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## Introduction

Rotary motion is the most common type of motion to be found in machines. In many machines rotary motion must be transmitted from one shaft to another. An example of this is the pillar drill. The exercise below requires you to combine several calculations explored previously in earlier examples. These involve the calculation of velocity ratio and the output speed:

Velocity ratio = No. of teeth on driven / No. of teeth on driver
Output speed = Input speed / Velocity ratio

You will use these calculations in the following exercise.

## Task 1: Velocity ratio of a chain drive Chain drive and motor

1. Open Yenka file Model 1.
2. The model shows a chain drive being driven by a motor. In what direction are the motor and the chain drive turning? Describe the type of motion illustrated by the motor.
The motor and chain drive are turning clockwise using rotary motion.
Gear wheel A is the driver as this is attached to the motor. B is the driven.
4. Does the above arrangement result in a speed reduction or increase? Explain your answer.
The driven gear wheel is larger than the driver. Therefore the ratio is greater than 1, resulting in a speed reduction.

### Summary

If the gear ratio is greater than 1, the result is a speed reduction.

## Task 2 : Calculating speed reduction & increase Chain drive and motor