Homemade high pressure pump

[FeLeX]

Oh I see. So the smaller the pump the higher pressures you can reach?

[joannaardway]

Oh I see. So the smaller the pump the higher pressures you can reach?

In terms of diameter, yes. A good counter for the reduced volume from this is increasing stroke length.

[FeLeX]

Dang and do these really go up to 300 psi?
They don't seem that hard to make. I think im gonna give it a try this weekend. Should I use copper pipe as the "chamber" of the pump or would sch 80 pipe work too??

[Hawkeye]

I regularly take mine to 350 but you don't need to take it that high unless you are using a small chamber. I use that pressure for a .25 calibre pistol.
You should use copper as it is easier to assemble and find washers that will fit as a piston. Also it is smooth inside so the piston has less friction yet still seals well.

[FeLeX]

Ok thanks guys. I was going to replicate BTBs Pirate Pistol and I was wondering what the heck I could pump it with. I guess I am going to make one this weekend then.

[Marco321]

Sorry to kick up a dead topic, but this is relevant...

I'm going to make one of these for my up-coming copper gun. I understand the whole concept of how it works except for the piston. How is it made so it lets air in but prevents it from going out? I looked at the diagram but i can't figure it out. Any help would be appreciated.

[SpudBlaster15]

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[Marco321]

The o-ring fits loosely between 2 washers. The lower washer has deep grooves cut out of it. On the downward stroke, the o-ring (which is a tight fit in the copper pipe) is forced against the upper washer, where it seals. On the upward stroke, the o-ring is forced against the lower washer, and due to the grooves cut into it, air is allowed to move past the o-ring and into the pump cylinder.

Thanks, it makes sense now.