OpenRC 540 motor mod modified rear axle

This is the rear axle from the OpenRC Tractor 540 motor mod, with a thinned out shaft center so the servo wires can pass through the chassis without the wire coating being worn through.

The thinned axle isn't a weak point. My 4 year old son has been playing with the tractor for some time, and despite breaking two rear wheel hubs the axle has been fine.

Two 18x12x4mm ball bearings are required for the rear axle. See the OpenRC Tractor's bill of materials for suggested links.