Do you guys have access to a mill? If so I envy you. You know the only time I have ever even seen a mill in person was in the portable machine shop at the portland regional last year? And I want to be a machinist too.... I think I am gonna buy that really cheap grizzly drill/mill. Thats not the point. When I said you shouldnt use the FP motor clearly I was wrong, and I should point out our team didnt use them last year (our first year) so I realy wouldnt know.
What we did do last year was use the window motor to drive a sprocket which drove the shaft our arm was on. It worked pretty well too, especialy after we put in some springs to act as counter weights without the weight. The problem was that there was no chain tensioner, so when this one genius got the idea to run a chunk of 1" square thick wall aluminum through the sprocket it cost us about a day. Anyway that worked pretty well, and we cut the power by a factor of three (in the program) and we can still pick up trash cans and chairs and such. The arm had a good ten pounds of pneumatics and such on it too. If you want strong, those motors got strong.
This is the best pic I could find just now. The arm drive I am talking about is on the left side of the picture and the motor is almost cut off.