Legal Counterweights

[Christopher149]

For 2005, 857 had a 'tetra cannon' which was counterbalanced by the battery. So, since the rules haven't changed "that" much, so long as it's the only battery, is safe, and can be removed for robot weighing, it should be okay.

[Al Skierkiewicz]

The rule is
R31
The only legal source of electrical energy for the ROBOT during the competition, the ROBOT battery, is one of the following approved 12VDC non-spillable lead acid batteries:

And

R35
The one ROBOT battery, the one main 120-amp (120A) circuit breaker...
Emphasis mine.

One and only one please. As to counter weight for your trebuchet, by definition that would add significant electrical loss through the long #6 or larger wire. If you were to mount the 120 amp circuit breaker on the robot, then a significant length of wire would be unprotected should a short occur. While this is not specifically addressed in the rules, it is bad electrical practice to do so.

[KevinG]

You'll be spending a lot of time justifying that the design is safe to the inspectors. I would suggest focusing on a different approach.

[FrankJ]

Shifting the battery around to move the CG is one thing. The shock from it being a counter weight for a trebuchet is another. It already gets banged around enough just being on the robot.