No doubt the reason you're getting through so many drills Ellis is you're simply taking them to the limits of reasonable voltage and wheel size combination, there could however be the added element of flex in the gearbox adding to the problem. If a planetary gearbox is taken out of alignment (with the shaft twisting relative to the ring gear) then some of the planet gears will be periodically under greater stress than the others. In this regard it's good to have a rigid gearbox structure in order to maintain alignment and distribute the load more evenly, something which the GR01 seems to have been able to do (judging by the lack of reports of stripped gears). The same applies for the carrier plate pins, if alignment is maintained they should be less likely to loosen.

There's an additional component of quality of manufacture which is hard to put any figures to. As I've mentioned some time before the components for the GR01/2 come from a factory manufacturing drills for the American market which retail for $30-40 a piece. It's possible that they have better quality control at such prices over £10 European retailed drills, I haven't come across any badly formed or loose-pin parts so far at least.

It will be interesting to see whether there's any problems at all with gears stripping on the 24:1 versions which feature the same size of gear on the output stage which will of course be under a smaller torque load.

All this said though combat robots are such a volatile environment that you can never be sure of any completely foolproof combinations, hence why a full range of spare gears and carrier plates will be available for the GR02!