:

10©-0" = (10 x 12) = 120 inches

4©-4" = 52 inches

Then:

120 --- = 2 pieces with a waste of 16 inches 52

Following the same procedure for the 12-, 14-, 16-, 18- and 20-foot standard lengths we obtain:

12-foot--2 pieces, 40 inches of waste

14-foot--3 pieces, 12 inches of waste

16-foot--3 pieces, 36 inches of waste

18-foot--4 pieces, 8 inches of waste

20-foot--4 pieces, 32 inches of waste

It should be evident that using an 18-foot standard length is the most economical.

Column 8 for the long collar is computed to be:

4 - = 1 standard length 4

This item when completed should read: ______(7) (1) (2) (3) (5) (6) Number of (8) Item Part Number Length Standard pieces per Number of of pieces in place length standard standard length lengths ______

3 Collar (long) 4 4©-4" 18©-0" 4 1 ______5-16

Note: If 18-foot standard lengths are not available, 10-foot lengths would be used instead of 14-foot lengths. Two 10-foot lengths are needed to give the 4 pieces required, with a total waste of 32 inches. Two lengths are also required for the 14-foot length.

Although there is only 12 inches wasted from the first length, only one more piece 4©-4" long is needed. This gives a total waste of 12 inches + 116 inches, or 128 inches of waste.

Proceeding in the same manner for item 4 (stringer) the completed tabulation is:

______(7) (1) (2) (3) (5) (6) Number of (8) Item Part Number Length Standard pieces per Number of of pieces in place length standard standard length lengths ______

4 Stringer 2 12©-0" 12©-0" 1 2 ______

Item 5 (Scabbing) is similar to item 2 (short collar). The only difference is the number of pieces required. This item can be developed exactly like item 2. A waste of 59 inches is obtained (only 2 pieces are required).

Also, item 6 (sill) is similar to item 1 (cap). The only difference is the nomenclature of the part.

The completed tabulation for items 5 and 6 are:

______(7) (1) (2) (3) (5) (6) Number of (8) Item Part Number Length Standard pieces per Number of of pieces in place length standard standard length lengths ______

5 Scabbing 2 1©-6" 8©-0" 5 1 6 Sill 10 4©-0" 8©-0" 2 5 ______

The completed takeoff list for the timber box culvert is shown in table 1.

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11. BILL OF MATERIALS

After the materials takeoff is tabulated, the actual bill of materials is compiled.

The bill of materials is arranged in tabular form with column headings to include item number, item, unit, quantity, board feet, and a brief description of the item and where it is used.

The items are listed according to materials (wood, metal, etc.). Within each group of materials the items are listed according to size, usually beginning with the largest piece. Items of like size are consolidated.

Consolidation is the process of combining into one listing all identical items, regardless of nomenclature.

Items of the same size and standard length are consolidated.

The unit of measurement of lumber is the board foot. By definition a board foot is the volume of a board 1 inch thick, 1 foot wide, and 1 foot long. BF, bf, MBF, mbf are all commonly employed abbreviations for board foot. M in front of the abbreviation stands for 1000 board feet. Thus, 4 MBF would indicate 4000 board feet.

From the above definition the following formula is derived:

thickness in inches x width in inches x length in feet x number of lengths BF = ------12

Example 3: Determine the board feet of 5 pieces of 3" x 12" lumber, 8 feet long.

Solution: From the above formula:

3 x 12 x 8 x 5 BF = ------12

BF = 120 board feet

Estimated quantities are also incorporated into the BOM. These are quantities known to be necessary but which may not have been placed on the drawings, such as nails, cement, concrete-form lumber and tie wire, temporary bracing or scaffold lumber, and so on. Table 2 can be used to determine the quantity of nails needed per 1000 board feet of a particular size of lumber (the symbol "d" is the common abbreviation of pennyweight).

Nails are listed on a bill of materials as pounds of nails required.

Example 4: Determine the nails required for 2000 board feet (2 MBF) of 1 x 6 material.

Solution: From table 2, it is seen that 40 pounds of 8-penny nails are required for 1000 board feet of 1 x 6 material. Therefore, 80 pounds are needed for 2 MBF.

Example 5: Determine the quantity of nails needed for the lumber of example 3.

Solution: Referring to table 2, note that 145 pounds of 60-penny nails are required for every 1000 board feet of 3 x 12 lumber.

120 BF = 0.12 MBF

Multiplying 145 pounds per MBF by 0.12 MBF gives 17.4 pounds of 60-penny nails needed. Rounded up to the nearest whole pound gives 18 pounds of nails required.

For simple objects the amount of nails needed can be obtained by a direct count.

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Example 6: By a direct count you determine that 760 20-penny nails are needed for the completion of a project. Determine the number of pounds needed for this job.

Solution: Referring to table 2, note that there are approximately 29 nails in a pound of 20-penny nails. The number of pounds is obtained by dividing the total number of nails needed by the number of nails per pound:

total number of nails pounds needed = ------nails per pound

760 = ---- 29

= 26.21 pounds, say 27 pounds

The completed bill of materials lists all the material needed for the project and is used in the ordering of this material.

Example 7: You are required to draw up the bill of materials for the timber box culvert (fig. 16), using the materials takeoff compiled in example problem 2 (table 1).

Solution: The first step in the finalization of a bill of materials is consolidation. Re- ferring to table 1, notice that the largest size of lumber is 3 x 12 material, with a standard length of 8©-0". Both the cap (item 1) and the sill (item 6) require this size lumber and are therefore consolidated. Since 5 lengths are required for each item, a total of 10 lengths are needed. The first listing in the BOM would read.

______

(1) (2) (3) (4) (5) (6) Item No. Item Unit Quantity BF Description ______

Lumber 1 3 x 12--8 ft pcs 10 -- Caps and sills ______

Notice that column 5 (board feet) is not filled in. It is normally easier to compile all items of the BOM first and then go back and determine the board feet.

The next size item is the 2 x 12 material. Since this is used for only one item (stringers) there is no consolidation. This entry is. ______

(1) (2) (3) (4) (5) (6) Item No. Item Unit Quantity BF Description ______

2 2 X 12--12 ft pcs 2 -- Stringers ______

The last size material is 2 x 10 lumber. Notice, however, that both an 8-foot (table 1, items 2 and 5) and an 18-foot (table 1, item 3) standard length are required; therefore, two separate entries are required. Also note that there is 23 inches of waste for the short collar (item 2) and 59 inches of waste for the scabbing (item 5). This gives a total of 82 inches of waste. If a 2 x 10 x 10-foot standard length is now chosen the waste would be only 12 inches. (4 pieces 18 inches long (short collar) and 2 pieces 18 inches long (scabbing) gives a total requirement of 108 inches. Since a 10-foot standard length is 120 inches, we can get both items from one 10-foot length.) Therefore, in consolidating this item, change the original choice of two 8-foot standard lengths to one 10-foot standard length. We can consolidate and use only one standard length for both items. The final entries would be:

5-19 ______(1) (2) (3) (4) (5) (6) Item No. Item Unit Quantity BF Description ______

3 2 x 10--18 ft pcs 1 -- Long collars 4 2 x 10--10 ft pcs 1 -- Short collars, scabbing ______

Now we can complete the lumber portion of our BOM by determining the board feet of each item: thickness (in) x width (in) x length (ft) x number of lengths BF = ------12

3 x 12 x 8 x 10 2880 Item 1: BF = ------= ---- 12 12 = 240 board feet

2 x 12 x 12 x 2 576 Item 2: BF = ------= ---- 12 12

= 48 board feet

2 x 10 x 18 x 1 360 Item 3: BF = ------= --- 12 12

= 30 board feet

2 x 10 x 10 x 1 200 Item 4: BF = ------= --- 12 12

= 16.67 board feet

The completed BOM for the lumber requirement is:

______(1) (2) (3) (4) (5) (6) Item No. Item Unit Quantity BF Description ______

Lumber 1 3 x 12--8 ft pcs 10 240 Caps and sills 2 2 x 12--12 ft pcs 2 48 Stringers 3 2 x 10--18 ft pcs 1 30 Long collars 4 2 x 10--10 ft pcs 1 16.67 Short collars, scabbing ______

To complete the bill of materials, we now have to determine the amount of nails needed. Referring to table 2, it is seen that 145 pounds of 60-penny nails are needed for 1000 board feet of 3 x 12 lumber. Also, 52 pounds of 20-penny nails are needed for 1000 BF of 2 x 12 and 60 pounds of 20-penny nails are needed for 1000 BF of 2 x 10 lumber. Then:

For item 1: 145 x 0.24 MBF = 34.8 pounds of 60d nails

For item 2: 52 x 0.048 = 2.49 pounds of 20d nails

Since items 3 and 4 are the same nominal size lumber, the board feet are combined. There- fore, for items 3 and 4: Total BF needed = 30 + 16.67 = 46.67.

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Then, 60 x 0.047 = 2.82 pounds of 20d nails.

Notice that items 2, 3, and 4 all require 20-penny nails. The totals are consolidated just as the same sizes of lumber are consolidated. Therefore, 2.49 + 2.82 = 5.31 pounds of 20d nails. Round up to 6 pounds.

The final bill of materials for the timber box culvert is shown in table 3.

12. ANSWERS TO SAMPLE EXERCISES

1. Visible lines or outlines 10. L

2. Dimension lines 11. 1 1/2"

3. Extension lines 12. 2"

4. P and S 13. 3"

5. K, L, J, and X 14. 1"

6. H 15. 1/2"

7. D 16. 1"

8. M 17. 3"

9. G 18. 2"

EXERCISES

First requirement. Solve multiple-choice exercises 1 through 3 to show that you understand the types of drawings and line conventions used in construction.

1. Military drawings are either construction or production drawings. What constitutes a production drawing? a. parts suitable for production in quantity b. parts necessary for the construction of a structure

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c. drawings for production of a utilities system

d. tools needed to produce the finished structure

2. You are viewing a construction drawing and have found a medium weight line of evenly spaced short dashes. Lines are symbols used on drawings to show information necess- sary for construction. What does this line mean?

a. stitching

b. center of a circle

c. alternate position of a part

d. edge not visible in that view

3. A break line is used to save space on a drawing. You have found a break line used on the drawing you are reviewing. How would you determine the length of the object on which the break line is used?

a. specified dimension

b. use of graphic scale

c. from different views

d. from drawing notes

Second requirement. Multiple-choice exercises 4 through 7 enable you to demonstrate your ability to understand construction drawings and provide a chance to show your knowledge of drawing interpretation.

4. In learning to read a construction print, you must develop the ability to visualize the object. This is nothing more than getting a three-dimensional picture of the object from the different views shown on the print. What is this three-dimensional drawing of an object called?

a. perspective c. orthographic b. isometric d. box

5. A three-dimensional drawing of a concrete abutment is shown in view "X", figure 17. Which of the other four views also shown is the correct front view for this abutment?

a. A c. C

b. B d. D

6. Sectional views are formed by cutting an object with an imaginary plane, removing the portion of the object in front of the plane, and viewing that portion behind the plane (see fig. 11). What is the primary purpose of a section view?

a. determine dimensions

b. show the material of the object

c. explain the primary notes of the drawing

d. show details which cannot otherwise be shown

7. Dimensions are placed on a drawing to give additional information and to aid the construction worker. Which of the following dimensions is a location dimension?

a. groove depth

b. overall width of object

c. diameter of a circle

d. distance of a circle from an edge

Third requirement. Multiple-choice exercises 8 and 9 are designed primarily to point out the additional information that can be obtained from prints.

8. The title block on a drawing provides useful information to the construction worker. Which of the following would be included in the title block?

a. notes

b. specifications c. sheet number

d. revision block

5-22 5-23

9. Your squad is required to construct a concrete abutment similar to that shown in figure 17. Where would you find information concerning the ultimate compressive strength of this concrete?

a. notes

b. specifications

c. sectional view

d. bill of materials

Fourth requirement. Multiple-choice exercises 10 through 14 provide you with an opportunity to display your knowledge of a materials takeoff tabulation.

General situation. Your battalion has been given a directive to construct a road for supply purposes. The battalion S-3 assigned your company to construct three bridges for this road. Your squad is to construct a timber trestle bent from the print shown in figure 18. Your squad leader gives you a materials takeoff for this bent and tells you to go to S-4 for the necessary supplies. Below is the takeoff list (table 4) that your squad leader has tabulated. Questions 10 through 13 pertain to this takeoff.

10. The first step in a materials takeoff tabulation is to list all the parts of a structure. What part (col 2) should be listed for item 4 (col 1)?

a. sill

b. stringer

c. short collar

d. longitudinal bracing

11. You notice that you need 7 footings (item 3, col 1). What size (col 4) lumber (in inches) is required for this item?

a. 2 x 6 c. 3 x 12

b. 2 x 10 d. 6 x 6

12. You realize that in order to determine the number of standard lengths (col 8) for an item you must know the length in place (col 5) and the number of pieces per standard length. How many pieces per standard length (col 7) can be obtained from the standard length (col 6) shown for the scabbing (item 5, col 1)?

a. 18 c. 20

b. 19 d. 21

13. The number of standard lengths is not necessarily the same as the number of pieces of an item, since more than one piece can generally be cut from one board. What entry should be made

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for the number of standard lengths (col 8) for the footings (item 3, col 1) if the standard length (col 6) shown is used?

a. 1 e. 5

b. 3 d. 7

14. For economical reasons, the standard length used for a particular item should be selected so as to produce the least amount of waste. What standard length (in feet) is the most economical for 8 pieces of 2 x 4 lumber 6©-3" long?

a. 8 c. 16

b. 14 d. 20

Fifth requirement. Multiple-choice exercises 15 through 20 finish your instruction in construction planning by enabling you to show your ability in reading and completing bills of materials.

