FAO FOPFORESTRY ESTRY PAPERPAPER 39

fao/f oisidtf#-. sida sawmillsawill manualsmanuals

frame7Fa) me) saw saw manual manual

FOOD AND AGRICULTUREAGRICULTURE ORGANIZATION OF THE UMTEDUNITED NATIONSNATIONS Rome 19821982 The designations employedemployed and the presentationpresentation of materialmaterial inin this publicationpublication do not implyimply thethe expression of anyany opinionopinion whatsoeverwhatsoever onon thethe part ofof the FoodFood andand AgricultureAgriculture OrganizationOrganization of thethe United Nations concerning the legallegal status of anyany country, territory, city or areaarea or of itsits authorities,authorities, oror concerningconcerning thethe delimitationdelimitation of itsits frontiersfrontiers oror boundaries. boundaries.

M-30 ISBNISBN 92-5-101248-292-5-101248-2

AllAll rights reserved. No partpart of tthishis pubpublicationlication rnaymay bebe reproduced,reproduced, stored in aa retrievalretrieval system,system, oror transmittedtransmitted inin anyany formform oror byby anyany means,means, electronic, mechanical, photocopying or otherwise, withoutwithout the prior permission of thethe copyrightcopyright owner.owner. Applications for suchsuch permission,permission, with aa statementstatement ofof thethe purpose purpose andand extentextent ofof the the reproduction, reproduction, shoulcishould be addressed toto the Director,Director, PublicationsPublications Division,Division, FoodFood and AgricultureAgriculture Organization ofof the UnitedUnited Nations,Nations, ViaVia delledelle Terme Terme didi Caracalla, Caracalla, 00100 00100 Rome, Italy.Italy.

© FAO 19821982 - 1 -

INTRODUCTIONINTRODUCT ION

This manual deals with the construction and operating principles ofof thethe frameframe saw.saw. Many different kinds and makes ofof frameframe sawssaws areare inin use.use. A very common type of SwedishSWedish origin,origin, originallyoriginally mademade inin 1946, has been chosen asas thethe exampleexample inin thisthis manual.manual. Today's modern frame sawsaw hashas thethe samesame basicbasic function,fUnction, althoughalthough capaCity,capacity, infeedinfeed andand sawingsawing accuracyaccuracy isis increased.increased. Where frameframe sawssaws ofof otherother makesmakes differdiffer considerably,considerably, this isis pointedpointed out.out. FAO gratefully acknowledgesacknowledges itsits indebtednessindebtedness toto the Government ofof Sweden whosewhose financialfinancial aidaid mademade possiblepossible the publication ofof thisthis manual and to the Employers Federation of Swedish Industries,Industries, whowho providedprovided thethe original material.

CONTENTS

pg.e~

1. Construction and operating principles ...... •••••• 2 2. FCrcesFbrces and movements ••••••••••••••••••••••• 38 3. settingSetldng sawbladessawblades intointo frameframe saw sash ••••••• 68 4. How to feed logs intointo a frameframe sawsaw...... 79 5· Maintenance ...... 00000 OOOOOO 000000004100,0000p00000 92 6. Revolutions, cog numbers and peripheral speedsspeeds 97 - 22- -

3--

2

1

PART II -CONSTRUCTION AND OPERATINGOPERATIm PRINCIPLESPR!NCIPLES page~ 1. Foundation with base plateplate ...... 3 202. Crank section 00000000000000000000000000000000•••••••••••••••••••••••••••••••• 7

3. Bottom frame .0000000,0000000000000000000000000...... ~ ...... 14 4. Upper frame .00,30000000e000000000000.70000p00o0o...... 15 5· Guide symtemsystem ••.••...•••..•.••..•..•.•••••••...... 16 6.60 Sash ...... 00000000000000000000000000000060000000000 19 707. Roll frame and feed rollsrolls .000000000o00o0c0,3000...... 24 8.80 Feeding mechanism ...... 31 Appendix •••••••••••••••••••••••••••••••••••••000000000000000000000000e000000000000 36 - 3 -

1. FoundationFbundation with Base PlatePlate

The saw frame mustmust be builtbuilt onon a strong foundation of reinforced concreteconcrete of about 60-803m3.60-80 m3• Sometimes, however,however, up to 90-100 m3 is necessarynecessary to get a strong enoughenough base for thethe sawsaw frameframe whenwhen ground conditionsconditions areare bad.bad. The foundation should be somewhat longer inin the longitudinallongitudinal directiondirection ofof the saw mill than in the transverse direction, since the principal direction of motion of the moving partsparts ofof thethe framefr~e coincides with the directiondirection ofof sawing.sawing. Accurate drawingsdrawings shouldshauldbe be supplied by the manufacturer. The function of thethe foundationfoundation is:is:

too support the frame saw's weight and too absorb all the powerful forces that arere created and that cause strong vibra-vibr tionsions when thethe sawsaw frameframe isis working.working.

The foundation must therefore be erected on solidsolid ground.ground. If there isis no such ground available, pile drivingdriving mustmust bebe done. At the same time, the foundations must not be directly on solid rock, which can carry vibrations to adjoining areas some distance away.

( , ! / I I / I / I , ! / I /i I - 4 -

A foundatfoundation ion onon rockrock needsneeds an inter-inter­ vening layer of a suppressingsuppressing material, for C172 t)-71 Ri example, clay or sand.sand. Sand especially isis good at absorbing vibrations.vibrations.

It mustmust be repeated thatthat, when the pre-pre­ ...... - liminary studies for anchoring the frame saw 411i foundation are done, aa good solidsolid ground basebase , 1 must be found. If there is any doubt,doubt, alwaysalways A - consult a specialist,specialist. becausebecause the consequencesconsequences of error could be serious.serious. , .

% . It is also unwise to run all the saw ...... frames withinwithin the mill at the same speed .., (number of revolutions). It is best to makemake the frames work outout ofof sequencesequence inin orderorder toto I. 1(1 counterbalance each other's motions, the samesame ri as a group of soldiers breaking stepstep whenwhen cross-cross­

ing a slender bridge. The idealideal situation isis i % to have the moving partsparts ofof oneone frameframe atat thethe upper dead centre when thethe moving partsparts ofof thethe other frame are at thethe bottombottom deaddead centre.centre. In _ practice, however, thisthis isis not possiblepossible toto , . , , #4:f ....::, / iir',:.I achieve and insteadinstead oneone tries to vary thethe speedspeed '*- #7:4 . , 47 of each frame. 4%4 o 41: Al . - aiZa 7* fis,::: ...... Usually the cantcant frame works fourfour toto fivefive revolutions faster perper minute than thethe loglog frame,frame, aNfigig-a f: ' i. 5 which avoids harmonic peakspeaks ofof vibration. In ,AmmillowIlllikoloolimre addition, it also avoids thethe sympatheticsympathetic vibra-vibra­ tions in the surrounding ground which createscreates disturbing shaking to buildings in the vicinity. I

To obtain the necessary working height on the ground floor ofof thethe sawingsawing building,building, thethe foundation should be built up toto aa suitablesuitable I height above the floorfloor toto makemake enoughenough spacespace forfor 0 . necessary conveying machinery, etc.etc. i

InIn thethe pastpast thethe cant frame has often been o mounted too low.low. The trend now is to raiseraise , 01'lf ' ' it toto a better working height on the upper 7,7. 7r-,..,- 1 tfl ' ". I floor. ..li' V

V

I

,

I

I

o

k''' 4 '.4 7 - 5 -

When installing modern rollroll conveyersconveyers the aim isis to obtain a working height of 700 mm.

On top of the foundation a BASEBASE PLATEPLATE is fixed:

by~ embeddingembedding itit inin the concreteconorete bed, and by 8 anchor boltsbelts (45 mm) embedded inin the concrete bed.bed. These anchor boltsbelts must penetrate the whole foundationfoundation toto get adequate anchorage.anchorage.

The base plate consists of a deep U section frame.frame.

The U-shapeUshape isis partlypartly chosenchosen becausebecause this design has very highhigh "bending"bending resistance",resistance", especially where the bearingbearing housingshousings areare positioned. (For(Fbr technicaltechnical explanations of this seesee PART II - FORCES AND MOVEMENTS.MOVEMENTS.

This U-shapeUshape makesmakes aa strongstrong plate,plate, butbut other types of beamsbeams cancan alsoalso bebe used.used.

Another advantage ofof thethe U-shapeUshape isis thatthat it can be filled with concrete, so that the anchorage of the plate to the foundation isis strongly reinforced.reinforced.

In thethe basebase plate there are bearing housings for the roller bearings of the crank-crank­ shaft.

The lower half of the housing isis placed in the base plateplate itself.itself.

The upper half (called(called the bearing cap) is fastened with boltsbelts inin thethe basebase plate.plate.

There isis one disadvantage with this system. If thethe outer ring of the crankshaft roll bearing,bearing, which isis normally fixedfixed inin thethe bearing housing,housing, startastarter toto rotate inin thethe basebase plate, the whole basebase plateplate must be substitutedsubstituted or reconstructed inin situ.~. - 6 -

Therefore the most modern types ofof frame Detachable bearing· saws are fitted with detachabledetachable bearing housIDgshousinosmade made of cast steelsteel forfor the crankshaftcrankshaft roll bearing. Some older frame sawssaws havehave "white metal"metal" ring lubricated bearings.(See appendix.)appendi~

The function ofof thethe basebase plateplate is:is:

to hold the constructionconstruction ofof thethe frame together;together; to support the wholewhole weightweight ofof the frame sawsaw (about(about 1010 tons);tons); to absorb and tranamittransmit to thethe foundation the powerful "inertia"inertia forces" that arisearise duringduring sawing.sawing.

The predominant forcesforces thatthat influenceinfluence the base plate are:

1. VERTICAL FORCESRlRCES that arise due to:to: _ the up and down movement ofof thethe upper endend of the connecting rod. _ the up and down movement of the sash.

2. HORIZONTAL FQRCESFORCES that arise mostly duedue to: the flywheel counterweights which,inwhic~in certain positions,haveposition~ have a horizontalhorizontal component ofof movement.movement. the lower end of the connecting rod which, inin certaincertain positions,positions,has has a horizontal component of movement. the pressure of the log against thethe saw blades.

3. SIDESEDE RlRCESfrom:FORCES from: the belt tension.tension. the power from the motor. TheseThese forces can vary considerably;considerably, dependingdepending on the size of the motor and how the power is transmitted, i.e. _ through direct drive, or _ through transmission drive.drive. MoreMore detaildetail on these stresses is explained~------~--~explained in Part 2 - FQRCESFORCES AND MOVEMENTS.IDVEMENTS. -7- 7 -

2. Crank Section

The crank sectionsection consistsconsists of:of:

a crank shaftshaft of:of: 2 centre shaftsshafts 2 flywheels with counterweightsoounterweights 1 crank pin Connecting -a connecting rod.rod.

A. Crankshaft with flywheelflywheel

The crankshaft isis mounted inin thethe basebase o-pulley Driving plate by means of two sphericalspherical SKFSKF rollerroller bearings (see(see appendix). (Some frame saws Eccent ric have white metal ring lubricatedlubricated bearingsbearings instead.) .

It is a detachable type, which means that itit isis built upup ofof severalseveral parts.parts.

The crankshaftcrankshaft isis divideddivided intointo twotwo similar halves. Each half consistsconsists of:of:

one centre shaft pressed intoint o an eccentric; an eccentric; Fl;yt-rheel Count er Centre axle onto this eccentric has been weight bolted a flywheel with a counter-counter­ weight.

The crankshaft halves are joined together byby means of a crank pin.pin. The connecting rod . is attachedattached toto thisthis pinpin byby thethe lowerlower connect-connect­ ing rod bearing. Crank Centre journal The crank pin isis fittedfitted withwith mechanicalmechanical axle joints in bothboth the crankshaft halves, which Eccentrió make it easy to disassemble. (In some frame saws the eccentric and thethe flywheelflywheel areare castcast 4,11411

in one piece). I .7dmiAg, When the two halves have been joinedjoined MO together byby the crank pin, the flywheels are positioned on either side of the connecting rod, placed as close as possible to the si connecting rod bearing. This is done to reduce the strain inin thethe shaft.shaft. The shorter imer the crank pin, the more rigid itit isis and the better itit resists strains. (In otherother models Qóunterweigh the flywheels are located outside the base Fly wheel plate and the counterweights are positioned .%. on either side of the crank pin.) - 8 -

On the ends of thethe crankshaftcrankshaft out-out­ side the bearings in the base plate are fixed:

a crankshaft pulleypulley onon thethe feedingfeeding side which, inin turn,turn, drives thethe friction disc oror pulleypulley forfor thethe loglog feeding mechanism.mechanism. A variable drive mechanism (see(see pagepage 33) can be mounted.mounted. When this is done, there is no need for a drivingdriving pulley,pulley, since loglog feedingfeeding isis poweredpowered byby aa separate electric motor.motor.

a keyedonkeyed-on drivingdriving pulleypulley onon thethe driving Bideside toto transmittransmit thethe driving powerpower fromfrom thethe motormotor toto the crankshaft. The driving pulley hashas aa two-piecetwopiece hub,hub, whichwhich makes it easy to disassemble.disassemble.

The above appliesapplies whenwhen eacheach frameframe saw is direct - driven from its own separate motor.motor.

Brake lining

Driving pulley

N - 9 -

If there is a system withwith oneone motormotor driving more than one sawsaw through a trans-trans­ mission gear, itit isis necessarynecessary toto have,inhave,in additio~aaddition,a free running pulley -- anan o-pulley­0-pulley- running on strong double-row roller bearings adjacent to the driven pulley,pulley, onon anan extensionextension of the crankshaft.crankshaft. The transmission beltbelt from the motor pulley isis connected to either the driven pulley or toto thethe adjacentadjacent freefree running 0-pulley.o-pulley. WhenI'lllen thethe powerpower isis toto bebe disconnected, the belt isis movedmoved byby meansmeans ofof a belt guide from the driving pulleypulley overover toto Direot the 0-pulley.o-pulley. When powerpower isis toto bebe connected,connected, IDOtor the belt is moved back fromfrom thethe 0-pulleyo-pulley toto drive the driving pulley.pulley.

The belt guide consists ofof aa clampclamp through which the belt passes.passes. A lever atat the operator's position onon thethe infeedinfeed sideside of the saws,saws, closeclose toto thethe loglog feedingfeeding control,control, moves the belt sideways.Sideways .

Braking the crankshaft rotation can be done in two different ways,ways,depending depending on whetherwhether the saw is powered by direct motor drive or transmission gear: Brake lining- - Direct driven saws.saws.

The brake system consists of an ordinary brake lining surrounding aa brakebrake drum on the driving pulley.pulley. The lining isis tightened aroundaround the brakebrake drum by means of a lever placed at the operator'soperator's position Transmission on the upper stand close to the infeed gear controls.

- Transmission gear driven saws.saws.

The belt guidebar is connected with a brake lining that surrounds the brake drum of the fixed driving pulley.pulley. The brake isis actuated when the belt guide lever is moved to its bottom position, which moves the belt over to the 0-pulley.o-pulley. - 10 -

The forces on the crankshaft and thethe connecting rod areare veryvery complex.complex.See See PARI'PART 2 -- FlJRCESFORCES AND MOVEMENTS).MOVEMENTS). It isis there-there­ fore not possiblepossible toto fullyfully balancebalance aa frameframe saw. • To enable the moving parts toto work asas smoothly and quietly as possible thethe crank-crank­ I shaft is fitted with flywheels and fixedfixed t counterweights, which together counterbalancecounterbalance some of the rotating partsparts ofof thethe frame.frame.

The parts thatt hat movemove upup andand down,down, however,howev er, cause high free vertical forces.forces. ByB,y using ( ) extra counter\o1eightscounterweights it is possible to reduce or eliminate these vertical forces.forces. But, in doing so, free horizontal forces will develop.

The difficulty isis toto findfind thethe degreedegree of balancing that isis bestbest forfor eacheach individualindividual machine. Count·er \-,eight ~venEven if total balancing isis not achievable,achievable, at least by partialpartial balancing,balancing,free free forcforceses are ""'w--- Extra reduced and distributed moremore evenly bothboth in weights the vertical and horizontal directions.

To achieve the best balance, thethe fixedfixed counterweights are provided with\o1ith cavities,cavities, where iron or lead weights can be inserted to fine-tune thethe balance.balance.

Above all, itit isis essentialessential toto counter-counter­ balance:

the high force (+)(+) on the lower connecting rod bearing inin the n9"9 to 6 o'oclock" section and the "3"3 to 12 o'clock" section and, in addition,

the negative force (-)(-) on the lowerlower connecting rod bearing inin the "12"12 toto 9 0'o'clock" clock" section and the "6"6 toto 33 0'o'clock" clock" section.sect ion.

In addition, the counterweights help to overcome: forces at TDCTDC andand BDC,BDC, thethe "12"12 andand 66 o'clock" positions. -11-

The functionfUnction ofof thethe flywheelsflywhee'ls andand thethe counterweights isis therefore:therefore:

to balance the inertia caused by the up andand clowndown movementmovement of the sash and the connectingconnecting rod.rod.

Part 2 -- FORCESFORCES ANDAND IDVEMENTSMOVEMENTS explains / balancing inin detail.detail.

B. The connecting rod

The connecting rod isis mademade fromfrom oneone piece of I-sectionI-section steel 22 m. long.long.

The functionfUnction of the connectingconnecting rodrod is:is:

to transmit the rotating movement of the crankshaft to the sash and to transform this rotating move­move- ment into a reciprocating movement.movement.

This means that the connecting rodrod must turn 700 times/minutetimes/Minute whenwhen the number of revolutions is 350 revolutions/minute.

The forces that act on the connecting rod depend on:on:

the weightweight of the sash (250-400 kgkg with insertedinserted blades). - the weight of the connecting rod itself, 250 kg. the number of revolutions perper minute.minute.

In total,total, the connecting rod must absorb inertia forces of about 2020 tons.tons.

ToTo enable thethe connectingconnecting rodrod toto with­with- standstand these strains it isis necessary:

to make itit ofof spe'cialspe'cial steel. to design it for strength. This is the reasonreason whywhy the I-sectionI-section is chosen. - 12 -

The connecting rodrod isis subjectsubject toto bothboth compressioncompression andand tension.tension. (See Part 22 - FORCESFDRCES AND MOVEMENTS.)MOVEMENTS.) These are notnot constantconstant butbut alternatealternate duringduring eacheach turnturn ofof the crankshaft.crankshaft. These stress variations couldcould causecause thethe materialmaterial ofof thethe connectingconnecting rod to weaken andand failurefailure mightmight occuroccur fromfrom fatigue.

ForFbr anythinga.n;rthing thatthat isis exposedexposed to repetitionrepet it ion of stress, therethere isis aa "fatigue"fat igue limit", which isis the maximum repetionrepet ion ofof stress that the body inin questionquestion cancan bebe exposed to without fracturingfracturing fromfrom fatigue.fatigue.

The fatigue limitlimit ofof thethe connectingconnecting rod depends on:on:

the type and structurestruct=e ofof itsits material; Undamaged connecting rod the surface conditioncondition ofof thethe material.

This means that the more eveneven andand smoothsmooth the connecting rod is, the more repet~tionrepetition of stress it will stand before it fract~esfractuTes from fatigue. One nick •.•.•

Therefore, the connectingconnecting rodrod mustmust be protected from anyany nicks. Under 'v-~r~I ~: ~··~_5~~ 1 :""..,/ no conditions must itit bebe hithit againstagainst any solid object or be tapped ,lithwith '" might cause • a hard or sharpsharp tool.tool. breakage ••

(~" '" ~i' .• •.. '" '.~ ,. . -y/ . . . . Every nick creates a concentration of stressstress whichwhich gets bigger the deeper the nick is. • nick is.

