1. Two-Gear Gear Trains Using different size gear allows change in speed
Gear ratio calculates this change
Driving gear is attached to motor
Driven gear is attached to wheel
Gears spurs (teeth) mesh together
Gears rotate in opposite directions

2. Two-Gear Gear Trains Given the gear on the left is the driving gear:
Calculate the gear ratio for these two gears
Gear Ratio = 8/24 = 1/3
Calculate the gear ratio for these two gears
Gear Ratio = 40/8 = 5
Calculate the gear ratio for these two gears
Gear Ratio = 24/24 = 1
Why might you want to do this?

3. Two-Gear Gear Trains A Gear Ratio <1 is called Gearing Down
Will the speed of the wheel go up or down compared to the motor?
Gearing Down = Speed goes Down
But, power (torque) goes up
Always some loss to friction
Why might you want to do this?
A Gear Ratio >1 is called Gearing Up
Will the speed of the wheel go up or down compared to the motor?
Gearing Up = Speed goes Up
But, power (torque) goes down
Always some loss to friction
Why might you want to do this?