TRANSMISSION OF MOTION AND

POWER

By : Taher K D

MOTION TRANSMISSION SYSTEMS

Motion Transmission is the mechanical function of relaying

a motion from one part to another without altering the

nature of the motion.

A Motion Transmission System is a set of components that

perform the function of transmitting motion.

SOME DEFINITIONS Driver component: receives the force required to activate the system

Eg: crankset on a bike

Driven component: receives the motion and transfers it to another part

Eg: rear gears on a bike

Intermediate component: located between the driver and driven component – not all systems have this.

Eg: the chain on a bike

4

CHARACTERISTICS OF MOTION IN TRANSMISSION

SYSTEMSThe most common rotational transmission systems are:Gear TrainsChain and Sprocket SystemsWorm and Worm Gear SystemsFriction Gear SystemsBelt and Pulley Systems

5

GEAR TRAINSThe direction of rotation changes from one wheel to the next.

The system can be reversed.

6

GEAR TRAIN FACTORSGear teeth: all the gear teeth in a system must be

identical – same shape, direction, size and be equally

spaced. E.g. Straight or helical

Gear type: the rotational axis of the gears can be

positioned different ways (eg: car differentials)

Gear size: the higher the number of teeth, the lower the

speed of rotation – or bigger diameter slower speed.

7

SIMPLE GEAR TRAIN Arrangement of gears in series is known as simple gear

train.

Intermediate gears are provided between the driver and driven.

The function of the idler gears is

1. To cover the space between the driver and driven gears and to

2. Obtain the desired direction of driven

8

9

COMPOUND GEAR TRAINWhen two or more gears are compounded, then the gear train is known as compound gear train.

10

FRICTION GEAR SYSTEMS

The direction alternates from one gear to the next.

It is reversible.

The smaller the diameter of the gear, the faster its rotation

Friction gear systems are similar to gear trains except that motion

is transferred by FRICTION and not by the GEAR TEETH.

Factors that affect friction gear systems are: gear type (straight,

bevel or spherical), gear size and choice of material.

11

SPEED CHANGES IN MOTION

TRANSMISSION SYSTEMS

A Speed Change occurs in a motion transmission system

when the driver does not turn at the same speed as the

driven component(s).

The speed change depends on the ratio of gears/threads

of the driver compared to that of the driven component.

SPEED CHANGES IN A PULLEY OR SPROCKET

TRANSMISSION SYSTEMTo increase the speed, the driven component should have a smaller diameter.

To decrease the speed, the driven component should have a larger diameter.

To keep the same speed, the two pulleys should have the same diameter.

E.g. Driver Diameter = 15cm

Driven Diameter 5 cm

So the driven pulley is 3 times FASTER

CALCULATING GEAR RATIOS

15

CHAIN AND SPROCKET SYSTEMS

The direction of rotation of all sprockets on the same side of

the chain is the same.

A sprocket on the other side of the chain rotates in the

opposite direction.

It can be reversed.

The smaller the sprocket the faster it turns

Requires frequent lubrication

16

BELT AND PULLEY SYSTEMS

Power is to be transmitted between the parallel shaft.

Consists of two pulleys over which a endless belt is passed encircling the

both.

Rotary motion is transmitted from driving pulley to driven pulley.

The choice of the belt material and the tightness of the belt affect the

friction and hence the efficiency of the system.

The direction is the same for any pulley on the same side of the belt.

It is reversible.

The smaller the pulley, the faster its rotation

17

18

RACK AND PINION SYSTEMS

Converts rotational motion to translational motion or vice

versa

The rack is the straight bar with teeth.

The pinion is the gear part.

It is used in many steering systems.

The greater the number the teeth on the pinion, the slower its

rotation

Thank You