Rawge's Mini Chopper Information Site www.minichoppers.info

A live-axle is probably the most common axle setup used on mini choppers. The "live" term indicates that the axle spins along with the wheel, sprocket, and other pieces anchored to the axle. Since the axle spins, bearings are mounted to the swing arm frame. 

This is a very simple axle setup, and components are relatively easy to change. Each piece, such as wheel hub, disc brake rotor, sprocket, etc, are slid onto the axle and are held in place by set-screws or locking collars. The components can also be separated by bushings that are cut to the desired length. Since the axle spins, the wheel, brake, and sprocket components must be locked to the axle. This is accomplished by using a square key that fits into a groove on the axle and the components. 

Here are pictures of some examples of the various components. 

Wheel hub - locking collar - disc brake rotor - caliper - sprocket holder - Misc.

You can purchase complete axle kits or all of the associated parts at Northern Tools