General situation continued. You finally take the completed materials takeoff to the battalion supply officer who informs you that requisitions are made from a bill of materials and that the materials takeoff is a preliminary step in the preparation of a bill of materials. Below is the bill of materials (table 5) partially completed for the timber trestle bent shown in figure 18. Exercises 15 through 19 pertain to this BOM.

15. The bill of materials provides all necessary information for the requi- sitioning of supplies. What quantity (col 4) should be entered for item 1? a. 1 c. 3 b. 2 d. 4

16. Item listings for lumber show the size and length of material required for a particular part. What entry should be made in column 2 (item) for item number 2?

5-25 a. 3 x 12 - 8 ft b. 3 x 12 - 12 ft c. 6 x 6 - 8 ft d. 6 x 6 - 12 ft

17. The description shows where each particular item is to be used. What should be entered under the description (col 6) for item number 4? a. scabbing b. stringer c. transverse bracing d. longitudinal bracing

18. The board foot is used as the measure of lumber, and the cost of lumber is based upon it. What do you determine the board feet (col 5) of item 4 to be? a. 20 c. 240 b. 80 d. 960

19. You are told that the nail requirements are to be determined by direct count. Your platoon sergeant also told you that 7 20-penny nails are required for each piece of scabbing and 20 20-penny nails are required for each transverse brace. What is the 20-penny nail requirement (in pounds) for the timber trestle bent shown in figure 18? a. 2 c. 8

b. 5 d. 11

20. For a different project you are told that 2300 board feet of 3 x 12 lumber is required. What quantity of 60-penny nails (in lb--round up to nearest 10-lb) is needed for this job?

a. 230 c. 300

b. 270 d. 340

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LESSON 6

CREDIT HOURS ______TEXT ASSIGNMENT ______Attached Memorandum. MATERIALS REQUIRED ______None. LESSON OBJECTIVE ______To teach soil characteristics and how they may be improved for construction purposes.

______

ATTACHED MEMORANDUM

1. SOIL DEFINED

The term soil is applied to the rock particles produced by the mechanical and chemical breakup of rocks. In most soils these rock particles are mineral grains which are not cemented together. The voids or spaces between the grains may or may not contain water. In addition, some soils contain organic matter, shells, or other material in various forms and quantities.

2. UNIFIED SOIL CLASSIFICATION SYSTEM

The Unified Soil Classification System is a means of determining those soil characteristics which indicate a soil©s behavior as a construction material. In this system a soil can be put into one of several soil categories. The suitability of each soil category for engineering work has been determined by experience so that a reliable estimate of the expected behavior of the soil in question can be made.

Principal soil categories as defined by the Unified Soil Classification System are: coarse- grained soils, which consist of gravel and sand; fine-grained soils, which consist of silt and clay; and organic soils, which are any soils, regardless of grain size, containing a considerable amount of organic (decayed or decaying vegetation) material.

3. GRAVEL

Gravel is a mass of rock particles, generally waterworn, which pass a 3-inch sieve and are retained on a no. 4 sieve (0.187 inch).

Next to solid bedrock, well-graded and compacted gravel is the most stable natural foundation material. It is classified as coarse or fine; well- or poorly-graded; angular, flat, or rounded. It is desirable material for both bases and subgrades if well-graded. When used for road surfaces, sufficient fine-grained material must be included to bind the larger individual particles in place.

Gravel is easy to drain, easy to compact when well-graded, little affected by moisture, and not affected by frost action.

Deposits of gravel commonly contain a considerable percentage of sand and even silt or clay.

4. SAND

Granular material composed of rock particles which pass a no. 4 sieve and are retained on a no. 200 sieve (.0029 inch) is called sand.

It is difficult to distinguish sand from silt when the sand particles are small and uniform in size. Dried sand, however, differs from silt in that it has no cohesion and feels more gritty.

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Sand is classified as coarse, medium, or fine; well- or poorly-graded; angular or rounded.

Well-graded and compacted sand is desirable for concrete aggregate and for foundation material. It is easy to drain, little affected by moisture, and ordinarily not affected by frost action.

5. SILT

Silt is a fine, granular material composed of particles which pass the no. 200 sieve.

Silt lacks plasticity (plastic soil is generally soft and can be molded) and has little strength when dry.

To identify silt, prepare a pat of wet soil and shake it horizontally in the palm of the hand. If the soil is silt, the shaking action will cause water to come to the surface of the sample, making it appear glossy and soft. Squeezing the wet sample between the fingers causes the water to disappear from the surface and the sample quickly stiffens and finally cracks or crumbles.

Allow the sample to dry thoroughly and test its cohesion and feel by crumbling with the fingers. Typical dry silt shows no strength and feels only slightly gritty in contrast to the rough grittiness of fine sand.

All types of silt are treacherous. Because of their inherent instability, slight distur- bances in the presence of water, such as traffic vibrations transmitted to a wet silt subgrade, may cause them to become soft or to change into a "quick" (by "quick" is meant easily moved or shifted) condition.

When ground water or seepage is present, silts exposed to frost action are subject to severe ice accumulation and consequent heav- ing.

Silts are difficult to compact and drain.

6. CLAY

Clay is also fine-grained material composed of particles which pass the no. 200 sieve.

To identify clay, work a sample with the fingers, adding water when the stiffness requires it. The moist sample is workable enough to be kneaded like dough.

Make a further test by rolling a ball of kneaded soil between palm of hand and a flat surface. Clay can be rolled to a slender thread, about 1/8-inch in diameter, without crumbling; fine silt, which resembles clay, crumbles without forming a thread.

Measure the hardness of the sample by the finger pressure required to break it. Much greater force is required to break dry clay than dry silt.

Clay feels smooth in contrast to the slight grittiness of silt.

The character of undisturbed clay, especially its hardness, is quite different in the natural state than that of a sample removed for testing. As found in undisturbed natural conditions, clay may be hard, medium, soft, or extremely soft, depending upon the natural moisture content and density. Hard clay that cannot be remolded with ordinary finger pressure requires a pick for excavating. Soft clay that can be easily remolded by hand can be readily excavated with a shovel.

Low resistance to deformation when wet, imperviousness to water, especially when wet, and large expansions and contractions with changing moisture content are typical of clays.

Wet clays are impossible to compact.

Clays absorb surface water or ground seepage slowly and retain it well, making it impossible for additional surface water to be absorbed or to drain downward through the already saturated soil.

Too much clay in a base course is harmful and must be avoided whenever large changes in moisture content may be expected. Example 1: A sieve analysis yields the following data: 60 percent retained on no. 4 sieve, 30 percent passing no. 4 but retained on no. 200 sieve. No organic material is present. What classification would you assign to this soil?

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Solution: Since most of the material is retained on no. 4 sieve, the soil is primarily a gravel, and may be classified as such. In addition, the soil contains some sand (the 30 percent passing no. 4 but retained on no. 200) and fine material (90 percent is retained on no. 200, so 10 percent must be fine material).

7. ORGANIC SOIL

Soil which is primarily composed of decayed or decaying vegetation is termed organic soil. Fine-grained mineral sediments may also be found in this soil.

Organic soil is identified by a coarse and fibrous appearance and an odor. The odor may become more noticeable when the soil is heated.

Another aid in identifying organic soil is that a sample can be rolled into a soft, spongy thread.

Organic soils are unsatisfactory subgrade materials because of their low strength and low resistance to deformation. The Corps of Engineers requires complete removal of all organic materials.

8. GRADATION

Soils may be divided into several different types on the basis of grain size. The proportion of various grain sizes in a soil sample determines its gradation, or grain-size distribution.

A soil may be termed either well-graded or poorly-graded, depending on the distribution of grain sizes in the soil.

A soil having a good representation of all particle sizes is defined as a well-graded soil. A diagram of a well-graded soil is shown in figure 1 1 .

Any soil not meeting the requirements of a well-graded soil is termed a poorly-graded soil. There are two types of poorly-graded soils, uniformly-graded and gap-graded.

A uniformly-graded soil consists mostly of particles nearly uniform in size.

A gap-graded soil contains some large and some small particles but the con- tinuity of gradation is broken by the absence of some sizes of particles.

Uniformly-graded soils and gap-graded soils are shown in figures 1 2 and 1 3 .

Determination of gradation. The gradation or grain-size distribution of a soil is determined by mechanical analysis. The methods of mechanical analysis in use are sieve analysis, wet mechanical analysis (sedimen- tation), and a combination of these two methods.

Sieve analysis. A sieve analysis is sufficient to classify most materials, especially those with little or no fines (very small particles).

The test procedure for a sieve analysis is as follows:

Oven dry the soil sample.

Weigh the sample.

Transfer the soil sample to a set of sieves and shake the stack vigorously for 5-15 minutes.

Record the weight of the material retained on each sieve.

Compute the percentage of material passing each sieve.

6-3 The percentages obtained indicate the gradation of the soil sample.

Wet mechanical analysis. Wet mechanical analysis is suited primarily for fine material, although it may be applied to coarse-grained material as well. Particle size is determined by the rate of settling in water.

Combined method of analysis. A combination of the two methods is required to completely determine grain-size distribution of a soil with a wide range of grain size. This degree of thoroughness is not normally necess- sary in routine tests, however.

Effect of gradation on bearing capacity. Coarse materials that are well-graded are usually preferable for supporting a load because good gradation usually means the soil can be compacted to high density and consequent stability.

Specifications controlling the percentages of coarse- and fine-grained materials needed to make up a well-graded soil make it possible to provide for maximum density. Such pro- portioning develops a sort of interlocking of particles with smaller particles filling the spaces between larger particles. This makes the soil stronger and more capable of supporting heavy loads.

9. PARTICLE SHAPE

The shape of individual particles has an effect on the suitability of a soil as an engineering material.

The rough, angular shape particles such as are produced by a rock crusher are generally the best shaped particles for construction purposes, especially when well-graded.

The rounded type particles, such as river run gravel, are usually satisfactory for any theater of operations work if well-graded. Uniformly-graded round particles, however, can cause stability problems.

10. FIELD IDENTIFICATION

Classification of soils in the field must often be made without laboratory equipment. Soil properties must be estimated and tentative classifications assigned. Such a procedure is called field identification.

Principal tests are the shaking test, the roll or thread test, the ribbon test, the breaking or dry strength test, and the odor test.

Shaking test. In this test a wet pat of soil is alternately shaken horizontally and squeezed between the fingers. The soil is said to have given a reaction to this test when, on shaking, water comes to the surface giving a wet, shiny appearance. When the sample is then squeezed, the surface water quickly disappears, leaving the surface dry and dull in appearance. A rapid reaction of this type is typical of silts and fine sands that contain little or no clay. A slow reaction or no reaction at all will result if organic material or clay is present in moderate to large amounts.

Roll or thread test. This test is performed only on material passing the no. 40 sieve. A moist soil sample is repeatedly rolled into a thin thread (about 1/8-inch in diameter) until it breaks or crumbles. A sample which quickly breaks or crumbles is predominately fine sand or silt. A sample which shows little or no tendency to crumble contains considerable clay.

Ribbon test. Only material passing the no. 40 sieve is used in the test. A roll of moist soil is flattened into a ribbon 1/8 to 1/4 inch thick. The maximum length of ribbon which can hold together when the ribbon is supported only at one end indicates the amount of clay present in the sample. If the soil sample holds together for a length of 8 to 10 inches without breaking, the material is then considered to have a high clay content. If it cannot be ribboned, or can be ribboned only into short lengths, then the sample is fine sand or silt with little or no clay content.

Breaking or dry strength test. Use only material passing the no. 40 sieve. A wet pat of soil about 1 1/2 inch in diameter and 1/2 inch thick is allowed to air dry and is then broken with the thumb and forefingers of both hands. Samples which cannot be broken are primarily clay. Samples with little or no clay break and crumble easily.

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Odor test. Organic soils usually have a dis- tinctive, musty, slightly offensive odor which, with experience, can be used as an aid in identification. This odor is especially apparent in fresh samples. It is gradually reduced when exposed to air, but can be brought out again by heating a wet sample.

11. SOIL STRENGTH

Soil strength is a measure of the ability of a soil used as a base or subgrade beneath a road or airfield to support a load.

Soil strength is measured by the California Bearing Ratio (CBR) test, the field plate bearing test, and the airfield cone penetrometer.

The CBR test is a widely used method which measures the strength of soil samples removed from the subgrade at various locations. Special equipment and trained personnel are required.

The field plate bearing test is an expensive and time-consuming method which requires good judgment in interpretation of results. The strength of the subgrade soil in place is measured by this test.

The airfield cone penetrometer gives a measure of in-place soil strength called the airfield index. It is a simple technique which may be used by inexperienced personnel.

The penetrometer consists of a 30-degree cone of 1/2-square inch base area, an aluminum staff 19 inches long and 5/8 inch in diameter, a proving ring, a mi- crometer dial, and a handle. When the cone is forced into the ground, the proving ring is deformed in proportion to the force applied. The amount of force required to move the cone into the ground is indicated in the dial inside the ring. Readings are normally taken at 6-inch intervals as the cone moves downward.

12. SETTLEMENT

Settlement of a highway or airfield may result from a consolidation of underlying soil. By consolidation is meant the reduction in volume of a layer of soil due to the weight of overlying soil.

Settlement is generally most severe in clays and loose sands.

Dense sands and gravels usually change very little in volume after completion of construction and are therefore very good foundation materials.

13. COMPACTION

By compaction is meant the process of mechanically densifying a soil. Compaction implies the application of moving loads (compaction equipment) to the soil mass. This is in contrast to the consolidation process in which a soil mass becomes more dense as the result of the application of a static load (weight of the overlying soil).

The density obtained by compaction is normally expressed in terms of dry density (weight of solids per cubic foot) expressed in pounds per cubic foot.

Advantages gained from compaction. Prin- cipal soil properties which are affected by compaction include settlement, soil strength, movement of water, and volume change.