A relatively small nick on a connect­connect- inging rodrod might,might, becausebecause ofof the strong con­con- centration of stress around it, eventuallyeventually result in an apparently inexplicable break-break­ age.

Every nick on the connecting rod must be ground down with an emery oror polishing cloth. - 13 -

Another thing toto notenote isiS ,thatthat corrosion,corrosion, e.g. formation of rust, reduces the fatigue limit considerably and increasesincreases the risk of fatigue breakdown.breakdown.

Saw mills situated near corrodingcorroding air or water shouldshould paintpaint connect-connect­ ing rods with anti-corrosive pedntpaint

The connecting rodrod hashas twotwo bearings,bearings, oneone lower and one upper.

The lower connecting rodrod bearingbearing is,is, mounted on the crankshaftcrankshaft journal.journal. A spherical SKF-roller bearingbearing (see(see appendix)appendix) has been chosen for thethe lowerlower endend toto lower connecting eliminate: rod bearing

- any alignment defects inin thethe vertical direction of thethe frame.frame. - any side forces working on the connect­connect- ing rod, for instance, due to sash im-im­ spherical balance. roller bearing Such an imbalanceimbalance mightmight occuroccur ifif thethe massmass of the frame is not symmetrically distri-distri­ buted 'around itsits centre;centre; for example,example, ifif the blades are not perfectlyperfectly centred.centred. 'i The upper connecting rod bearing con-con­ sists of a needle bearing (see(see appendix).appendix). ~) There is a hole in the piston pin which serves as a tank for lubricating oil.oil. I A needle bearing isis chosen to ensureensure that all the parts above the crankshaft are as small and lightlight asas possible.possible. A needle bearing is smaller and lighter than upper connecting other bearings. rod bearing VIZI

N mumw ...... A,A ; LOIL -pA. ,i7e,7; . eau AIMM,5

needle bearing ------

--14-14 -

3. Bottom Frame

The bottom frameframe isiB placedplaced atat thethe lower floor level of the sawmill building. It oonsistsconsists of:ofl

A. two lower side frames whiohwhich are both fastened toto thethe base plate by

B. four bolts at the bottom,and joined together by

c. two stay bolts at the top.

The function of the bottom frame is:is:

to extendextend thethe sashsash heightheighi toto enableenable connectingoonneoting rod toto bebe larger;larger; to support the twotwo upperupper sideside frames;frames; to BUpportsupport the brake and belt guideguide systems;syBtems; to serveserve asas aa supportsupport bodybody forfor parts of the feeding meohanismmechanism and lubri­lubri- oator.cator. 15- 15 -

4-4. 11121,21222Upper hame The upper frame isis attachedattached toto thethe lower frame byQy bolts.bolts. It consists of:of:

A. two upper sideside frames,frames, B. one top piece, and c. two connecting platesplates at thethe bottom,onebottom, one onon eacheach side.side.

The function of the upper frameframe is:is:

to support the system ofof guides; to support the roll frame and the feeding mechanism; to transmit toto thethe foundation,foundation, through the bottom frame, the vertical forcesforces createdcreated when the sash presses againstagainst thethe guides.

To be able to supportsupport thethe rollroll frames attached to both the infeed and outfeed sides of the upper frame there are: D. at the driving sideside aa verticalvertical cylindrical shaft, the attach­attach- ment shaft, or the swingiIJgswinging shaft. E. at the feeding side, a similar shaft called locking shaft.shaft. - 16 -

5. Guide SystemSYstem

To the side frames four guides, twotwo upper and two lower,lower, are attached with bolts. A saw frame guide isis describeddescribed as: a guide rail having - a polished surface that isis - mademade ofof castcast iron.iron. This material has low friction for thethe wear platesplates to run on.on.

The function of the guides is:is:

to locate the sash inin relationrelation toto the centre line of the frame, and to guide the sash whenwhen it is mov~moving vertically (up(up andand down).dOwn).

There are two different kinds ofof guides:

A. Flat guides, whichwhich have completely straight and plane slideslide faces.faces. They are positioned on the infeedinfeed side.

B. V-Guides,V-Guides, which have slideslide facesfaces shaped likelike aa V.V. They are posi-posi­ tioned on the outfeedoutfeed side.side.

Thus the sash is guided on both thethe infeedinfeed and outfeed sideside duringduring itsits movementmovement up-up­ OUTFEEDOUT1IEED ward andand downward.downward. The front guides (as(as seen from the infeed side)are alwaysalways I adjustable. The reason for thisthis isis thatthat the tolerance between guideguide andand frictionfriction plate, (the(the "play"),"play"), must bebe adjustableadjustable -+ to correct wear onon guides andand wearwear plates.plates. t If thethe guideguide is too tight (the(the "play" made too small) overheating,overheating, and a risk of damage to guides and friction plates could result. If thethe guideguide is notnot tight enough (the "play"'~l~" tootoo big) the sash will be loose and this could be transmittedtramsmitted to the sawlines, Adjust­ resulting inin poor sawing.sawing. There ing nut is alsoalso a risk that the guide,guide, Stay Adjust- _,""rAI'l the friction plate and guide boltsbelts tighten r will break,withbreak, with the risk of furtherf'urtheI ing screw damage. - 1717 -

Some frame saws havehave thethe guides mounted, as sshownhown inin the figurefigure alongside. Feedi4gFeeding mechanism side

'"• ...'! >1>, I" g [5 Driving side

LUBRICATING SYSTEMSYSTUI

Flat guide VguideV-guide 1I lubrication 2 lubrication tube tubes The guides are lubricated from aa 12-tube12tube greasegrease pump,pump, aa highhigh pressurepressure lubricator. The lubrication isis pro-pro­ portional to the speedspeed ofof thethe sawsaw frame,frame, stopping when the sawsaw frameframe stops.stops. The lubricant flows with aa pressurepressure ofof upup toto 100 atmospheres (10(10 mPa).mPa). The lubricator is mounted on one ofof thethe sideside frames.frames. It is driven byby an eccentric directly from the crankshaft.

To each V-guideVguide twotwo lubricationlubrication tubes are connected, and to each flat guide one lubrication tube is connected.

Lever forfor eccentrice"';entrj.c -1818 -

The loadload on the lowerlower guides isis heaviest asas theythey areare mountedmounted closestclosest toto the upper endend ofof thethe connectingconnecting rod.rod. Therefore, they take the horizontal forcesforces created by the upper endend of the connectingconnecting rod at certaincertain positionspositions ofof movement.movement .

Because of this highh~h pressure these guides are providedprovided with waterwater cooling,cooling, making itit easiereasier toto carrycarry awayaway thethe heatheat caused by the highh~h pressure.pressure. Expans i on

This makes itit possiblepossible toto adjustadjust thethe guides ofof thethe sashsash Withwith minimumminimum tolerance,tolerance, which markedly improvesimproves the efficiencyefficiency of sawing.

The water cooling device is a closed system where the water isis continuously pumped. It consists of:of:

a systemsystem ofof radiatorradiator cells,cells, an electricelectric fan, and a pump.

This self-containedselfcontained equipmentequipment cancan bebe placed beside the frame,frame, or on the bottombottom floorfloorlor,, or inin anyany otherother suitablesuitable place.place. Water isis ledled through tubes to the guides which are hollow, so that the waterwater cancan pass through them.them.

Fan

Pump -19-- 19 -

6. Paah~ The sash consists ofof fourfour parts:parts: A. one upper cross beam 3 B. one lower cross beam

C. two columns,onecolumns, one on eacheach side.side.

The lower cross beam has a bracket on its under side inin the form ofof twotwo wings. Attached to these is the upper crank pin which connects the sash with the connecting rod.

The distance between the upper and the lower cross beam isis adjusted, soso thatthat thethe upper blocks inin the lowest position of the frame and the lowerlo~r blocks inin thethe highesthighest position of the frame do not touchtouch thethe log.log.

The columns are made of . steel tubing to keep weight down.down. In relation to itsits weight tubing has high resistance to com-com­ pression and tensiontension stress.stress.

The two columns and the two beams make up the sash intointo which the saw blades are inserted.inserted.

To hold the sawblades each crosscress beam is provided with a slot, i.e. a clearance into whichwhich are inserted:inserted:

D. top hangers atat.the. the top, and

E. bottom hangershangers atat the bottom.bottom

The saw blades are fitted intointo thesethese hangers when the sawsaw blades areare set.set.

Bottom hangers Top hangers - 20 -

The sash isis constructed:constructed:

if 11 1 II i to withstand the stressesstresses created when the blades areare fitted.fitted. Each blade is fitted with a tensiontension ofof rrinar 7-9 tons. If seven blades are fifitted, tted, the total tension will be 50-65 tons.tons. Fitt ing to enable, in particular,particular, the lowerlower 5665 cross beam to absorb forces from thethe TON moving connectingconnecting rod.rod. These forces are of a magnitude of 15-20 tons and they alternately putput the beam under bending stressstress upwardsupwards and downwards.

At the top dead centre,centre, wherewhere thethe whole sashsash must slowslow down, stopstop and change direction,direction, thethe connectingconnecting rodrod willwill 15-20 TON bend thethe beambeam down.down. LoHer cross beam At bottom dead centre, wherewhere thethe sash once againagain must slow down, stop and change direction,direction, the force from the connecting rod will bend thethe beam up.

The cross beam, seen inin aa cross section, is in principle likelike twotwo U-beams back to back.

The U-beam isis chosenchosen because itit givesgives advantage both in manufacturing and in strain distribution, such as: strain distribution, such as: Centr e of bending the U-form is easy to manufacture inin the foundry.

in resistingresisting stress, the U-form has an advantage because thisthis shapeshape givesgives a high bending resistance (i.e. resis­resis- tance against bending stress).stress).

Too 10,[ Correct Too high

~ . ~

Centret of bending - 21 -

In the centre of the cross beam there are two strongly dimensioned angular stiffeners or ribs, the function of which is to steady the beam against thethe forcesforces mentioned above.

The tension stress acting on the sash throught.hrough the set of blades depends on, and vavariesries with, the number of blades and how tight eacheach bladeblade hashas beenbeen fitted.fitted. ,

The stress that the connecting rod transmits to the sash, mainly the lower cross beam, primarily dependsdepends upon:upon:

the weight ofof thethe sash,sash, andand

the number ofof revolutionsrevolutions perper minute.minute.

The sash must be dimensioned according to the diameter timbertimber toto bebe sawn.sawn. The bigger the timber, the bigger the sash and the higher thethe weight.weight.

The width of thethe sashsash cancan varyvary betweenbetween 18" and 34", which isis the insideinside dimension and also the diameter limit of any log that can pass through thethe frame.frame.

The weight of the sash varies betweenbet,Teen

about 250 kg for a 15" frame with inserted blades, and

about 400 kg for a 34" frame with inserted blades.

The stress transmitted by the connect­connect- ing rod to the lower cross beam ofof thethe sashsash will increase:increase:

with"ith increasedincreased weightweight ofof thethe sash;sash;

with increasedincreased speed (rev./Min.)(rev./min.)

There isis a limit to the stress placed Weight of on any piece ofof machinery and,and, inin thisthis case,case, the connecl the manufacturers place restrictions on the ing rod weight and speedspeed as under:

for a 18" frame ... 380-390 rev./Min.rev./min. for a 24"24" frameframe ... 360-365 rev./Min.rev./min. for a 30" frameframe around 320320 rev.hlin.rev.}nin. - 22 -

To the columns of thethe sashsash fourfour gauge attachments are fastened, oneone inin eacheach corner. Between these andand thethe outerouter blades on either side, blocks oror gaugesgauges (measuring(measuring bodies located between adjacent bladesblades to determine the thickness ofof thethe sawnsawn timber) are located.located. This makes itit possible toto align 'the whole set of bladesblades with screwsscreWS fixed inin the gauge attachments.attachments.

In the four corners ofof thethe sash,sash, thethe ends ofof the cross beams are provided with brackets for thethe slidingsliding blocks.blocks.

The function of the slidingsliding blocks isis to guide thethe sashsash intointo thethe guidesguides ofof thethe upper frame.frame.

The surfacesurface ofof thet h eblocks blocks is is mad..) mad., up of interchangeableinterohangeable frictionfriction platesplates mademade ofof a low friction, low wear material such as aluminium blocks with a specialspecial bakelitebakelite finish, npockenholz""pockenholz" oror otherother lowlow frictionfriction material. The aluminium blocks areare pre-pre­ ferred for weight andand maintenancemaintenance reasons.reasons.

The aim is to get friction as lowl ow asas possible between the friction plates anandd the guides, inin orderorder toto preventprevent overheating,overheating, because overheating cancan causecause thethe guidesguides tot o buckle.

The sliding blocks onon both sidessides ofof the sash are made inin thethe samesame way:way:

on the infeed side as flat blocks, and

on the outfeed side, as pointedpointed blocksblocks to steer the sashsash inin thethe guides.guides.

So the sash is guided bothboth onon thethe feeding mechanismmechanism sideside andand the driving side of thethe frame.frame.

The system with flat blocks andand flatflat guides makes adjuetmentadjustment ofof thethe sashsash easiereasier and the number of surfaces requiring care­care- ful clearance adjustmentadjuStment isis reduced.reduced. - 23 -

Blades mustmust be fittedfitted intointo the sashsash with an overhang setting, to make the blade at thethe upward strokestroke move away from the cutting lineline inin thethe log,log, whichwhich is continuously fed.fed.

Overhang settingsetting meansmeans thatthat thethe tooth lineline isis setset awayaway fromfrom thethe vertical and has a slope away from the log at the bottom.

This overhang mustmust bebe obtainedobtained withoutwithout fitting the blades soso thatthat thethe tensiontension line falls diagonally throughthrough thethe blades.

To get a correct overhang, the two cross beams are not vertically oneone aboveabove the other. In relation to a vertical plumb line through thethe centre ofof thethe sawssaws the upper sliding blocks are displaced towards the front (log(log infeed)infeed) andand thethe lower sliding blocks towards the rear (log outfeed). The overhang is about 50 mm from vertical.vertical. - 24 -

7. Roll :r'rameFrame andad Fiaed Feed rollsrolls/NM

The functionfUnction of thethe rollroll frameframe is:is:

to support the upper andand lowerlower feed rolls;rolls; to create a roll pressure between the feed rolls

It consists oftcf:

the upper roll frames, oneone inin frontfront and one at the back.back. (Seen from the infeed side).side).

the lower roll frames, one inin front and one at thethe back.back. (Seen from the infeed side).side).

FRONT

The upper roll frame Upper The frame is supported on bothboth thet he roll infeed and outfeed sides by shaftsshafts frame attached to the upper frame:

on the driving side ofof thethe frame, by vertical holding swingingswinging shafts;shafts; Lower Lower roll roll on thethe feeding mechanism side of the frame by locking shafts.shafts.

Each upper roll frame is fixed on and can swing out on the swinging shaftshaft toto givegive access to the sash (e.g. whenwhen changing blades). EachRach roll frame carries an ] upper feeding roll.roll.

Swing" LockiLock" shafts " shafts ' "

VII : 1 - 25 -

The roll frame isis cast and providedprovided with: F a vertical hole A for the holding shaft on the drivingdriving side.side.

a vertical notch B for the lock and the lockinglocking shaftshaft onon thethe feedingfeeding mechanism side.side.

two vertical holes B'forB'for thethe clamps.clamps.

a horizontal holehole CC forfor oneone sprocketsprocket shaft on thethe drivingdriving side.side. G--';-"

two horizontal holesholes DD andand D'Dr forfor 8' the supporting shaftshaft toto thethe upperupper roll clamps.clamps. C F Each roll frame can be raised and H 8 lowered along the vertical .swinging shaft to make it possible toto adjust itit toto different diameterdiameter logs.logs. This is done manually byby meansmeans ofof thethe hand-wheel.handwheel.

The hand-wheelhandwheel actsacts onon aa toothedtoothed trans-trans­ D mission gear F of which thethe teethteeth areare mesh-mesh­ D' ing withwith the corresponding rack of teeth of the swinging shaft G. Clamps The toothed transmission gear isis provided with a locking device in the form of a catch H which meshes aa ratchetratchet wheelwheel I.I.

ThisThis is placed on the shaft between the hand-wheelhandwheel andand thethe gear.gear.

With · this device the gear and the roll frame can .be locked inin the correctcorrect positionposition for any given log diameter. When raising and lowering the frame the catchcatch mustmust bebe inin the raised position.

~open ~r 26- 26 -

The lower roll frame

The lower roll frames are constructed on the samesame principleprinciple asas thethe upperupper ones.ones. Since they must give firmfirm supportsupport toto thethe log during sawing,sawing, theythey areare fixedfixed vertically.

Like the upper roll frames they swing outwards. Nowadays they are made of cast steel forfor strength.strength.

Each roll ·frame supports a lower feed roll. Both the upper and lower rollroll frameframe oancan be locked inwards, (i.e.(i.e. the operatingoperating position) by a simple catch on the feeding mechanism side of the stand wwhichhich is then turned so that itit totallytotally enclosesencloses thethe locking shaft.shaft . This also eliminates any play inin the roll frame.frame. The locklock isis inaccessible when the saw isis workingworking.. The feed rollsrclls f Closed The feed rolls arear e called:called: upper feedfeed rollsrolls ~ Open lower feed rolls.r olls. ~J The function ofof thethe feedfeed rollroll isis toto feed the log through the frame saw in the smoothest possible way.way.

The upper rolls consistconsist ofof onecne frontfront and one rearrear rollroll which:which:

rotate on shaftsshafts mounted inin risingr1s1ng and falling clamps (roll(roll clamps)clamps) on the upper rollroll frame.frame. Such a roll isis also called a pendularpendular roller.roller. (In somesome modelsmodels the roll shaft isis mounted directly on the rising and falling roll frameframe - a fixed roll.roll. The roll frames are adjusted verti­verti- cally withwith aa hand-wheelhandwheel andand thenthen they Roll stan are automatically self-adjustingselfadjusting from the bottom position.)

