1. Gears

2. Gears Used to transfer energy from one place to another
Rotary motion and force transferred from one part of a machine to another part
Gear Wheel: a wheel with matching teeth around its edge
Gear Train: two or more gear wheels that mesh
rotary motion from one gear is transferred to another gear

3. Driving Gear (Driver): supplies the driving force in a gear train
Driven Gear (Follower): The gear wheel that the driving gear applies it’s force to
Mesh: gears must mesh, or interlock neatly as they rotate

4. Gears Can Increase Rotational Speed
A gear train can increase the rotational speed of a device
Ex. a hand mixer, bike
The driving gear is larger (has more teeth) than the driven gear so the driven gear travels faster
Driving gear
Driven gear

5. Gears Can Decrease Rotational Speed
Reducing gears are drive trains that decrease the rotational speed of a device so they decrease speed
Ex. bicycle, car
Driving gear
Driven gear

6. Gears can Change Direction
Parallel gears are the same size, so they have the same rotation speed, but they change the direction of the rotary motion
Drive wheel: clockwise; Driven wheel: counterclockwise
Ex car transmission

7. Gears can change rotary motion into straight line motion
Load

8. Gears can transfer a rotary motion from one shaft to another without changing direction

9. Mechanical Advantages of Gear Trains
To calculate the increase or reduction in rotational speed calculate the ratio of the size of the driving gear to the size of the driven gear
This is called the speed ratio

10. Multiplying Gears Driving gear = 10 teeth = 2 Driven gear = 5 teeth
The speed of the gear has been changed by a factor of 2, the driven gear will move twice as fast as the driving gear
5 teeth
10 teeth

11. Reducing gears Driving gear = 4 teeth = 1/2 Driven gear = 8 teeth
The speed of the gear has been reduced to ½ it’s original speed
8 teeth
4 teeth

12. Sprockets Sometimes gears are connected with a chain called a sprocket
Used to gain a multiplying effect, reduce effort or a parallel effect
The gears both rotate in the same direction
In a 10-speed bike there are 5 gears on the rear wheel and 2 gears on the pedal crank

13. Wheel and Pinion A gear train that has 2 different sized gears
Larger gear is called a wheel
Smaller gear is called the pinion
Ex. a push lawn mover: the wheels transfer power to the blades (the pinion) which move faster than the wheels