One of the principal advantages which result from the compaction of soils used in embankments is that it reduces to a minimum the settlement which might occur as the result of consolidation of the soil within the body of the embankment.

Increasing the density by compaction will prevent later consolidation within the embankment, but it must be remembered that the embankment might still settle as a result of consolidation of the soil on which the embankment rests.

Increasing density by compaction usually increases soil strength. This permits use of a thinner pavement and steeper embankment side slopes than would otherwise be possible.

When soil is compacted, the amount of voids in the soil is decreased. This reduces the permeability (ease with which water moves through the soil) which reduces seep-

6-5 age. The movement of capillary water is also minimized, reducing the tendency for the soil to take up water and suffer later reductions in strength.

Volume change in relation to compaction is generally not a matter of concern, except for clay soils. Clays are subject to large volume changes as they go from wet to dry (or vice versa) unless restrained, but generally may be compacted so that volume change is a minimum.

14. COMPACTION EQUIPMENT

To achieve the desired properties listed in paragraph 13, care must be used in selecting types of compaction equipment to be used on a given material.

Generally, steel-wheeled rollers are recommended for angular materials with limited amounts of fines; crawler-type tractors or rubber-tired rollers for gravel and sand; and sheeps-foot rollers for coarse-grained or fine- grained soils having appreciable amounts of cohesive materials.

Rubber-tired rollers are recommended for final compaction operations.

15. CONCLUSION

The best materials for construction are the coarse-grained soils of the Unified Soil Classi- fication System (sand and gravel). They should be well-graded and free of organic material.

The fine-grained soils are less desirable, being more difficult to compact and requiring more careful control of construction methods.

Compaction is used to improve soils which would not be suitable for construction work in their natural states. Improvements which result from properly controlled compaction are minimization of settlement, increase in soil strength, reduced permeability to water, and reduced volume changes caused by changing moisture content.

EXERCISES

First requirement. Multiple-choice exercises 1 and 2 deal with the definition of soil and basic size groupings.

1. Soil is composed of several materials. Which of the following materials is the primary component of soil?

a. organic material

b. water

c. rock particles

d. air

2. You are examining a soil which is primarily composed of fine-grained material. Which of the following groups could this soil fall into?

a. sand and gravel

b. sand and clay

c. silt and clay

d. sand and silt

Second requirement. Multiple-choice exercises 3 through 11 are designed to enable you to demonstrate your knowledge of soil characteristics and identification of soils.

3. Given the following sieve analysis: 30 percent retained on no. 4 sieve, 55 percent passing no. 4 but retained on no. 200 sieve, and 15 percent passing no. 200 sieve. No organic matter is present. How would you classify this soil?

a. coarse-grained

b. fine-grained

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c. organic d. cannot be classified

4. Your sieve analysis yields the following results: 7 percent retained on no. 4 sieve and 83 percent passing no. 4 but retained on no. 200 sieve. No organic material is present. What classification would you assign to this soil? a. a sand containing some fine-grained material b. a sand with no fine-grained material c. a silty gravel d. clay

5. You are to use a silty soil for subgrade construction. Which of the following statements best describes this soil? a. it is easy to compact and drain b. it is little affected by water c. it is preferable to sand for this purpose d. it is composed of material passing no. 200 sieve

6. Silt may easily be mistaken for fine sand by an untrained observer. How is silt most easily distinguished from fine sand in the field? a. silt has an odor, especially when heated b. silt has a very rough, gritty feel compared to the smoothness of fine sand c. silt has only a slightly gritty feel compared to the rough grittiness of fine sand d. silt cannot be distinguished from fine sand in the field

7. You are trying to determine whether the fine-grained material at your construction site is silt or clay. How is clay most easily distinguished from silt in the field? a. silt has an odor, especially when heated b. clay feels smooth in contrast to the slight grittiness of silt c. clay feels slightly gritty in contrast to the smoothness of silt d. clay has a distinguishing yellow color

8. Which of the following soils is most nearly impervious to water? a. wet clay b. dry sand c. dry silt d. uniformly-graded gravel

9. Certain soils drain well in their natural state. To minimize drainage construction, which soil would you recommend using? a. any impervious soil b. clay c. silt d. gravel

10. How would you most easily identify organic soil in the field? a. gradation c. density b. particle shape d. odor

11. Given the same sieve analysis as in exercise 3, except that the soil consists primarily of organic matter, how would you classify this soil? a. coarse-grained b. fine-grained c. organic d. cannot be classified

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Third requirement. Solve multiple-choice exercises 12 through 15 to test your understanding of the requirements for soils to be used in construction.

12. You are to build a subgrade for a road on which heavy vehicles will travel. Which of the following soils is most suitable for this purpose?

a. a uniformly-graded soil

b. a well-graded soil

c. a gap-graded soil

d. a poorly-graded soil

13. When selecting a construction material, you must remember that particle shape can affect stability. Which of the following soils would generally be most desirable for construction purposes?

a. well-graded, rough angular gravel

b. uniformly-graded, rough, angular gravel

c. well-graded, rounded gravel

d. uniformly-graded, rounded gravel

14. Certain soils have unfavorable settling characteristics. Settlement is generally most severe in which of the following materials?

a. clays and loose sands

b. loose gravel

c. compacted gravel

d. compacted sand

15. A soil is to be selected for an airfield base course. What type of soil should you select?

a. a soil which changes little in volume after construction

b. a soil with primarily uniformly- graded material

c. a soil with primarily gap-graded material

d. a soil which has little dry strength

Fourth requirement. Work exercises 16 through 20 to demonstrate your understanding of compaction.

16. Compaction is the process of mechanically densifying a soil by what means?

a. application of static load

b. application of moving loads

c. use of a cone penetrometer

d. use of consolidation techniques

17. At a proposed road site you observe that the topsoil is a well-graded, loose sand. What recommendation would you make concerning economical construction at this site?

a. excavate until bedrock is reached

b. construction here is impractical

c. compact the loose sand

d. lay pavement over the loose sand to minimize settlement

18. Your unit has built an embankment over a soft clay soil. The embankment is of quality fill material and properly compacted. An asphalt-surfaced roadway was then built over the top of the embankment. What might happen to the roadway concerning settlement?

a. the roadway cannot settle because the embankment is properly constructed

b. the roadway may settle because of compression of the clay under the embankment

c. the roadway will not settle because it is well surfaced

d. the roadway may settle because of consolidation within the embankment

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19. You are given the task of assigning compaction equipment to various sections of a road under construction. You can best utilize your steel-wheeled rollers by assigning them to what type of soil? a. gravel such as that produced by a rock crusher b. river run gravel containing considerable fines c. any fine-grained soil d. organic material

20. Your unit is completing compaction operations on a sandy soil which contains a small amount of fine-grained material. What equipment would you recommend for the final compaction operations? a. sheepsfoot rollers b. steel-wheeled others c. crawler-type tractors d. rubber-tired rollers

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LESSON 7 ROADS AND CULVERTS

CREDIT HOURS ______2 TEXT ASSIGNMENT ______Attached memorandum. MATERIALS REQUIRED ______None. LESSON OBJECTIVE ______To provide you with a working knowledge of the construction of expedient roads and culverts.

______

ATTACHED MEMORANDUM

Section I. EXPEDIENT ROAD MATERIALS AND SURFACES

1. INTRODUCTION

Expedient roads are usually constructed as an emergency measure for crossing difficult terrain. The two basic types of expedient roads are hasty and heavy.

2. HASTY ROADS

Hasty roads require the least time to construct. They are generally used to cross a terrain obstacle such as a beach or marsh. Often they will be constructed during darkness, so they must, of necessity, be simple and constructed of light, easily handled materials.

Army track is a portable timber expedient used to pass vehicles over sand or wet ground. It can be constructed as shown in figure 1.

Chespaling mat roads are composed of mats 6 1/2 by 12 feet long. They are made of small saplings wired together to form the mat and are laid as shown in figure 2.

Bamboo mats (fig. 3) are sometimes used for expedient road surfaces. They are especially adaptable for beach roadways and for entrances and exits to fords. The mats should be laid with the long axis of the bamboo perpendicular to the direction of traffic.

Wire mesh expedients may be composed of chicken wire, chain-link fence, and cyclone fence. They are adaptable for use in sand with burlap or similar material underneath. They require a great deal of maintenance and are used only in emergencies.

3. HEAVY ROADS

Heavy roads are generally used because of special ground conditions or lack of standard construction materials. Standard road construction procedures which should be followed whenever possible are as follows:

Clear road location.

Install drainage facilities.

Grade the foundation, crowning it as necessary.

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Lay the expedient material.

Construct one-way roads with turnouts or two-way roads with tracks side by side.

Maintain the road.

Replace expedient roads with more durable roads as soon as possible.

Airfield landing mats are the most commonly used of heavy expedients. They are laid as shown in figure 4.

Plank roads (fig. 5) may be used where lumber is in plentiful supply.

Corduroy construction may be used over muddy terrain when sufficient natural material is available. There are three types of corduroy construction--standard corduroy, corduroy with stringers, and heavy corduroy. The general rule to be followed is, the softer the ground, the heavier the corduroy to be constructed.

Standard corduroy (fig. 6) is the most common corduroy used. It is constructed of 6- to 8-inch logs laid adjacent to each other (butt to tip) across the roadway. Curb logs are laid along the ends and are drift-pinned or wired in place. To provide a smooth surface, brush, twigs, or rubble can be placed in the chinks and covered with dirt or ground (fig. 7). Side ditches and culverts should be constructed as for normal roads.

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7-4

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Corduroy with stringers (fig. 8) provides a more substantial road than standard corduroy. It is made by placing log stringers parallel to the centerline of the road on about 3-foot centers. Corduroy is then spiked or securely fastened to the stringers.

Heavy corduroy is constructed by the use of sleepers on about 4-foot centers under the stringers as shown in figure 9. The road is then constructed as for corduroy with stringers.

Fascine corduroy, another type of heavy road, can be constructed for use in swampy or boggy ground where neither standing timber nor logs are available. They are constructed by bundling secondary growth, brush, or saplings and used as for standard corduroy. De- tails of construction are shown in figure 10.

Plank tread roads can be constructed easily and rapidly. They require less material than plank roads. Construction details are shown in figure 11.

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4. PIONEER ROADS

The expedient roads which have been dis- cussed are often constructed under circumstances which prevent the use of standard methods of construction. Pioneer roads, which are sometimes constructed and used as expedients, are the simplest and least

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expensive types of ordinary roads, but are built by standard methods of construction. They differ from higher type roads mainly in the matter of location and are justifiable by primitive conditions and low service requirements. They should be located so that they can be improved by stages rather than be abandoned for another route.

Section II. CLEARING, GRUBBING, AND STRIPPING

5. LAND CLEARING

Land clearing is a construction operation consisting of clearing a designated area of all trees, brush, other vegetation, and rub- bish; removing surface and embedded boulders; and disposing of the material cleared. Clearing operations may be accomplished with pioneer tools, but normally it is most rapidly and efficiently accomplished with heavy engineer equipment. Excess materials created in the clearing operation may be disposed of by use of waste areas or by burn- ing.

Felling equipment includes handtools, power tools and heavy equipment. In hand clearing, axes, two-man saws, pick mattocks, machetes and brush hooks are used to clear standing timber and brush. Portable chain- saws, electric, pneumatic or gasoline-engine powered, are items of issue. They are used for felling larger trees and cutting logs into shorter lengths which can be manhandled to the disposal area or used for construction.

Heavy equipment used in land clearing includes tracked tractors equipped with bulldozer or land clearing blades, winches, and as expedients, motor graders and scrapers. A tracked tractor equipped with a land clearing blade is 30 to 40 percent more efficient than a bulldozer blade in medium to large trees. The land clearing blade cuts the trees at ground level rather than uprooting them as the bulldozer does. Heavy duty winches can be used to uproot trees and stumps and are especially effective in soft muddy soil where the tree is easily uprooted and the soil is too soft to support a tractor. Motorized graders and towed scrapers can be used in land clearing but their application is limited to clearing grass, weeds, and small brush from the construction site.

The use of fire in clearing is an expedient which will be used only when suitable equipment and personnel are not available for other methods. To minimize detection, fires are not permitted at night unless tactical conditions are favorable and approval has been received from higher headquarters.

Explosives may be used to advantage in felling trees and uprooting stumps. They are most widely used for clearing where terrain prevents the use of other methods.

6. GRUBBING

The use of heavy engineer equipment for grubbing is standard where the terrain permits. Explosives are often used to loosen trees stumps: rooters cut shallow roots and loosen boulders. Scrapers can be effectively used to haul loosened stumps and boulders to a disposal area. Power shovels or front loaders may be used to load stumps and boulders into dump trucks for disposal.

7. STRIPPING

The process of stripping consists of removing and disposing of top soil, sod, and other material not suitable as a subgrade, as a foundation under a fill, or as borrow material. Stripping is done concurrently with clearing and grubbing by use of dozers, scrapers, and power shovels. In an emergency, it is done by hand.

8. SAFETY

Careful consideration must be given to safety of personnel during all clearing, grubbing, and stripping operations.

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9. DISPOSAL AND SALVAGE

Disposal and waste areas should be designated at the start of construction in order to keep the construction area clear for essential operations. Timber useful for logs, piles, and lumber is trimmed and stockpiled for future use in bridges, culverts, and other types of construction. This type of material can be pushed or skidded into a salvage area for later removal to a sawmill. Generally, the material disposed of is pushed or skidded off the construction site and into the sur- rounding timber to speed disposal. The disposal areas should be selected carefully so that the debris is piled where it will not in- terfere with the drainage of the construction site.

Section III. DRAINAGE

10. DRAINAGE FACILITIES

Drainage facilities which are properly planned and constructed are essential to continuous serviceability of roads. The washout or blockage of a single culvert may close a road to traffic at a vital time. In the TO surface ditching is used almost exclusively for drainage.

