Legality of Gearboxes

Hello, my team and I were wondering about the legality of the AndyMark’s GEM planetary gearboxes. Furthermore which rule would decide whether these gearboxes are legal

What would make you think they’re illegal?

The rules outline what you can’t do more than they outline what you can do. If there’s nothing that says you can’t, then you can. I can’t cite a section saying you can use them, but since there aren’t any sections that say you can’t, then go ahead and use them (plus people have used them in the past).


I agree 100%, however we wanted to make sure that we wouldn’t run into any problems. We Posted a similar questionon the Official Q&A and the answer was vague. We decided to come to CD for more insight.

GDC answer wasn’t vague, there are limitations. They cannot weight more than 120 lbs, cannot exceed $400, etc.

Check the definition of COTS parts (Section 1.6), <R27>, <R28>, <R29>, and <R19-B>. I think you’ll find that an AM GEM gearbox meets all the criteria. If there are no other rules against them, then you’re good to go.

The GDC’s vague answer was probably in response to a vague question. Limits on gearboxes may include weight, space, cost, laws of physics…

Thank you all,

We pretty much came to the conclusion that we could use the gearboxes because, aside from the price, weight and COTS rules, there was nothing that explicitly limited the use of gearboxes. However there was no rule or citation that stated they could be used. We just wanted to be doubly sure before we went any further with our design.