Quote Originally Posted by NickG View Post
Hi Loki, I don't think parachutes actually seal better, I have compared like for like tunes , with parachute o ring X ring and piston ring, the piston ring makes the most power, followed by the X ring ,
If parachutes don't seal any better, then I don't see how they can have greater friction either? To increase the friction enough to slow down the piston must surely improve the seal? Not convinced either way, just seems logical to me.

It would be interesting to measure the actual air volumes (e.g. captured in a balloon / water tank) to confirm that any difference in power correlates to leaking air rather than friction, or rather dynamic friction.

This is all from memory, but taking a chamber pressure around 700psi, 25mm piston seal and 2mm lip, the peak piston friction force for nylon on steel is about 50N, so barely anything compared to the spring forces involved. I think it needs to be around 500N to start having any noticeable effect on piston position and compression volume. Could all be completely different of course with your lighter springs!