£" -...:---- - 27 -

are self-adjustingselfadjusting verticallyvertically (because(because of the rising and falling clamps)clamps) toto small variations in the diameter of the Oil tub log. If, however,however, sawing isis donedone butt· ,.. end first, the rolls have to be lifted Yoke by a special device because theythey cannotcannot dr open themselves up from thethe smallsmall endend of one log to the butt endend ofof thethe next 1111r1i 44Hydraulic -ItN: - pi.sbon one. ...14 Hydraulic This lifting isis one by means of a 111111!cylinder hydraulic cylinder which the sawyer can controlcontrol from the loglog carriage.carriage. TheThe -, cylinder has a piston mounted between 'oil stand 4841ï\ v the pendular roll clamp andand thethe rollroll 'endular frame. The pressure comes from a , roller hydraulic pump on the upper side of the side frame.frame. aoR

(In somesome frame saws the lifting isis done Ali" by pneumatic valves operated by the I sawyer from the log carriage. The lifting device consists of a pneumaticpneumatic fr. cylinder withwith aa piston whichwhich is mounted 4ftletAPI on the roll frame. The air pressure comes from a separate motormotor driven compressor.) ,_;----1) . are driven from the feeding mechanism by means ofof aa chain.chain. A sprocketsprocket isis mounted on the roll shaft on the side (lut , of the feeding mechanism. When the revolving frame is recessed, this chain wheel will mesh with a corresponding chain driven from the feeding mechanism.mechanism. ltrie,v4, *VIM?Or, Appipw-- The lower feed rolls, one front and one :'*-0; It% 4% f 0 rear:

. .7. consist of roller sections that are , mounted on a cylinder of castcast steel.steel. These centre cylinders are mounted .._ 4 vertically, fixed inin interchangeable 1 = metalmetal bushes in the lowerlo"er rollroll frame.frame. i, ,... Because the bushesbushes areare interchangeable there is nono risk of the rolls pulling sideways because ofof wearwear in the bearing boxes. 1Ht are driven from the feed mechanism by means of a cog wheelwheel transmission.t~ansmission. On the side of the feeding mechanism the ft( tLve0% shaft journaljournal of the roll isis provided ,. - with chain wheels thatthat mesh with a cog 11P '-6 wheel of the feeding mechanismmedhanism whenwhen the swinging roll frame isis engaged.engaged. - 2828 -

Pattern ofof feedfeed rollsrolls

The function ofof thethe feedfeed rollsrolls hashas earlier been describeddescribed as:as:

to feed the loglog throughthrough thethe frame by rotating,androtat ing, and also to restrain thethe loglog while be­be- ing fed to prevent itit turning or moving sideways.sideways.

This task IIlIl8tmust be done under veryvery different conditiOnsconditions dependentdependent upon:

- the form of the material

LOG or CANT

that is round that has two and has smallsmall flat sawnsawn sill,- SU!'- contact sus,-SUI'- faces against faces against the feed rolls the feed rollsrolls

- the hardness and surface of the material,material; for example,example, logs with bark on or off, frozenfrozen or un­un- frozen timber.

The demands on the function of the feed rolls are:

- that the timber is not damaged byby pressures that leave marks on the sawn surface.

- thatthat thethe loglog isis fedfed evenlyevenly and steadily without slipping. SlippingSlipping results in the wrong relationship between feeding and overhang setting which results inin poorer sawing and more strain on the blades. - 29 -

ForFbr the feed rolls toto function properly twotwo thingsthings areare required:required:

1. The right pattern for different conditions.

2. Satisfactory maintenance (as(as part of thethe preventivepreventive maintenancemaintenance syntem)system) of thethe patternpattern ofof thethe feedfeed rolls.rolls.

The roll pattern is mademade inin oneone of two different wayn:ways: B A. a roll core is provided with patterned rings, or

B. the pattern isis cut directlydirectly intointo the roll.roll.

The rollroll patternpattern can,can, inin principle,principle, be of two differentdifferent kinds:

spiked or toothed,toothed, i.e.i.e. thethe contactcontact points have been made pointedpointed toto grip the log better and reduce slipping between log and feed rolls to a minimum.

flat or grooved, i.e.i.e. thethe contactcontact points have been made smoothsmooth soso asas not to damage soft timber. Log In the log frame the spiked pattern isis frame usually used both for the upper and lower10l1er feed rolls.

Since the stresses are biggest onon thethe lower feed rolls, these areare usuallyusually pro­pro- vided with replaceablereplaceable spikedspiked rings,rings, oftenoften with cleaning ironsirons betweenbet'oJeen them.them.

InIn thethe cantcant frameframe only feed rolls with aa smooth pattern aarer e used to prevent any roll marksmarks on the surfaces of the sawnsa,m block.block. These surfaces aarere normally the finalfinal product surface. 30

In frames that are used for both log and cant cutting, thethe lowerlOl-ler feedfeed rollsrolls areare often provided with:Hith:

one centre partpart consistingconsisting ofof spikedspiked rings.

side parts consistingconsisting ofof flatflat rings.rings.

The spiked ringsrings inin thethe centrecentre areare positioned a littlelittle lowerlower thanthan thethe flatflat rings on the sides.sides.

The form and pattern of the rolls depend upon whatHhat logslogs areare toto bebe cutcut andand the clima-ticclimatic conditions,conditions, etc., during Hhichwhich sawingsal

2. The maintenance ofof thethe feedfeed rollsrolls must, regardlessregardless ofof theirtheir formform andand pattern,pattern, aim

to keep the pattern of the feed rolls inin good condition.condition.

This is done either by exchanging Hornworn rings oror byby re-cuttrecutting ing oror grindinggrinding feed rolls of fixedfixed pattern.pattern. - 31 -

8. Feed Mechanism

The feed mechanism isis mademade forfor con-con­ tinuous feeding.feeding. This means that thethe log is fed when the blades areare moving up as wellHell asas when theythey areare movingmoving down.down. It is done, asas has been said before, byqy the lower andand upper feedfeed rolls.rolls.

The feed mechanism consistsconsists of a gear box with a frictionfriction drivedrive mountedmounted on one sideside stand.stand.

The frame isis saidsaid toto bebe aa right-right­ hand or left-hand frame, depending on which sideside ofof thethe stand,stand, rightright oror left,left, the feedingfeeding mechanism isis mounted.mounted.

The function of the feeding mechanism is to transmit a rotating move­move- ment from the crankshaft to the feed rolls.

The friction drivedrive consistsconsists of:of:

a friction wheel A mountmounteded on a horizontal shaft, and

two fibre rollers, one upper BBand and one lower B', mounted onon verticalvertical shafts.

Both rollers can be movedmoved against thethe common frictionfrict ion wheel.~Iheel.

The upper roller B isis movablemovable along a splined shaft and is used for the feeding. It is automatically pressed against the friction wheel~Iheel by aa springspring device with a force that increases >lithwith the resistance toto feeding.feeding. Contact between the roller and the friction wheel is made by means of a knob DD closeclose toto the frame.

The lowerlower rollerroller B',B', mountedmounted onon itsits shaft, is only used for return feeding and is otherwise lifted fro~from the friction wheel. It starts to work when aa wheel-wheel­ handle CC isis turned, thereby releasingreleasing aa strong spring. This spring isis mounted in such a way that it will press the friction roller againstagainst thethe wheel.wheel. - 32 -

The function of the friction drivedrive is to enable the feed rolls to turnturn at different speeds.

The speed can be varied from 1010 toto 40 rnrn/strokemm/stroke (with(with special arrangementsarrangement's up to 50 mm/stroke).rnrn/stroke).

The speed of the friction rollerroller BB can be adjusted by 'contact with aa longerlonger or shorter radius of the friction wheel A.A.

The speed is increasedincreased as the friction roller B moves towards the periphery of the friction wheel.

The transmission of power isis donedone as follows:

A belt from aa drivingdriving wheelwheel mounted onon thethe crankshaftcrankshaft drivesdrives the friction wheel A.A.

The wheel drives the friction roller B, which then starts toto rotate together with itsits vertical shaft E.E.

A mitre-wheelmitrewheel gearinggearing FF transmitstransmits the rotation from the vertical shaft E to a horizontal shaftshaft G.G.

On this horizontal shaft G areare mounted both a cog wheel HH thatthat meshes with the cog wheels I of the lower feed' rolls and a sprockelJsprocket J that transmits thethe move-move­ ment to the upper feed rolls through a driving chain K, the out­out- sides of which mesh with,lith sprocketssprockets LLand and L'.L'. These sprockets areare mounted on horizontal shafts inin thethe upper feedfeed frame.frame.

The feed rolls are finally set to work by a driving chain M that runs over a sprocketsprocketN, N, on one of the hori­hori- zontal shafts and also over a sprocket 0 mounted on the shaft of the feedingfeeding mechanism.mechanism. - 33 -

Feeding mechanism m/Variatorm/Variator

The main parts of this feed mechanism are:

7.5 hp motor A whichwh i ch drivesdrives byby meansmeans of V-belts.It-belts.

the variable drivedrive consistingconsisting ofof twotwo tapered discsdiscs (B(Band and C).C). These discs transmit the movement throughthrough a V-beltV-belt D to two other tapered discsdiscs (E(E and F). These latter discs are mounted onon aa shaft G, which isis connectedconnected to:to:

the gear drive HH which,which, inin turn,turn, drives the feed rolls II ofof thethe frame saw.saw.

the 0.25 hp motor JJ which changeschanges the feed speed.speed.

the stand K on which the parts of the feed mechanism are mounted and which is fixed to the frame by four bolts.

Both,motorsBoth-motors are controlledcontrolled byby aa con-con­ trol panel placed on the loglog carriagecarriage oror on a specialspecial stand.stand.

It worksworks as follows:

The motor of the feedfeed mechanismmechanism drives,drives, with V-belts,V_belts, a shaft L.L. TwoPo taperedtapered discsdiscs (B andand C) are mounted on thisthis shaft.shaft. The inside discdisc BB is fixedfixed on the frame and cannot be moved sideways.sideways.

The outside disc C, however, isis mounted directly onon aa movable shaft.shaft. By moving the shaft L the position of the outside the shaft L the position of the outside Thli disc C can be changed Lnin the longitudinallongitudinal 111E1111 IP- direction of the shaft.shaft. a ar Between these two discs runsruns the wide V-belt D.D. The other endend of the beltbelt drivesdrives pulleys E and F on driven shaftshaft G.G. - 3344 -

The inner of these discsdiscs EE is movablemovable along the shaft. In the longitudinal direction of thethe shaftshaft (as(as seenseen outwardsoutwards from the frame) this disc is spring-loaded b,yby a coil springspring insideinside thethe hubhub andand isis therefore alwaysalways pressedpressed against the out-out­ side disc.disc. Through this the beltbelt isis stretched.

The driven axle G is in driving contactcontaot with the lowerlower feedfeed rollsrolls II through a spur gear unit H.H. The upperupper feed rolls M are driven by a chainchain transmissiontransmission NN fromfrom thethe feeding mechanism.

The feed speed is varied byb,y changing the position of the outside disc C in relation to thethe insideinside discdisc onon thethe shaft.shaft.

Through this the belt will run on a bigger or smaller diameter between the two tapered discsdiscs E and F.F. Since the length of the belt andand thethe distancedistance betweenbetween the axles G and L are unchanged, the tapered discs E and F on the drivendriven axleaxle willwill auto-auto­ matically adjust themselvesthemselves toto newnew conditionsconditions by the spring load that aotsacts on the inside disc.

If the discs B and C are pressed closer 10 together the belt will run on a bigger 20 diameter between discsdiscs E andand FF onon thethe drivendriven 30 shaft. Through this the &rivendriven shaft G - 40 will rotaterotate fasterfaster thanthan thethe shaftshaft L.L. 50 60 Since it is the driven shaft G that 70 is connected with the feed rolls

the rotation speed of the feed rolls will increase when the out-out­ side disc CC isis moved closercloser toto the insideinside discdisc B.B. - 35 -

OnOn the other hand, the belt will run on a smaller diameter ifif the discsdisos B 10 and C are moved away from eacheach other.other. AtAt 20 the same time, the belt isis runningrunning onon aa 30 bigger diameterdiameter betweenbetween the tapered disc-sdiscs E 40 and F on the driven aTie.CL%le. 50 60 SinoeSince it is the driven axleule G thatthat isis 70 connected with the feed rolls

.. "II the rotation speed ofof thethe feedfeed rolls will decrease when the discs B and CC on thethe axleule shaftshaft are moved away from eacheach other.other.

In thisthis wayway the gear ratio between the engine of thethe feedfeed meohanismmechanism andand the geargear box canoan be varied infinitely in the ratio of 1:7. This means that the feeding can be infinitely varied from 10 to 70 mm/stroke.mmistroke.

The adjustment of thethe feedfeed speedspeed isis read on an indicating devioedevice placed above the feed mechanism.mechanism. - 36 -

9. Appendix BearillgsBearings

The bearings dealt with in this manual, viz:vizl lubricating White metal be.arl.ll2bearing lubricating - whitewhite metalmetal bearingsbearings White metal device - needle bearings, and bushor cupcup - spherioalspherical roller bearings halves are all radial bearings, which means that theythey ' bearing mainly take up stress working inin thethe radialradial housing direction. '4,,,, , White metal bearings consistconsist of:01'1 ..,,., - a bearing housing,hOUSing, made ofof oneone piece;pieoe; a lining inin the shape of a bush or two-oup halves;halves; _ a lubricationlubrioation device.devioe. It oil The bearing cups are made of bronze, which The bearing cups are made of bronze, whioh 1.1... e, ....-L- cup halves oancan stand a high bearing pressure andand a highhigh numbernuMber of revolutions. \ 1 They are mounted in the bearing housing I with a round fit.fit. TapsTaps and collars prevent them from turning withwith the axle oil

The lining castoast intointo these bearing cupscups is made of tin,tint antimony, copper andand lead.lead. --''' This compositionoomposition metalmetal isis calledcalled whitewhite metalmetal or babbit. bush To fix the white metal properly onon thethe bearing cup face aa fewfew shallowshallow holesholes areare drilled into the surface, alternatively, itit oil - o is provided with a few dovetail slots.slots •

wa 1 Ns= IIwhite .BeoauseBecause white metal has a low meltingmelting ' metal point, any overheating means that only the point, any overheating means that only the dovetail Amilcomposi- metal lining isis damageddamaged andand notnot thethe bearing.bearing. slot tiont ion It is easy to castcast aa newnew metalmetal lining.lining. $1. . ll The movement inin a slidedide bearing isis mademade while the shaft journaljournal is sliding against the MII: bearing cups.cups. Friction then occursooours but itit isis Mr very muohmuch reducedreduoed by an oil film createdoreated between the two bearing surfaces by means of special oil-011- ways.wayB. //IF rr '''.- oilfilm \"',_:-7. oilfilm When the shaft starts to rotate inin thatthat bearing itit brings withwith itit anan oiloil layerlayer thatthat isis - ... pressed in under the shaft like a wedge, whioh lifts the ¡shaftshaft fromfrom thethe lowerlower bearingbearing cup. TheThe faster the axle rotates,rotates, thethe thickerthioker thethe oiloil wedge. Therefore, it is important that bearing "play" is bigbig enough to make it possible for the oil011 wedge to grow andand liftlift thethe shaft.shaft. - 3737 --

Roller bearings isis the comprehensiveoomprehensive term for cylinderoy1inder bearings andand needleneedle bearings.bearings. Spheric roller These types of bearings conaistconsist ofofs bearing

outer ring Inner inner ring

rollers, and

holders for the rollers, which keep themthem apart and inin position.

The bearing pressure isis absorbed byby thethe ring rollers, positioned betweenbetween thethe twotwo rings.rings. Roller bearings offer less rolling resistance than ordinary bearings and resistance is nearly independentindependent ofof velocity.velocity.

These two types of bearings aleoalso requirerequire less lubrication and, at the same time, the risk of overheating isis smaller.smaller. Contrary to white metal bearings, these bearings are lubricated with grease.

The lower connecting rod bearing andand thethe bearings of the oraIlkshaftorankmhaft pins consist of spherical double rowrow rollerroller bearings.bearings. The two rows of rollers have a common spherioalspherical roll conveyer in the outer ring, which makes them self-oontrollingselfcontrolling andand ableable toto adjustadjust themselves to the taper ofof thethe shaft.shaft. wer connecting rod bearj..ng and The upperupper connecting rod bearing con­con- . s of the crankshaft pins sistssiste of a type of needle bearing oalledcalled gudgeon pin bearing. Needle bearing The reason for having a needle bearing Grease ways here isis that this type of bearing isis suitable when the lIIOVementsmovements are to and fro, whichwhioh isis Needles the case for the upper endend of the connectingconneoting N.1111.21111My. 6 rod. Needle bearings also have good resis-resis­ ,-:1314401A46.141b14..":\ -,11.1414*.7 tance against shockshook loads.loads.

Since the friction in a needle bearing is threethree times biggerbigger thenthan in a roller beal'­bear- ' Ili Lubrica- ing, it is not suitable for the lower =It ting tank conneotingconnecting rod bearing, where speed and friction are high.

Instead ofof rollersrollers thethe needleneedle bearing has two rows of needles, each needle being 70 II1IImm long and 6 mmDID inin diameter.diameter. The gudgeon pin isis holed and serves as a tank for the lubricant. - 3838 -

PART IIII FORCESRlRCES AND MOVEMENTSIDVEMENTS

~ 1. BodiesBodies, , MotionsMot ions andand PUreesForces •••••••••••••••••••••01,00000000000 39

2. Stress and Strain...... 43 PrimaryPriJDar;r Stress:Stress, Compression ••••••••••••••••••o.oeooeeopeetegeoey 44 Tension 00000000DOO.0.00000000•••••••••••••••••••••• 45 Seoondar,rSecondary Stress:StreBs: Shear ••••••••••••••••••••••••00000000000,7000000900000 46 Torsion ...... OGOOOODOOGOODOCOOO0000..... 47 Combined Stress:Stress. Bending ...... 48 Compression andand. Bending ...... •..•.• 51

3. Static and Dynamicn,n&mio StressStress OOOOO•••••••••••••••••••••• ...... 0000000 53

4. Factors that influenceinfluence struotural strengthstrellgth .....••••• 55 ConcentratedConoentrated strainsstrains ...... ••••••••• 5555 Surface cpaalityquality .00000000000••••• • •••••••• 5656 CorrosionCOTTOSiOn 09000.001,005,0000440••••••••••••••••••• 56 Heat treatment ...o.n.o....."••••••••••••••• 57 CheeksChecks oesoec0000m0000p000gao••••••••••••••••••••••• 58

5. The Movement MeohanismMechanism of the Frame Saw •••••••• 59

6. PiercesForce. actacting ing onon thethe sash,sash, thethe conneotconnecting ing rod and crankshaft journaljournal...... 00000 ...... 61 7. The cuttingoutt ing conditionsoondit ions of the Sash ...... o..••••••••••••• 66 Appendix ...... Append1%: •••••••••••••••••••••••••••••••••••••••ec000000comeoaag0000000ragoo 67 - 3939 -

MassJ>!ass 1. :Bodies,Bodies, MotionsMot ions andand DiorcesForces

In mechanicsmechanics a car or the sash of a gangsaw is called a body. _...I I -The weight of a bodybody or, more correctly,correotly, its mass, is given L4, 6, 4*. -4....,. in kilograms.kilograms. r .-?At ' A moving body hashas a certain velocityvelooity which isis defineddefined inin Velocity metres per secondsecond (or(or minute) or in kilometres perper hour.

I 1 A changechange inin velocityvelocity isis called:called: ,

4 . Acceleration, ifif thethe velocityvelooity is increasd, and /^ , ..__.) -' '111111.1 1I I *:-. W Retardation, if the velocity - is reduced. AccelAcceleration erat ion The acceleration or retardation isis thethe change in velocityvelocity (e.g. m/sec)m/sec) over a oertaincertain 1.Dlitunit of time (each(each second). It is,is, therefore, measuredmeasured in a unitunit thatthat is = -_,A-T-=T== === metres per seoond,second, every second; so itit f---- __ consists of: ,C-7- --7'.., i ,_, A -.A0 .... .t ..W.- -.:(-_-_0 a length unit, and -= a squared time unit.unit. There isis a 1.Dlitunit for acceleration called RetardationRet ardat ion 'metres"kuetres perper secondsecond squar!'!d",squarRd", written as m/sec2m/seo2 or m/S.m/s2• ..

\I w I I. I . II- "f-4 ...4. ..A '''' , ,. .If 4WP , . . _ .74 1--;---'A`VV A b - P - 40 -

To make a body (a(a mass) accelerateacoelerate or retard (acoelerate(acoelerate negatively) a force A cold .,interwinter morning the car "ill not o • • ~ ()" oJ start. is needed. The relationship between force, mass and acceleration issiSI . .

