antonio franco

Brakes   use friction to reduce speed.They are activated by certain levers.The  lever  transmits force to an output receptor,which put pressure on the wheel.This produces friction which slows down the wheel. Disc brakes.Brake pads apply pressure to the disc. Band brakes.A flexible band applies pressure to the outside of the drum. Drum brakes .A pair of brake shoes apply pressure to the inside of the drum.

A  ratchet  is a mechanism that controls the direction of motion.It allows motion in one direction,but not in the other. Some ratchets are reversibles.

A  cam  is an irregularly shaped device that rotates on a shaft.When the cam rotates,it pushes a special bar called a  follower .The  follower  can move other parts or it can turn a switch on and off.

We can connect multiple  rods  to one shaft.The   rods   are connected to  cranks ,and the  cranks  are connected to the   cranksh aft.

This mechanism was important for the first steam engines.Today we find  cranks  and  rods  in internal combustion engines,as well as  windscreen wiper  mechanisms.

A winch its a cilinder that rotates around a horizontal axis.We attach the rope to the winch and to a load. Then we turn the crank to rotate de winch. The rope roles up around the winch and lifts the load. Fxd= Rxr

A nut and bolt mechanism transform rotary into linear motion. It has two parts:a bolt with an expiral grove and a nut thats turn arround it.

The rack and pinion mechanisnm has two parts. The rack is a bar with many teeth and pinion is a gear with teeth that interlock with the rack.

We can use the direction of rotation or the axis of rotation in a belt drive. We can also vary the distance between wheels WORM DRIVE :A  worm drive  is a gear arrangement in which a  worm  meshes with a  worm gear .The two elements are also called the  worm screw  and  worm wheel