Surgical Tubes per-stetched before Match Start

So, we are using surgical tubes to launch the balls, but we were wondering if we can have them pre-stretched before the match starts. We thank you for any responses.

Yes. Stored energy is allowed.

Yes, it is allowed by R36, emphasis mine.

[R36]
The only legal source of electrical energy for the Robot during the competition is one MK ES17-12 12VDC non-spillable lead acid battery, or one EnerSys NP 18-12 battery, as provided in the 2012 KOP. This is the only battery allowed on the Robot.

Batteries integral to and part of a COTS computing device are also permitted (i.e. laptop batteries), provided they’re only used to power the COTS computing device.

Non-electrical sources of energy used by FRC Robots, (i.e., stored at the start of a Match), shall come only from the following sources:
A. Compressed air stored in the pneumatic system, stored at a maximum pressure of 120 PSI.
B. A change in the altitude of the Robot center of gravity.
C. Storage achieved by deformation of Robot parts.

We have found that anything like surgical tubes or bungie cords aren’t reliable. They seem to get “tired.” So if the tubing is tensioned before the match and waits for a few minutes the shot will be different than if you tension and shoot at once. So for that reason we have been using metal springs for this kind of application.

Jim Wick

To add to Jim Wicks comment, the tubing also returns less energy over time, i.e. the energy for shooting the ball may not be constant over a season, a regional, or even a match.

Agreed. We used surgical tubing to make a roller during breakawy, and found that if we weren’t careful, we’d rip them off and fling them across the room. We changed before competition, needless to say. But over time, the tubing will stretch, and eventually break.