FORCE .- MASS x ACCELERATION

whiohwhich isis writtenl written: F _F.mxa m x a

wherewhere: 1 F -. the force affecting the body or the mass; m . - the mass ofof thethe body;body;

a . - the acoeleration. high force is ed to accelerate The unit for massmasa of a body isis it from ,stand.still kilogram (kg).(k€). to motion.

The unit of force isis thethe Newton.Newton.

1 N -. the force that givesgives2aa mass of 2 1 k€kg an accelerationacoeleration of 11 misecm/seo .•

The unit for force used to be the poundal, which was the force required to give an llblIb mass an acceleration of Once it moves, less force is needed 1 foot/seofootieec2.2• This text uses the metric keep it . going until one wants to stop Newton. • AlgyAny forceforce thatthat actsacts onon aa bodybody always creates a resisting force insideinside thethe body.body. .. ' ~ • 0 ' .. .. . , ~,.. " .... J 1'1 .. '/ .. . .. A body is reluctant to change its A body is reluotant to ohange its o state, whether itit isis at rest oror inin motion.motion. If it is moving, it is also reluctant to 3 changechnnge itsits direction.direction.

FbrFor instance,instanoe, ifif the movement of a car or a gangsawgaogsaw sash is to be changed in speed or direction, these bodies trillwill try Then a higherr force idr. guirecr to to maintain their existing velocity or 'bring-bring i"tit .l.t;;ll"ato a standstill.15""'-I1ClB'L _°_,--. .6 direotion.direction. These resisting and internalinternal llj forces are calledoalled inertiainertia forces.forces. They are givengiven inin Newtons.Newtons. r ..,

2 If one tries to change the velocity oror LI " the direction of, for instance, a car or a the direction of, for instance, a oar or a "' "~:~~::=:::'~~~~~!:'!~~ sash, such bodies will resist with forces ~ 4' ~~ = called inertiainertia forces, that are measuredmaasured inin~------=~ __~==~ __ ~~~~~~~=1 Newtons. - 41 -

What we have dealt with so far are bodies with inertia forcesforoes in linear move­move- ment: i.e. trying to move strai€htstraight ahead with unchanged velocity.velooity.

IfIf aa body,body, for instance,instence, aa weightwei€ht attaohedattached to a rope, isis swungBW1lllg inin aa circlecircle it will,will, due to inertia forces,foroes, try to move straight ahead, i.e. to move away from the centre. This type of inertia force is called centrifugal force.foroe.

The magnitude of the centrifugalcentrif'ugal forceforce depends on the maBSmass of the moving body,body, thethe radius of the oirclecircle and the velocityvelocity ofof the body. If the velocity isis unchanged, but its weightweight oror thethe radiusradius ofof thethe circle is mademade two, three or fourfour timestimes bigger,bigger, the centrifugalcentrif'ugal forceforce willwill alsoalso becomebecome two,two, three or four times bigger.b~er. On the other hand, if the velocityvelocity (for instance the number of revolutions perper minute) isis doubled, trebled, etc., the centrifugalcentrifUgal force will increase with thethe squaresquare ofof thethe velocity, i.e.i.e. itit will becomebecome 22 ix 2,2, 3 x 33 or 4 x 44 times greater.

This means in practice that, forfor frameframe saws, it is the rotational velocity,velOCity, i.e.i.e. the number of revolutions, that has thethe greatest influence on the magnitude of the centrif'ugalcentrifugal force.force, If the number ofof revolu­revolu- tions is doubled, the centrifugal force is increased four times. - 42 -

A car has a wei8htweight of 1000 kg. We want to accelerateaocelerate the car fromfrom standstillstandstill to a velocity of 7272 Ian/hourkm/hour in 10 seconds. What magnitude ofof massmass forceforce iis-B required for this aooelerationacoeleration (presuming(presuming thatthat thethe accelerationacceleration isis uniform)?

The mass .- 1000 kg The velocity =a 72 km/hIan/h .a 20 m/sec. The accelerationacoeleration is:is: VelooityVelocity _ 20 2 2 m/sec2m/sec Time = 'iO10 = The requiredrequired force force is isthen: then: F _ F.mxam x a

F =a 1 000 (mass)(mass) xX 22 (acceleration(acceleration .a 22 000000 Newton.Newton.

2000 Newton

72 Ian/hour Standstill

ForFbr comparison we can find out what forceforoe is requiredrequired to accelerate a moving gangsaw sashsash weighingwei8hing 345345 kg from bottom dead centre where it is stationarystationary (at 66 o'clock)o'clock) toto maximummaximum velocity, whichWhich at 330 revolutions/Minrevoluticns/min isis equalequal to 10.3 m/secm/éec and takes place at the 3 o'clock InertiaInert ja position. 142 140140 : Newton . = The acoelerationacceleration of a sash is not uniform 11 '. 14 . 1 as the acceleration of the car inin the above 10 . ' example. This makes ourOUT calculations some­some- 9 what more complicated. Without going intointo , details of how the calculations are made, the maximum acceleration at the upper turning point 411111i0'' (at(at 1212 o'clock) isiB 412 m/secm/sec22 (see(see figure along-nlong­ side). AccelAcceleration erat ion ofof the SashSash The required force isis then:thenl 345 (the(the ma's's) mass) = 140 Newton. x 412 (the(the acceleration) - 142 140 Newton. mng This is the force that is transmitted by the .m.. upper crankshaftcrankshaft bear5rg.bearing. The magnitude of thisthis force canoan be compared w,ithwith the lesser force ' 2 12 11 10 .-emammw 1 12 required inin thethe carcar example.eX!llllpl e. KL KL -NEEff- ,x7.7_!!_ - 43 -

2. Stress and Strain

All bodies oonsist of very smallsmall particlesparticles calledcalled molecules.molecules. These are attached to eaoh other byby certainoertain internalinternal forcesforoes inin thethe materialmaterial itself,itself, so-so­ called cohesiveoohesive forces.foroes.

When a mechanical part isis influencedinfluenced byby outsideoutside forcesforoes itit undergoesundergoes aa changeohange of form or shape, usually soso smallsmall thatthat itit cannotcannot bebe seenseen oror measured.measured. These outside foroesforces strive to changechange thethe locationlocation ofof thethe molecules (and(and soso thethe shape).shape). At thethe samesame timetime thethe cohesivecohesive forcesforoes insideinside thethe materialmaterial resistresist toto preventprevent thesethese changes of location.location.

The external force isis calledcalled aa stress:stress: it is the force on aa body exertedexerted over a given area. The internal forceforoe resisting the changechange of shape isis calledcalled strain, and isis measured inin thethe samesame way,way, aa forceforoe overover aa givengiven area.area.

If the externalerlernal forces are biggerbjgger than the internalinternal ones, a changeohange of form of the material takes place.place.

If the body recovers itsits originaloriginal formform completelycompletely whenwhen thethe stressstress isis removed,removed, the change of form isis called elastic.elastic.

Depending on the material ofof thethe bodybody andand thethe magnitudemagnitude ofof thethe force,foroe, aa permanent deformation sometimes occurs.occurs. This change of formform isis thenthen saidsaid toto bebe plastic.

If the erlernalexternal forces are even greater, the changechange ofof form cancan go soso farfar that the material will break.break. ThisTIAB is called fracture.fracture.

roTHBOTH STRESS AND STRAIN ARE FORCES THAT ACT ON A GIVEN AREA OF THETHE MATERIAL, i.e. THE RELATIONSHIP 1:,F, WHERE F ISIS THE FORCE THAT ACTS ONON THETHE CROSSCROSS SECTIONSECTION A. A 2 2 They areare measuredmeasured in Newton/mmNewton/Mm2 or Newton/omNewton/Cm2.•

NOte:Note: Strain is a force induced as a reaction to stress: it is independent ofcf thethe ~rialmaterial under stress.stress. This is distinct from structural strength, which is: THE ABILITY OF A BODY TO RESISTRESIST BREAKAGEBREAKAGE OROR DEFORMATIONDEFORMATION (CHANGE( CHANGE OFOF FORM)FDRM) CAUSEDCAUSED BY P_ATERNALEXTERNAL FDRCES.FORCES.

The structural strength properties of a material areare usually given as limitslimits that result in permanent changes of form or breakage. A given body hashas differentdifferent

structuralstructural strength for different kinds of stress, viz.viz0 tension, compression,compression, bending,lending, etc.et c • There are three main groups of stresses: , SF, 1. Prime.r,yPrimary stress,stress, i.e. compression andand - A tension.

1 ~ our£oco of ,', 2. Secondary stress, i.e. shear, where ,... '"'''' F the stress isis tangential toto thethe stressstress (see(see figure alongside). Twisting stress - torsion is an example of shear.shear. 2 ~/_ .. _ A ... , - "," 3. Combined stresses oocuroccur whenwhen moremore thanthan oneone stress acts at the same time. This , A. ~:~{ l. ~ F groupgroup incorporates bending. -4444 -

Primary stress:stress: Compression

The figure to the rightright showsshows aa partpart underunder oompression.compression.

A compression in any material is calculated by the following formula:formula: The compressive force ComCompression ression _. The ?ompressive force p SectSectional l.onal a.I:eaarea of rod

Compression occurs inin a sawsaw frameframe in the following places:places:

In thethe columns of the sash due toto the tension from the insertedinserted saw-saw­ blades.

In thethe oonnectconnecting ing rod when itit reduces the downward movement of 0" the sash, roughly betweenbetween 9 and 6 o'clock, where compression isis i" : greatest. (See figure and ," appendix). ~ - -

In the oonnectingconnecting rod when itit aoceleratesaccelerates thethe sashsash upwards,upwards, roughly between 66 andand 33 o'clock.o'olock.

strain 500.000- 650.000 -4545 -

PrimaryPrima- stress: TensionTension

The figure to the rightr~ht showsshows aa partpart under tension.tension.

The tension in any material isis cal-cal­ culated u.rby the following formula: The stretching Tension E. The stretching force Sectional areaarea of the rod

Applied to the above example:

T 1 Newton 2 T = 1N/cm2 - 1 cm2 1 N/cm IZJ 1 em Fbr a saw frame the biggest tension stress isis inin thethe connecting rod:rod:

when the velooity of the sash going up is being reduced (retarded), which is ringhlyroughly between between 3 and 12 o'clock as it heads for the upper deaddead centre,centre, where the tension in the connecting rod is greatest. (See figure and appendi:z:.appendix.) )

when the connectingconneoting rod pulls the sash downwards, roughly between 12 and 9 o'olock.o'clock. - 46 -

Secondary stress:stressl Shear

The figure toto thethe rightright showsshows aa partpart under shear stress.stress.

These stressesstresses arisearise whenwhen thethe actingacting forces occur in the planes of the surfaces concerned, soso thatthat twotwo adjoiningadjoining surfacessurfaces are pressed pastpast eacheach other,other, asas when aa pair of scissorsscissors areare cutting.cutting.

This is often the case inin riveted joints. In frame saws shear stress occurs inin the rivetsrivets atat thethe basebase ofof thethe sawblades.

Shear stress isis calculated byb,y the formulafomula below:belowl

The shear force Shear -1= Area of the shearing material

rivet -4747 -

açcada_a-Secondary stress: Torsion

A special formfonn of shear is twisting usually called torsion.torsion.

This stress occursoccure when, for instance, a shaft isis subjected to a turning movement, for example, when aa screw or boltbolt isis tightened.tightened.

Imagine aa shaft consisting of an infinite number of thinthin discs.discs.

IfIf suchsuch a shaft is turned, all these discs will turnturn slightly,slightly, which results inin shear stress between thethe discs. iii This type ofof shearshear isis calledcalled torsion,torsion. ---..1AOMUMORAMVXMONSUIMMNI The figure shows how torsion increasesincreases 1111=11111111111111.1111 from the centre of shaft towards thethe rifiti periphery. NENNINEN MON" Because of this,thiS, shafts can bebe made hollow without significantly reducing torsionaltorsional strength,strength, yetyet markedly reducinereducing weight.weight,

Torsional strength isis proportional to the cubecube ofof thethe diameterdiameter ofof thethe shaft.shaft. If we double the diameter, the torsional strength will increaseincrease eight times, which means that we cancan increaseincrease thethe twistingtwisting force eighteight timestimes withoutwithout increasingincreasing thethe stress onon thethe shaft.shaft.

D=l • G •

D=2 - 4848 -

.Combined stress:stress: Bending

BendingBending stressesstresses occuroocur if,if, forfor instance,instanoe, a bar iBis under pressure perpendicular toto itsits centreoentre lineeline. Bending stresses are composedoomposed of both tension andand compression.oompression. I • At the centreoentre lineline thethe stressstress isis I I zero. I Above the centreoentre lineline therethere isis compression.oompression.

Below the centreoentre lineline therethere isis tension.

To calculateoaloulate the magnitude ofof thethe bending stress isis complicatedoomplioated andand itit is notnot pursued inin this manual.manual.

A praotioalpractical example, however, canoan?======~ assist our understanding. Version A It is muohmuch easier to bend a ruler as shown in version A inin thethe figure,figure, than as shown in version B.

We oancan see that the measure H (taken in thethe same direotiondirection as the bending force) is more importantimportant to bending resistanceresistanoe thanthan thethe measuremeasure B.B.

These two factors,faotors, i.e.:i.e.:

the relationship of stress around the axle beambeam centre;centre;

thethe influence ofof the measure H onon thethe resistance to bending, Version B are behindbehind thethe designdesign ofof thethe I-secticnIsection beam, oror I-girder.Igirder. B .------. - 49 -

When constructingconstruct ing thethe I-girderI-girder the aim isis to make thethe waist-line:waist-line:

"narrow'narrow (measure B) to reducereduce thethe amount of material inin those sections where itit isis notnot neededneeded (the stressstress is minimal in the centre line), and

_ high (measure(measure H)H) to concentrateconcentrate the mass of material as far away as possible from thethe beambeam centre,centre, therebythere~ locating asas muchmuch materialmaterial as possible to sectionssections wherewhere thethe magnitude ofof tensiontension andand corn-com­ pression isis strongest.strongest.

A given cross sectional area (see figure) of differing distribution, illustrates in this series of drawings how the structural strengthstrength ofof girdersgirders can vary. We have obtained a bending strength in d) more than three times stronger than the originaloriginal one in a).

2000 :Q: Weight KG/CMKG/eM I in all alternatives , j 1.2751,275

150 125-1 25

a) brealcloadbreakload b) breakload 150 50 130 2600026 000 KGKG 4040000 000 KGKG O

125 25

125 50 IIU

250 150 d) breakl.oad breakload 175 75 c) breakloadbreakload

N7. 4545000 000 KGKG 8000080 000 KGKG 50 50 - 50 -

In a saw frame bending stressesstresses occur in the conecting rod due to inertia that origina-tesoriginates whenwhen thethe lowerlower part of thethe connectingconnecting rodrod isis foroedforoed toto follow the rotatingrotating movementsmovements ofof thethe crank shaft journal.journal. These stresses are strongest at thethe upward strokestroke atat 3 o'clock and at thethe downwarddownward stroke atat 9 o'clock. (See figure and appendix.) The connecting rod must therefore 3~ be:bel

as light as possible to reducereduce inertia. 6 as strong as possible to resistresist bending stress.

ForFbr these reasons connecting rodsrode are I-shapedI-shaped inin thethe cross-beamscrose-beams duedue toto stress from sawblade tensiontension (about(about 7~9070-90 000 N/blade) and alsoalso fromfrom thethe inertia of the sash and the connecting rod (about(about 150-20015~200 000 N).N).

ForFbr thethe samesame reasons,reasom, appliedapplied to the construction of Ingirders,I-girders, cross-beamsorose-beams are made deep (measure(measure H) in order to obtain thethe greatest bendingbending rigidity.rigidity. - 51 -

Combined stress: Compressionand BendingBending

Another example of multiple stressesstresses is that which exposes a bod3body to both com- pression andand bending strains.strains.

IfIf aa barbar (for instance, a conneotingconnecting rod) isis longlong inin relation to itsits cross-cross­ section and comes under influenceinfluenoe of a oompressionalcompressional strain, the direction of which isis not completelyoompletely inin lineline with the oentrecentre line of the bar, the bar will bow.bow. r------.::=~-..::::::===~_l If the stress is high enough, the bar F might finally break.break. F

F

Strains in a Connecting Rod due to Tension, CompressionCompress-ion and BendingBendil!g

----- 1,,\ TotaIota

660 - 52 -

In a saw frameframe thethe greatestgreatest riskrisk ofof this stressstress isis inin thethe connectingconnecting rod.rod.

The risk ofof damagedamage occurringoccurring isis increased if,if, atat thethe samesame time,time, bendingbending forces are present inin thethe connectingconnecting rod.rod. As previously explainedexplained (see(see alsoalso appendix)appendix) in certain positions the connecting rod is subject to bendingbending stress.stress.

As can bebe seen from the figure,figure, the maximum compression occursoccurs atat B.D.C.B.D.C. (6 o'clook),o'clock), and decreases to zero at 3 0'o'clock. clock. Maximum bending occursoocurs between 33 o'clock andand 22 o'clock.o'clock.

The greatest risk of the combinationoombination is between 5 o'clock and 4 o'clock onon thethe upstroke.upstroke.(Figure (Pigure andand appendix.)appendix. ) Compression Bending

9 39 3

6 6 - 53 -

Statical Constraint Stress, 3. Static and DynamiCDynamic Stress

The force creating strsssstress on a bod3"body can be of twotwo differentdifferent kinds,kinde, static or dynamic.dynamiO.

A staticstat ic force maintains thethe samesame magnitude independent ofof time.time. If the force is increased, breakage will eventually occur.occur. The actualactual force at which thethe material will fracture isis called the breaking force andand itit occursooours at breaking point.point. Breaking C) A dynamic force isis characterisedcharaoterised by the fact that the magnitude of the foroeforce Dynamical Constraint varies (pulsates)(pulsates) betweenbetween twotwo extremes,extremes, whichwhioh means that the strains within the body also vary (pulsate)(pulsate) inin thethe samesame way.way. ~.7?t If a mechanical part comesoomes under the continuous influenceinfluence ofof aa forceforce thatthat pulsates repeatedly, fracturefraoture might occur in spite of the fact that the magnitude of the force may be conniderablyconsiderably belowbelotl the static breaking point of the parti-parti­ cular mechanical part.part. The pulsating stress finally strains the mechanicalmeohanioal pastpart so that itit reaches the fatigue limit of thatthat material.material.

Fatigue limitO r:::> - 5454 -

The fati,guefatigue limitlimit ofof aa material isis the maximum static and dynamic stress that can be putput onon aa materialmaterial withoutwithout an unlimited number of pulsatingpulsating stressesstresses causingmusing breRkage.breakage.

The fatiguefati.gue limitlimit ofof anyF;Y materialmaterial isis always well below itsits breakingbreak1ng point.

FbrFor materials frequently used inin mechaniesmeohanios the magnitude of permitted stressesstress es areare knownknown andand tabulated.

One of the best examplesexamples toto bebe foundfound is thethe alternating tension/compression inin the connectingconnectinJ rod and thethe lowerlower cross-croSll­ beam that is alternatively pushed and pulled.

The design of mechanical componentsoompcnents under dynamic stress is always much heavier than corresponding parts underunder statiostatic stress only.

This is the reason whywhy the lower cross beam is so heavily dimensioned.

