[JesseK]

Wait! Wait! You guys are totally missing the obvious FRC legal engine! It runs on compressed air. This is a fun thought exercise since the GDC doesn't put any direct restrictions on it except for weight, volume, and the restrictions on the source of the compressed air (the only FRC-legal compressors, powered by FRC-legal batteries).

I'm sure we could make a drive train, lift, arm, rollers, or some mechanism "move" using it! The utility of such an engine is up to the designer -- who are we to mock it given that we haven't gone through the exercise?

I'm thinking of a robot that looks like the amalgamation of balloons in the movie "Up", where the team has to start filling the tanks as soon as they get to competition and then continue filling the tanks at every spare moment so they don't run out of air during two back-to-back matches. Maybe that's a bit far-fetched; maybe it won't take as much air.

If anything, it may make a cool Hybrid approach to the drive train: extra "boost" in a pushing match for a single-speed robot that's geared for 11ft/s. Maybe it's worth the weight to an outside-the-box type of team; maybe it's not.