St/Est 404 the Technological World

ST/EST 404 THE TECHNOLOGICAL WORLD CHAPTER 13 NOTES CHAPTER 13 Mechanical Engineering (pp. 424 - 454)

Invention of the wheel Invention of gears Invention of the bicycle Invention of the internal (3500 B.C) (200 B.C) (1816) combustion engine (1859) 1 What is Mechanical Engineering?

Engineering is divided into several fields. For example, civil engineering involves anything to do with infrastructure, like roads, bridges and viaducts. Computer engineering deals with information systems and electrical engineering deals with electric circuits.

 Mechanical engineering is the branch of engineering that focuses on the design, production, analysis, working and improvement of technical objects with moving parts.

Mechanical engineering must take into account all aspects of motion in an object, namely the guiding, transmission and transformation of that motion. But before discussing these subjects, we must first understand how the parts of an object are connected together.

2 Links in Technical Objects

A link holds two or more components of a technical object ______.  In mechanics, a ______is a part or fluid that performs a mechanical function.

 ______is a mechanical function performed by any component that ______different parts of a technical object.

2.1 CHARACTERISTICS OF LINKS  See Handout “Types of Links” and Table 13.3 on p. 428 of your textbook Observatory.

1 ST/EST 404 THE TECHNOLOGICAL WORLD CHAPTER 13 NOTES

3 Guiding Controls

 Guiding is the mechanical function performed by any component that controls the ______of one or more ______parts.

In many pieces of furniture, slides allow drawers to open and close. In this situation, the slides are the guiding components since their mechanical function is ______.

 A guiding component or control is a component whose mechanical function is to guide the motion or moving components.

In technical objects, there are three main types of guiding controls:

1. ______2. ______3. ______

3.1 TYPES OF GUIDING (3 TYPES)

1. ______guiding ensures the straight translational motion of a moving part (ex. ______or ______)

2. ______guiding ensures the rotational motion of a moving part. (ex. ______)

3. ______guiding ensures the translational motion of a moving part while it rotates about the same axis. (ex. C-clamp or vice)

4 Motion Transmission Systems

 Motion transmission is a mechanical function of relaying a ______from one part to another ______altering the ______of the motion.

For example, on a bicycle, the rotational motion applied by the cyclist’s legs to the crankset is transferred to the rear wheel by a set of three components: a sprocket linked to the ______, the sprocket linked to the ______wheel, and a ______.

 A motion transmission system is a set of components that perform the function of motion transmission.

Table 1: TYPES OF COMPONENTS IN A MECHANICAL SYSTEM Type of component Description Driver (motor) Component that receives the force required to ______the system. Driven Component that receives the movement and ______it to another component. Intermediate (idler) Component located ______the motor and the driven. It is not present in all systems.

4.1 CHARACTERISTICS OF MOTION IN TRANSMISSION SYSTEMS

The most common motion transmission systems found in technical objects are:

 gear trains  chain and sprocket systems  worm and worm gear systems  friction gear systems  belt and pulley systems

All these systems transmit ______motion. Rotational motion can be either ______or ______. F A system is reversible if the driven can become the ______.

GEAR TRAINS

DIRECTION OF ROTATION IN EACH COMPONENT: Alternates from ______gear to ______

REVERSIBLE? ______

CHAIN & SPROKET (COG) SYSTEMS

DIRECTION OF ROTATION IN EACH COMPONENT: According to its configuration; except for the wheels that are touching the ______side of the chain

REVERSIBLE? ______(Click on link below to see animation) http://en.wikipedia.org/wiki/Chain_drive Worm (driver) WORM AND WORM GEAR (wheel) SYSTEMS

DIRECTION OF ROTATION IN EACH COMPONENT: Worm gear (wheel) Varies according to the direction of the threads on the worm screw shaft. REVERSIBLE? ______http://www.oilanalysis.com/article_printer_friendly.asp?articleid=1080 FRICTION GEAR SYSTEMS

DIRECTION OF ROTATION IN EACH COMPONENT: Alternates from ______gear to ______

REVERSIBLE? ______BELT & PULLEY SYSTEMS

DIRECTION OF ROTATION IN EACH COMPONENT: According to its configuration; except for the pulleys that are touching the ______side of the belt

REVERSIBLE? ______http://autorepair.about.com/library/faqs/bl047d.htm

4.2CONSTRUCTION CONSIDERATIONS FOR MOTION TRANSMISSION SYSTEMS

1. GEAR TRAINS

 Made up of at least ______gears in which the teeth ______together.  The more teeth a gear has, the ______its diameter and the ______it will turn.

Applications: ______and ______.

2. CHAIN & SPROKET SYSTEMS  Made up of at least ______gears connected by a ______.  Used to transmit rotational motion between two or more ______parts.  The smaller the sprocket, the ______it turns.

3. WORM AND WORM GEAR SYSTEMS (Worm and worm wheel)

 Made up of one ______(screw) and one or more ______.  The threads in the ______must mesh with the teeth in the ______.  The motor (driver) must be the ______.

Applications: ______

4. FRICTION GEAR SYSTEMS (Straight, bevel, and spherical)

 Similar to a gear train system except that the wheels have no ______.  The motion is transmitted by ______contact between two wheels.  Less efficient than gear train systems because wheels can ______.

