1B: Power Transmissions

Shafts and Bearings

Shafts

Shafts transmit rotational power along an axis, with hex shafts being the most common in FRC. These hexagonal shafts, typically in 1/2" and 3/8" diameters (measured from flat to flat), may sometimes have rounded corners, known as "rounded hex" or "Thunderhex."

Bearings

Bearings allow shafts to spin independently of plates and/or things to spin independently of shafts. Standard hex shafts use 1/2" hex bearings, while rounded hex shafts can use round bearings for easier assembly.

A rounded 1/2" hex bearing (Left) and 1/2" rounded hex shaft (Right). (Image Source: WCP)

Example

Example of a Shaft Spinning in a Bearing

A spinning shaft in bearings

Bushings

Bushings are a cheap and low friction alternative to bearings and are used with metal shafts such as shoulder bolts, hex shafts, and round tube, mainly to save space. They are made out of a self-lubricating material such as bronze or acetal/delrin and typically used in applications with relatively low RPM, such as for pivots and linkage joints.

Bronze Bushing (Image Source: WCP)*

Modeling

The easiest way to model shafts is to use the Shaft Featurescript, which you learn how to use in the following exercises.

For bearings, insert your desired bearing from the MKCad app.