Another example of a componentcompcnent subjectsubject to fatfatigue i,gue is the crallkshaft,crankshaft, which,which, in addition to torsion, isis alsoalso under bendingbending stress oocurringoccurring eacheach upward andand downwarddownward movement of the sash and the connecting rod.

Referring back to bending stress,stress, the upper half of the crankshaftcrallkshaft is in tension and the lowerlower halfhalf inin compression.compression. (See figure). But,Bit, as the crankshsftcrankshaft rotates, the part that was in tension will develop oompressioncompression halfhalf aa turnturn later.later. FbrFer anya:t13 given point of the crankshaftcrankshaft the stresses are constantly alternating from tension to compression:compressions a typioal example of a component subjectsubjeot toto fatigue.fati,gue. -55-- 55 -

4. Factors that in:fluenoeinfluence StructurelStructural MreRgthStrength

There areare many di~erent different factors that influenceinfluence the structuralstructurel strengthstrength of a component, particularlyparticularly againstagainst fatigue. Some of of thethe most importantimportant are:

Concentrated strains

Sharp corners,oorners, holesholes not properly drilled, different types of nicks,nioks, hackhaok and uneven surfacessurfaoes result inin strainsstrains looallylocally concentrated.ooncentrated.

These cause cause abrupt abrupt restriotions restrictions inin the transmissiontransmission of forceforce throughthrough thethe component.oomponent. This leads to stressesstresses greater thanthan those only due toto thethe reduced seotionalsectional area of thethe nick.niok.

The surfaoesurface of machinemaohine partsparts under dynamiodynamic strain strain mustmust thereforetherefore have allall oornerscorners and edgers well rounder, i.e.i.e. with large radius. (See figure.) --56-56 -

Surfaoe quality

Bodies with polishedpolished andand groundground surfaces demonstrate more resistanceresistance and strength thanthaJl bodiesbodies withwith rough, uneven surfaces.

Corrosion

Rust and other chemicalohemioal corrosionoorrosion reducesreduoes struoturalstructural strengthstrength oonsiderablyconsiderably

This is correotedcorrected by surface conditioning,oonditioning, painting and the useuse ofof rust proofproof materials.materials. -57-- 57 -

Heat treatment

A metal part that hashas been repaired through weldingwelding usuallyunually has a lower B A B fatigue limit duedue to:to: / \]11 I unfavourable structure of the weld material.

builtinbuilt-in heatheat stressstress inin thethe material, followingfollowing thethe welding.welding. a Firstly, (figure(ngurea) a) thethe weldweld material material A as well as the surrounding originaloriginal material B, are heated up duringduring thethe welding procedure above thethe temperaturetemperature at which a structural changechange takestakes placeplace in the materials.

In thisifollowedthis, followed byby uncontrolled cooling of A and BIB, a zone C usuallyunually results which is stiffer and UNremore brittle than the original material B9B, whichwhich reduces itsits fatigue limitlimit (figure(figure b).

In orderorder toto retainretain the structure and improve the strength of the material inin the weldweld joint, annealing isis practised. This meansmeann thatthat zones AA andand B areare heatedheated up to 750 - 850'C (depending(depending onon carbon content) forfor halfhalf to one hour, followedfollowed by cooling inin normal air.air. (Electric welding, however, does not normally c require this procedure.)

Seccndly,Secondly, when welding a given part (see figurefigure c)c) thethe material heated at point CC tends:tends toto expand. The rest of the material B is still cool and does not expand, but rather prevents expansionexpansion andand strives to press together thethe materialmaterial ofof the C zone which is plasticplastio and workable due to high temperature and therefore d causeecauses bulging (figure(figure d).d). Expanding and compressive forces more or less eliminateeliminate eaoheach otherother andand thethe frame remainsremainn rectangular An exampleexampl e of how heatheat as long as C material isis hot.hot. stress can occur when a machine foundation isis welded togethertogether atrointat !Oint c. - 58 --

But&.t then the componentcoJDpOnent coolscools off,off, the material aroundaround CC oontracts,contracts, whiohwhioh resultsresults c in stress and shapeshape change.ohange. To eliminate this, the componentcomponent mustmust bebe heatedheated upup inin

one of thethe followingfollowing threethree differentdifferent ways:Waysl I" I i ! "' II I i •I I I 1. The material at G isis heatedheated up toto I I I I I I I approlimatelyapproximately the samesame temperaturetemperature I ' . I as the material atat pointpoint C.C. This I I , I creates a uniform expansionexpansion andand oompression.

2. The whole partpart isis heatedheated upup toto 5-600°C5-600"C during the welding, whichwhioh makes thethe material plasticplastio soso thatthat stressstress isis eliminated, so-calledso-called hothot welding.welding.

3. The whole part is stress-relief annealed at 5-6000C5-600·C within aa fewfew hourehours after thethe completioncompletion ofof thethe B welding.

Nbte:lbte: Welding of more complicatedcomplioated partsparts should be left to experienced workshops.

CheoksChecks

As we have seen, the sash isis under significant stresses and somesome componentsoomponents are JIlOremore subject to fatigue thanthan others.others. ToTb ensure proper functioning ofof thethe frameframe saw, these vulnerable parts:partsl

the lower crose-beamcross-beam the connecting rod the crank pin the cranks must be checkedcheoked regularly and given maintenanoe.maintenance. Incorporate checksoheoks intointo thethe preventivepreventive maintenance programmeprogr8Jlllle - 5959 --

Upper guides 5. The II'JOvementMovement MechanismMeohanism of thethe PrmneFrame SawSaw

The osoillatingoscillating movementmovement meohanismmechanism of the frmneframe saw is based on crankorank motion, i.e. aa rotating movement is convertedoonverted throughthrough aa oonnectingconnecting rodrod into aa to-and­to-and- fro movement.

The figure is an explanatory sketchsketoh of the moving parts of a frame sawsaw where:

A c. the centreo entre of the crankshaftorankshaft Lo"TerLower guides B .c the oentrecentre of the crankorank pin Lower turning C -= the oentrecentre of the sash pin.pin. • . -.J_ PbintPoint A rotates at an eveneven speedspeed whichwhioh isis 'H'H o 0 the number of revolutions ofof thethe frameframe .<:: Q) saw, for instance 350 r/min. for instanoe 350 r/min. j-g~ Q).p cd Point B will then desoribedescribe a oirclecircle aroundaround ...:lllllll point A. point A. This isis done atat anan evenevan speed,speed, Upper -.- as BB isis directlydireotly linkedlinked toto A.A. turning point Point C is given a movement that isis identicalidantioal to the movemantmovement of the sashsash as it oancan be regarded as a part of thethe sash.

At the same time it canoan be regarded as a part of the upper connectingoonneoting rod bearing and the distanoedistance that it travels a. the length of the stroke of the sash ._ (in our case) 600 mm.I11III. As thethe sash isis steered inin itsits guides, the rotatingrotating move-move­ ment of A and B is transformed to a move­move- ment upup andand down.down. - 60 -

During the movement of point CC the speed at which itit travels and itsits direction vary. c--;-- The figure shows thethe speedspeed ofof pointpoint C.C. The horizontal axis has beenbeen divideddivided intointo the 12 points ofof the clock face. The verticalvert ical axis showsshows the speed of C at a certain clock face position of B.B.

The speed is at itsits lowest,lowest, i.e.i.e. 0Om/min m/min at:atl

top dead centre (TDC), i.e. when B is top dead centre (TOC), i.e. when B is A -T----7'ii at the 12 o'clock position and at: B---,->-_,.

bottom dead centre (BDC),(BDC), i.e.i.e. when B is at the 6 o'clock position.position.

The speed isis atat its highest during:during:

the downward movement when BB isis atat Velocity of Sash the 9 o'clock position and duringduring

the upward movement when B isis atat the 3 o'clock position.

As the speed of movement of the sash changes during oneone revolutionrevolution ofof thethe crankshaft, this meansmeans thatthat thethe sashsash isis alternatively acceleratedaccelerated andand retarded.retarded.

The figure shows the acoeleration of point C.C. It indicates that the acceleration

is greater at the TDC and BDC, or the turning points, when point B is at 12 and 6 o'clock positions Acceleration of SashSash and that

accelerationacoeleration is greater at the upper dead centre (point(point B at 12 o'clock)o'clock) than at thethe lower dead oentre (B(B at 66 o'clock).o'clock). - 61 -

6. Forces acting onon the Sash,Sash, thethe Connecting Rod and the CrankshaftCl'anksha:f't journalJournal

The sash and the lower cross-beamcross-beam inin particular are under forces that originate from:

the moving parts of the frame saw (sash, sawbladessawblades and parts of the connecting red),rod), particularly the acceleration and retardationretardation ofof thethe sash

-the cutting force at sawing.sawing.

With insertedinserted blades an 18" sashsash weighs around 245 kg, a 26"26" sash weighs 345 kg and a 34" ,Bashsash 400400 kg.kg.

The upper end of the connectingconnect ing rodred moves up and down likelike thethe sash.sash. Ther&-There- fore a certain part of the massmaas of the connecting rod (around 55 kg) can be added to the mass that moves upwardupward and downward.

We have seen earlierearlier that:that:

ForceFbrce =c MaasMass x Acceleration.

In this case, the total forces cancan be calculatedcalculated by multiplying the acceleration of the sash at different positions by the weight of the sash plus the weight of the sawblades and the hangers plusplus 55 "kg of the connectingconnecting rod.rod. - 62 -

ByB.y their weight the fitted sawblades inoreaseincrease the foroesforces but they also influenoeinfluence the sash because ofof thethe fittingfitting tensiontension whiohwhich can bebe 70,00010,000 NN oror moremore forfor eacheach blade. A frame saw that holds 9 blades thus has a fitting tension of 630 000 N in total. Apart from these forces, the sash isis also subjectsubjeot toto cuttingoutting forces that arise from sawing. strain 630.000 NEWTON These forces,foroes, at leastleast the ones that act at right anglesangles toto thethe sawblades,sawblades, inoreaseincrease withwith the square of the feed speed. The stress onon thethe bladesblades is,is, strangely enough, greater while return-return­ ing than while sawing.

When sawi1'lJ5sawing a 40 cmom cant at a feed speed of 33 mmmm/strcke, stroke, thethe forceforoe thatthat originatesorigirates from feeding isis 22 000000 NN atat return sawingsawing justjust afterafter thethe turnturn ofof thethe stroke at the BDC.ROC.

Under the very same oantcant size and 2 000 feed speed, the force at the cuttingoutting movement is biggest justjust before the ROCBDC and reaches 1 400 N/blade.N/blade.

The oonneotingconnecting rod is subjectsubjeot to forces that consistoonsist of:of:

foroesforces from the upward and down-down­ ward moving parts (sash,(sash, blades and part of the connectingoonneot ing rod).rod).

outtingcutting foroesforces at sawing.sawing.

inertia forces.

The first two of these inertia forces have alreadyalrea~ beenbeen dealtdealt with.with. Here we disoussdiscuss the third group of influenoinginfluencing forces.

6 - 63 -

When the lower endend of the connectingoonneot ing rod isis rotating itit isis influencedinfluenoed byby" forcesforoes of'of inertiainertia that strivestrive toto bendbend it.it.

These forcesforoes are spread along the oonneotingconneoting rod but,but, toto makemake itit simple,simple, we canoan assumeaeeume thatthat theythey act fromfrom one point only,situatedonly, situated one-thirdon_third downdown thethe length of the connectingoonneoting rod from the centreoentre of thethe crankorank pin.pin.

The connectingoonneoting rod is under maximum bending stress atat thisthis point.pOint. How the 9 3 9 inertia foroesforces that act on the connectingoonneoting rod changeohange their sizesize andand directiondireotion atat different positions ofof thethe crankorank pinpin isis given inin thethe figurefigure alongside.alongside. 6

From this figurefigure we canoan seesee thatthat these forcesforoes are zerozero atat thethe turningturning points (12(12 and 6 o'olook),o'clock), while they reach their greatest at a point situated roughly where the connectingoonneoting rod and the radius of the flywheelflywheel formform aa rightright angle, whiohwhich occursoocurs justjust beforebef'ore thethe 3 o'olooko'clock and justjust after thethe 9 o'clocko'olook positions.

As indicatedindioated in the appendix, the 9 other stresses onon the connectingoonneoting rod,rod, tension and compressionoompression are smallestsmallest when thethe bending stressstress isis largest.largest. 6 But on thethe otherother hand,hand, tensiontension andand com,- 001&­ pression increaseinorease when bending decreasesdeoreases Bending strains towards the dead centres.oentres.

Stretching su'aulS - 64 -

The crankshaft journaljournal isis subject to all these forces, transmittedtl'8llBmitted to the crank pin through the lowerlower connectingoonnecting rod bearing. The biggest force acting on the connectingconnecting rodrod bearingbearing occursoocurs atat the upper deaddead centre,oentre, i.e.i.e. thethe 1212 o'clocko'clook position.

The whole ofof thisthis forceforce isis notnot trans-trans­ mitted throughthrough thethe crankshaftcrankshaft bearingbearing toto the base plate and the foundation butbIlt isis reduoedreduced through counteroounter balancing of the flywheel.

Flywheels are made with permanent counterweights placed on the opposite side of the crankshaftcrankshAft from the crank pin, which shifts the centrecentre ofof massmass towards that side.side. The distance from the centre of mass to the centre of rotation is thus modified soso thatthat allall the rotating mass forces eliminateeliminate eacheach other as much as possible.

As shown inin thethe figures:figures: Ertra Countenle ight 01Cl is the centrifugal forceforce of the rotating part of the connecting rod, the connect-connect­ ing rod bearing and the crank pin, while

02C2 is the centrifugal force of the eccentrically placed counterwsightscounterweights of the two flywheels.

ItIf thesethese twotwo oentrifugalcentrifugal forcesforoes (C1(01 and C2)02) have the samesame magnitude,magnitude, 02C2 willwill counterbalance Cl.01.

When the orankcrank pin isis at the 6 and 12 o'clock positions, the upward Tension and downward moving inertiainert ia forces of the sash and part of the connecting rod alternatively put compression and tension on the lower connecting rod bearing. (Appendix.)(Appendix.)

CompreBsion -65-- 65 -

These up and downward acting inertia forces cancan be reduced,reduced, however,however, C2 Cl if the force C202 iBis made bigger than the force Cl.01.

Part of the up andand downwarddownward forceforce F whichwhioh isis transmitted through the connect-connect­ ing rod from the sash and the up and downward moving part of the connecting rod will then be counterbalancedoounterbalanoed verti­verti- cally.oally. The force F,F, however,however, isis zerozero at the 3 and 9 o'clock positions.positions.

02C2 can be increased by melting lead into speciallyspecially provided holes inin the fly-fly­ wheel.

To obtain the bestbest resultsresults fromfrom thethe counterbalance,oounterbalance, thethe sizesize ofof thethe leadlead weight must be tested individually for each frame saw,saw. Cl C2 The out-of-balanceoutofbalance that that thisthis createscreates inin thethe flywheelflywheel willwill cause forces that do not counterbalance when~lhen the crank taptap is in thethe 3 and 9 o'clock positions where F a O. This willwill cause some horizontal vibration but these are lessless ~::::::::::::::::;:::::::::::::::::::~ than those that would occuroccur ifif nono balanc- r ing was done of thethe flywheel.flywheel. The up and downward forces would then create very strong vertical vibration. '\\, /: \ Cl.r ~C2 . \ \ ) \',\, !. r - 66 -

7. The Cutting Conditions of the Sash

The working stroke (cutting)(cutting) Bi

Bj

~. ~ 1 2 3 44

äoOD DirectionDirection of feed 0

The returnr eturn strokestroke (free.(fre.e.. Wb!l!llixlg)wheeling)

A. Efficient cuttingcu ing B. Less efficieiltefficient cuttingcutting c. Wood crushing D. Return sawing E. Free wheeling ~ F. Middle of the stroke - 5 6 i.e. where cuttingoutting potential cannot bebe maximized.marimiz ed. AppendixAppend1%

_TensionTension and Compression ThThee forces f orces inin thet he connectcormeet ing rod aatt different positipositionsons 0 0I 0 0 I 0 during one turn of flywheelflywheel 0:0: 0 2 I o o / . I 1 / i . . i I i ... 11039irlii9o03 o 39 0 3 (49 0 .39 0i- 9 0 0 3i 011i gkiNi 4110_,I . s s , , fi 6 6 E. 0" 30°30 • 60*60' 90900' 120*110 ' 150150°' 180180*' 210°110 ' 240°140' 170270°' 300°300' 330330°' I I I I I I I I I I 1500150000 I I ; -- - I I 1000001000 I ' i ~ I I I I I I I I "; '50050 000 ;-I-Tension ! ...- ...... ~ I ...... I I 0I ..- ,.e- -- J I I -,...... , W 50050 000HCompress+ eompress J 1 I I I 10001100 000 0 ->'" I I , I I I I I I I T 1500150 000, --

BendingLending :o~ 0 0:O~ 0 I I 0 S I 1 i 0 S . 1 I wit 1 0 WI Ilie 1 o 0 :0:0 0 I VW el 0 II Il NI I II 11( I SI I i 1 . 11 II 1 III 39 404,I 9 01k', 9 -):I 2 1 0 0 0 99 o"I/0139 --0 , l.

1 --68-68 -

Tools of Operat Tools of HelperHelper

renCb Hamner er . ."..--," ~ ~f

F+ with er with extension

PART IIIIII - SFl'TIOOSETTING SAWllLADESSAWBLADES IND°INTO FRAME SAW SASH MO. 1. Removing bladesblades from from the the sash sash ...... 70

2. Setting blades blades into theinto sash the sash ••••••••••••••••••••••••••••••009.00DOODOO00000001,0"0000.0010 71 InsertInserting i.rJg hangershal'lg'ers 00p000000000000.000000000000000000000108••••••••••••••••••••••••••••••••••••••.•• 71 Inserting sawblades 000000.00000000000c00000002.00000000Beco••••••••••••••••••••••••••••••••••••••• 72 In.sertizlgTnrierting blocksblocks ••.•••••••••••••••.•••••••••••••.•••••.•..00000m000m000.o0000000s000eopooloom0000d 73 Adjustment of overhang setting Oe0004103O000001,00000o00001110-0•••••••••••••••••••••••••••• 74 Setting right right angle ofangle a set ofof sawblades a set of sawblades ••••••••••••••••• 1575 Plumbing inin aa setset ofo£ sawbladessawblades .....•••••••••••••••••••••••••••• ...... 76 Adjustment of splitters.splitters. (Knife guides.) •••••••••••••••••...... 77 Safety equipmentequipment •••••••••••••••••••••••••••••••••••••••••• 78 - 69 -

The setting of bladesblades cancan bebe divideddivided intointo twotwo mainmain parts:parts:

Removing bladesblades fromfrom thethe sash.sash.

Setting bladesblades intointo thethe sash.sash. Here the two jobsjobs are described inin sequence,sequence, asas performedperformed byby anan OperatorOperator (usually the sawyersawyer oror sawdoctor)sawdoctor) andand aa Helper.Helper.

The sash must be securely lockedlocked inin itsits upperupper position.position. Front upper and lowerlower rollroll framesframes mustmust bebe open.open. SI-litchSwitch off thethe current.

