Foster Style Check Valve?

[rsterne]

Any reason I can't use a shortened Foster style check valve in a pumper? It will ride in a 5/32" (or maybe 0.160") hole in the front of the valve, and only has about the same area around it for headspace as a 0.040" - 0.060" hole of the same length (I was thinking about 1/4" - 5/16" long for the stem).... They don't use springs in a Foster to help it seal and I'm thinking of trying it that way, just a small pin in the valve to prevent it from falling/blowing inside on the fill stroke....

Anybody done this, or forsee a problem doing it?....

Bob

[AirGunEric]

Other than the moving pin issue you mention, I don't see a problem if you can get everything to fit together. However, the question is "why"? You want to attach a bottle directly to the valve to avoid pumping?

[rsterne]

It seems to squish to 50% easily

Hmmmmmmm.... not good, that would require about 0.035" stem end clearance.... or maybe not, perhaps the O-ring will just try and fill the gap without the head of the stem moving much.... dunno....

Bob

[rsterne]

The swept volume is over 50cc.... However, the headspace should be a small as possible as it has a HUGE effect on the compression ratio.... The headspace around the stem of my check valve will only be about 0.05 cc.... so adding 0.1cc would be a 200% increase.... trippling the headspace will cost me about 60 psi inside the valve at 10 pumps.... and take an extra 2 pumps to reach 1500 psi....

Bob

[rsterne]

I don't intend to use the Foster fitting, just the check valve from one.... It would be inserted into a hole in the end of the valve, sitting against a shoulder from the inside.... My reasoning is that it should be easier to get to seal than a Delrin check, and take up less volume inside the valve.... I should add that I'm scratch building a new front end for a Disco valve for this project.... It will incorporate a gauge mount and have an internal volume of about 5cc (3 times the volume of a 13XX valve)....

Bob

[AirGunEric]

Shoot- should have read your mounting specifications, didn't think about it- just figured it was going in a QD fitting...

[rsterne]

Thinking about how the O-ring should seal.... it should not be an issue anyway.... The O-ring should seal against the end of the valve body and the stem, there should not be any force on the metal head of the stem....

Bob

[rsterne]

A 6mm increase in stroke would increase the pressure 28 psi in 10 pumps.... or take about 0.6 strokes less to get to 1500 psi.... Can you tell I made a pumper spreadsheet?....

Pump swept volume is obviously important.... Headspace is more important at higher pressures.... It is the primary reason an F-T-P outperforms a conventional piston in a 13XX....

Bob

[SeanMP]

A 6mm increase in stroke would increase the pressure 28 psi in 10 pumps.... or take about 0.6 strokes less to get to 1500 psi.... Can you tell I made a pumper spreadsheet?.... Bob

I should have guessed that

[Gippeto]

Will be less efficient than a check with a spring...there's always going to be some bleed back before it seats and seals.

You may also wish to check out floating o-ring/check valve for the pump head...might allow a slight increase in swept volume over the Crosman design.

http://www.network54.com/Forum/27568...ng+check+valve

Al