Friction wheels
Friction wheels are a set of two wheels located one next to the other. Motion is transmitted between the wheels (driver and driven) by the friction between them.
The transmission ratio is the ratio between the size of the friction wheels and the speed of rotation:
where w1 and w2 are the speeds of rotation of wheels 1 and 2 and d1 and d2 are their diameters,respectively.
Belt and pulley system
This system is made up of two pulley wheels joined by a belt that slots into the grooved rim of the wheels.
Gears
A gear is a mechanism consisting of two wheels with teeth
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