Continuous emphasis must be placed on construction drainage from the start of any road project in order to prevent construction delays due to ponding of water and sub- sequent subgrade failure. During clearing and grubbing operations, drainage channels must be kept clear and holes and depressions filled and compacted to grade.

Rough crown and grade must be maintained to permit rain water, runoff water, and spring water to move from the construction site.

One of the first steps in construction operations is to provide drainage from the construction site.

Diversion and outfall ditches are used to concentrate surface water into natural channels.

Existing ditches and drainage features are used to the maximum to reduce the work- load.

If the road is to be used for only 1 to 2 weeks, detailed drainage design is not justi- fied. If improvement or expansion is anticipated, great care must be given to design. Drainage problems are greater when all- weather operation is required than when in- termittent use is expected.

The two basic types of drainage are surface and subsurface.

Surface drainage (fig. 12) provides for the collection and removal of water from the surface of roads as well as underdeveloped areas. It also provides for the interception, collection, and removal of surface water flow- ing toward roads from adjacent areas.

Subsurface drainage is designed to inter- cept, collect, and carry ground water away from the base course or subgrade; to lower high water tables; to drain water from pockets or perched water tables; or for a combination of these.

Ditches collect and channel surface runoff and carry it to a convenient disposal area. The two most common types are the V-type and the trapezoidal.

The V-type ditch is the most common type used due to ease of construction and maintenance. A motorized or towed grader is the ideal piece of equipment for use in constructing these ditches. Where the depth of a ditch is fixed and the volume of water is great a trapezoidal ditch of varying width can be used. Graders or towed scrapers with experienced operators can be used to construct these ditches. The shape of the trapezoidal ditch more readily lends itself to use in sandy or easily erodable soil as excess flow

7-10 will cut into the sides and fill in the bottom of "V" ditches. Figure 13 depicts the recommended shapes, side slope ratios, and sizes of ditches for use in TO construction.

11. FUNCTIONS OF DITCHES

Longitudinal side ditches (fig. 12) collect the surface runoff and carry it alongside the road to a disposal area.

Where a relatively large area outside the limits of a construction project drains toward the project, interceptor ditches (fig. 12) may be constructed to prevent water from reaching and eroding cut and fill slopes. They are also used to prevent direct flooding of operational areas.

Wherever possible, diversion or relief ditches should be constructed to move water from collecting channels or ditches into natural drains to be carried away from the construction site.

12. EROSION CONTROL IN DITCHES

When the slope of a ditch is too great it tends to increase the speed of the water, thus eroding the walls or bottom of the ditch.

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The minimum slope for side ditches is set at 0.5% and the maximum desirable slope is 4%. When the ditch slope is between 3% and 5%, checkdams are normally constructed to reduce the speed of the water. Checkdams may be constructed of timber, sandbags, concrete, rock, or similar materials. Height of the checkdam should be at least 12 inches but not more than 36 inches. A notch must be cut with a capacity large enough to discharge anticipated flow to prevent water from cutting around the edges of the checkdam. An apron is normally constructed at the face of the checkdam to prevent erosion. A typical checkdam is shown in figure 14.

Section IV. CULVERTS

13. CULVERT CONSTRUCTION

Culverts are required to:

Cross roads.

Provide ditch relief.

Continue side ditches at intersections of roads and access routes.

Factors to consider in selecting culvert sites are:

Bedding conditions.

Cover.

Jamming by debris and ice.

Quantity of flow.

Culverts are designed to carry the maximum amount of water that is likely to flow in the drainage channel.

14. CULVERT TYPES

The most common material used for culverts in the TO is corrugated metal pipe (CMP); CMP is a standard item of issue in sizes from 12- to 48-inch diameter (in 6-inch increments) and 60- and 70-inch diameters.

Box culverts of timber, logs, or concrete are often used when CMP is not available. Concrete and CMP are seldom used in the construction of expedient roads; however, when they are available, a considerable sav- ing in time can be realized.

Improvised culverts which can be constructed on the site from local materials, or fabricated from materials originally used for other purposes, can save considerable time and transportation. Examples of these expedients are:

Open-top culverts made of logs, sized lumber, or stones.

Sandbags with airfield landing mats.

Petroleum product drums (gasoline, diesel, asphalt) with ends removed and tack welded together.

Note: Extreme care should be used when removings the heads of drums that have been used for petroleum products. Fumes re- drained and there is extreme danger of explosions unless all fumes are removed.

Examples of drum and airfield landing mat and sandbag culverts are shown in figures 15 and 16.

Examples of log and timber box culverts are shown in figures 17 through 22. 7-12

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Open top culverts (fig. 17) are generally used on steep grades where heavy flow is expected down the road surface. When used as ditch-relief culverts they are placed at about 60ù to the centerline of the road.

Empty drum culverts (fig. 15) normally will require a cradle of wood or other stable material as a foundation. In order to increase the load-carrying capacity of these culverts a distributing layer of logs can be placed over the culvert after 12 inches of earth has been placed on top. The logs should be placed parallel to the centerline of the road with the ends resting on undisturbed earth. When logs are not used, a minimum of 3 feet of earth should be used over the culvert.

Culverts constructed of airfield landing mats and sandbags (fig. 16) are easily fabricated and can serve a useful purpose for expedient roads. The mat should be covered with sandbags or a like material to prevent the covering soil from filtering through the openings.

Log box culverts may be constructed with either a square or rectangular section and must be designed to prevent side as well as roof collapse. When the soil beneath the cul-

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vert has low bearing strength, stringers or sleepers should be used as a foundation. Pre- ferred method of construction is as shown in figure 18 with the spreaders and stakes placed inside the logs to provide greater stability. This culvert may be modified by placing the stakes on the outside of the culvert (figs. 19, 20) or by use of sized timber instead of logs.

Timber box culverts can be built with outside bracing or collars, or with internal bracing. Internal bracing should be used whenever possible since collars do not provide the rigidity and strength of internal bracing (figs. 21, 22).

15. HEADWALLS AND WINGWALLS

The reasons for construction of headwalls and wingwalls (figs. 23, 24) are:

Prevent or control erosion.

Guide water into culvert.

Reduce seepage.

Hold ends of culvert in place.

These structures, although necessary, are expensive in time and materials. Thus, on the inlet end the culvert should be extended only so that the minimum length and height of headwall are required.

Generally they can be omitted on the outlet except on steep grades, when they are used to hold the culvert sections in place.

Headwalls should not protrude above grade and should extend at least 2 feet outside the shoulder.

When they are not used, the culvert will be extended at least 2 feet beyond the top of the fill.

They should be constructed of materials as durable as the culvert, but sandbags or rubble can be used in emergency.

16. ALINEMENT AND ELEVATION

Culverts are placed in natural drainage channels (fig. 25) unless this would require an unusually long culvert or produce a sharp bend in the channel on the upstream side.

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Culverts should be installed at a right angle to the centerline of the roadway (fig. 25) wherever possible. On sidehill cuts or steep grades, ditch relief culverts should be installed at an angle of 60ù to the centerline for more direct entrance of water into the culvert.

The elevation at the bottom of the culvert is placed at or below the level of the stream bed. When necessary, the culvert may be placed below the level of the stream bed. Drop inlets may be used for the purpose, but extreme care must be exercised to keep them clean.

EXERCISES

First requirement. Solve multiple-choice exercises 1 through 5 to show what you have learned about expedient road materials and surfaces.

1. Your unit has been assigned the mission of constructing an expedient road in preparation for an impending assault. What are the two basic types of expedient roads?

a. primary and secondary

b. corduroy and chespaling

c. hasty and heavy

d. temporary and operational

2. It will be necessary for your unit to quickly construct a road across a marsh at night. Which of the following will characterize that construction?

a. generally constructed of wire mesh

b. built for extremely short life

c. constructed of light, easily handled materials

d. designed for permanent improvement

3. Your unit is constructing an expedient road in an area where the supply of bamboo is adequate to make bamboo mats. When these mats are used, in what direction should the long axis of the bamboo be laid with respect to the direction of traffic?

a. parallel c. diagonal

b. perpendicular d. interlaced

4. Due to the type terrain to be crossed, your unit has been instructed to construct a corduroy road. What is the general rule for selection of the type corduroy construction required?

a. the softer the ground, the heavier the corduroy

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b. diagonal corduroy is preferred under all conditions

c. the softer the ground, the lighter the corduroy

d. corduroy with stringers is most substantial, thus is best for all uses

5. A corduroy road is to be constructed across swampy terrain. What can be done to provide a smooth surface on this road?

a. lay the logs perpendicular to the direction of traffic

b. lay the logs diagonally across the roadway

c. lay the logs parallel to the direction of traffic

d. fill the chinks with brush, rubble, and earth

Second requirement. Solve multiple-choice exercises 6 through 9 which deal with clearing, grubbing, and stripping.

6. In construction of an expedient road through a timbered area, an excess of brush and waste timber has been accumulated. Of the following, what is considered as an accepted method of disposal of these cleared materials?

a. use waste areas or burn

b. use for fill material in the road

c. push to side of the road

d. use for camouflage of the road

7. It is often necessary to remove major obstacles such as downed timber, boulders, and brush when constructing expedient roads. Which of the following provides the most rapid and efficient means of clearing this excess material?

a. explosives

b. pneumatic and gasoline chain saws

c. heavy engineer equipment

d. handtools

8. Your unit has encountered un- desirable materials such as organic soils, humus, peat, and muck which must be stripped in the process of construction of an expedient road. At what stage of construction should stripping be accomplished?

a. before clearing and grubbing is started

b. concurrently with clearing and grubbing

c. as a last procedure before placing corduroy

d. after the windrows of rock are removed

9. You are told to select an area to dispose of the debris resulting from clearing trees from a roadway under construction. Which of the following is the most important consideration?

a. limit interference with natural drainage

b. create an obstacle at trees line

c. keep piles less than 20 feet high

d. piles should be parallel to roadway

Third requirement. Solve multiple-choice exercises 10 through 15 which emphasize considerations in drainage of expedient roads.

10. Your unit has been trained to recognize that drainage is designed to promote continuous serviceability of roads. What is the distinguishing characteristic of drainage in the TO?

a. underground, closed drains

b. surface ditching

c. riprapping of ditch walls d. bypassing of poorly-drained areas

11. In order to overcome the problems of surface water on roads during

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construction, certain steps should be taken. Which of the following represents one of these steps? a. maintain a rough crown and grade b. provide ditch relief culverts c. locate and drain perched water tables d. provide outfall ditches

12. The problems of drainage, if not properly solved during the initial stages of construction, can cause continuous road failures. What are the two basic types of drainage? a. ditch relief and culvert b. snow and rain runoff c. surface and subsurface d. design storm and average

13. Your unit must construct ditches to remove surface water from its construction site. What are the two most common types of ditches? a. trapezoidal and diversion b. longitudinal and interceptor c. deep "V" and diversion d. "V" and trapezoidal

14. Ditches are not only classified with respect to shape, but also with respect to function. What kind of ditch would you build at some distance from a project in order to prevent water from reaching and eroding cut and fill slopes and also to keep water from the project itself? a. longitudinal side b. diversion c. erosion control d. interceptor

15. Your unit is constructing a road through rough terrain where the drainage ditches have excessively steep slopes. What can you construct to slow the flow of water and reduce erosion in the ditches?

a. diversion canals

b. checkdams

c. ditch relief culverts

d. interceptor ditches

Solve multiple-choice exercises 16 through 20 to show what you have learned about the construction of culverts.

16. Your unit is directed to construct culverts to remove water from a construction site in order to prevent its interference with other construction activities. What is the basic requirement in designing culverts?

a. drainage of the immediate area

b. carrying the maximum amount of water that is likely to flow in the drainage channel

c. placement where the quantity of flow and velocity is the least

d. acceptance of the minimum free flow in a specified channel

17. Your crew is installing open top culverts on steep grades where heavy water flow is expected on the road surface. When used as ditch relief culverts, how are they normally oriented?

a. parallel to the centerline of the road

b. perpendicular to the centerline of the road

c. at about 60ù to the centerline

d. herringbone pattern

18. Your unit is installing expedient culverts made of petroleum product drums. Since they have a low compressive strength, what can be done to increase their load-carrying capacity?

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a. place airfield matting under them b. use stringers and sleepers under them as a foundation c. extend them 3 feet on each side of the road d. place a distributing layer of logs and fill over them

19. Timber box culverts with either internal bracing or with collars may be constructed when sized timbers are available. Why should culverts with internal bracing be used rather than those with collars? a. collars do not provide the rigidity and strength b. excessive lumber is required for the collars c. excessive cutting and fitting is required for the collars d. culverts with internal bracing are more readily transported

20. In order to conserve materials, headwalls may sometimes be omitted on the outlet end of pipe culverts. Why is it necessary that they be used at the outlet on steep grades? a. to prevent erosion back under the culvert b. to hold the culvert sections in place c. to provide an even distribution of water d. to provide durability to the outlet fill

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LESSON 8 MILITARY BRIDGES

CREDIT HOURS ______4 TEXT ASSIGNMENT ______Attached memorandum. MATERIALS REQUIRED ______None. LESSON OBJECTIVE ______To increase your knowledge of military bridges; their uses, capacities, and characteristics.

______

ATTACHED MEMORANDUM

Section I. RECONNAISSANCE AND CLASSIFICATION

1. RECONNAISSANCE

Bridges are categorized for military purposes as either existing civilian type or military type constructed during field operations.

Reconnaissance of existing bridges may be hasty or deliberate depending upon the time and personnel available.

The factors to consider in selecting a bridge site are:

Access roads.

Approach roads.

Character and shape of banks.

Stream flow characteristics.

River bottom conditions.

Availability of construction resources.

Existing natural concealment.

The information needed to plan construction on existing bridges includes:

Type and dimensions of abutments.

Type and dimensions of supports.

Number, type, size, and spacing of stringers.

