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Homemade air pressure regulator

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 air pressure regulator

Unread postAuthor: Demon » Fri Dec 04, 2009 5:51 pm

Hello all,

My current project is an bullup pcp airgun that will shoot 6 mm .42 grams bb's at 450 fps (anything higher is a firearm in canada) with at least 160 psi of air (from a bike pump)

By calculations, if the airgun is perfectly regulated, i could get 12 good shots easely, but can i regulate and release air without using two airchambers , i mean :

refill air chamber 160 psi---60psi air reg---ball valve---air chamber---piston valve

or can i simply make :

160 psi airchamber---60psi air reg---hammer valve

The goal here is to get the same fps at each shot until there is less then 60 psi in the 160 psi air chamber.

So here is my regulator, red is o-ring.
(Is there something that woul'nd make it work?)

The spring force will have to be tweaked with an air pressure indicator
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Unread postAuthor: bradisfun » Fri Dec 04, 2009 8:05 pm

well i like it and this would be perfect for me
BUT..................... i dont get it
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Unread postAuthor: ohspyro89 » Sat Dec 05, 2009 2:46 am

I don't fully understand how it works either, can you explain a little more?

The easiest way I see to do it, can be done similarly to how I understand your current drawing.

All the spring would have to do, is account for the other 100 psi that you aren't letting in.

Pressure=force/ area

Simply sum the forces on each side of the piston, to see how much extra force would be needed from the spring.

Say you have a 0.5" piston, that's 0.7854 square inches.

It'd come down to Sum of the forces in the X direction =0. We will assume there is no y or z forces and that the system is in equilibrium with the given pressures. Negative

(60 lbs /sq in)(0.7854 sq in)+( Spring Force)-(160 lbs/ sq in)(0.7854)=0

Then you can do some algebra and get this:

(60 lbs /sq in)(0.7854 sq in)-(160 lbs/ sq in)(0.7854)= -Spring Force

47.124 lbs - 125.664 lbs= -Spring Force

78.54 lbs = Spring Force

I think that's right. So you'll need a spring that can support around 75-80 pounds. You could get the adjustment just perfect by adjusting your springs output force.

It's about 3 AM, so if I am wrong, feel free to rework it! :D
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Unread postAuthor: inonickname » Sat Dec 05, 2009 2:59 am

Have a look at BTB's balanced push button valve (far cry also did one). With a well placed spring they can be used as a regulator so the output will equal the spring force. A gas spring like JSR used in his automatic prototype would be ideal for quick and accurate adjustments.

Pushbutton valve

BtB wrote:Side note:
If you put a strong spring on the button side this valve will work as a regulator..closing when the spring force is equaled by the pressure.

The valve must be connected to a closed system of course..for it to regulate pressure..


But perhaps I'll have to make one to show you guys how... Very Happy


Gas spring
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Unread postAuthor: john bunsenburner » Sat Dec 05, 2009 4:42 am

Thinking along the lines of simplicity: A shrader has a crack pressure of 70psi, so if 90psi instead of 60 would be suitable, just use a shrader valve between your chambers.
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Unread postAuthor: inonickname » Sat Dec 05, 2009 4:49 am

Experiment with the schrader first. I've had ones that crack at 30-60 psi, so grab a few to try. Leaving the gun pressurized for long periods of time will cause damage.

The flow rate will be quite low, though you get the benefits of it being extremely cheap, reliable, easy to make/get etc. Perhaps make the schrader replaceable for different amounts of power.

You could also make your own poppet valve and experiment with spring strengths.

Edit: about the schrader, it isn't a regulator, it just reduces the pressure by the (crack pressure) each shot. The shots wont be consistent, though you will still get more shots than normal.
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Unread postAuthor: john bunsenburner » Sat Dec 05, 2009 5:36 am

Well, its the simplest thing after an un regulated chamber. Give it a shot, you can get loads of them for free at any car repair store, i picked up nearly 50 the other day.
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Unread postAuthor: Demon » Sat Dec 05, 2009 9:46 am

I don't fully understand how it works either, can you explain a little more?


Its very simple, when there is 60 psi on the regulated side, the "pushbutton " counters the spring force, closes and no more air can go , so we have 60 psi.

Experiment with the schrader first. I've had ones that crack at 30-60 psi, so grab a few to try. Leaving the gun pressurized for long periods of time will cause damage.

The flow rate will be quite low, though you get the benefits of it being extremely cheap, reliable, easy to make/get etc. Perhaps make the schrader replaceable for different amounts of power.


I am aiming pretty high, i am looking for something like Audriusize :

http://www.youtube.com/watch?v=xcFQBIUQiGI

Is it possible that it is the same design then mine, but with a adjusting screw on the non regulated side to vary the spring power?



As i know a little bit in microcontroller programming and i have a small lcd display, i could make a program that would tell how many shots i have left depending on air pressure left and a mini speed calculator on the muzle end.
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Unread postAuthor: velocity3x » Sat Dec 05, 2009 9:59 am

I don't quite understand your drawing but, I think the spring needs to be on the low pressure side.
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Unread postAuthor: Demon » Sat Dec 05, 2009 10:26 am

The theory is very simple: when there is 60 psi on regulated side, the valve shuts closed.

so that the valve closes when there is 60 psi on regulated side, the piston as to counter a spring to block the air that goes by the holes (green line)

When the piston is pushed towards the A side enough to block the holes with the o-ring, the valves shut and no more air can go to b side, so there is 60 psi.
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Unread postAuthor: Ragnarok » Sat Dec 05, 2009 10:59 am

I'd suggest this old idea of mine as less effort to construct and more serviceable...

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Does that thing kinda look like a big cat to you?
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Unread postAuthor: Demon » Sat Dec 05, 2009 11:09 am

I am making a 6mm pcp airgun, so it needs to be instalable in a cooper pipe and pulled of easely, as aurdriusize.

http://www.youtube.com/watch?v=xcFQBIUQiGI

I posted here to get the approval of te community, will it work as i want, will it regulate air?
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Unread postAuthor: inonickname » Sat Dec 05, 2009 7:59 pm

I'd go with Ragnarok's design. It's easy to make, simple, reliable and could be rigged up inline.

How much consistency do you actually need? Hammer valves automatically compensate for lower pressures as the valve can stay open longer/open faster already.

If you really want a regulator, I'd contact Aurdriusize or go with Rag's idea.
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need a port/hole

Unread postAuthor: jean » Sun Dec 06, 2009 6:43 am

hi demon

you design is not to bad but you need a venthole between the spring site of piston and outside of chamber.
the outsidepressure is the referencepressure.

hope you understand me here a quick pic (note it is not scale, show not on the squares)
note the 0psi area in the pic

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Unread postAuthor: Demon » Sun Dec 06, 2009 8:55 am

Thanks a lot Jean,

But i dont think that a vent hole is nescessary, as in auridruize, there is one, but it does'nt vents with ambient air, its stays in the airchamber.How can that be possible?

http://www.youtube.com/watch?v=O-uQCV9V ... re=related

I tried to contact him without success, does anyone has his email address?


How can the screw get to seal ? or else air will leak outside of the air tank.
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Last edited by Demon on Sun Dec 06, 2009 9:35 am, edited 2 times in total.
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