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Homemade high pressure pump

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Homemade high pressure pump

Unread postAuthor: Gunner » Tue May 12, 2009 4:03 am

Hey! I quickly drew this scetch http://www.aijaa.com/v.php?i=4183888.jpg and I have little question from it.

Because that pump should work when you push the piston down, but how about then when you pull the piston back, how the "new air" gets into the pump chamber? Should I do the somekind of check valve to piston or?
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Pump piston design

Unread postAuthor: Technician1002 » Tue May 12, 2009 4:36 am

Many pumps of this style don't use o rings on the plunger but use a rubber cup so when the handle is lifted, the edges of the cup pull in and let the air pass.

If using o rings, simply grooving the side of the o ring groove in the piston will make it leak in one direction and seal in the other. Make the o ring groove slightly wider than the o ring so it moves back and forth in the groove. Make the groove deep enough so the piston is not squeezed flat in the groove but is loose so air can pass underneath the o ring.

Don't panic that air will leak under the o ring. It doesn't seal against the bottom of the o ring groove. It seals against the flat wall of the o ring groove and leaks on the back stroke against the non flat wall.

A video showing how this floating ring works in a cannon piston is shown here. It would work the same in a stirrup pump.
This is the video on o rings most spudders have already seen.

The o ring would be sized to expand out to the cylinder to seal against it, not to fit in the bottom of the o ring groove.

Cheezy paint diagram attached.
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Piston showing floating o ring with a leak in one direction.
Piston.GIF (3.22 KiB) Viewed 390 times
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Unread postAuthor: far_cry » Tue May 12, 2009 6:45 am

floating O ring like what the Technician1002 draw exactly
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