For the high pressure experts out there

[inonickname]

Here's what I'm looking for:

A fill valve, check valve or ball valve (as small as possible), in the smallest sizes possible. However, they need to handle a 3000 psi pressure, and then a 25,000 (roughly) shock, for an extremely short duration.

Any ideas? Initial fill will be from a stainless steel schrader valve, with a working pressure of 3000 psi. So, chances are I'll need to protect it.

Larda used what appears to be a hydraulic ball valve for a similar application, which often have a rating of around 5000 psi. A Hydraulic ball valve would probably be suitable for this application, though I'd rather something much more compact.

If I were not to protect the stainless steel schrader with another valve, what would be a suitable flow restriction?

[POLAND_SPUD]

I am not a really HP expert but my answer is -> hydraulic valves...

anything else will be difficult to find and much more expensive..

[inonickname]

That's what I was looking at, but a general rating for them is around 5000 psi. Given that most valves will take more pressure than they're rated for, and this is only for a short time a BV would probably hold.

Though I'm still looking for something smaller and more compact..

[jeepkahn]

are you familiar with quickdsconnects used for paintball rigs, the filler nipples are tiny and you can get them with built in checks for about $15 usd at the pb shop...

heres a link

http://store.customproducts.us/index.cf ... tegoryID=7

and a pic...

they're rated at 5k psi

[maggotman]

i think balvalve woulf be fine ive used 1/2 valves rated to 30 bar at to hold back 180psi

[inonickname]

I dunno if you've seen the scale I'm building on Maggotman.

When I get my lathe here I'm gonna start making chips from ta block of stainless. I'll just use a charder valve (saw a 4k psi stainless steel one) and buy an extremely small drill to reduce flow to and from it.

Working pressure of the chamber will be 50k ish psi, which I believe is sufficient. I'll probably have to make a sleeve up for the barrel though.

[jeepkahn]

I dunno if you've seen the scale I'm building on Maggotman.

When I get my lathe here I'm gonna start making chips from ta block of stainless. I'll just use a charder valve (saw a 4k psi stainless steel one) and buy an extremely small drill to reduce flow to and from it.

Working pressure of the chamber will be 50k ish psi, which I believe is sufficient. I'll probably have to make a sleeve up for the barrel though.

50kpsi??? What are building??? High Powered rifles don't generate 50k psi... I doub't even D-Halls toys generate those pressures....

[maggotman]

if your bilding on a large scale a small hole will make refuling take forever
what sort of chamber volume are we talking about??

i have read on the inter net that tank guns produse 90kpsi

[spudtyrrant]

wrong the abrams main battle tanks main 120mm smoothbore produces 73950psi upon firing but by the time it reaches the muzzle it drops to 1950psi and it is currently the most powerful cannon mounted on a tank besides china's type-98 but it doesn't produce as much energy as the abrams upon firing (can't count self propelled artillery)

[inonickname]

well chamber will be 2x1 centimeters, or up to 3x1. After seeing a post of Ragnaroks, I probably don't need to actually have a 20k pressure rating. A lower pressure will suffice for this I guess.

I think I've got my heart set on a lathe..$3500 fully tooled.

[mark.f]

Ever thought of checked grease fittings?

[inonickname]

Yeh, it was serious consideration but after reading a post from a member who tried to use a grease check valve it would not seal against air. However, if I cannot find a suitably small drill that would be a consideration to limit flow.

[KineticAmbitions]

50kpsi??? What are building??? High Powered rifles don't generate 50k psi... I doub't even D-Halls toys generate those pressures....

High powered rifles often reach a peak pressure of 50 or 60k psi, and I'd bet that Mr. Hall has some *toys* which exceed that significantly.

As to your valve: would you consider making one? A piston-based valve could be built which would easily survive the firing pressure by having only a very small opening to the chamber.

This valve has three ports, and two pistons. One small port at the bottom for the chamber, another port above that for the inlet. The diameter of the tube increases above that, and at the top of the wider tube there is a final inlet, probably attached to your HPA source. Both tubes have a piston that fits inside them, and they are attached to each other via a rigid connection. There is an appropriately strong tension spring connecting the top piston to the top of the assembly, which tries to hold it open. In "open" position, there is no pressure in the top cavity, and fuel/oxidizer is pumped through the middle opening, into the chamber. To close the valve before firing, HPA is pumped into the top chamber, with the larger surface area overcoming both the spring and the chamber pressure to hold the pistons closed. Some arbitrarily small opening to the chamber would prevent firing pressure from moving the pistons. After firing, there is no pressure on the chamber side. You vent the air in the top portion and the spring pulls the two pistons back to the top, bringing the valve back to the "open" position.

I wouldn't suggest hydraulic valves at all. Larda uses 500bar hydraulic valves in his hybrid, and the seals crack on nearly every shot. Did you hear the hissing after the high power shots on the videos? That's the sound of about a hundred dollars worth of high pressure valve which recently had its guts ripped out.

McMaster-Carr sells appropriately tiny drill bits. If you don't live in the USA, find someone who does and set up a deal with them to send to you. Either that, or test your luck on eBay...

Good luck with this, I'd love to see another 200x or so cannon floating around here

[Technician1002]

McMaster-Carr sells appropriately tiny drill bits. If you don't live in the USA, find someone who does and set up a deal with them to send to you. Either that, or test your luck on eBay...

Good luck with this, I'd love to see another 200x or so cannon floating around here

Another source of small drill bits is an electronics store that carries materials to make printed circuit boards. (Not Radio Shack) Many of those bits are tiny.

[Gippeto]

Sounds like you're looking for a snubber.

http://www.wika.com/WIKAWeb/Product/pdf/910.12.pdf

If it helps at all, I have purchased .010" drill bits from a lapidary supply company before. (Babington waste oil burner project)

Another idea, is to use a metal seat check valve, but "damage" the metal seat causing it to leak slowly in one direction. You[ll have to build one to take the pressures you're talking about I suspect.

A philips head screw driver lightly driven into the seat comes to mind.