Type and dimensions of flooring.

Work estimate to restore to original capacity.

Work estimate to strengthen to attain specified capacity.

2. CLASSIFICATION

Before a driver can determine whether or not his vehicle may cross a given bridge, he must know the classification of his vehicle and the classification of the bridge. If the classification of his vehicle is equal to or less than the classification of the bridge, he may cross. Signs on the vehicle and bridge tell him their classification. The driver must also know the height of his vehicle as compared to the overhead clearance of the bridge.

The classification number assigned to a vehicle represents the loading effect of the vehicle on a bridge. The classification number does not represent the actual weight of the vehicle. The bridge classification number represents the safe military loading capacity of the bridge in terms of vehicle classification.

All army vehicles, except those with a gross weight of less than 3 tons, and trailers with a rated payload of 1 1/2 tons or less, are classified. FM 5-36 lists classification numbers for most standard U.S. military vehicles.

Vehicles not listed in FM 5-36 may be given a temporary class by the expedient vehicle classification method as follows:

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Temporary Class (wheeled vehicles) = 0.85 x Gross Weight in tons

Temporary Class (tracked vehicles) = Gross Weight in tons

Example 1. A truck assigned to an engineer float bridge company has a gross weight of 24 tons. What class would you assign to this wheeled vehicle?

Solution: By using the expedient vehicle classification method,

Temporary Class = 0.85 x Gross Weight

= 0.85 x 24

= 20.4, say 21 tons

= 21

A combination vehicle is a vehicle consisting of two or more single vehicles which operate as one unit. If one vehicle is towing another and the distance between them is less than 30 yards, they must be considered as a combination vehicle.

The class of a combination vehicle is obtained as follows:

Add the class of one vehicle to the class of the other. If the sum is more than 60, such sum is the classification of the combination vehicle. If the sum is 60 or less, the classification of the combination vehicle is .9 x the sum.

Example 2. A class 28 tractor is towing a class 20 trailer with a 35-foot chain. What is the class of this combination?

Solution: 28 + 20 = 48 and 48 is less than 60

Combination Class = 0.9 (28 + 20)

= 43.2, say 44

= 44

Bridges may be given a dual classification when the capacity is greater than class 30.

3. MARKING

Bridge classification signs give the bridge class.

The signs in figure 1 give the following information:

Sign (a), shows one-way classification and the minimum sign diameter.

Sign (b), shows classification for a two- lane bridge and the minimum sign diameter; 34 and 48 are, respectively, the vehicle classification limits when vehicles are traveling two ways and one way.

Sign (c), shows one-way classification for wheeled and tracked vehicles.

Sign (d), shows two-lane classification for both wheeled and tracked vehicles.

Sign (e), shows one-way classification with width limitation.

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A special class number represents the load- carrying capacity of a bridge under special crossing conditions. These numbers are not posted on standard bridge marking signs, but on supplementary signs.

A normal crossing is defined as one in which the vehicle class number is equal to or less than the bridge classification number, where vehicles maintain 30-yard gaps, and where speed is restricted to 25 miles per hour.

Special crossings are authorized by the local tactical commander under exceptional operating conditions and are either caution or risk crossings.

Caution crossings permit vehicles to cross whose classification is up to 25 percent above the capacity of the nonstandard bridge.

Risk crossings may be made only on standard prefabricated fixed and floating bridges.

Section II. FIXED BRIDGES

4. INTRODUCTION

In general, the term fixed bridge includes all but floating bridges.

Military bridge construction in a theater of operations normally is limited to temporary and semipermanent structures. A temporary bridge is one designed to meet immediate tactical and supply needs, while a semipermanent one is intended to last at least until the end of hostilities.

Standard fixed bridges are stock items available for issue from U.S. Army supply centers. The remainder of this section is concerned with nonstandard fixed bridges which are constructed from supply system and locally available materials, and designed to meet the requirements of a particular site.

In the construction of temporary and semipermanent military bridges the principal materials used are timber and steel.

Span lengths of timber stringers are limited to 25 feet. Steel stringer spans range from 25 to about 60 feet.

Decks distribute the live load to the stringers. Abutments provide support for the superstructure on the banks of the gap.

Figures 2 through 10 illustrate the various components of nonstandard fixed bridges and their nomenclature.

Nonstandard fixed bridges include:

Timber stringer bridges--used extensively in the theater of operations for short span crossings or a multiple of short spans for longer crossings. The spans are simply supported and rarely exceed 20 feet. The deck normally is either plank or laminated timber decking.

Steel stringer bridges are used in simply supported spans up to 90 feet and in continuous span bridges with clear spans up to 120 feet. Steel stringers consist of either standard rolled shapes or beams built up with welded steel plates.

Other nonstandard fixed bridges encountered in the theater of operations include: reinforced concrete T-beam bridges, composite steel-concrete stinger bridges, steel girder bridges, truss bridges, suspension bridges, and arch

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8-4 bridges. The military does not often construct these types of bridges but may be tasked to repair, reinforce, or classify them.

8-5 5. DESIGN

The design of nonstandard, semipermanent fixed highway bridges is basically a two-phase process. First is the determination of the design loads. Second is the selection of members of sufficient strength to resist the effects of the loads on the bridge.

The dead load is the weight of the bridge itself, to include the weight of the stringers, the deck, and accessories. The accessories include the curb and handrail system, lateral bracing, and hardware and connection materials. The design live load is the maximum vehicle class for which the bridge is designed.

The most economical bridge, considering both materials and construction efforts will normally contain the minimum number of stringers. The maximum center-to-center spacing of stringers in timber-decked bridges is 6 feet; for concrete decks, 8 feet.

The deck system includes the deck, the wearing surface that protects the deck, and the curb and handrail system. The plank deck is the simplest to design and construct, and provides considerable savings in time compared to other types of decking. The minimum thickness of deck is 3 inches in all cases. Plank decking is normally placed perpendicular to the bridge centerline (direction of traffic) for ease and speed of construction.

A better structural arrangement is provided if the decking is placed at a 30-45ù skew to the centerline. A space of about 1/4 inch should be provided between the planks

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to allow for swelling, to provide better water drainage, and to permit air circulation.

When the required thickness of plank decking exceeds 6 inches use a laminated type decking. Normally a thick deck is required for large stringer spacing and the higher design classes. A laminated deck is much stiffer than a plank deck.

6. ABUTMENTS

Fixed bridge abutments include many types. The timber sill abutment can be used to support tion up to 25 feet long. They are used on highway bridges and are not more than 3 feet high.

Timber bent abutments are used with steel or timber stringers on highway bridges with

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spans up to 30 feet. A deadman is used to provide horizontal stability. They do not exceed 6 feet in height.

Timber or steel pile abutments may be used to support spans of any length. They use steel or timber stringers and can reach a maximum height of 10 feet.

Mass or reinforced concrete abutments will also support any span length and may be as high as 20 feet. They are the most permanent type and can support either steel or timber stringers.

7. BENTS AND PIERS

Bents and piers provide support for the superstructure at points in the gap other than the banks. A bent consists of a single row of posts or piles, while a pier consists of two or more rows of posts or piles.

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Spans on pile bents usually can be used economically for crossings of shallow streams, swamps, tidal waters ,and floodways in wide valleys. Pile piers, consisting of two pile bents driven close together and united into a rigid structure by bracing, are most economical for bridges of intermediate height and longer spans across narrow streams and floodways.

Timber crib piers are constructed of logs stacked on each other in log-cabin fashion and filled with rock for ballast if desired. They can support a combined span length of 50 feet and may have a ground to grade height of 12 feet.

Timber trestle bents and piers normally are constructed in dry shallow gaps in which the soil is firm. They are not suitable for use in soft soil or swift or deep streams. The bent can support a combined span length up to 30 feet and can be 12 feet high. The pier can be 18 feet high with a capacity to support a 60-foot combined span length.

A timber pile bent consists of a single row of piles with a pile cap. It should be braced to the next bent or to an abutment in order to reduce the unbraced length and to provide stability. This bent will support a combined span length of 50 feet.

Timber pile piers will support combined span lengths of 200 feet. A steel pile bent will support a 70-foot combined span length, while a steel pile pier will support any span length. In all cases where piles are used, the height of the structure is governed by the unbraced length of the piles.

Concrete piers are normally used in permanent bridges rather than in semipermanent bridges.

8. PANEL BRIDGE, BAILEY TYPE, M2

The Panel Bridge, Bailey type, M2 (fig. 11) is a through-truss bridge supported by two main trusses formed from 10-foot steel panels, called bays. The bridge is used both as a tactical bridge and a line of communications bridge. It is valuable to field com- manders because of its ease of construction, speed of construction, mobility, and versa- tility.

The engineer panel bridge company is the TOE unit designated to carry one bridge set and provide technical personnel and equipment to transport and supervise erection of panel bridging (see table 1). The bridge parts may be transported on twenty-five 5-ton dump trucks and eight pole trailers. The loading plan is based on the experience that the double-single truss assembly provides for most bridging problems which require the panel bridge.

The abbreviated nomenclature of the various types of truss assemblies is given by two letters. The first letter specifies the number of trusses. The second letter specifies the number of stories.

Example 3. What does the abbreviated nomenclature DS describe?

Solution: DS = double-truss, single-story (see table 2).

Trusses may be one, two, or three panels wide and up to three panels high. The only trusses not erected are the single-truss, double- or triple-story because they would be unstable.

When triple-story bridges (double- or triple-truss) are erected with the deck in the bottom story they must be braced at the top by transoms and sway braces.

The class of existing single- and double- truss bridges can be increased by the addition of extra trusses. Construction starts from the center of the bridge, and panels are added toward each end. The class of existing single- story bridges can also be increased by adding extra stories.

The bridge set contains 33 different items of bridge parts and 30 different items of erection equipment which are enough for two 80-foot DS bridges or one 130-foot DD bridge. Each set has 126 panels (weighing 577 pounds each), 56 transoms (618 pounds each), 48 ramps (338 to 349 pounds each), and chess, end posts, bracing, and erection equipment.

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The panel is the basic member of the bridge. Panels are joined end to end by panel pins through the male and female lugs.

The transom supports the floor system of the bridge. They rest on the lower chords of the panels and are held in place by transom clamps.

The raker connects the end of the transom to the top of the panels of the inner truss and prevents the panels from overturning. At each end of the raker is a hollow dowel for the bracing bolts; it fits through a hole in the panel and a hole in the transom.

The bracing frame is used to brace the inner two trusses on each side of the double- and triple-truss bridge. Bracing bolts attach the bracing frames horizontally to the top chords of the bridge and vertically on one end of each panel in the second and third stories. The sway brace is hinged at the center, and adjusted by a turnbuckle. At each end is an eye, through which a pin on a chain is inserted to secure it to the panel. The sway brace is given the proper tension by inserting the tail of an erection wrench in the turnbuckle and screwed up against the turnbuckle. Two sway braces are required in the lower chord of each bay of the bridge and all except the first bay of the launching nose, and in each bay of overhead bracing.

The tie plate is used only in triple-truss bridges; it secures the second truss to the third truss, using the unoccupied raker holes in the panels at each joint and at the ends of the bridge.

Chord bolts join the panels one above the other to form double- and triple-story bridges. Two bolts per panel pass upward through holes in the chords of the panels and are tightened with nuts on the lower chord of the upper story. They are also used to fasten overhead bracing supports to the top panel chord.

Stringers carry the roadway of the bridge. There are two types of stringers: plain stringers weighing 260 pounds, and button stringers weighing 267 pounds. They are identical except that the latter has 12 buttons which hold the ends of the chess in place. Each bay of the bridge has six stringers: four plain stringers in the middle, and a button stringer on each side. The stringers are positioned by the lugs on the top of the transoms.

Chess form the road surface. Each bay of the bridge contains 13 chess, which lie across the stringers and are held in place by the buttons on the stringers. Chess are held down by ribands. The steel riband (guard rail) is fastened to the button stringer by four J-type riband bolts. The clear roadway between ribands is 12 feet 6 inches.

The riband bolt fastens the riband to the button stringers and ramps. The hook end of the bolt grips the lower flange of the outer I-beam of the button stringer or ramp.

End posts are used on both ends of each truss of the bridge to take the vertical shear. They are placed only on the story carrying the decking. They are 5 foot 8 inch columns made of two 4-inch channels and plates welded together. There are two types, male and female, having male and female lugs, respectively. These lugs are secured to the end panels of the bridge by panel pins through holes in the lugs. The male and female end posts weigh 121 and 130 pounds, respectively. End posts have a step to support a transom outside the panel at one end of the bridge. In jacking the bridge, the jack is placed under the step. The lower end of the end post has a half-round bearing block which fits over the bearing.

The bearing spreads the load of the bridge to the base plate. A bearing is a welded steel assembly containing a round bar which, when the bridge is completed, supports the bearing blocks of the end posts. During assembly of the bridge, it supports the bearing block of the rocking roller. The bar is divided into three parts by two intermediate sections that act as stiffeners.

The base plate is a welded steel assembly with built-up sides and lifting-hook eyes on the top at each corner. It is used under the bearings to spread the load from the bearings

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over the ground or grillage. The area of the bottom surface of the base plate is 13 V2 square feet. The base plate weighs 381 pounds and is large enough for the bearings at one corner of a single-, double-, or triple- truss bridge. Bearings can slide 9 inches longitudinally on the base plate. The numbers 1, 2, and 3 are embossed on the edges of the base plate to indicate the position of the plate under the inner truss of single-, double-, and triple-truss bridges respectively.

Ramps are similar to stringers, but consist of three 5-inch, instead of 4-inch, steel I- beams. They are 10 feet long and are joined by welded braces. The lower surface of the ramp tapers upward near the ends. There are 2 types of ramps: plain ramps weighing 338 pounds, and button ramps weighing 349 pounds. They are identical except the latter has 12 buttons which hold the ends of the chess in place.

