1. Mechanical Engineering: Gears

2. Wheel and axle
F1 x D1 = F2 x D2
Lower force x longer distance = higher force x shorter distance

3. Wheel as force multiplier
Wheel as speed multiplier
Can you think of other examples?

4. Gears – wheels with teeth
Gears have teeth that can be meshed together to effectively transfer motion from one gear to another.
Gears are used for:
Changing the direction of rotation
Changing the speed of rotation
Changing the force required to move an object
Moving the rotational motion to a different axis

5. Drawing Gears
It can be difficult to draw all those teeth so gears are often drawn as two circles and the number of teeth noted.

6. Changing direction
What direction do the driven gears move, given that the driving gears move clockwise?

7. Changing speed Would the driven gear move faster, slower
or the same speed as the driver?
Driver
Driver

8. Gear Ratio
To find quantitatively how the motion will change in gear system you can use gear ratios
With gears, you can compare the radii of the gears (as in wheels) or you can compare the number of teeth.
The driven gear makes two rotations each time the driver rotates. So it moves twice as fast.
Speed out = Speed in / gear ratio

9. Gear Ratios What are the gear ratios for these systems?
Driven gear moves 1/3 the speed of driver
Driven gear moves 1/4 the speed of driver

10. Gear speed
If the driver is moving at 60 rpm (revolutions per minute) what speed is the driven gear moving?
Speed out = Speed in / gear ratio

11. Compound Gear Ratios
When faced with multiple gears systems: - find each gear ratio - multiply them together to find the overall ratio

12. Changing force
Gears can be used to change the force needed. Force with rotation involved is called ‘torque’.
The change in torque can be found with gear ratios
Speed out = Speed in / Gear ratio
Torque out = Torque in x Gear ratio
There would be 3 times the force on B than on A

13. Changing axis of rotation
Gears can be used to change the axis of rotation by using
Bevel gear
Worm gear

14. Complex Gear Machine
Use two gear ratios to find the speed of the final gear in this system

15. Complex Gear Machine
Use two gear ratios to find the speed of the final gear in this system