5. MECHANISMS THAT CONTROL MOTION

5. MECHANISMS THAT CONTROL MOTION


5.1. Direction control: ratches
A ratchet is a mechanism that controls the direction of motion. It allows motion in one direction, but not in the other.

Uses: We find ratches in watches, cable-tensors and elevator brake systems.


5.2. Speed reduction: brakes 
Brakes use friction to reduce speed. They are activated by certain levers. The lever transmits force to an output receptor, which puts pessure on the wheel.
There are various types of brake systems according to where the friction is produced:

• Disc brakes: A disc is connected to an axle. Brake pads apply pressure to the disc. 

                                                   


                                                    

• Band brakes: A drum is connected to an axle. A flexible band applies pressure to the outside of the drum. These brakes were used in carriages and they depended on the strength of the driver. 

• Drum brakes: A drum is connected to the axle. A pair of brake shoes apply pressure to the inside of the drum.