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Homemade HP 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 HP pump

Unread postAuthor: The_Guerilla_Guy » Fri Dec 24, 2010 5:13 pm

Hi guys,

After browsing the Forum for topics about homemade pumps, I came up with the idea of a pump that could some higher pressures, because a little part of the pressure in the "Chamber" is used to press the pump down which helps at higher pressures one couldn't archieve by hand. Think the pic attached could work? the part between the pump and the chamber would need another BV I didn't draw and ofc the lower connection would be a onewayvalve
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Unread postAuthor: Hotwired » Fri Dec 24, 2010 5:20 pm

Flawed plan.

Push the pump piston down and all you're going to get is the air flowing back behind it.

The air pressure will not only be pushing downward but upward as well = no gain and a huge amount of dead space.
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Unread postAuthor: saefroch » Fri Dec 24, 2010 6:09 pm

Agreed with Hotwired. If you want high pressures, your best bet is probably just a small-diameter two-stage. But don't let me discourage you from coming up with designs... you may very well hit on something that allows the air pressure produced by pumping to assist. I've got a few ideas bopping around in my head now from that design...

EDIT: Would this work? Assuming that the black rectangles at the top of the pump are seals, and that the pump head has a floating o-ring like the ones on Tech's pistons, not a normal pump head.
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Unread postAuthor: Gaderelguitarist » Fri Dec 24, 2010 9:22 pm

That "static high pressure" area would vent to be atmospheric before you even began pumping. Even if you found a way to seal off an air assist line, it would still deplete into the air being pumped into the compression chamber by the piston head, by virtue of the floating o-ring.
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Unread postAuthor: saefroch » Fri Dec 24, 2010 11:46 pm

I understand how the section of high pressure could leak to atmospheric, but vent? Explain...

Okay, so maybe a floating o-ring isn't such a great idea :roll:. But a normal o-ring would probably work...
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Unread postAuthor: Hotwired » Sat Dec 25, 2010 4:47 am

TBH the original plan looks like it was hoping for a free lunch in the slaving-over-the-pump department but no such luck.

However it is entirely possible to use a hand pump (or any pump that can deal with the pressure) to further pump and compress pre-compressed air, that is a saving of work as long as you are not personally doing both stages of compression.

For example, you feed your hand pump 150psi from your workshop compressor and then squish it to say 300psi, very doable.

I'm aware of fridge compressors round here being daisy chained so the output of one feeds the input of the next so the second has less work to do reaching a higher pressure.
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Unread postAuthor: more_eggs » Sat Dec 25, 2010 4:56 am

I'm aware of fridge compressors round here being daisy chained so the output of one feeds the input of the next so the second has less work to do reaching a higher pressure.


I was under the impression that chaining them together just increased the air flow.. i.e takes less time to fill something up.. What do you mean by "has to do less work" ?
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Unread postAuthor: Hotwired » Sat Dec 25, 2010 5:58 am

more_eggs wrote:I was under the impression that chaining them together just increased the air flow


Unless you let the pressure build up (to the maximum possible that the pump will do) you will only see a flow increase.

And I mean if you feed the output of fridge compressor 1 to the input of fridge compressor 2 and then start pressurising a sealed container it will reach a higher pressure than if one was acting alone.

We had a member here who had a claim of 1800psi with three pumps chained together. No one disputed his claim, had pictures and a video but about half the replies he got were to flame him due to poor written communication and stereotyping.
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Unread postAuthor: al-xg » Sat Dec 25, 2010 6:54 am

I've managed to basically double the output pressure by linking two compressors in series, but also with increased flow.

Nothing as crazy as 1800psi, but a single compressor reaches about 510psi, in series they make it just past 1000psi, in very little time.

My original plan was to use a fridge compressor with a buffer cylinder feeding air into a balanced small cross section pump, but then just got lazy as I already have 1000psi available.
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Unread postAuthor: The_Guerilla_Guy » Sat Dec 25, 2010 10:43 am

I know it has some mistakes in it, but I kinda like the idea. I'll work on it some more in the future. I'll update the post when I have made a nice animation of it ;)
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