Get SCH 40 2 inch barrel (36 to 48 inches), 2 to 1-1/2 threaded bushing, a 2 inch coupling and some of these for a fun time. Check at your local dollar stores for best prices! Digging this up to say that this was user dewey-1's last post on this forum, ten years ago today. I believe he passed away ...

Piston and cylinder matching 101 For me the piston side clearance is kept between .0005 and .001 with the O-rings just taking up the clearance. You adjust the O-rings fit by the depth of the groove in the piston. The O-rings should fit the piston snugly but not so tight it stretches the wall thin c...

I had doused it with oil several times to prevent wear, and made sure there were no sharp edges on the ports, but apparently that is not enough. The other draw back was the higher the chamber pressure, the harder it became to open at the o-rings are pushed into the cylinder walls increasing frictio...

Reliability stacks, the more parts, the more often the machine stops. Theoretically, a spool valve like you built with one moving part should be very reliable. However, you probably need to look into how the seals on DCV's are done, O rings rarely like to move past porting, having the o-rings seal i...

Many interesting and good things have been said. I think it's all been covered. I'd just like to suggest maybe trying X-shaped o-rings. I tried them and love them. They are less picky about being squeezed too much and having too much friction while still sealing perfectly. They are made for sliding ...