It depends on the number of teeth on the weapon as well, not just speed. In fact the fast you go the less bite you get.

If its single tooth, gear it for 10'000rpm, but unless someone is ramming you that is still to fast to engage. If you are in close, dropping it down to half throttle (which with increasing resistances at high speed means around 6000rpm real world) which will be much better.

If its a dual tooth weapon, then gear it for ~8'000 and be prepared to run it at a slower speed to get engagement.