Four plain and two button ramps are used as continuations of the stringers and lead from the bridge to the banks. If the slope is too steep, ramps are joined end to end on transoms supported by ramp pedestals. This type of ramp construction is continued as far as required to provide the slope called for by the class of expected traffic. For loads of 45 tons or over, the ramps are supported at their midpoints by timber cribbing and wedges. The ends of the ramps fit into lugs on the transoms at the ends of the bridge.

Ramp pedestals are built-up welded steel assemblies weighing 93 pounds. They prevent the transoms supporting multiple- length ramps from overturning and spreading the transom load over the ground. They are held in place by spikes or pickets driven through holes in their base plates.

Supported on footwalk bearers, footwalks are laid along the outer sides of the bridge for use by foot troops. Footwalks are constructed of wood.

Footwalk bearers are attached to all transoms except reinforcing transoms, fitting over and under special lugs welded to the web near the ends of the transom. The footwalk fits between lugs on top of the bearers. A socket at the end of the bearer holds the footwalk post. A footwalk post is fitted into every footwalk bearer.

Hand ropes are threaded through two eyes on each post and secured either to holdfasts on the banks or to the end footwalk posts. The overhead bracing support is used to clamp overhead transoms and sway braces to trusses for overhead bracing of triple-story bridges. The frame is a welded metal assembly that weighs 150 pounds. It is fastened to the tops of third story panels by means of chord bolts. A transom is seated over the pintles on top of the frame and secured by cleats over the lower flange held by 4 nuts and bolts.

A skeleton launching nose is employed in launching the bridge. The bridge is assembled on rollers on one bank and then pushed across the gap utilizing the cantilever method. This method keeps enough weight behind the rollers to balance the bridge and prevent its tipping into the gap.

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Section III. FLOATING BRIDGE EQUIPMENT

9. LIGHT STREAM-CROSSING EQUIPMENT

The aluminum floating footbridge (fig. 12) provides a standard means of crossing foot troops rapidly. The footbridge set furnishes 472 feet 6 inches of bridge, and can be used in currents up to 11 feet per second.

One bay of bridge which provides 11 feet 3 inches of bridging, consists of one ponton, one treadway, and four handrail posts. The bridge is erected by succes- sively connecting individual bays to the near shore end and pushing the entire bridge toward the far shore.

Capacity, in men per minute with a current velocity up to 8 feet per second, is: day--75; moonlight--40; blackout-- 25. This is based on troops crossing single file at a 2-pace interval in daylight and moonlight at double time. Reduce the capacities by 20 percent in currents of 9-11 fps.

Normally, one-half the quantity of each component of the set is carried on a combination vehicle consisting of a 2 1/2-ton cargo truck towing a 2 1/2-ton utility pole type or 4-ton bolster type trailer. The bridge set can also be carried on three 2 1/2-ton cargo trucks, each carrying one- third of the major components. One complete set of aluminum footbridge is air transportable in one C-130 airplane.

Guy lines are needed in any current velocity to maintain alinement of the bridge because the treadway joint provides little lateral strength.

Assembly of the bridge begins on the near shore by laying a treadway across two pontons (forming an H-bay) 80 that the small lugs beneath the stringer at each end of the treadway fall inside the gunwales of the pontons.

Then, the two spring-actuated retainers on the downstream side of the ponton are flipped into position to hold the downstream side of the treadway in place.

Each bay following the first bay, an H-bay, is in the shape of a T with the tail of the T pointing inshore.

Each ponton has two holes (1 inch x 2 inch), one in the bow and one in the stern, just above the false bottom to make the ponton self-bailing.

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The light tactical raft (fig. 13) can be used to assemble either rafts or floating bridges. Both raft and bridge consist of a deck built of aluminum sections supported on aluminum pontons.

With a trained crew, during daylight hours, and in still water, this bridge can be hand erected at a rate of 3 1/2 feet per minute. Time and manpower required for assembly of light tactical rafts:

Four-ponton, three-bay = 3 NCO 27 EM @ 30 minutes

Five-ponton, five-bay = 3 NCO 27 EM @ 35 minutes

Six-ponton, four-bay = 3 NCO 27 EM @ 45 minutes

Each bay provides 11 feet of bridging with a deck width of 9 feet.

This equipment is issued as a light tactical raft set. The light tactical raft components normally are transported on two 2 1/2-ton cargo trucks and one 2 1/2-ton pole type or 4-ton bolster type trailer.

The raft is assembled with overhanging ramps. Articulated panels can be installed in the ramps if the site requires changes in ramp elevation.

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10. HEAVY STREAM-CROSSING EQUIPMENT

This type of equipment is used when vehicles and other heavy equipment must cross a stream.

The class 60 floating bridge (fig. 14) bay consists of two steel deck-tread panels, two curbs, and one filler panel with an effective bridging length of 15 feet and a roadway width of 166 inches. The floating support for one bay consists of two 24-ton pneumatic floats spaced 15 feet center-to-center.

The deck panels are pinned together end- to-end to provide rigid connections. The deck has the stiffness to transmit the load of class 65 vehicle to approximately 10 floats, with only minor deflection.

The standard bridge set contains components for the complete assembly of one floating bridge 135 feet long. This does not include the length of the 16 foot tapered ramp used at each shore connection or the length of two short (5 ft) bays of superstructure by which the length of shore connections can be increased.

The number of rafts which can be assembled from the set is limited to one because the raft requires the use of the two ramp bays in the set.

The superstructure bay is assembled from two deck-tread panels, one deck- filler panel, and two curbs. One ramp bay is used in each shore connection. It is assembled from two ramp-tread panels, one ramp-filler panel, and four short deck curbs.

Ramp stiffeners are issued as a part of the bridge set. They are needed when abutment conditions are likely to bring about a major difference in settlement between two adjacent deck panels. Once used, the stiffener assembly usually cannot be reused because the members bend with use of the bridge.

Usually, one 6-by-6 military bridge truck carries a complete 15-foot bay of bridge, including a 24-ton float, saddle assembly, and deck components. The bridge set is a part of the equipment of the Engineer Float Bridge Company. This unit is equipped with two truck-mounted crane- shovel units, 20-ton 3/4-cubic yard, gasoline-driven which are used in the assembly of the bridge. Air compressors are required to inflate the pneumatic floats.

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The M4T6 floating bridge (fig. 15 ) is a hand erected high capacity bridge. It is built by combining the deck balk from the M4 floating bridge and the pneumatic floats from the Class 60 floating bridge. These components are combined through the use of deck balk connecting stiffeners and saddle adapters. An air compressor is required for assembly. The saddle assembly for a float includes eight interior and two end saddle panels, and two saddle beams. The deck forms a continuous beam action over the pontons and provides an effective bridging length of 15 feet per bay with a roadway width of 166 inches.

One M4T6 bridge set can be used to construct one 141-foot 8-inch floating bridge or one 4-float and one 5-float reinforced raft.

The pneumatic float consists of 2 identical half-floats, each 9 by 22 feet, joined stern-to-stern to form a complete float 9 feet wide, 44 feet long, 3 feet high. Each half-float is made up of three tubes laced together longitudinally. Each tube is divided into four inflation chambers, fitted with a valve. The half-float weighs 750 pounds.

Three types of aluminum deck balk are used in the bridge: normal, short, and tapered. The balk are watertight and will float. The components of the bridge can be carried on any standard military cargo truck or trailer having a rated capacity of 2 1/2 tons or more. Handrail posts are metal rods 3 feet 3 inches long used to mark the roadway of bridges.

Standard kedge anchors weighing 100 pounds are used for anchoring the bridge when stream conditions permit. Pre- fabricated holdfasts for use with the anchorage system are issued with the bridge set. Nine steel pickets and a length of chain constitute each holdfast.

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The M4T6 floating bridge is class 50 for normal crossings in currents up to 3 feet per second.

The rafts normally assembled from the bridge set are -- 4-float normal raft, 4-float reinforced raft, and the 5-foot reinforced raft.

To increase bridge capacity, reinforced floating sections are constructed by placing the floats closer together than for normal construction and using offset saddle adapters.

Four deflated air rollers are positioned at the launching site 80 that two half- floats are unloaded from the truck onto them.

After the floats are completely assembled and ready for launching, the air rollers beneath them are then inflated and the float assembly is launched.

After the launching, the float inflating crew retrieves the air rollers. The rollers are repositioned, and their valves opened allowing them to deflate.

Section IV. ANCHORAGES, BOATS, REINFORCEMENT AND REPAIR

11. ANCHORAGES FOR FLOATING BRIDGES

Shore guys are used primarily to hold the bridge during assembly. If the current does not exceed 3 feet per second, shore guys are used as a primary anchorage.

Kedge anchors lie in the stream bed and are secured to the bays or rafts with anchor lines. The kedge anchor depends on the stream bed for holding power, and is useful only when the bed is composed of sand, silt, loose rock, or other material into which the fluke can take hold.

Combinations of kedge anchors and shore guys may be used in stream velocities of 5 feet per second or less.

Overhead cable systems consist of one or more tower-supported cables spanning the river parallel to the bridge on the upstream side. Bridle lines are used to make the bridge secure to the cable.

Deadmen are used at each end of the bridge to anchor the main cables.

12. BOATS

The pneumatic assault boat is made of nylon fabric with a capacity of 15 men with equipment. It has 10 separate air compart- ments and weighs approximately 250 pounds.

The 27-foot bridge erection boat is gasoline powered aluminum, twin-screw, 2-section aluminum-alloy hull boat. It is used to propel the heaviest types of rafts assembled from floating bridge sets. The boat is powered by two separately controlled, 6-cylinder, 90- horsepower marine type gasoline engines. When carrying cargo, the maximum allowable load is 3,000 pounds.

The latest version of the bridge erection boat, referred to as Bridge Erection Boat, Shallow Draft (BEB-SD), is an easily transported, hydrojet propelled, shallow draft, aluminum hulled boat designed to maneuver components of floating bridges. The boat can also

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be used to propel rafts, support diving operations, assist in maritime construction projects, serve as a troop and cargo carrier, and patrol inland waters. The boat is powered by two 6 cylinder, 212 horsepower water cooled diesel engines, which will provide an unloaded top speed of 21.6 mph, and a fully loaded (4400 lbs) speed of 16.2 mph.

13. REINFORCEMENT AND REPAIR

Existing timber floors may be reinforced by adding an additional layer of decking and tread.

Stone masonry bridges can be patched up with concrete. Cracks can be repaired by banding the structure with steel straps or beams which are pulled tight in a direction tending to close the crack.

Knee-braces, A-frames, and king or queen trusses can be used to provide additional support for stringers.

Steel floorbeams may be reinforced by welding plates to the top and bottom flanges, provided the two flanges can be exposed.

The reinforcing of trusses by adding intermediate supports is the simplest and most effective means of strengthening. When steel truss members have been damaged by bending or twisting, it is best to replace them by new fabricated sections identical to the original parts.

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EXERCISES

First requirement. Multiple-choice exercises 1 through 8 provide an opportunity for you to test your knowledge of preliminary in- vestigations, classification, and marking of military bridges.

1. Many factors must be considered in selecting a site for bridge construction. Which of the following characteristics would you consider in the selection of a site?

a. type of bridge supports

b. character and shape of banks

c. dimensions of supports

d. spacing of stringers

2. You have received information about the condition of an existing bridge which was gathered during a recent reconnaissance. Which of the choices given would you use in planning for construction on an existing bridge?

a. stream flow characteristics

b. river bottom condition

c. dimensions of abutments

d. existing natural concealment

3. You are driving a 5-ton truck and approach a timber trestle bridge. The bridge class posted on a sign near the bridge is larger than the classification number assigned to your vehicle so you may cross. What does the vehicle classification represent?

a. loading effect on a bridge

b. weight distribution of the vehicle

c. gross weight of the vehicle

d. weight of the maximum load

4. Vehicles not listed in FM 5-36 may be given a temporary class by the expedient vehicle classification method. A wheeled vehicle has a gross weight of 20 tons. What is its temporary class? a. 11 c. 15 b. 13 d. 17

5. You are driving a vehicle of class 40 which is towing another vehicle of class 19. If the distance between them is 29 yards, what is the combination class? a. 44 c. 54 b. 49 d. 59

6. You are in charge of four vehicles and must cross a bridge with the classification as depicted in figure 16. Which of your vehicles must cross when there is no oncoming traffic on the bridge? a. tank (class 24) b. grader (class 26) c. dozer (class 27) d. tractor-trailer (class 29)

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7. In a normal crossing the vehicle©s class number is equal to or less than the bridge classification number and the vehicles maintain 30-yard gaps. What is the maximum speed in miles per hour you are restricted to in a normal crossing?

a. 10 c. 20

b. 15 d. 25

8. The second bridge your small convoy encounters is a one-lane, class 20, timber trestle bridge which spans a gap of 29 feet. Which of your vehicles is the largest that can use this bridge in a caution crossing?

a. tank (class 24)

b. grader (class 26)

c. dozer (class 27)

d. tractor-trailer (class 29)

Second requirement. Solve multiple-choice exercises 9 through 19 to show what you have learned about fixed bridges.