OPERATOR HELPER Operator Helper stands in front of the r"'"""~ is on thethe out-feedoutfeed sideside sash. of thethe frameframe elevatedelevated on a board that hashae been placed between the knife guideseuides to enableenable him to loosen the top hanger.

feeding.~ - 70 -

REOOVINGREMOVING BLADES FROM THE SASH

OPERATOR HELPER 1. Loosens upper and lower 2. Loosens each hanger in blockblook attachments on thethe three steps (otherwise(otherwise righthandright-hand side,side, thethe upperupper there is a risk of ones justjust enoughenough forfor blocksblocks breaking the hanger onon to remain inin place.place. the last blade). Starts with centre blade. Con­Con- tinueson alternate sides with eacheach step.step.

Step Right order of0 each step 3---/ 2 ?l 2 553 3 1 24 "' . .\ 1 . 3- .1 1 ffl~ffl

2. KnocksKnocks away right lower ;:'. Knocks away left upper support block. Then support (seen(seen from the takestakesaway away other blocks Helper's position).position). one by one from right to TakesTakesaway away the blocks left, so that the blades one by one from left are completely free.free. to right. Meanwhile,Meanwhile, keepsremainingkeeps remaining blocksblocks in position by push-push­ ing side of lastlast blade against them.them.

3. Collects two or three 3. Collects the tops of blades together and pulls two or three blades them out of the bottom together (the(the samesame asas hangers. the Operator) and puspushes he the blades outout from top hangers.

4. Takes the blades and puts 4. Checks blocks.blockn. Discards them in the sawdoctor's if damaged. Cleans un­un- box. broken blocks and puts them inin their respectiverespeotive boxes.

The blades have now been removedremoved fromfrom thethe sash.sash. - 71 -

SEl'TIIDSETTILU BLADESBLAllES INTOIN'ro THE SASH Inserting the hangershangers

OPERA'roROPERADOR HELF'ERHELPER

1. Cleans the cross beams from sawdust, etc.etc. Brushes carefully, or preferably uses com-oom­ pressedpreeeed air. If a wear­wear- ing plate isie used on top of the upper crosscroee beam,beam, checks that it isie in the right position.

2. Checks hangers and makes Problems inin a Hanger 2. Checks the hangers and sure the contact surfacessurfaces non,Tarall 1 makeemakes sureeure the contactcontact and the blade hooks are bladerhóókA surfacessurfacee and bladeblade straight and parallel,parallel, hooks are straight and the rivet is fixed, the parallel, the rivetrivet isis opening between the fixed, the opening bet-bet­ blades corresponds to ween the bladesblades corres-corree­ the thickness of the ponds to the thickness blades and that there of blades and that therethere are no indicationsindicatione of Indicationsdications there areare nono indicationsindicatwna fractures. Dff fractur~fractUrel '~ of fractures.

3. PutsPute the bottom hangers 3. Puts the top hangers through the lowerlower cross through the cross beam beams fromfrom thethe toptop down,-down­ from the toptop downwards.downwards. wards (with(with thethe attach-attach­ Then turns them one-one­ ments first).first). Then quarter of a turn BOso turns them one-quarter that the hanger wedges of a turnturn toto makemake thethe are straight acrossacross attachments comecome intointo the beam. Turns the contact with the lower ecoentriceccentric lever a side of the beam and little more thanthan half-half­ lock into position. way down to make itit eaeiereasier to slip on thethe spanner. - 72 -

Inserting the sawblades

OPERA'roROPERAR HELPER

1. TakesTakes thethe bladesblades oneone atat aa 1. Takes the blade by time carryingcarr,yillg the bladeblade atat graspinggraspillg upper end the back with the leftleft with the rightri8ht hand. hand and balancillgbalancing it with Holds the hallgerhanger withwith the r~htright hand, holdingholdillg the left hand.hand. the :!'rentfront at the bottom,bottom, (the teethteeth faoillgfacing Operator). Passes upper endend to the Helper.

2. Inserts thethe bottombottom end of 2. Inserts upper end of the blade into the leftleft the blade into the bottom hanger.llm1ger. Then con-con­ corresponding top tinues withwith the rest of llm1ger.hanger. Adjusts the the blades. wedgewe<18e inin the top hallgerhanger so that the blade is located in the hanger.hallger. (If the blade isis "standing"nstanding" treefree it couldoould fall forward ontoonto Operator.)Operator.)

Insert :!'remfrom left to right.r~ht. When all the blades are inserted,inserted, positionposition thethe blades (the hallgers)hangers) sideways to the approximate positionpoSition they will havehave laterlater when the blocks are inserted.inserted.

3. AdjustAdjust the blades in the r------, 3. Adjust thethe bladesblades intointo bottom hangershallgers inin the the toptop hangershangers inin thethe Outerouter blades Lower direction of sawingsawing sothat80 tmt sameBame way as the put forward cross Operator does with the the outsideoutaide blades be Operator does with the bottom. are a little for-fo~ ward of thethe centrecentre blades, i.e.i.e. they will cut first. - the blades are same placed symmetricail.y.symmetriCally. ~.. distancedistanc FeedingFeedillg - thethe wholewhole setBet of blades isis perpendi- cular to the direction of sawing.sawing. - the fittingfittillg tension will be correctcorreot in the blades. Since blades are positionedposit ioned as above and are often of different width a rule on positioning is difficultdiffioul t toto state.state. As farfar asas possible oentre of hangershallgers shouldshould coincide with aa lineline asas shownshown in f~e,figure, or the :!'rentfront of the hangerhallger be inin lineline withwith gullets.gullet •• - 73 -

InsertillgInserting ofof blocksblocks

OPERATOR HELPER

1. Inserts with the left hand 1. With the right handhand the lower leftleft supportsupport inserts the upper block (i.e.(i.e. onon thatthat sideside support block corres-corres­ where thethe blockblock attachmentEattaclunentE; ponding to that of have not been touched and the sawyer. Presses are therefore atat right the blade with the anglesangles). ). left hand against thethe block to keep itit inin With the right hand pressevpresseE; place. Taps the the free blade against the wedge with the hammer block so that the bottom soBO that the blade isis hanger isis correctly posi-posi­ stretched a little - tioned and the block isis the block is then held in place. held in plaoe. fixed and stays inin Continues until all the position by itself.itself. blades and blocks are in-in­ (The top hangers are serted. Finally inserts now positioned a the last support block.block. little to one side.) Continues like this until all the blades and blocks are in-in­ serted. Finally, inserts the support block.

The last support blockblock isis oftenoften aa bitbit biggerbigger thanthan thethe distancedistance allows.allows. If the difference is small the support block canoan be tapped down (the Helper drives hishis block upwards). If the difference isis big, thethe blockblook attachmentattachment mustmust bebe un-un­ sorewed..screwed. Never force the last supportsupport blockblock withwith heavyheavy blows.blows. The support block could become deformed andand bebe pressed soso hardhard thatthat laterlater adjustment will be more difficult.difficult.

2. TightenstheTightensthe upper block 2. Loosens the eccentrics attachment a little when Stet1_ 2 Right order of the top hanger a all the blocks are in-in­ .~ - ' ~in each step little and adjusts thethe serted so that theythey dodo position of the top not fall out.out. hangers sidewayssidevlays soso . -~ 3ffl~ffl that they are directly At the samesame time,time, adjustsadjusts in line with thethe blade.blade. the blocks so that they Then completes thethe are all inin a horizontal first step inin the ten­ten- line together. sioning of the blades. At this stage alsoalso adjusts the hanger wedges. StartswithStar1swith the outside blades and works alternately fromfrcm left toto rightright towards the centre.centre. - 74 -

Adjustment of overhang Bettinasetting

OPERATOR OPERA'roR HELPER 1. Adjusts the right overhang -r------, If thethe overhangoverhang setting on the overhang setting alreadyalready setting board. Holds the adjusted isis too board against oneone bladeblade atat small, gently taps a time, presses againstagainst out the blade at tooth line and taps with upper end.end • .<: the hammer at upper end of ::l blade in the direction of III saWing,sawing, so that the right .... In£eed 0 Direction overhang setting isis ., of sash obtained. .!04 2 Umovement [Q+>

Overhallg I-~

1/

;, Ii \;

At this stagestage the bladesblades mustmust notnot bebe stretchedstretohed soso muchmuch thatthat theythey riskrisk damageclaJuage or that the stretching platesplates ofof thethe bladesblades getget jolted.jolted.

2. Taps top hanger wedges to achieve a slight stretch-stretch­ ing of the blades.blades. -75 -

Setting right angle ofof aa setset ofof sawbladessawblades

OPERA'roROPERATOR BELPERHELPER

1. Puts the aligning edge on thethe bearing pivot of the frame saw stand. Puts the aligning T square onon thethe aligningal igning edge.edge. Checks by moving it against the sides of the blades that the the blades are atat rightright anglesangles to the edge (i.e.(i.e. parallelparallel to the TT square).square).

If the set of sawblades isis not at right angles, adjusts thethe angles by tightening thethe frontfront and back screws of the block attachments differentially.differentially. Do not use any~y force which might result inin a deformation of the blocks without the blades reaching thethe rightright position. Then itit would be difficultdifficul t to continue settingthesetting ihe r"!..--."'-,------;--,--;--.,-, angles oftheof the rest of thet11e blades.blades.

2. When all the blades areare atat right angles, tightens the rightright-hand- hand side block attach-attach­ ment but makes sure that the setting does not change during tightening.

3. Loosens the sash and pushespushes itit toto bottom dead centre.

4. Checks thethe angle of the blades inin thethe samesame wayway asas in 1 and 22 above,above, whenwhen thethe sash has reached thethe lower position. The adjust­adjust- ment is made with the upper line of blocks. - 76 -

Pl._bill+;PluMbing inin aa setset ofof Efawblades....wblades

OPERATOR HELPER

1. BoldstheHoldsthe T square 1. Pushes the frame to against the aligning make the sash move edge with one edgeedge slowly up andand down:down'. of the square close to one sidee ide ofof aa blade.blade. The setBet of sawbladessawblades will be vertical if the side ofof thethe blade,blade, when making itsits move­move- ment up and down,down, isis always at the sameBame dis­dis- tance from the fixed measuring point.po int • If the distance to the side of the blade isis not the sameBarne goinggo ing up as going down, the upper block rowrow mustmust be adjusted sideways.sideways. ..-4-11111 Loosens both screws Tighten-.Tighten--1 l Loosen equally on that side both scrf'sscr .both of the block attach-attach­ ment where the setBet \~~ UpopU u . ~~ of sawblades needs l' adjustadjusting ing and corres-corres­ ...miummmommmillapp. ", 1111 II • ~ pondingly tightens pondingly tightens ill- move-inmove-= both screws at the .uecliion.e other bblockl ock attach­attach- ment. The Betset of 2. Tightens thet he setset of blades will move in blades inin stages.stages. the right way.way. (Steps(steps 2 and 3).3). StartsStarts with thethe outside outside IflPries ~B and works alternatively towards centre.centre. Steg 1 OrdningsfoltdOrdnirgsf61jd Tightens centrecentre blade varje .-oi~ I vaqe stegsteg last inin every step. IfIf 13 5 4 sawing does not start until followingfollowing day,day, delay tightening until sawing isis toto start,start t thus avoiding cross-cross­ ~3M~M beamsbeams andand bladesblades beingbeing underunder pressurepressure forfor anan unnecessarilyunneoessarily longidme.long time. It is essentialessent ial thatthat all blades are equally tightened oror loadload onon crossoross beams will bebe un-un­ evenly distributed and result inin curvedcurved sawing.sawing. Checks strain inin blades by pressingpreSSing eacheach bladeblade hard withwith hand.hand. -77-

Adjustment of splitters (knife(knife guides)

OPERATOR HELPER

1. Puts-thePu1sthe aligningaligning edge 1. LooseneLoosens the against insideinside of oneone ofof splitters andand the bladessawingblades sawing the moves them a main yield. (Note: ForFbr little together. cant frames:frames put the edgeedge along the insideinside of oneone of the outside blades of the cantcant boards).boards).

2. Indicatesby signssignsalready already 2. Moves the agreed upon how Helper splitter as IllUStmust move "theihe splitter directed by so that itit bears against Operator sothatso tmt the inside of the align­align, it bears againstagainst ing edge. insinside ide edge of aligning edge.edge.

3. Fixes and locks splitter.

4. Repeats this procedure 4. Repeats this with the othereplitter.othersplitter. procedure with the other splitter.splitter.

5. Checks adjustment once more, seesee above.above. - 78 -

Safety equiEmentequipment

A newly sharpenedsharpened blade is easily damaged even by gentle nudges and bumps. Contact with other objects can damage bothbeth edges and teethteeth setting.setting. , ., I , .;' To avoid damage,damage, thethe edgeedge cancan bebe protectedproteoted by stripsstrips ofof plasticplastio thatthat areare placedplaoed over thethe teeth.teeth.

Even more easilyeasily damageddamaged areare thethe hands of the Operator, which cancan bebe cutcut when blades are handled, especiallyespeoially whenL-~when ' ~" ~ ____~~~~ __-L ______~ the Operator isis insertinginserting blades,blades, blocksblooks'r-_ or tightening thethe blockblock attachments.attachments.

By using the plastic strips thethe Operator isis protected duringduring thethe wholewhole procedure, except when the overhang setting isis adjusted.adjusted. The strips are II' easy to put on and taketake off.off. -79_ 79 _

HOWROW TO TO FEE:DFEED LOGSLOGS INTOIm'O A A FRA10E FRANE SAW SAW

PART IV HOW TO FEEMFEED LOGSLOGS INTOINl'O A FRAME SAW

122E2~ Cant Sawing PrinciplesPrinciples ..... 0.000..000000000 *0000.0000 ...... O80 1. .... " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 2. Sawing Symmetrical LogsLogs ••••••••••••.•••••••••••••••••••••••••••....00000.0.000.000000 OOOOOOOO 00000. 82

3. sawingSal'ling Logs withwith FormForm DefectsDefects ...... """,,"""""""""""""""""""""""""""""" ...... OOOOOo 84 Crooked Logs ...... 84 3.1 Crooked Logs " " " " " " " " " " " " "...... " " " " " " " " " " ...." " " " " "00000,000000.000 " " " " " " " " " " " " " " " " Straight Sawing ...... 3.1.1 Straight Sawing " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 85 3.1.2 Curve Sawing *****000000000000 000 3.1.2 " " " " " " " " " " " " " " " " " "...... " " " " " " " " " " " " " " " " " " " 86 3.1.3 A ComparisonComparison ofof StraightStraight SawingSawing oror CurveCurve SawingSawing ..•• 86 Straightness 3.1.3.1 Straightness "00000009eavey.************* " " " " " " " " " " " " " " " " " " " " " " " " " " 87 Positioning of the Pith 301.3023.1.3.2 Positioning of the Pith 0000.00000000000" " " " " " " " " " " " " " " " 87 3.1.3.3 Wane "eb000**000.00000000"00.00***00 " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 87 Practical Performance 0000.m000cac0000po 3.1.3.4 " " " " " " " " " " " " " " " " " " 87 3.2 Logs with IrregularIrregular CrossCress SectionsSections ...... ,...... 87 " " " " " " " " " " " " " " " " " " " " " " " 87 oval Logs 3.3 Ov"al Logs """"""""""""""""""""""""""""""""""""""""""""""""0000000000000000000000000000000000000.9*****900* 88 Sawing Logs with Bole Defects 4. Sawing Logs Bole "00***0.00000.50060.0*****800000*Go " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 90 Sawing Logs with Heart Shakes 5· Sawing Logs with Heart Shakes "s000pcloocapooseep00000.00acoopeoe " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " 91 6. Sawing LogeLogs with Quality Defects ...... 00300000000.00000 91 --8o-80 -

1. Cant Sawing PrinciplesPrinoiples

The prinoiplesprinciples of cantoant sawing consistoonsist of two stepssteps (figure(figure 1).

Step I. The log is edged inin the loglog frame, whichwhioh gives a ~cant and one or more boards on eacheaoh side.side.

Step II.II. The cantoant isis resawn inin the oantcant frame whichwhioh gives aa main yieldyield of planks, and a numbernumber of boardsboards on each side.side.

The main yield hashas now been blockblook sawn, i.e. the sawblades have touchedtouohed all four sidessides andand normallynormally canoan bebe marketedmarketed asas theythey are.are.

The boards from both steps are further processedprooessed inin oneone oror more edgers.edgers.

I :II The oant to ~ resawing Resawing Edgesa~Iing V --. I ~..•

Planks LOB ~lain yi Id L-----Blab8s------~ Fig.l - 81 -

The sawing is usually done inin two frames, one loglog frame saw and one aantcant frame saw, which operateoperate oneone afterafter thethe other.other.

The sawing,sa~ling, however, can be done inin juntjust one frame that isis set up periodically for edgingedging oror resawing.resawing. In this case, the cantscante must be piled up between the two operations.operations.

Whenlfuen processing thethe logs,logs, thethe purposepurpose isis toto achieve:achieve:

a good result bothbeth as regardsregards qualityquality andand quantity.quantity.

the highest possible economiceconomic yield.

The logs must, therefore, be correctlycorrectly fedfed intointo thethe frameframe saw.saw.

The log can be of:of:

different size andand treetree speciesspecies

different formform andand quality,qualit~, (see ,figure~igure 3) and must be treated accordingly.

lfuenWhen the log sawyer or oantcant sawyer has each log or cant beforebefore him,him, hehe mustmust make an assessment quickly and position the log, or the cant, for the sawing procedure, toto ensureensure thethe bestbest resultresult possible. Fig.2 Once the sawblades havehave startedstarted to cut into the log, there is no 'Jammed against the to cut into the log, there is no ---'steering knives possibility of making anyany adjustment.adjustment. Such action might very wellwell causecause aa breakdown. (See figure 22 and 3.1.2 - Wrenched set Curve Sawing). of blades

.' "'/.,',

o 0, I';I, Repositioni ,',I" of log ,I:, ' 1\ , '. Centre lin 'Centre line of of log 'set of blades

Result ofof.tryingtrying to move loglog sidewayssideways after sawingsaW1ng hashaS started. --8282 -

SyDllletricalSymmetrical log Logs with form defec . Irregular 1. Crooked log cross sec

3. Oval log 4. Log wi bole Sc

Lo~thLog with quality defect

5.Log with heart che

I

Fig.3

Logsawing Cant resawireresaw 2. Sawing Symmetrical LogsLoge (Figure 3)

A symmetrical log is round and straight withoutwithout any et of formfonn defects;defeotsl blades

has quality faults in the formfonn of Centre knots distributeddistributed evenlyevenly inin numbernumber line of and size.size. blades

Infeed RuleRule for SymmetrioalSymmetrical Logs il CentreC"nicre line1ine in Log and Cant Frame:I in Log and Cant Frame of log Centre line of loglog or thethe cantoant shall ooinoidecoincide with centreoentre line of the set of blades.blades. (Figure 4). Centre line of ExceptionExoeption toto rule:rulel If, forfor instance,instanoe, cant too small a log for the actual setting has been included,inoluded, the sawn surfacesurfa.oe of the cantoant may bebe tootoo smallsmall for the main yieldyield- •. o

Fig.4 - 83 -

Figure 5a shows this caseoase where the sawing procedureprooedure hashas followedfollowed thethe rule,rule, i.e. the oentrecentre line of the cant follows_folloWB_ the centre line ofof thethe setset ofof blades.blades. Both plankmplanks have gotgot wane.wane.

Figure 5b shows a side movement of Figure5b Wane the cant so that thethe twotwo centrecentre lineslines do not coinoide.coincide.

This hashas resultedresulted inin oneone ofof thethe twotwo planks being fully edged. The other one has got more wane but, duedue toto thethe natural taper of the log, not markedly longer.

