Carriage Module for FLSUN Cube

This is to be a set of carriages for the FLSUN Cube, suitable for the three different extruders supplied in the kit. Each carriage can be swapped in and out with minimal effort by clipping Iand optional bolt) on to the universal belt bracket.
Two problems with the standard carriage are:
1. wrong height for the carriage limit switch - lowered by 2mm
2. Hot end crash into the bed - the new carriage can lift off the front bearings on crash

The universal belt bracket (or bridge) would be permanently fixed to the belt, and have the limit switch fixed to it; the bearings will be permanently on the rods.

A new carriage, with its extruder(s), heater(s) and thermistor(s) can be placed over the rear rod, and the rear bearings slid into the carriage housing from either side. The carriage can then be rotated to fit onto the front bearings, where it will be held by the weight of the extruder.
The bridge will clip into position with the carriage, and can be fixed firmly with two M3 screw