9. You are assisting in planning the construction of a timber trestle bridge. What is the limit, in feet, for span lengths of timber stringers?

a. 20 c. 30

b. 25 d. 35

10. The deck system on a bridge includes the deck, the wearing surface that protects the deck, and the curb handrail system. What is the main purpose of the deck?

a. provides a smooth surface for traffic

b. protects the stringers from wear and tear

c. adds strength to the superstructure d. distributes the live load to the stringers

11. You are designing a nonstandard, semipermanent fixed highway bridge as basically a two-phase process. Determination of the design loads was the first phase. What would be the second? a. selection of members b. determining the bridge class c. selection of crews d. establishing a centerline

12. You have ascertained that the most economical bridge contains the minimum number of stringers. What is the maximum center-to-center spacing of stringers you could use in timber- decked bridges in feet? a. 4 c. 6 b. 5 d. 7

13. You are placing plank decking perpendicular to the bridge centerline. What is the minimum required thickness of all decking, in inches? a. 2 c. 4 b. 3 d. 5

14. You have decided to use a laminated deck because it is much stiffer than a plank deck. Laminated decking is used when the plank decking required exceeds how many inches? a. 6 c. 8 b. 7 d. 9

15. After studying several sites for a new bridge, you recommend to your platoon sergeant the site where a pile abutment could be constructed at one end. What is the maximum height, in feet, to which a timber or steel pile abutment could be constructed? a. 4 c. 8 b. 6 d. 10

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16. At the other end of the bridge you recommend a timber bent abutment. What is the maximum span length, in feet, which a timber bent abutment will support?

a. 25 c. 35

b. 30 d. 40

17. The timber crib piers you constructed of logs stacked on each other in log-cabin fashion and can support a combined span length of 50 feet. What is their maximum ground to grade height, in feet?

a. 8 c. 12

b. 10 d. 14

18. Timber trestle bents and piers can only be used when certain favorable conditions exist. Under which of the following conditions might you choose to use a timber trestle bent?

a. soft soil c. deep stream

b. swift stream d. firm soil

19. A steel pile bent will support a 70-foot combined span length, while a steel pile pier will support any length. What factor governs the height of these structures?

a. unbraced length of the piles

b. velocity of stream

c. maximum span length supported

d. dead load of superstructure

Third requirement. Multiple-choice exercises 20 through 22 relate to the panel bridge, Bailey type.

20. Your unit has built a Bailey bridge which is a through-truss bridge used both as a tactical and a line of communications bridge. The bridge is described as being two stories high with three trusses. What is the abbreviated nomenclature for this assembly?

a. DT c. DD

b. TS d. TD

21. Your company has the mission to erect a 130-foot DD bridge from one bridge set. Your squad is to install the ribands. What is the clear roadway, in feet, between the ribands?

a. 8.6 c. 12.5

b. 11.0 d. 15.0

22. Your platoon has assembled a Bailey bridge on rollers and pushed it across the gap, with enough weight kept behind the rollers to balance the bridge and prevent its tipping into the gap. What is this method of launching called?

a. cantilever c. flotation

b. cableway d. crane

Fourth requirement. Solve multiple-choice exercises 23 through 35 to test your understanding of floating bridge equipment.

23. Your squad has assembled 8 interior and 2 end saddle panels, and 2 saddle beams. What is this configura- tion called?

a. substructure assembly

b. saddle adapted assembly

c. saddle assembly

d. reinforced float assembly

24. The capacity of the footbridge is normally dependent on the stream velocity and the degree of visibility. What is the footbridge capacity, in men per minute, in a stream velocity of 7 feet per second during daylight hours?

a. 55 c. 85

b. 75 d. 95

25. You can use the light tactical raft as both a raft and a floating bridge. At what rate, in feet per minute, can

8-22 this bridge be erected by a trained crew? a. 3.5 c. 6.5 b. 5.0 d. 8.0

26. Your unit has erected a light tactical raft (LTR). Each bay of the LTR provides 11 feet of bridging. How wide is the deck of this bridge, in feet? a. 6 c. 8 b. 7 d. 9

27. The class 60 floating bridge bay has an effective length of 15 feet. How many feet of bridge can you erect with one set? a. 110 c. 150 b. 135 d. 175

28. Only one raft can be assembled from the class 60 bridge set. What is the reason for this? a. superstructure bay requires two curbs b. bridge bay requires two deck-tread panels c. raft requires two ramp bays d. each shore connection requires a tapered ramp

29. Ramp stiffeners are issued as a part of the class 60 bridge set. For what purpose would you use them? a. prevent different settlement in adjacent panels b. increase the capacity of the superstructure c. prevent the collapse of inflated pneumatic float d. increase the strength of the aluminum pontons

30. The M4T6 floating bridge is built by combining deck balk from the M4 floating bridge with pneumatic floats from the Class 60 floating bridge. Which of the following equipment do you use to combine these components?

a. filler panel

b. saddle adapters

c. tapered ramps

d. short bays

31. The M4T6 floating bridge has a roadway width of 166 inches. How many feet of bridge can you erect with one set?

a. 114.40 c. 134.40

b. 121.66 d. 141.66

32. The M4T6 bridge components are carried on standard military cargo trucks. What is the minimum rated capacity, in tons, of the trucks that you can use for this purpose?

a. 3/4 c. 5

b. 2 1/2 d. 10

33. It is important for you to take into account the velocity of the stream in determining the class of floating bridges. What class M4T6 floating bridge would you assign for normal crossings in currents up to 3 feet per second?

a. 30 c. 50

b. 40 d. 60

Fifth requirement. Multiple-choice exercises 34 through 38 deal with anchorages, boats, and reinforcement and repair of bridges.

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34. Shore guys are used primarily to hold the bridge during assembly. What is the maximum stream velocity, in feet per second, which limits the use of shore guys as primary anchorage? a. 3 c. 7 b. 5 d. 9

35. You have used a combination of kedge anchors and shore guys in a stream with velocities up to 5 feet per second. What does the kedge anchor depend on for holding power? a. anchor cable c. deadman b. bridle lines d. stream bed

36. Boats are used in the theater of operations to assemble floating bridges, to propel tactical rafts, to help with general utility work, and to cross troops. Which of the following boats carries the fewest personnel? a. 19-foot bridge erection boat b. M2 assault boat c. 16-foot plastic assault boat d. pneumatic assault boat

37. It is sometimes necessary to reinforce existing structures. You would use knee-braces, A-frames, and king or queen trusses to reinforce which bridge members? a. floors c. posts b. piers d. stringers

38. Adding intermediate supports is the simplest and most effective means of strengthening trusses. What is the best procedure when steel truss members have been bent or twisted? a. welding c. replacing b. banding d. reinforcing

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LESSON 9 Expedient Stream Crossings

CREDIT HOURS______2 TEXT ASSIGNMENT______Attached memorandum. MATERIALS REQUIRED ______None. LESSON OBJECTIVE ______To provide you with a working knowledge of expedient river crossing devices to include the use and assembly of expedients from materials available through normal supply channels and native materials available at or near the site.

______

ATTACHED MEMORANDUM

Section I. GENERAL

1. INTRODUCTION

Expedient stream crossings are stream crossings made when time is a limiting factor, and serviceable bridges and standard raft materials are not available.

The tactical situation will normally be the factor which will determine the urgency of the stream crossing, and therefore the simplicity or complexity of the method chosen.

This lesson will illustrate several expedient methods that may be used for stream crossings. Many other methods may be developed, depending upon imagination and ingenuity.

2. DETOURS

When a stream must be crossed and an existing bridge at the intended crossing site has been damaged beyond serviceability, you should first investigate the possibility of a detour.

In determining whether to use a detour, or alternate route, you must consider whether it is available immediately or only after some delay, how much more travel time is involved, how much labor will be saved, and how much exposure there may be to enemy action.

3. EMERGENCY REPAIRS

If a damaged bridge exists, and there is no suitable detour available, consideration should be given to the possibility of making emergency repairs to the bridge and utilizing any part of the existing structure which may be useable. This may frequently turn out to be the most expedient means of crossing a stream. Before attempting such repair, consideration must be given to the following:

Type of bridge.

Nature of damage.

Tactical situation and bridge requirements.

Nature of surroundings and possible by- passes.

Troops and equipment available.

Materials available.

Time required for bridge repair versus time required to detour or construct bypass.

Standard tactical bridging units are generally well suited to emergency repair of damaged existing bridges. However, it is 9-1 not within the scope of this lesson to go into the use of standard bridging materials. TM 5-312 includes methods for repair of damaged bridges using standard bridging materials.

Following are listed some of the more common materials and methods used in repair of damaged bridges:

Standard dressed lumber is a stock item and therefore available under most circumstances. It is very flexible in use and can be built up to carry any weight classification desired.

Repair by means of log construction in- volves more time and effort, but will provide an effective repair job if accomplished properly. Native logs may be available when other materials are not.

You may also use earth or rock fill to build up damaged parts of most bridges, especially over waterways of low velocity. Except in extreme emergencies, provisions should be made for the passage of any water that may be dammed up by such a structure. If the proper equipment and personnel are available, this method may prove to be rapid, especially where low structures are involved.

4. FORDS

The word ford, as applied to an expedient stream crossing, is a shallow place in a stream where troops can cross by wading or driving vehicles (fig. 1).

9-2

The most important characteristics of a good ford site are a slow current (not over 3 feet per second); an even, hard, and tenacious bottom; a stream not subject to rapid flooding, and approaches which slope gently and provide good traction for both vehicles and foot troops.

Ford sites will rarely be found in such condition that they can be used without improvement. If the stream bottom is not firm or level enough, it may be built up with rock or gravel, sandbags, mats, or other materials which will not float. The approaches should be stabilized so they will not become slippery from rain, snow, or water dripping off vehicles.

Approaches and ford edges should be marked and one or more marking posts should be gaged to indicate changes in water depth. An increase in depth due to flash floods may cause a ford to be unreliable.

Minimum requirements for military fords are given in table 1.

5. DIPS

Dips are paved fords used for crossings of wide shallow arroyos or washes in semiarid regions subject to flash floods and in other locations where the construction of a bridge is impractical.

The pavement should be protected on its upstream side by a cutoff wall, and on its downstream side by an apron.

An apron may also be provided on the upstream side to prevent erosion.

The pavement may be macadam, concrete, or timber. The cutoff wall should extend 18 to 24 inches below the paved surface.

Riprapping, rubble masonry, concrete, timbers, or logs may be used for the surfacing of the aprons. Protection should be carried well away from the roadway edges.

Culverts should be constructed to take the normal flow of the stream.

In areas where the stream channel normally is dry, the dip should be constructed about 6 inches below the bed of the channel. This procedure will minimize scour, and the soil deposited during flood time can be easily removed.

Alinement should be straight and the pavement location should be shown by two marking posts at each end and by as many intermediate posts as necessary. One or more of the posts should be gaged to indicate the depth of water during floods.

6. CULVERTED CAUSEWAYS

Causeways provide a dry crossing. Cor- rugated metal pipe (fig. 2) or 55-gallon drums are placed in the streambed on a cushion

9-3 layer of sand or sandbags. Additional sandbags are placed between successive rows of culverts to keep them in place. Then, a layer of sand or sandbags is added to prevent the culvert from crushing. Finally, a surface layer of gravel, sand or sandbags is placed to form the roadway. The built-up crossing should be rocked in on both the upstream and downstream sides to prevent washing and scouring.

7. SWIMMING AIDS

If you are unable to swim, almost anything that floats can be used as an aid in crossing a stream.

Two gas cans lashed together will support about 60 pounds and provide a very serviceable set of water wings.

A quickly improvised swimming aid can be made from your trousers.

First be sure they are wet, then knot each leg and button the fly.

Next, grasp the waistband on each side and swing the trousers over your head from back to front bringing the waistband down hard on the water so as to trap as much air as possible in each leg.

The trousers then will form water wings (fig. 3). The length of time they will remain serviceable depends upon the type and condition of the trousers.

8. ICE CROSSINGS

Crossings can be made over bodies of water in areas where the temperature has been below freezing for sufficient time to form an adequate thickness of ice.

Table 2 gives required thicknesses of ice for several different loads. These loads apply at the interior portions of the ice slab.

Ice conditions adjacent to the shore line may be different due to the nature of the bank and rising or lowering of the water

9-4 level due to tidal action or change in volume of flow.

Section II. RAFTS

9. INTRODUCTION

Rafts provide a very flexible method for expedient stream crossings. The following will illustrate a number of methods of constructing light, expedient rafts and stream crossing devices from materials normally on hand or readily available.

Empty containers such as 55-gallon drums, gasoline and water cans, ammunition boxes, and inner tubes are suitable for providing support for rafts, and are normally available.

If tops or caps are available which can be fastened down tightly, they become closed type contains. Without the lid or top, they are open type containers.

The closed type container will give its maximum support even when submerged, whereas the open type gives no support when submerged.

10. DETERMINING RAFT CAPACITY

When used as closed containers, a 55-gallon drum will provide approximately 440 pounds of flotation support, and a five-gallon gasoline or water can will provide approximately 30 pounds of flotation support.

Therefore, if a raft is made up of 55 gallon drums or 5-gallon cans, it is only necessary to multiply the number of containers by the support capacity of the types container used, to get an approximation of the raft capacity.

If ammunition boxes or other containers are used, it is first necessary to determine the volume of the container in cubic feet, then

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multiply that figure by 60. The capacity of such a raft can be found by using the following formula:

Capacity (lb) = (60 x container volume in cu ft x number of containers) - (weight of raft in lb)

Example 1. A raft is constructed using six containers, each having a capacity of two cubic feet. The total weight of the raft is 300 pounds. What is the capacity of the raft in pounds?

Solution: Apply the formula given above:

Capacity (lb) = (60 x 6 x 2) -

300 = 720 - 300 = 420 lb

11. USE OF 55-GALLON DRUMS

Fifty-five gallon drums may be bound together to form a raft to carry personnel and/ or equipment across a water gap. Planks or logs could serve as a decking for this raft. The drum can also be lashed to the sides of light vehicles and used as a floating support to transport vehicles across a stream (figs. 4 and 5).

12. USE OF GASOLINE OR WATER CANS

Empty gas or water cans can be used as an effective light raft. Six gas cans lashed together will provide a serviceable light raft to transport personnel and equipment.

The equipment may be placed on top of the raft, with men holding onto the raft with one hand and paddling with the other to propel the raft across the stream (fig. 6).

