Pulley

The pulley mechanism allows a wire or rope to go over it to provide a force transfer. If the wire is attached to the pulley then the pulley experiences a force at a radius which results in a torque. There are many mechanisms for pulleys and belts and they will be discussed here.

Hopefully a parametric design will be created that will have the flexibility to be used as a subsystem into many other complete systems.

Options
belt and pulley

chains and sprockets

pulley and wires or ropes

Belt and pulley
This is a widely used option and there was lots of work done on this one, so will just copy paste a open source library into here, in this option the pulley has teeth and the belt has teeth and the torque of the pulley creates a force on the belt.

There are problems with this design:

Particularly the fact that the teeth have to be strong or they will break easily, so plastic is a poor option here.

And the belt can start to slip or sheer and has to be tensioned or loss of accuracy can occur.

Chains and Sprockets
This is how bikes work,

These are meant for high power applications, these do however have a loss of accuracy and are usually not used for precision applications. Also because of the high forces involved metal must be used.

pulley and ropes or wires
Using a pulley it is possible to apply a force on a rope, that rope can then transfer that force as a linear force or turn a additional pulley for torque load transfers. The image to the right is of a pulley.

Since we need to operate in both directions we need two ropes one in each direction.

There are multiple ways to attach the pulley onto a fixed shaft or to allow it to rotate if need be.

A difficulty needing to be resolved is a method to tighten each individual wire so that they are tight and there is no slack and hence high accuracy can be achieved.