One drawback here,here, however,however, isis that-that· the full eagededged plankplank hashas becomebeoome "-pith-'~ith­ inoluded".included". In some species distortion on drying is often worst inin pith,pith­ inoludedincluded planks, therefore their value may be reduced. (See figure 5c).5c)0 \\ ,.,...--_-Cedge Before aligning a straight cantcant with a sawnsawn surfacesurface whichwhich isis tootoo small,small, Wane one should bear in mind that:that I

in some species the sideways move-move­ ment (figure(figure 5b) mustIllUst not become so big that excessive distortion or pith cracks:cracks appearappear when the log is dried;

alignment following the basicbasio rule (figure(figure 5a) is reconmendedrecommended when the log isis of such a quality that knots, decay,decay, blueblue stain,stain, etc,etc. make wane acceptable.

Pith plank Heart checks amddis . l=l.Oll.-~~~..::

Fig.5 c - 84 -

4.5 IIID

3. Sawing LogsLogs with Form DefectsDefects I t 3.1 CrookedCrooked LogsLogs ''.. .. :; :_'._ .-.....: -.. : ,>-~.. k .. . _>.. '.• .".;"0.;"

The most common form of crookedness I 75 mm is "sweep""sweep" or "long"long crook".crook". The sweep may not, according to previous Swedish Fig.6 log quality standards, exceed 2525 mmIIID forfor each 1.51.5 m.m. A 4.5 m long log could therefore havehave aa maximum-evenmaximum ·even sweepsweep notnot exceeding 75 IIID.mm. (See figure 6).6).

Infeed Rule for Crooked Log,loS'. LogLog Ftame:Frame:

Turn log so that the sweep is on downward side.side. (Seen from side in figure 7a). Then alignal~ loglog so that its centre line coincides with centrecentre lineline of the set of blades. blades. (Seen from above inin b figure 7b).7b). -b.:~· -_-. :.:. , ~ ,' , --j I I: 1 The cant from a crooked log sawn in this way isis crooked but the surfaces are Fig. 7 evenly sawn. (See figure 8)

Infeed Rule for Crooked Cant, CantCant Frame:Fi-ame:

Align the cant and saw it so that main yield justjust falls within sawnsawn surfacesurface on insideinside of the sweep. (See figure 9a).

Fig.8

CantGant boards within sawn surface of Sa.. cuts block

Fig.9 a - 85 -

If one does not follow the rule and sawssa~IS insteadinstead in accordanceaocordance with figure 9b:

wane will appear inin thethe middle ofof oneone of thethe main planksplanks butbut

at the same time the amount of wane atat thethe endsends ofof thethe otherother plank will decrease.

If thethe qualityquality of the log is low because of knots, blue stain, etc., such a sawing approach maymay bebe recommenf,ed.recollUJleni',ed. (See figure 10).10).

Sawlines

Normally not likethis

Fig.9b Fig.10

The rule is that the main yield should fall within thethe sawnsawn surfacesurface inin the inner sweep. If thisthis rulerule is followed, resawing in the cant frame can be done in accordance ~lithwith either of two principles:

3.1.1 S"trStraighta i ght SaSawingwil1ff The cant is sawnsa~m straight,st raight, i.e.i . e. itit c is fedfed throughthrough the frame so that the blades make straightstraight cuts.cuts. The~'he align-align­ ment isis then made as indicatedindicated inin figure 11. The main yield should thenthen fallfall within thethe sawnsa~m surfacesurface ofof thethe block,block, at the points A and B, and the middle cutcut should fall 'lithinwithin the sawn surface in point C.C.

Fig.11Fig. 11 - 86 -

3.1.2 Curve SawingSawinR The cantcant isis sawnsawn curved,curved, i.e.i.e. itit is fed so that the saw cuts follow the sweep of the cant as inin figurefigu:re 12. The possibilitypossibUity ofof doingdoing thisthis inin aa cant frame isis limitedlimited dependingdepending on:on:

the distance between the knifeknife guides and the blades.blades. (The closer they are, the greater the possibility.possibility.) )

the length of the knife guides;

the distance between the separating Fig.12 plateeplates for thethe mainmain yield.

Fig.I)Fig.13 - Procedure forfor CurveCurve SawingSawing

Position 1 - InfeedInfeed Position 22 Position 33 Blade A cuts ~within sawn Blade A now at edgeedge surface of cant so80 main of sawn cant. CentreCentre yield becomes fUllyfnay edged.edged. line through topardtopand Direction of of cant: cants lart-tend b,l'tt end butt ende of block of block isis moved sidewayssideways is ininline line butehiftedbut Iilifted so centre line1 ine through top in comparison with and butt ends isis off-lineoff-l ine centre line ofof setset compared to centre lineline ofof blades. through set of blades.blades.

Sawing of first half. Butt end of cant is shifted side-sid~ way!!ways so that blade A foDowsfo11ows edge of sawn Sawing of butt end surface afcantof cant is done without any~ shiftingshift ing of cant. The cuts become straight. Sawn sur-IIlU'­ faoeface is wider here due to loglog taper,taper, soso straight sawing Middle sectionsection isis should not resultresult sawn with slightslight in timber with wane. shift ofof thethe cant.cant.

3.1.33.1.3 A Comparison of Straight SawingSawing oror CurveCurve SawinaSawing ofof cantecants fromfrom logslogs withwith sweep is made below. - 87 -

3.1.3.1 Straightness Straight sawing results inin straightBtra~ht main ydeld.yield.

CUrveCurve saw~sawing gives main yield with bow.bow. The thicker the plank or board, the more importantimportant a defect bow becomes. DuringDur~ drying, restraint inin a stack will tend to straighten8tra~hten bowed pieces.

3.1.3.2 PbsitioningFbsitioning of the pith Straight sawingsa>1ing results inin spread and therefore poor positioning of the pith in the main plahksplanks as itit falls .-- , I Direct ion of po. th inside both planks, which cancan leadlead toto IV '- distortion andand crackscracks duringduring drying.drying. , Curve sawing can more favourably position the pith, which reduces risk \J Heart shra,nks of distortion and checks.checks. -- 3.1.3.3 waneWane I~ il Straightstraight sawing usually results inin , more wane onon oneone ofof thethe mainmain planks.planks. ,I , Curve sawing reduces thethe wanewane and,and, f:-- I<- Fig: 14 if the sweepBweep isis not~ot too great, wane can ~i !'" be eliminated,eliminated, resultingresulting inin full edgededged ~ "1 main yield,yield. 3.1.3.4 Practical performance Straight sawing is simpler than curve sawing. Curve sawing may, there- fore, slow production levels unless there Cross section is special infeed equipment toto simplifysimplify Oval Cross sectio the procedure.proCedu:r6. rlhetherWhether crooked cants are straight or curve sawn at the cant frame is up to the individual sawmill. B,yBy applying curve sawing, however, itit isis possible to increase the sawn timber recovery.

3.2 Logs with Irregular Cross Sections In figurefigure 15«15a logs withwith irregular CroBScross sections are shown, one be~being oval, the other irregular. If these logs are positioned inin the way that is shownsho>1D in figure 15b, where each is resting against points on the upper and lower rollers that are not in a verticalvertical line, the log will turn during sawing, resulting inin a twisted cant.cant. rnreedlafeed RuleRule forfor LogLog withwith Irregular Crosseross Section, Log Frame:

Align log so that contact points I between log and upperupper andand lower rollers formforo verticalvertical line. (See figure 15c)150

This gives thethe log thethe safestsafest steeringsteering Fig: 15 through the frame. - 88 -

3.3 Oval Logs Size When measuring anan ovaloval log,log, Measurement Class different diameters can be recorded Flat side depend~depending on how the measurement isis B done. (See figure 16).16). The loglog (min.measure) can therefore be designateddesignated forfor different sizesize classes.classes.

To avoid this, ovaloval logslogs mustmust be measured by crosscross measurement.measurement. In practice;practice, one measurement is made of the maximum diameter and oneone of the Mean minimum diameter,diameter, following which the value mean value isis calculatedcalculated andand used.used.

To prevent an oval loglog from turn-turn­ ing duringduring the sawing process, according to the infeedinfeed rule for logs with irregular cross-sections, itit can only High side 9 be positioned resting eithereither onon itsits (max.measure) flat or high side.side. (See figure 17).17).

F; g: 16

Positioning on Positioning on higJLside flat side

fi 9: 17 In figurefigure 1818 thethe toptop sideside of an oval log isis shown:shown:

positioned on itsits highhigh side,side, positioned on itsits flatflat side.side. In the figure lines have been drawn that indicateindicate 125, 150150 and'and 175 rommm wide planks, as well as 50, 63 and 75 rommm plank thickness. The intersection between any of these two lines shows.howshows ' how the cornercorner of a cant board will fall inin relation toto the top area ofof thethe log.log. - 89 -

The table inin figure 1818 indicates:indicates: the different ways to measure logs,logs, andand to which size classolass thethe loglog would havehave beenbeen assignedassigned dependingdepending onon thethe results from these. InIn addition, we cancan see:see: alternative dimensions for thethe differentdifferent sizesize classesclasses andand aa descriptiondescription of the edgeedge of the main yield.

We can draw the following conclusionsconclusions fromfrom thethe tableetable: Measuring the maximum diameter resultsresults inin thethe highesthighest amountamount ofof wane no matter how the log isis positioned. Measuring the minimum diameterdiameter gives thethe greatest certaintycertainty ofof fullfull edged main yield.yield. Positioning the log on itsits flatflat sideside givesgives anan advantageadvantage inin oneone casecase only,only, when cutting 50 x 175 mm.IIID. To position the log on itsits flatflat side,side, however,however, necessitatesnecessitates thatthat thethe loglog is straightstraight if any benefit isis toto bebe gained.gained.

Fig.Fig.18 18 Alignment on high A~ignment on high Cant widthwidth Alignment onon flatflat side for log frame side for log frame CantGant widthwidth II1II side for 10g frame B1de for 1f fr~5125 150 175 mm 12,12 1 0 175 IIImm 1 ~-...... Fl ank Plank 75 ""- Plank 75175 t------".I""'p.'0~-

Edge of planks when

Way of Size Alternative Sawing on Sawing on measuring class dimension high side flat sideside mm

Minimum 200 75 x 125 Pull:f'ul1 edgeedge :f'ul1full edge diameter 63 x 150 It" it" II" II" Mean 212.5 50 x 175 wane,wane,little 1itt1e full:f'ul1 edge diameter 63 x% 163 ?I" It" wane,littlewane, li1tle _ Maximum 225 63 x 175 wane, much wane,muchwane, much diameter 75 x 150 H" "il u t, _ " " - 9900 -

It is, however,however, common that ovaloval logelogs also have sweep. A soft\foodsoftwood tree that grows crooked formeforms "compression"compression ~Iood",wood", on the low sideside ofof thethe log,log, resulting inin an ovaloval stem.stem. Figure 19 shows how crookedness andand ovaJovality.ity occuroccur at the same timetime inin aa log.log. If the Plane of crook crook is placed downwards, the oval isis High side oflqg on its high side.

Infeed Rule for Oval Log,Log, LogLog Frame:Frame:

The log is normally positioned on High si its high side. InIn additiaddition,on, of log adjust log so that resting pointspoints between rollers and log are inin a vertical line.line. (Figure 15.)

4.4, Sawing Logs l~ithwith Bole DefectsDefects

A bole soarscar \fillwill occur on a standing tree following external damage and sub-sub­ sequent healing.

The bole scar usually takes the form of a depression in the log which can be so deep thatthat thethe mainmain yieldyield isis affected.

Infeed Rule for LoLog with BoleBole ScarScar, Log Frame:

Turn log so that the .bole scarscar isis onon the top side.side. (See figure 20.)20.)

If the log is positioned withwith thethe bole scar on the side, both planks can be affected so that they needneed cutting.cutting. (Figure 21.) - 91 -

Heart shake 5. Sawing Logs with Heart Shakes Pr.'

Heart shakes occur mostly inin large diameter logs.logs. They originate in the standing tree.tree. Al3As the heartwood gets s \ "-; V7i olderolder and dries, it ~may shrink to the _-- ; } ///7 stage of checking. If'If suohsuch hgs1gs areare ( ,,--' storedstored in water, the crackscraoks will swell up and disappear, only to widen again ., when the sawn timber isis dried.dried.

Infeed Rule for Log with HeartHeart Shakes,Shakes, Log Frame,Frame: F"iFi 9:g: 2222

PositionPosition the log so that the biggest crack lies horizontallyhorizontally.. (See Fig.22.) FleartHeart shake

Icrack If thethe log is positioned with the . ----... heart shake vertically, itit willwill affectaffect ,--" _ , 2,--e. -- both planks after resawing. (Fig.23.) i both planks after resawing. (Fig.23. ) -"--'",---,""<.- e.';'' I _:) e.

6. Sawing Logs wwithith Quality DefectsDerects - '11 A log with knots distributed evenly '.-.... _-_-_-%1 over the surface~ace must be positioned pr~i1yprimarily according to itsits form.form. / VeryVer,y often, however, a loglog hashas mostmost FFii 9g:: 2323 of its knots concentrated on oneone side.side. This can be due to the fact that the tree has been growing next to an open space soBO that the branchesbranohes have developed more on i..ottysid: eg, upwards that side. Or the tree might have been .\ N e knot on crooked and the branchesbranohes have developed . o 0 .. flat side more on the oppositeOPPOSite side in order to I , ' ,# even out the load distribution. 0.. 'O:: i 9 even out the load distribution. ,0.. ,-: 4 9 co 0 o Tnfeed Rule for Log with most knots on - ?,-;-- o if Infeed Rule for Log with most knots on ,-,-s-).-1 .-;,.,./. 0 ,.., one side,side! LogLog Frame:Frame: 1 -,-- .- o .1...-----1--'- Turn the log so that the worst side * ," o#ei is upwards, (Figure 24.)24.) B.Mr MIY1 Fig: 24 The smaller cross section of the knots~======knots ======~~======; Fig: 25 will then appear on the facefaoe of the planks.planks. If the log is positioned with thethe worstworst s\ .'?'.; knots to one side,Bide, larger crossCroSB section knots (or(or wing knots) will appear on the face of the cant "boards, depressing quality more.more . ,_..:-. 49,,,,,, ...

. I Iotty , . ,..../ side ,41111 Mt/ MO.414otsan edges

The above rules describe the procedure for aligning logslogs with only oneone defectdefect at aa time.time. But a log can have many differentdifferent defectsdefects atat thethe sameBame time, soso itit isis necessarynecessary toto determinedetermine whichwhich ofof thesethese defectsdefects willwill havehave thethe greatestgreatest influenceinfluenoe onon thethe sawnsawn yield.yield. - 92 -

PART V - MAINTENANCE

Check-ups Paat 1. DailYDaily ...... 0000000000000000000000000...... 00000 00 93 2.20 WeeklyWeeklY •••••••••••••••••••••••••••••••00000000000500000004000000000000 93 Monthly 3...... OOOOOOOO 000000000000000000000 94 Every three monthsmonths 4...... 000000000000000000 94 Twice a year 5· ...... 0o0000000000000000000000 94 6. Once a year ...... 0000000000006000000000000 94 7. LowerLeMer connecting rod bearing ...... 94 8. Upper connecting rodrod bearingbearing ...... 95 9. Guide controloontrol ...... 95 10. Control of sash movement ...... 95 11. Guide cooling system ...... _____0000. " ...... 96

In order to achieve an effective production the frame sawsaw hashas toto be maintained regularly:regularly: daily check-ups should be carriedcarried out andand repairsrepairs made by skilled personnelpersonnel andand withwith originaloriginal sparespare parts.parts .

Detailed maintenance andand greasinggreasing instructionsinstructions must be provided byby eacheach frameframe sawsaH manufacturer.manufacturer. BeloHBelow are some more generalgeneral statementsstatements onon frameframe saw maintenance.

There are twotwo kindskinds ofof maintenance:maintenance:

-pre-maintenance, suchsuch asas greasing,greasing, oiling,oiling, controls and adjustments.

- minorminor repairs repairs oror servicesservices toto eliminateeliminate previous disturbances inin production.production.

Pre-maintenance isis of the utmost importanceimportance inin order to reduce the rate of breakdown. - 93 --

Check-upsCheck,-ups

1. Dailz

a) Before startingstarting thethe machine,machine, check:check: the lubricating system,system, ensuringensuring thatthat greasegrease flowsflol

b) While sawing:sawing: adjust feeding speed according to instructions.instructions. if the speed of the sash isis reduced when feedirgfeeding logslogs through, infeed has to be stopped and the reasonsreasons forfor the disturbance found.found. if a piece of wood isis ;;edgedwedged betweenbet;;een blades oror betweenbetween blades and sash columns,columns, thethe frameframe mustmust bebe stoppedstopped andand the piece removed;removed; ignorance of this might cause accidents or overheating ofof blades.blades. if greasing or coolingcooling ofof thethe guidesguides isis notnot satisfactory,satisfactory, a certain smell from thethe slidingsliding blocksblocks cancan bebe noticed;noticed; if this happens, thethe reasonreason hashas toto bebe foundfound andand rectified.rectified. Cooling water must notnot bebe passedpassed throughthrough overheatedoverheated slidingsliding blocks until theythey havehave cooledcooled off.off.

2. Weekly

The temperature of the lower connecting rod bearing shouldshould be measured and registered.

The cross beams, columns and connectingconnecting rodrod shouldshould bebe cleanedcleaned andand checkedchecked for damage. To achieve the bestbest resultresult anan electricelectric oror pneumaticpneumatic brushbrush shouldshould be used.used. The connecting rod shouldshould bebe brushedbrushed lengthwise.lengthwise. DamagesDameges or nicksnicks on the cross beams are easiereasier toto discover when'lhen thethe bladesblades inin thethe sashsash areare tightened.

Smaller nicks should be grounded downdO>ln with anan emeryemery oror aa polishingpolishing cloth.cloth. - 94 -

3. Monthly

Adjust all chainschains and checkcheck forfor wear andand tear.tear. Check shafts and bearings of the feed rolls. Check the wear ofof thethe slidingsliding blocks.blocks. Check and tighten all bolts,belts, includingincluding anchor bolts.belts.

4. Every Three Months

The lower connecting rod bearings should be washed and cleaned.

5. Twice a Year

The bearing playplay of the upper andand lowerlower connectingconnecting rodrod bearingsbearings shouldshould be measured. If it exceeds the recommended limits,limits, thethe bearingbearing mustmust bebe replaced.replaced.

6. Once a Year

The frame saw should be thoroughly checked;checked; allall worn parts shouldshould be replaced; boltsbelts shouldshould bebe tightenedtightened andand bearingsbearings cleaned.cleaned.

The connecting rodrod bearingsbearings shouldshould bebe washed.washed.

The guides should be cleanedcleaned andand checked.checked.

The movement of thethe sashsash shouldshould bebe controlled.controlled.

The alignment ofof thethe frame sawsaw shouldshould bebe checkedchecked soso thatthat anyany changeschanges inin foundation oror basebase plateplate maymay bebe noted.noted.

7. Lower Connecting Rod Bearing

This bearing isis oneone ofof thethe mostmost importantimportant andand hashas toto bebe maintainedmaintained care-care­ fully. Grease typestypes andand working/greasingworking/greasing intervalsintervals cancan bebe foundfound inin thethe manumanu­ facturer's recommendations.

