LINEAR TRANSMISSION OF MOTION

The linear transmission mechanisms, use linear motion input to produce linear motion output.
  
- Levers.
A lever is a rigid bar that turns around a point called a fulcrum. Each force produces a specific torque, which is the force multiplied by its distance from the fulcrum.
Torque = Force x Distance
We say the lever is in equilibrium when the opposite end of a lever are equal.
Law of the lever: F x d = R x r
F: the force; d: the distance from the fulcrum; R: the resistance; r: distance from the fulcrum.

·Classes of levers.
Class 1: the force applied is increased or decreased. The fulcrum is between the force and the resistance.
Class 2: the force applied is always increased. The resistance is between the fulcrum and the force.
Class 3: the force applied is always decreased. The force is between the fulcrum and the resistance.

- Pulleys and compound pulley systems.
In a system of pulleys, the equilibrium between the forces depends on the path that the rope follows.

· Pulleys.
A pulley is a wheel that rotates around an axis and has a groove. We can divide pulleys into two basic types:
Fixed pulley: the forces are equal because the rope moves the same distance on both sides.
Movable pulley: the rope follows a double path around the pulleys. We need half the force to lift the same weight as with a fixed pulley.

· Compound pulley systems.
A compound pulley system is a combination of fixed and movable pulleys. It is also called a block and tackle system. The more pulleys there are, the less force we need to lift the load. We can combine the pulleys in various ways:
Vertical system: F = R/2 x n (n is the number of pulleys)
Horizontal system: F = R/2 x n
Exponential system: F = R/2 (2 elevated to the number of pulleys n)