HardWired II

[overkill]

You can always gear down with smaller wheels. To keep the inverted driving ability, add a set of friction driven wheels above the regular pair. By the time you get around to buying parts there may be a brushless motor option with the right KV or a 3mm shaft that will work on 26:1 Banebots gearboxes - just keep your options open as long as possible.

I did a very rough kinetic energy calc using a straight steel bar with the weight & diameter you mentioned - 11.1 Kj at 7K rpm! Your bar has more weight at the tips so its going to have an even higher energy. That would probably be the highest energy rating for a featherweight in the UK.

Update: with a 3.6Kg weight, a straight bar would have more like 13.5Kj