Applications: Photocopy machine, newpaper printing machine

5. BELT & PULLEY SYSTEMS  Similar to a chain and sprocket system, but gears are replaced with ______and the chain is replaced with a ______.  Like chain and sprocket systems, they are used to transmit rotational motion between two components that are far ______.  The smaller the pulley, the ______http://upload.wikimedia.org/wikipedia/co it turns. mmons/4/42/Keilriemen-V-Belt.png

Applications: ______

Click here to see video:  http://en.wikipedia.org/wiki/Conveyor_belt

4.3 SPEED CHANGES IN TRANSMISSION SYSTEMS

 A speed change occurs in a motion transmission systems when the driver ______turn at the same speed as the driven component.

This occurs when the ______of the wheels or ______of teeth on the gears in the system are ______. Speed Change Motion transmission system Speed ratio Increase DriveR diameter > driveN diameter # teeth on driveR > # teeth on driveN ______than 1 Decrease Driver diameter < driven diameter # teeth on driver < # teeth on driven ______than 1 No change Driver diameter = driven diameter # teeth on driver = # teeth on driven ______to 1

CALCULATING THE SPEED RATIO BETWEEN TWO GEARS/WHEELS

SPEED RATIO = Diameter of driveR or # teeth on driveR Diameter of driveN # teeth on driveN

Speed of driveR = Diameter of driveN or # teeth on driveN Speed of driveN Diameter of driveR # teeth on driveR 6 ST/EST 404 THE TECHNOLOGICAL WORLD CHAPTER 13 NOTES

Sample problems: Calculate the speed ratio in each of the following gear trains

Example 1:

Example 2:

This means that the rotational speed of the driven gear is ______times slower/faster than the rotational speed of the driver gear.

Example 3:

This means that the rotational speed of the driven gear is ______the rotational speed of the driver gear, the gears just move in ______directions.

Additional problems

1. If a driver gear has 48 teeth and a speed of 30 rpm (rotations per minute), how fast will the follower (driven) gear turn if it has 16 teeth?

2. If a driver friction gear has a diameter of 15.0 cm and a driven friction gear has a diameter of 3.0 cm and speed of 82 rpm, how fast will the driver gear be turning?

3. Of a belt and pulley system has one pulley with a diameter of 35 cm and a rotational speed of 10 rpm, what is the diameter of the second pulley if it turns with a speed of 50 rpm?

______5 Motion Transformation Systems

So far we have only looked at systems that transmit ______motion from one part of the system to another. These systems did not change the ______of motion, they only ______it.

 Motion transformation is a mechanical function of ______a motion from one part to another while ______the nature of the motion. 5.1 CHARACTERISTICS OF MOTION IN TRANSFORMATION SYSTEMS

RACK AND PINION SYSTEMS Possible transformations Rotational  ______Translational  ______

Reversible? ______

Click here for video: http://www.motorera.com/dictionary/pics/R/rack.gif  http://en.wikipedia.org/wiki/Rack_and_pinion  http://www.technologystudent.com/images3/rkpn2.gif SCREW GEAR (NUT) SYSTEMS (TYPE I) Possible transformations Rotational  ______

Reversible? ______

http://www-ece.rice.edu/%7Ejdw/figs/c_clamp_2.jpg SCREW GEAR (NUT) SYSTEMS (TYPE II) Possible transformations Rotational  ______

Reversible? ______

http://www.northerntool.com/images/product/images/558552_lg.jpg CAM & FOLLOWER SYSTEMS Possible transformations Rotational  ______

Reversible? ______Click here for video: http://en.wikipedia.org/wiki/Camshaft

SLIDER-CRANK MECHANISMS Possible transformations Rotational  ______

Reversible? ______Click here for video: PISTON ROD http://www.luiemotorfiets.nl/motoren/koppel/Koppel- Vermogen-Klein.gif

http://home.planet.nl/%7Eserem000/drawings/pet-in.gif Click here to see how the cam & follower and slider-crank mechanism work together in a 4- stroke engine: http://en.wikipedia.org/wiki/File:4-Stroke-Engine.gif

5.2CONSTRUCTION CONSIDERATIONS FOR MOTION TRANSMISSION SYSTEMS

1. RACK AND PINION SYSTEMS  Made up of at least one gear (______) and one toothed rod (______)  The more teeth the pinion has, the ______it will turn and the ______the rack will move.

2. SCREW GEAR (NUT) SYSTEM (TYPE I)  The ______is the driver and the ______is the driven.

Applications: ______and ______

3. SCREW GEAR (NUT) SYSTEM (TYPE II)  The ______is the driver and the ______is the driven.

Application: ______

4. CAM AND FOLLOWER SYSTEM & ECCENTRICS (p. 448-449)  Consists of a ______(rotational component) that pushes on a ______(translational component) causing it to move ______and ______.  A cam is usually egg-shaped and its rotational axis is ______.

 An eccentric has the same ______as a cam, but its rotational axis is ______- ______. To see various cam and follower mechanisms in action, watch this! http://www.youtube.com/watch?v=zCYKQlL0qxE

Application: used in modern machines for example for operating the valves in engines, textile machine tools, paper cutting machines, feed mechanisms of automatic lathes, switches etc.

5. SLIDER-CRANK MECHANISM (p. 449)  The ______connects the slider (piston) to the ______on the wheel.  The ______moves ______and ______while the crank

______. D t

Application: ______s

F Train wheel system: http://www.youtube.com/watch?v=CEkK50pbgMw F END OF CHAPTER 13: MECHANICAL ENGINEERING NOTES