Mechanisms – speed of movement

Mechanical systems can be used to increase or decrease the speed of movement and rotation. They can also change the direction of force, movement and direction.

Gear Systems

Gear systems can be used to increase and decrease rotational velocity

Gears are used to increase or decrease the speed or power of rotary motion. The measure of how much the speed or power is changed by a gear train is called the gear ratio (velocity ratio). This is equal to the number of teeth on the driver gear divided by the number of teeth on the driven gear.

To decrease the speed of the output, the driver gear is smaller than the driven gear.

(This will reduce the speed but increase the “torque”.)

This diagram shows a small gear (A) driving a larger gear (B). Because there are more teeth on the driven gear there is a reduction in output speed.

To increase the speed of the output the driver gear is larger than the driven gear.

(This will increase the speed of the output but decrease the “torque”.)

This time the diagram shows a large driver gear (A) driving a smaller driven gear (B). Because there are less teeth on the driven gear there is an increase in output speed.
Examples of Mechanisms which use simple gears to decrease or increase output speed and change rotation.