9-6 13. PERSONNEL RAFTS

A float to cross two riflemen©s individual equipment can be made by laying all the equipment on two shelter halves placed one on the top of the other. The rifles with scab- barded bayonets fixed should be crossed and placed on top of the equipment. The outer shelter half corners should be fastened to the scabbards and butts by tent rope. A light machine gun can be crossed in the same manner by using shelter tent poles instead of rifles.

The Australian poncho raft can be built very rapidly from individual equipment of two men. When completed the raft is capable of supporting an 80 pound load.

Construction is started by taking the draw- string from a poncho, twisting the hood and tying it into a gooseneck . Then lay one poncho out on the ground.

Place weapons (or sticks if you want to keep the weapons out) about 18 inches apart and centered on the poncho with the barrels going in opposite directions (the barrel should be covered with a pair of socks) and the receiver down and toward the inside. Place combat packs on each end between the rifles, with hel- met and liner on top of the pack. Cloth- ing, boots, canteens, etc., are then placed between the two packs.

Bring the sides of the poncho up and snap all snaps. Start rolling a tight roll until poncho is wrapped tightly around equipment. Take each end of poncho, twist them tight, bring the two ends up over the top and tie them together using a boot lace. Lay out the second poncho and repeat the procedure used in the first roll.

Next, take the two remaining boot laces and tie them around the center of the raft to give it more stability (fig. 7).

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This raft will allow one swimmer to transport two swimmers, or two non- swimmers may cross a stream by joining arms over the raft and paddling with the free hand.

A machine gun can be placed inside a single raft and floated with negligible wetting. A mortar squad of five men can, with its individual equipment, float the 81 mm mortar and allied equipment.

Two rafts are constructed from the equipment of four men. The fifth man can build a raft using his own equipment or can distribute his equipment within the other rafts.

Brush rafts can be made by binding brush into bundles about 18 inches in diameter and placing the bundles on canvas. The sides and ends of the canvas are wrapped over the bundles and secured with rope (fig. 8).

Four infantrymen with equipment can be carried on a brush raft using a 1/2-ton truck cover tarpaulin, forming a bundle 5© x 6 1/2© x 1©.

Six infantrymen and equipment can be carried by using a 1 1/2-ton truck cover tarpaulin, forming a bundle 6© x 9© x 1 1/2©, and up to 3,000 pounds can be carried by using a 2 1/2- ton truck cover, forming a bundle 8© x 9© x 1 1/2©.

14. VEHICLE RAFTS

A 1/4-ton truck can be crossed by using the 2 1/2-ton truck cover.

The truck is driven onto the cover at the water©s edge; the front and rear edges of the cover are raised and fastened to the truck. The sides of the cover are then raised and draw ropes are tightened around the truck. The truck is then slid into the water.

Propulsion can be obtained by towing, pol- ing, paddling or pushing. When there is a noticeable current, a frame made from saplings and placed at the base of the vehicle will provide better balance and should be used. Failure to do this may cause the vehicle to roll over (fig. 9).

The 20 x 40 foot canvas tarpaulin will float a loaded 1/2-ton or 3/4-ton weapons carrier, an unloaded 1 1/2-ton or a 2 1/2-ton truck. This raft as with all canvas rafts should be used only on a site that is free of stumps, rocks, roots, etc., and where the water is deep enough to float the vehicle.

Empty vehicles usually float with the water line just below the top of the fender.

The canvas tarpaulin is spread at the water©s edge and then dragged over the water, leaving a few feet around the tarpaulin to hold the edges clear of the water. With the front drive disengaged the truck is driven onto the tarpaulin. The tarpaulin is then folded and fastened to the vehicle. The truck is then pushed out until it floats.

Propulsion is provided by towing, pushing, or paddling.

15. LOG RAFT

Log rafts can be constructed with or without the use of rope or wire lashing. When lashing is used rather than notching much time can be saved.

Dry logs of any type will make a serviceable raft. Bamboo also makes a fine raft, especially when there is no rope or other lashing available to bind the raft. The only tools required are an axe and knife.

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Build the raft on two skid logs placed so they slope downward to the bank. Smooth the logs with an axe so the raft logs lay evenly on them. Cut four offset, inverted notches; one on the top and bottom of both ends of each log. Make notches broader at the base than at the outer edge of the log.

To bind the raft together, drive through each notch a three-sided, wooden cross- piece about a foot longer than the width of the raft.

Connect all the notches on one side of the raft before connecting those on the other. Lashing of the overhanging ends of the two crosspieces together at each end of the raft will give it additional strength.

When the raft enters the water, the crosspieces swell and bind the logs together tightly. If the crosspieces fit too loosely, wedge them with thin pieces of dried wood. These swell when wet, tightening and strengthening the crosspieces.

If rope, wire, or other lashing is available, the logs can be lashed without notching, resulting in much greater speed in construction of the raft (fig. 10).

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Section III. CABLEWAY AND ROPE WALKWAY

16. CABLEWAY

A simple cableway (fig. 11) is easy to construct and materials required are generally on hand of locally available.

A hasty, field method for determining cable capacity for fiber rope cable is by use of the formula T = Dý. For wire rope cable the formula is T = 8 Dý. In both cases: T = safe working stress in tons, D = diameter of rope in inches.

If either the fiber rope cable or the wire rope cable are in doubtful condition the working capacity determined by above formulas must be divided by two.

Example 2. Sufficient 3/4-inch diameter rope (in doubtful condition) is available for use in construction of a cableway. By use of the hasty formula given above, what load should this cableway carry safely?

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Solution: T = D2

T = (3/4)2

T = 9/16 Ton lbs = 9/16 Ton = (2,000 ---) Ton T = 1125 lbs

Since the rope is in doubtful condition, safe working capacity must be further reduced by dividing by 2. Therefore,

1125 ÷ 2 = 562.5 lbs

In many cases, wire rope is used instead of fiber rope. The rule of thumb when determining the safe working capacity of wire rope is the formula T = 8Dý

Example 3. A 1/4" wire rope used in construction of a cableway can be expected to successfully carry what load? The wire rope is in doubtful condition.

Solution: T = 8D2

T = 8(1/4)2 = 8(1/16) = 1/2 Ton

T = 1/2 Ton = 1/2(2,000 lbs) = 1,000 lbs

However, the wire rope is in doubtful condition; therefore T is divided by 2. Safe working capacity equals 1,000 lbs. ö 2 = 500 lbs.

17. THREE-ROPE WALKWAY

A rapidly erected footbridge with a minimum of materials may be constructed using three fiber ropes (fig. 12) or wire rope cables (fig. 13). The span should not exceed 150 feet as longer spans will be unstable when loaded at midspan. Trees of at least 10-inch diameter are required for anchorages for the tread ropes, and 8-inch diameter for the hand ropes. The fiber rope bridge is constructed of 1-inch tread rope, 3/4-inch hand ropes and 1 1/2-inch suspenders. If wire rope is used, 3/8-inch diameter will be satisfactory. Sus- penders for wire rope can be fabricated from wire rope and cable clips or of 1-inch pipe stanchions with cable clips at each end.

Erection procedures are as follows:

The length of the required span may be determined by tying tape or a line across the gap and allowing it to sag 5 percent. The required length must be sufficiently longer to allow for lashings to the anchorages.

The tread and hand ropes are laid out as shown in figure 14. The ropes are placed 3 feet apart. Suspender ropes, cut 12 feet long, are placed at 2-pace intervals. It stanchions are used, the same interval is used.

The suspenders are attached to the tread rope. A clove hitch is used in fiber rope. The two ends of the suspender ropes pass under the tread rope. Wire rope suspenders or pipe stanchions are attached with wire rope clips.

The hand ropes are then raised elbow high and the suspenders are attached. For fiber rope, the suspender is tied to the hand rope by a round turn and two half hitches. Wire rope and stanchions are attached with cable clips. All suspenders are attached in a similar manner. Sufficient length must be left on the tread and hand ropes to make the ties to the anchorage.

The assembled bridge is carried to the bridge site as shown in figure 15. The lines are pulled across the gap and then anchored on the far side with a bowline or a mooring knot. If a bowline is used, an extra turn is taken around the anchorage. The running end is tied back to the standing part with several half hitches. The wire rope is secured with the cable clips after passing around the anchorages. When all ropes are anchored on the far side, the tread rope is adjusted to the proper sag and secured. The hand ropes are then pulled tight and secured.

When the bridge is complete, it is tested to insure that all knots and ties are properly made and suspenders are adjusted. Frequent inspection, adjustment of ties, or tightening of bolts is necessary.

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EXERCISES

First requirement. Multiple-choice exercises 1 through 4 provide an opportunity for you to show your understanding of the preliminary considerations involved in expedient stream crossings.

1. An expedient method for crossing a stream is generally considered because of a pressing requirement. What factor normally determines the urgency of a stream crossings. a. weather forecast b. tactical situation c. stream velocity d. approaching darkness

2. Your engineer unit is on an urgent tactical vehicular movement. Upon arriving at a large stream, you find that the bridge has been damaged and is not passable. What is your first consideration in deciding upon your next move? a. await construction of another bridge b. return to site of march origin c. investigate the possibility of a detour d. commence crossing by use of rafts

3. The advance of an urgent tactical vehicular column is halted by a slightly damaged bridge across a wide stream. There is no feasible detour. What would you consider doing under this circumstance? a. possibility of making emergency repairs to the bridge b. request a change in march destina- tion c. await construction of a new bridge d. abandon equipment and cross personnel only

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4. The damaged bridge is a low structure, and the waterway is of low velocity. What action would you take to make the bridge passable with the minimum of delay?

a. requisition finished lumber

b. search for adequate standing timber

c. await construction of a new bridge

d. use earth or rock fill to build up damaged part

Second requirement. Multiple-choice exercises 5 through 12 are designed to enable you to demonstrate your knowledge in the construction of fords, dips, and causeways.

5. One of the most expeditious means of crossing a stream is by a ford. Which of the following reflects one of the most desirable features of a good ford site?

a. an even, hard, and tenacious bottom

b. a stream of clear water

e. steep uniform approach banks

d. protection from enemy observation

6. Approaches to fords normally receive some surface treatment such as gravel, metal matting or brush. What is the purpose of this treatment?

a. so they will not become slippery from rain, snow, or water dripping off vehicles

b. to mark the approach to the ford so that all traffic will be channelized

c. to improve the riding quality and thereby reduce vehicle maintenance requirements

d. to prevent erosion in the event of heavy rainfall

7. You are to construct a ford which will be used by infantry troops, trucks, and medium tanks. What is the maximum depth (feet) of water allowable? a. 1 c. 3 1/2 b. 2 d. 4

8. You are building a ford to be used by the infantry troops. What is the maximum allowable slope? a. 1:1 c. 3:1 b. 2:1 d. 4:1

9. Dips are paved fords used for crossing wide, shallow arroyos or washes in semiarid regions. Why would you construct an apron on the upstream side? a. to control water flow b. to increase traffic safety c. to prevent erosion d. to strengthen pavement

10. An arroyo is a watercarved gul- ley or channel, much of which is dry except following heavy rain or thawing conditions. In areas where the channel is normally dry, at what elevation would you construct the dip? a. at the channel bed level b. at level to expedite construction c. six inches above the channel bed d. six inches below the bed of the channel

11. There is one major difference between a causeway and a ford or dip. What is this difference? a. causeways are normally longer b. causeways are easier to construct c. causeways require less maintenance d. causeways provide a dry crossing

12. You are constructing a culverted causeway, and are placing sandbags between successive rows of

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culverts. What is the purpose for these sandbags?

a. to prevent crushing of culvert

b. to keep culverts in place

c. to prevent seepage of water

d. to provide smoother riding conditions

Third requirement. Multiple-choice exercises 13 and 14 deal with considerations involved in ice crossings.

13. When you consider an ice crossing, the thickness of the ice at an interior portion of the slab must be determined. What other condition must you investigate before initiating a crossing?

a. long-range weather forecast

b. ice conditions adjacent to the shore line

c. velocity of stream flow

d. temperature at time of crossing

14. Ice thickness for general determination of load carrying capacity is measured at an interior portion of the ice slab. What ice thickness in inches should you have existing before considering crossing 2 1/2-ton trucks with light loads?

a. 4 c. 8

b. 6 d. 10

Fourth requirement. Multiple-choice exercises 15 through 18 are designed to insure an understanding of some of the more common improvised rafts that may be used in expedient river crossings.

15. A closed type container is one which will not permit entrance of water even when completely submerged. An open type container allows water to enter when the opening is below the water line. What is the greatest advantage in the closed type container?

a. is more resistant to being deformed

b. gives maximum support even when submerged

c. requires less time to construct the raft

d. is more readily available than open type

16. Empty fifty-five gallon drums may be used to construct rafts for personnel and equipment. A load of equipment, personnel and the decking and lashing required is estimated at 4,200 pounds. How many 55-gallon drums do you need to provide the necessary buoyancy?

a. 10 c. 14

b. 12 d. 16

17. An empty 5-gallon gas can will provide flotation for approximately 30 pounds. How many gas cans do you need to support a soldier weighing 200 pounds? The timbers and lashing involved weigh 30 pounds.

a. 4 c. 8

b. 6 d. 10

18. Truck covers and tarps can be used to float vehicles across a stream. A cover from which of the following truck bodies would you use to float a 1/4-ton truck?

a. 1/4 c. 1 1/2 T

b. 3/4 d. 2 1/2 T

Fifth requirement. Solve multiple-choice exercises 19 and 20 to insure that you have an understanding of the use of cableways and rope walkways in expedient stream crossings.

19. A one inch fiber rope in doubtful condition is the only rope available for a cableway. Using the hasty calculating method, what load in pounds can you expect the rope to carry? a. 250 c. 750 b. 500 d. 1000

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20. You are constructing a three- rope personnel bridge. It is easily and rapidly constructed from either wire or fiber rope. What is the maximum recommended length in feet for this type bridge? a. 100 c. 150 b. 125 d. 175