Our team is trying to make a catapult using a pneumatic piston as the spring. The piston would be closed off completely on one end and a pressure gauge and release valve on the other. Concern has risen among some of the team that this is not legal. Can anyone say for sure if this allowed or not? 
Any help or advice would be greatly appreciated, Thank You.
I cannot find anything in the rules against it; in fact R81-D mentions use of the KoP vent plug.
Pay attention to R78-R80, if you add any pressure to the cylinder to pre-charge it you will need to use a robot controlled compressor that matches the set up in those rules. Also, with the system you described, according to the rules you will need a gauge and a regulator(even though you wouldnât use it). You would also be limited to 60 psi and if you compress the air in the cylinder you will have to do the math to find out if you will peak over 60psi when compressed.
Rules can be tough, I canât say for sure that all of these would be enforced in the full extent for your system, but I would think they should. It is really awful to get to a competition and find out something isnât legal. Itâs even worse to find out it is legal right after you tear your âillegal systemâ all out and replace it (oh 2012, you were cruel to usâŠ)
If youâre going to reference a rule, reference it RIGHT. R81 is the maximum stored pressure rule, no part D. R78-D requires the use of a Pressure Vent Plug as part of the pneumatic system; under R89, it must vent all pressure to atmosphere; under R78, it has to be hooked in as per the diagram (Figure 4-15).
The vent plug is also known as the âdump valveâ.
Also note that youâre asking in the wrong placeâtry the official Q&A.
So letâs see if I understand the setup of the cylinder-as-spring. One end of the cylinder is pluggedânothing in, nothing out. The other has a gauge and a release of some form (I would suspect a solenoid would be betterâŠ)
Now, per Q34 on Q&A, a quick release is illegal. You also have to be aware of the 60 psi working air limit (Q129/R82). A regulator might work, but Iâd guess youâd be losing air quite a bit.
To be honest, I would have to see the setup to pass it or fail it, but Iâd be leaning towards failing right now. If I might make a suggestion, try a closed-loop gas shock, or full pneumatics.
It seems that Q129 on the FRC Q&A would make this illegal IF (and only if) the pressure was to exceed 60 PSI.
However, it may be possible to find a gas spring (like they use to hold up the rear hatch on an SUV) to do that; it is not a pneumatic component.
Game - The Robot » Pneumatic System
Q129 Q. Does R82âs 60 psi limit apply to all components downstream of the regulator at all times? Examples where 60 psi could be exceeded: 1) Compress air cylinder faster than the regulatorâs response; 2) Compress air cylinder being controlled by a 3-position valve that has closed off both pressure ports.
FRC1619 on 2014-01-15 | 2 Followers
A. Yes.
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