ImurtantImportant toto notenote whenwhen greasing:greaSing: Before greasing,greaSing, grease nipples,andnipples, and the grease pump muzzle should be cleaned to avoid dirtdirt gettinggetting intointo thethe bearing.bearing. Greasing should be done immediately after the frame hashas beenbeen stopped.stopped. The temperature of the connecting rodrod andand thethe bearingbearing capscaps shouldshould bebe checked.checked. Maximum allowed temperature isis 60°C.60°C. At least once a week the insideinside temperature of the bearing should be measured.measured. This temperature andand the temperaturetemperature inin thethe sawmill should beDe registered.registered. Increased temperature is normally an indication of bearing pollutionpollution oror ofof wearwear andand tear.tear. By studyingstu~ing thethe registered temperature variations it isis possible to maintain or repair details oeforebefore complete breakdown.

Increased temperature can also be caused by faulty mounting ofof thethe guidesguides resulting inin abnormalabnormal sashsash movementmovement oror vibrations.vibrations. If the reason for increasedincreased temperature cannotcannot bebe detected,detected, thethe bearingbearing hashas toto bebe washedwashed andand greasedgreased severalseveral times before the resultresult isis satisfactory.satisfactory. - 95 -

8. Upper ConnectingConneoting RodRod BearingBearing

The gudgeon pin of this needle bearing should be checkedoheoked and cleanedoleaned onceonoe a year. The brake should be lockedlocked whenwhen thethe sashsash isis inin itsits toptop position.position. The sash should be fixed inin itsits upperupper positionposition byby usingusing aa pulley.pulley.

~eThe infeed guide bolts should be loosened and the guides pulled back as far as possible.possible.

The bolts in the crank pin brackets of the lower cross beams shouldshould be loosened. The slots inin the pin bracketsbrackets shouldshould bebe widenedwidened toto releaserelease thethe pin.pin. Using the pulley, the sashsash shouldshould bebe adjustedadjusted soso thatthat thethe pinpin cancan bebe removed. To prevent the bearing needles fromfrom fallingfalling outout aa provisionalprovisional pinpin shouldshould be insertedinserted when~Ihen removingremoving thethe originaloriginal pin.pin.

9. Guide ControlControl

The guides should be controled and aligned onceonce a year. The infeedinfeed guides areare checkedchecked byby usingusing aa straightstraight edgeedge atat leastleast asas longlong as the guide and an insertinsert knifeknife measuringmeasuring device.device. If the play exceeds recommendations, the guide mustmust bebe exchangedexchanged oror repaired.repaired.

The outfeed guides shouldshould bebe checkedchecked usingusing aa straightstraight edgeedge longlong enoughenough to cover upper and lowerlower guidesguides simultaneously.simultaneously. The check-upcheckup shouldshould bebe mademade having the guides mounted inin thethe frame.frame. For maximum play allowed between straight edge and guide, seesee manufacturer'smanufacturer's recommendations.r ecommendations.

To align the guides when mountedmounted inin thethe frame,frame, useuse aa plumbplumb lineline fromfrom thethe upper toto thethe lowerlower guides andand comparecompare withwith allowedallowed deviation.deviation. If this control indicates that the base line of the frame, for any reason, has been changed,ohanged, correction shouldshould be made by adjustingadjusting thethe basebase plate.plate.

10. Control of Sash Movement

This~is should be carried outout once aa year butbut alsoalso ifif abnormalabnormal vibrationsvibrations in the frame are noticed.noticed.

There~lere are two ways of controllingoontrolling this:this:

1. Open the caps of thet he lowerlower connectingconnecting rodrod bearingbearing andand measuremeasure the distance between thet he rollersrollers and thethe outerouter ring.ring. The dis-dis­ tance should be the same forfor anyany positionposition ofof thet he sash.sash. 2. A more accurate result is aohievedachieved usingusing two plumb lineslines andand two metal sheets with a holehole inin thethe centre.centre. See figure below. - 96 -

~ I o 5

1 Good 2-12-3 AcceptedAccepted 4--64-6 Correction requiredrequired

- Attach the two metal piecespieces toto thethe crahkcrank: shaftshaft bearingbearing housing as shown inin figure.:figure.

Pull the plumb lines through thethe holesholes inin thethe metal piecespieces and attach the line to thethe lowerlower crosscross beamsbeams ofo:f thethe sashsash and vertical to the holes. The sash should be in its top position.

- Adjust the metal piecespieces toto centrecentre thethe plumbplumb lineline inin thethe hole.hole.

Using a file,:file, mark thethe positionposition ofo:f thethe plumbplumb lineslines ofo:f thethe lower cross beam.

Lower the sash to itsits bottombottom positionposition andand attachattach thethe plumbplumb lines to their previous position,position, usingusing thethe file.marks.:file. marks.

IfI:f the movement ofo:f the sash isis incorrectincorrect thisthis cancan bebe seenseen :fromfrom the positionposition ofo:f thethe plumbplumb lineline inin thethe hole.hole. The figure:figure shows some typical faults:faults ofo:f whiChwhich somesome cancan bebe acceptedaccepted andand some have to be corrected.corrected.

11. GuideCuide Cooling System

Regular control o:fof the cooling system efficiencye:f:ficiency isit3 recommended. It is easily carriedcarried outout byby measuringmeasuring inin andand outgoingoutgoing waterwater temperature.temperature. Maximum allowed outgoing.temperatureoutgoing-temperature isis 65°065°C and maximum allowed di:f:ferencedifference between inin and outgoingoutgOing water temperature isis 15°C.15°0. -97-- 97 -

REVOLUTIONS,R Jl VOL UTI 0 N 5,

COGCOO NUMBERSBUKBERS

AND PERIPHERALPERIPHERAL

SPEED.S PEE D.

(FORMULAS(roRlHlLAS AND CALCULATIONSCALCULATIOIE) )

PART VI - REVOLUTIONS, COGCOG NUMBERSNUMBERS AND PERIPHERAL SFEEDSSPEEDS 2ad2 1. IntroduotionIntroduction •••••••••••••••••••••••••••••••••••••••00000000000000000060000110000000000 98

2. Abbreviations used inin texttext 00000000000000000000000DO••••••••••••••••••••••••• 98

3. How to calculate the number of revolutions of a shaftshaft 99

4. How to calculate the diameterdiameter ofof aa pulleypulley ...... •••••••••• 100

5. How to calculatecaloulate the numbernumber ofof teethteeth requiredrequired onon aa sprooketsprocket •••••••••••••••••••••••••••••••••••••••••••DO ******** 00000041.00a00000ODOooDOOD000o0O00. 101

6. HbwHow to calculate the number ofof revolutionsrevolutions ofof aa shaftshaft when power is trannmittedtransmitted overover severalseveral intermediateintermediate shafts ...... 0000000000000000060"0000000000000000000000et 102

7. HowHOw to calculatecalculate peripheralperipheral speedsspeeds •••••••••••••••••...... 103

8. SomeSome praotioalpractical examples ••••••••••••••••••••••••••••0600000000000000000O00000000 104 - 9898 --

1. Introduction

WitWithinhin the saw milling industryindustry it is often necessary to be able to calculate, for instance:instance I

the number of revolutions of a shaft in order to be able to fitfit a matching blade or grindinggrinding disc.disc.

the required diameter of a pulley to obtain a certaincertain number of revolutions.

the necessary number of teeth of a driven sprocket, inin order to match itit toto thethe desireddesired numbernumber ofof revolutionsrevolutions of,of, forfor instance, driving sprockets.sprockets.

the peripheral speedspeed ofof aa revolvingrevolving circularciroular sawbladesawblade ·inin order to determine thethe correctcorrect speedspeed toto feedfeed thethe saw.saw.

This manual uses practical examplesexamples toto showshow howhow answersanswers toto thesethese typestypes ofof questions can be obtained.obtained.

2. Abbreviations used inin TextText

Diameter ... 0 0 0 0 n 0 0 ...... 0 O 0 0 .O 0.. 0 ·... d Circumference ... 0 0 0 000 ... ·00.. 0 . c ~~eThe Constant Pi (=(= the'numberthe· number 3,1416)3.1416) which isis usedused toto calculate the circumference of a circle ...••• · ... J1 MetMetres res per second 0 .. ... 0 0 .0.. 0 m/Secm/sec Peripheral sreedspeed (Velocity)(Velocity) V Number of cogs or teeth 9 0 Z Number of revolutions (revs Number of revolutions (revs) •• ...00 . ..0 0 O n expressed as expressed as r/Minrjmin or r/secrlsec 99 -

3. RowHow to Calculate thethe numbernumber ofof RevolutionsRevolutions ofof aa ShaftShaft

i) TASK: To find the number of revolutions of the driven shaft A in the figure below

300mm300 mm 450 mmmm

n~ 1440 rj min

ii)ii TIIITIALINITIAL POINTS: WeIve start from what wewe know:know:

that the engine B runs at 1440 r/min.r/Min.

that the pulley CC has a diameterdiameter ofof 300300 mm.Mm.

that the pulley D has a diameter of 450 mm.mm.

iii) CALCULATIONS: To find out the unknown number of revolutions the following calculations are made:

The number of revolutions of thethe engineengine isis multiplied by the diameter, inin mm, ofof thethe pulleypulley ofof thethe engine.engine.

In thisthis case it isis 1440 x 300.

This figure isis divided by the diameterdiameter ofof thethe drivendriven pulley, which gives the unknown numbernumber ofof revolutions,revolutions, i.e.i.e.

engine speed x diameter of driving pulley _ unknown num-num, n ~ diameter of driven pineypulley ber ofof revs.revs.

In thisthis case the answer is:is:

300 n 1440 x 300 ~. 960 r/Minr/min = 450 - 100 -

4-4.How to Calculate the Diameter of a PulleyPulley

i) TASK: To find the suitable diameter of pulley A in the figure below.below.

400mm

1200 rj min n= 970 rjmin

ii) INITIAL POINTS:PO INTS: We start from whatwhat wewe know:know:

that the drivendriven shaftshaft BB hashas aa pulleypulley C,C, the diameter ofof whichwhich isis 400400 mm.mm.

- that this shaft needs to rotate at 1200 r/Min.r/min.

that the engine D runs at 970 r/min.r/Min.

iii) CALCULATIONS: To find the unknown diameter the followingfollol~ing calculations are made:

- To start with, we calculatecalculate thethe geargear ratioratio betweenbetween thethe pulley and the engine.engine. This is done by dividingdividing thethe number of revolutions of thethe pulleypulley byby thethe numbernumber ofof revolutions of the engine,engine, i.e.i.e.

number of revolutions of pulley/Minulle min .c ]1QQ1200 number of revolutions of engine/minengine min 970

- Then, this ratioratio isis multipliedmultiplied byby thethe diameterdiameter ofof thethe driven pulley C,C, i.e.i.e. 1200 d = 757 x400 =c 495 mm.nun.

This result can be rounded off to the higher figure of 500 DIDmm whiohwhich isis a standard diameter.diameter. - 101101 -

5. How toto Calculate the Number of Teeth rerequiredired onon a SSproket roket

To calculate the gear ratio for chain drives or cog transmission, i.e.i.e. the relationshiprelationship betweenbetween the number of teeth or cogsooge of the driving and the driven sprocket, thethe same prooedureprocedure can be used as inin the previous example.example. The onlyonly difference is thatthat instead of using the diameter of a wheel, the number of teeth or cogs isis used.

i) TASK: To find the necessary nuMbernumber of teeth of the driven sprocket A in the figure below.

n=60 r/min n= 100 r/min z=1 z= 20 •

ii) INITIAL POINTS:POINTS: We start from what we know:know: that the conveyerconveyer rollerroller BB willwill dodo 100100 r/6in.r/min.

that itsits sprocket hashas 2020 teethteeth

that the engineengine CC doesdoes 60 r/6in.r/min.

iii) CALCULATIONS: The following calculations are made according to the general formula:formula:

speed of cog wheel A speed of cog wheel A x the number of teeth of cog wheel B speed of cog wheel B the number of teeth of cog wheel B

.~ the unknown numbernumber ofof teethteeth ofof cogcog wheelwheel A.A.

Applied to ourour example:example: - divide the speedspeed of engineengine AA byby thethe speedspeed ofof conveyorconveyor rollerroller B,B, andand

- multiply thethe resultresult byblf thethe numbernumber ofof teethteeth ofof thethe chainchain wheelwheel ByB, i.e.

...2Eginee ine seedspeed A/minA/Min x number of teeth of wheel B conveyor speed B/minB min x number of teeth of wheel B

.- unknown number ofof teethteeth ofof wheelwheel A.A. With figuresfigures insertedinserted 6260 z .100a 100 xX 2020 .a 12 teeth - 102 -

6. How to CalculateCalculate the number of Revolutions of a Shaft when PowerPower isis transmitted overovsr several intermediateintermediate Shafts

i) TA:TASK: To determineTo determine the the rotation rotation speed speed of of machine machine CC when when powerpower is transmitted through an intermediateintermediate shaft B from the driving wheel A, asas illustratedillustrated inin figurefigure below.below.

d=600mm d=400mm d=3:X)mm

d =300 mm

ii) JJHTIALINITIAL POINTS: HeWe start from what wewe know:kncw:

- that the speed of thethe drivingdriving wheel A isis 600 r/Min.r/min.

- that the diameter of the driving wheel A isis 400 mm.rom .

- that the driven wheelwheel ofof thethe intermediateintermediate shaftshaft BB hashas aa diameter ofof 300300 mm.rom.

- that thethe drivingdriving wheelwheel ofof thethe intermediateintermediate shaftshaft BB hashas aa diameter of 600600 mm.mm.

that the diameter of thethe discdisc of machinemachine CC isis 300300 mm.mm.

iii) CALCULATIONS: To find thethe unknown number of revolutions,revclutions, the following calculationscalculations areare made:made: the number of revolutions of the intermediateintermediate shaftshaft BB isis first calculated asas follows:follows:

diameter of driving wheel c number of revs ofof drivendriven wheelwheel diameter ofof drivendriven wheelwheel -number of revs ofof drivingdriving wheelwheel

~:Note: Make sure which wheelwheel isis drivendriven andand whichwhich isis driving.driving.

With figures insertedinserted: n =492 number of revolutions of BB 300 600 600 x the number of revolutions of B = 600 x 400-400 =800 800 r/Min. r Imin. 300 I' - the number of revolutions of CC cancan be calculatedcalculated using the same formula::fonnula: 600 number of revolutions of CC n = -3003oo = 800 600 x 800 !. the number of revolutions of CC .c 300 =c 1600 r/Minrlmin 300 - 103 -

7-7. How to Calculate PeriPeripheral heral SSpeeds eeds Peripheral speed (henceforth(henceforth marked withwith thethe letterletter V)V) isis thethe speedspeed ofof anan imagined rotating point situated onon thethe circumferencecircumference ofof thethe rotatingrotating shaft.shaft. It is usually expressed asas metresmetres perper secondsecond (m/sec).(m/sec).

i) TASK: To find the peripheral speed (V)(V) of thethe tooth points of aa circular sawblade.sawb1ade. (See figure below).below).

d=1200mm

ii) INITIAL POINTS: We start from ~lhatwhat we know:

that the diameter of the sawbladesawb1ade isis 1200 mm.

thatthat the sawblade doesdoes 900900 r/Min.r/min.

iii) CALCULATIONS: To find the unknown peripheral speed, the following general formulaformula isis used:used:

The circumference of the sawbladesawb1ade (c)(c) (in(in metres)metres) isis multiplied by the number of revolutions of thethe sawbladesawblade (in(in r/sec).r/sec).

Using the formula for the circumferencecircumference ofof aa circlecircle (c(c =n-=~ xxd) d), we calculatecalculate thethe circumferencecircumference ofof thethe sawblade:sawblade: c =JTx=11rx 1.21.2 ' = 3.14 x 1.2 m = 3.77 m.m. The circumference, c, isis then multiplied byb,y thethe number of revolutions per second of the sawblade,sa~lblade, i.e.i.e.

V = 3.77 x 900 r/minr/Min =. 3.773.77 x r/sec = 57 m/sec. x09~6

revs/minute N (Note revs/second revs£~inute ) revs/second == 60 104- 104 -

8. Some Practical ExamplesExamples

A. How to calculate thethe maximum numbernumber ofof revolutionsrevolutions ofof aa grindinggrinding disc.disc.

i) TASKTASK: I To install a new grinding disc in a grinder mounted on a circular saw we need to know the maximum number of revolutions of aa discdisc ofof aa givengiven diameter.diameter. (See figure below.)

d=305mm

V=max

ii)ii INTTIALINITIAL POINTS:PACTS: We\,e start from what wewe know:knoWI

that when grinding free-handfreehand withwith aa ceramicceramic disc,disc, asas inin thisthis case, a maximum peripheral speedspeed of 2828 m/sec isis allowed.

that the diameter of the discdisc isis 305305 mm.

iii) CALCULATCALCULATIONS: IONS I The unknown number of revolutions (n)(n) can be calculated from thethe formula:formula I number of revolutions (rjmin)(r/min) peripheral speed V c. circumference c x peripheral speed V circumference c x 60 - -

InIn thisthis exampleexample V D. 28 m/secm/sec cc a:rr51. x diameter of disc a. 3.14 xX 0.305 =a 0.96 m Inserted into the above formula we find: 28 x 6060 nn -= 0.960.9d-- . 1750 r/min.r/min. --105105 -

B. How to calculate the necessary numbernumber ofof teethteeth ofof aa sprocket.sprocket.

i) TASK: To calculate the required number of teeth onon thethe sprocketsprocket of motor A (in(in figure below) to make thethe rollroll conveyerconveyer workwork at a desired speed.speed.

d =175mm 75m--/ m in d=175mm

nn=90 = 90 r/rninr/ min

ZE3='E-7 toethtooth •

ii) INITIAL POINTS:POINI'S: We start fromfrom whatwhat wewe know:know: - that the required speedspeed ofof thethe rollroll conveyerconveyer isis aboutabout 75 m/Min.m/min. - that the sprocket onon motormotor AA doesdoes 9090 r/Min.r/min. - that the driven sprocket BB hashas 2020 teethteeth (ZB)(~) andand diameterdiameter ofof 175175 mm.mm.

iii) CALCULATIONSCALCULATIONS:: ThisThis problem is solved Qyby using the formula

number of revolutions of sprocket A numoer of revolut~ons of sprocket A 2:numberx number ofafteeth teeth of sprocket B = number of revolut10nsrevolutions of sprocket B

~. the unknown number of teeth of sprocketsprocket A.

To be able to use this formula we must first calculatecalculate thethe number of revolutions of sprocket B.B.

We knowknow that the peripheral speed of B must correspondcorrespond to the desired peripheral speed of thethe rollroll conveyer,conveyer, i.e.i.e. 7575 m/Min.m/min. By usiDgusing the formula below we can therefore calculatecalculate thethe numbernumber ofof revolutionsrevolutions ofof B:B:

Peripheral speedspeed )IrJT x diameter x nuMbernumber ofof revolutions.revolutions. With figures inserted:inserted:

a X x n 75 =iTJT x 1000.ill 175 n a 21..E.122275 X 1000175 ~= 136 r/Minor/min. (Note:(Notel 175=175mm =~ lilt1000 m) JT x 175

We cancan now now calculate calculate the necessary the nuMbernecessary of teeth number of driving of teeth of driving sprocket A A Qyby using the firstfirst formula:formula:

Unknown number of teeth (ZA)(ZA) isis

a 13 teeth (rounded offoff toto nearestnearest zA.4x13 20= 13.25. 13 whole number) By checking thisthis example fcrfor ZA -= 13 teeth we find that roll conveyor willwillwork work aa little fasterfaster thanthan 75 m/mm.m/Min.