1. Defining Gear

2. Types of Gears Driver Gear: The gear that has power to it.
Idler Gear: A gear the transfer movement.
Driven or Follower: the end gear.

3. The Three ways to Find Gear Ratios
1. Count the number of teeth on
the gears.
2. Measure the diameter, radius
or circumference.
3. Count the rotations of

4. Direction of Rotation Even amount of gears, the end gears turn
the opposite direction.
Odd amount of gears,
the same direction.

5. Simple Gear Ratio
The red gear (12 teeth),can be divided by 12 = 1. The blue gear (36 teeth),can be divided by 12 = 3. The gear ratio is 3:1. If the red gear is the driver gear, the blue gear turns slower, it is geared “Down”. If the blue gear is the driver gear, the red gear turns faster, it is geared “Up”.

6. Gear Train Ratios

7. Compound Gear Ratios 1

8. Compound Gear Ratios 2

9. Torque
Torque: is rotational force (a distance X force). Torque is measured in: English units: Ftlb or Inlb Metric units: N.m

10. Trade-Off Newton's 3rd law of motion: for every action
there is an equal and opposite reaction.
Ride a bike up a hill, you trade speed for torque.
Smaller gear in the front and a bigger gear in the back for speed.

11. Trade-Off Ride a bike down a hill, you trade torque for speed.
Big gear in the front and a small one in the back for speed.