Qdv question

[fenrir]

Just a quick question: is it possible for the front oring of a qdv piston to blow off at high pressure? How can this be prevented?

[jean]

yes the o-ring can blow off.
there are ways to prevent.
use thick string diameter o-rings
use rubber washer instead of o-rings
cutting slots in the way tech did it on his qdv
jean

[fenrir]

Thanks, but what's a "thick string diameter oring" ?

[jackssmirkingrevenge]

He means a fat o-ring is better than a thin one

[tigerblues28]

Yes, what jack said.

You could always epoxy them to your pistons or washers like I did.

My first *valve* I ever made was a quick dump valve, and with a home depot near by I was able to make it with readily available bolts, washers, and o rings.

Nick

[Technician1002]

What do you consider "high pressure"? One of my early cannons using an o ring used to launch the ring at about 60 PSI. To prevent that, I went to the ported design, so the O Ring was simply too big to fit between the side of the piston and the ported cylinder. With the new design, I have never lost an O ring. Due to my compressor capacity, I have not tested above 100 PSI. Look in the links in my sig to see the port design that holds the rings in place. Part of the ring may pop out of the groove, but once open and unable to come off, it drops back into place.

The bars between the ports prevent the o ring from blowing off the end. Make sure the space between the cylinder and piston is very small so the o ring can't fit between them.


I filed and sanded the edges of the ports so there are no sharp edges that could cut the o ring.