COTS Closed loop systems

[DELurker]

Originally Posted by Dragonslayerend

In the rules it states any COTS closed loop system (gas shocks) are not considered pneumatics and therefore not under pneumatic rules. So to bypass the 60 PSI working regulation, we wanted to just pump 120 psi of air into a cylinder and use it as a gas shock and lock it off so no solenoids are controlling it. Will this mean it's no longer a pneumatic system and now labeled as a gas shock? This will be used for our catapult system, not that we are going with this, we are actually going with workout bands, but this is something we've prototype and found to work well.

Not being an Inspector, I would have to say that an air cylinder is always an air cylinder and is intended to be an open-loop system by design. A gas shock is a device that is designed and sold to be a closed-loop system. The air cylinder would not survive the loading and cycles, especially starting at 120 psi...

Mathy stuff...
* Assuming a 4" stroke cylinder
* Half Extended with 120 PSI on either side & plugged
compression of 1" = 240 psi (2" goes to 1", doubling the pressure) on the extension side and 80 psi (2" goes to 3", dropping the pressure by 1/3) on the retraction side
compression of 1.5" = 480 psi (1" goes to 1/2", doubling the pressure) on the extension side and 68.6 psi (original 2" goes to 3.5", dropping the pressure by 43%)
Most cylinders have a burst pressure that you will quickly exceed.