1. What are gears?
Wheels with teeth

2. Why gears? They transfer motion from 1 part to another.
Gears can increase speed.
Gears can be used to pull heavy loads.
But…
…not both.

3. Torque
Torque can be described as a force causing rotational acceleration, that is, causing something to spin.
Torque=Applied Force * distance to pivot
Greater force or longer distance means more torque

4. Motors Motors deliver torque in a small package
They can be used wherever rotational motion is needed.
Motors differ in the amount of torque they output and the speed at which they spin.

5. Gearing - Why? You don’t always have the perfect motor for the job
Gearing is used to change the speed and torque output of a motor to suit your design needs
Gearing results in a compromise between speed and torque.
To gain speed, you must sacrifice torque.
To gain torque, you must sacrifice speed.

6. Gear Ratio Gear ratio is defined as: Expressing the ratio:
Drive gear (input): driven gear (output)
Number of Teeth Input : Number of Teeth Output
Expressing the ratio:
5:2 = 5/2 = 2.5:1

7. Examples Therefore, drive gear must turn 3 times
Meshing 8-tooth gear with 24-tooth gear yields 1:3 gear ratio.
1 turn moves 8 teeth here…
…and here
Therefore, drive gear must turn 3 times

8. Ratios Drive gear Driven gear 2 2 2 1 1:1 2:1
Odd number gear meshes change direction

9. What is this ratio? 1:5 5 t Motor attaches here 25 t Input: Output
5:25
1:5

10. Gear train: a collection of gears
The ratios have a multiplicative effect.
8 t
Motor
24 t
8:24 = 1:3
3 x 2 = 6
1:6
24:48 = 1:2
48 t
8:48 = 1:6

11. Multiplicative Effect8 4 1
1:2
Drive
1:4
Overall ratio 1:8

12. Gearings effects on Torque
Force acting through a distance.
Radius of gear is the lever arm.
Small radius = small lever arm
Large radius = large lever arm

13. Gearing vs. torque r 2r
.2kg•m
.4kg•m

14. Worm Allow for VERY large reductions Unique feature:
gear
Allow for VERY large reductions
i.e. 20:1 to 300:1
Unique feature:
The worm can turn the gear but..
The gear cannot turn the worm