Compressor Rule Question

[seg9585]

This may have been answered somewhere but I couldn't find it on CD from this year or in the Q&A:
Are we allowed permitted to use an off-board compressor (powered via on-board relay and robot batteries) to fill our tanks pre-match, which is exactly equivalent to a compressor on-board, then use the on-board compressor during the match, or will this violate R79? Only 1 compressor would be plugged in and used at any given time.

This is the proposed setup:
- Prior to match, on-board relay connected to offboard compressor, connected through purge valve
- After filling tanks, disconnect offboard compressor and plug same relay into on-board compressor

The reason I don't see this as violating R79 is because one and only one compressor is ever plugged into the robot (effectively when pumping with the off-board, the compressor sitting on the robot is disconnected and dead weight). This would be equivalent to using the off-board as a spare part.

The reason we wanted to do this is the compressor gets extremely hot, and we want to go into a match with a cool compressor. Adding a large heatsink takes up space and weight.

I consider the setup above equivalent to a scenario in which you fill up tanks with an onboard compressor, that compressor is rendered broken, and a new, cool compressor is introduced as a replacement part prior to the match. Surely this scenario would be legal?