Idler-wheel

An idler-wheel is a wheel which serves only to transmit rotation from one shaft to another, in applications where it is undesirable to connect them directly.

For example, connecting a motor to the platter of a phonograph, or the crankshaft-to-camshaft gear train of an automobile.

Likewise, the pinch roller in a magnetic tape transport is a type of idler wheel, which presses against the driven capstan to increase friction.

An idler wheel is usually used for this purpose, in order to avoid having to move the power-transfer shafts.

Firstly, the idler gear will change the direction of rotation of the output shaft.

Likewise, the size of an idler wheel in a non-geared friction drive system does not affect the gear ratio between the input and output shafts.

A larger or smaller idler wheel maintains the same surface speed (which equals the surface speed of the input shaft), therefore the output shaft is driven at a constant speed regardless of the size of the idler wheel (unless of course there is slippage, which should not occur in most friction drive systems when operating correctly; however, there are instances where an idler wheel can double as a clutch, or if there is a sudden or unusually heavy load on the system.

Each roller has to be powered, but adding a motor to each one is wasteful (and it can be difficult to synchronize rotational speed with independent drive systems).

Instead of idler gears, of course, a toothed belt or a roller chain can be used to transmit torque over distance.

In higher speed applications, such as tanks and other AFV's, these road wheels are typically given some sort of suspension system to ease the ride, increase controllability, and decrease wear and tear.

This also allows the idler and drive wheels to carry some of the weight, as their lack of suspension is made irrelevant.

There are also certain pieces of equipment, such as the Caterpillar D9 bulldozer (and numerous other Caterpillar brand bulldozers), Tucker Sno-cat and Mattracks rubber track conversion kits, which configure their tracks in the shape of a triangle, or pyramid (when viewed from the side), with the drive sprocket at the tip of the pyramid.