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kenbo0422, that is a great idea. Now so I don't get any exercise, biggie size it?

You put it in a frame and pump it with a motor.

kenbo0422 wrote:

kenbo0422, that is a great idea. Now so I don't get any exercise, biggie size it?

You put it in a frame and pump it with a motor.

but what about the clearances the dead space, to reduce dead space you need near zero clearance at the extreme of the piston stroke, for this reason many diaphragm pumps use solenoids

it just occurred to me that most of the high pressure diaphragm compressors you mention are multi stage, in order to make it multistage both sides of the diaphragm must have the same starting pressure at the beginning of each stroke, which doesn't seam to be the case

A diaphragm pump is used to pump light gas because any tiny leak such as past piston rings is a huge leak to a light gas. Normal rings on a piston simply don't contain Helium or Hydrogen at high pressure. That is the only reason they use a diaphragm. The lower efficiency is a trade off from the low efficiency from high blowby.

There is no reason a pump has to have the same pressure on both sides of the diaphragm. A cylinder can run fine with the crankcase at 1 atm and the inlet at 10 bar and exit at 40 bar.

Only the first stage needs to drop below 1 atm to draw in past the valves.

The systems on the submarines I was on had a six stage pump for 6000psi. The cylinders were such that the push rod on one side diminished the volume of the stroke while the other side was open. Each stage progressively started out smaller until the last stage, which ported out to a storage bank. It was then regulated to about 2000psi to keep pressure on the primary loop of the reactor so as not to allow the water to boil around the fuel rods.

By exhausting into a smaller volume with each stage, you kind of make up for the 'dead' space, since the gas has no choice but to be compressed.

Edit: The pressure differential across each stage is what you want to consider. Orings, for example can block just over 1000 psi, if you were to want a higher difference, you would use more orings. If you want the strokes to be easy on your arm, make the pressure differential lower. Pumping from 15 to 50 psi is almost as easy as pumping from 1515 to 1550 psi with the exception of the seals pushing on the sides.

Technician1002 wrote: There is no reason a pump has to have the same pressure on both sides of the diaphragm. A cylinder can run fine with the crankcase at 1 atm and the inlet at 10 bar and exit at 40 bar.

a multistage compressor wouldn't have such a format (unless there were two alternating second stage cylinders connected to the crank shaft), assume the input is 100psi above atmospheric pressure and the output is 400psi atmospheric pressure and the crossectional area of the piston is 1inch^2; so in this system the force required to start pushing the piston is 100pounds force and towards the end of the stroke it is 400pounds force, with such a design you might as well not use multiple stages, what is supposed to happen is for the peak mechanical force to be based on the pressure difference between the input and output

Pumping from 15 to 50 psi is almost as easy as pumping from 1515 to 1550 psi with the exception of the seals pushing on the sides

tha'ts the reasoning I used when I suggested that the air input of a fridge compressor could be fed with compressed air

Apparently, tech and jimmy thinks it's wrong and I must say that their explanation seems logical

sorry I have to find a thread on it
EDIT I found them
http://www.spudfiles.com/forums/two-fri ... 18219.html
http://www.spudfiles.com/forums/compressor-t18078.html
http://www.spudfiles.com/forums/fleebay ... rt,15.html

I would personally look into the workings of scuba compressors like this one. Are they scroll, diaphragm, piston?

I believe most are two-stage piston or else scroll.

Pumping from 15 to 50 psi is almost as easy as pumping from 1515 to 1550 psi with the exception of the seals pushing on the sides

Only if the crankcase is under 1500 psi of pressure, and then the seal is the same.

I believe those are piston compressors, multi staged, I think possibly with an unloader mechanism rather than a pop off valve. The one pictured looks like it does have a pop off valve, though.

what about those presure amplifers if seen them at paintball the put a 100psi in and it make a poping soud then u add low presure co2 and it compreses it to 900psi. you coud do this with air and amplify even more.

http://www.haskel-usa.com/gas_booster.htm

@pimpman
that's what I had in mind... I don't think you can build a simpler/cheaper one...

also I don't expect that that traditional compressor design will become common as a HPA pump for future spudders

just think about fridge compressors.. they are as cheap and easy to build as possible but there are not as popular as one would expect them to be (IDK the exact number.... there are 10 maybe up to 30 of them on this site??)

Pressure amplifiers work by using a large duplex piston with low pressure ( your lp air) to move a smaller piston which is supplied by the same air pressure. The larger surface on the driving piston allows it to push the smaller piston to a much greater pressure ( Pressure = Force (lbs) x area).

The discharge from the larger pistons goes into the intake of the smaller pistons and some is bled off with an upstream regulator or blow off valve in some cases. It cycles like a locomotive piston arrangement, so you 'pump' to a higher pressure using the supply air. There doesn't seem to be any reason why you couldn't cascade these to achieve even higher pressures unless the mechanism isn't made for it.

EDIT: http://www.mcmaster.com/#pressure-amplifiers/=4nnvgh

They aren't cheap!

A pressure multiplier is an idea I have toyed with for a while. They seem expensive to buy but cheap to build if one has a lathe. I know Ragnarok has an idea for a mech. for these.

Really the problem is that since there is no fly wheel to push the piston back you need to make a mechanism todo so, that would most probably be the trickiest part, esp. if you want to cost down and pressures reasonably high.

Another question is how efficient they are, after all to get the piston back into it's place one needs to relieve the pressure on the big bore side, or over come it, doing this without venting may provide tricky.

Anyway, i think a pressure multiplier(PM from now on) is a better idea than a multi-stage pump, as a DIY source of HPA.

Really the problem is that since there is no fly wheel to push the piston back you need to make a mechanism to do so

yo can either use
2 DCV valves that would switch the air flow when the air cylinder extends and retracts

or just use a timing circuit ( fully pneumatic circuit )

also I don't think there is any need for machining... it might be useful to build the check valve and maybe the piston of hte pump... but you might as well use a ready made PCP pump

meh, a pcp pump is 200-400$, the stock i would need to make that is under 100$.