10 replies to this topic

[pizlo]

Just read this please.
I'll explain, those two sheets of paper were both layed right across the barrel of a homeade pneumatic (compressed air) gun. the first sheet was shot with 70 psi and triggered with a ball valve. the second sheet was placed the exact same way but was triggered by a burst disk valve. a burst disk is a layer of material screwed into a union joint that will burst at a certian pressure. this is just to show how much difference a valve makes when using air.



heres the original topic.
valve opening tests

Edited by pizlo, 19 January 2008 - 12:25 PM.

[aetherguy881]

Yay for spudfiles!

Anyway back on the topic, what was your intent here? just trying to see what the force of air would do to the paper? Also, shouldn't you be more interested in the muzzle velocity instead of the destructive force. That's just my take on it.

Anyway, at 70 psi that's pretty nice. What's the specs of cannon/gun?

[ltvills]

ball valve are effective in large tanks requiring you long barrels. using ball valve will be most effective because you are not really working with the speed of release but the mas of air coming out.

[pizlo]

My point really is that not only the pressure, but the release of air is a huge part of the effectiveness. even with longer barrel there will be a VERY noticeable difference in performance, it really doesn't take much to push a nerf out a barrel, and compared to a burst disk (totally impractiical, but the best)or a piston valve, the ball valve will let much lles air actually push the dart. Just letting you guys know that people have broken the sound barrier with guns like these, only difference is higher pressures, and you to actually get past moch 1 you cant use air, because its expansion rate is too slow.

Im not sure about the material but it is most likely a few layers of aluminum foil.

@itvellis a burst disk will open to any diameter that your union joint it is so It will dump the most air possible into the barrel when it ruptures. the ultimate limit of air flow is your barrel, so if your valve can open to the full diameter of the barrel the only possible way to increase performance is to make the valve open faster, and a burst disk even surpasses a well made piston valve in speed of opening completely.

It was shot with no ammo, buy this beast Heres all the details

Edited by pizlo, 19 January 2008 - 07:31 PM.

[CaptainSlug]

I'm not really sure why they've been used in so many home mades here though.

There are very very few commercially available and affordable high flow-rate valve options usable for firing darts.

[pizlo]

I would gues that it is more the availability. If these people knew what Mcmaster was they could pick up a 3/4 in QEV for 15 bucks and have the best non burstdisk, non homemade valve out there. Also a one inch sprinkler valve slightly modded to be pneumatically triggered would work just as well and that is also only 15. I guess it is that people do not care enough about efficiency. weather or nit these would be good for darts, but I don't know why they wouldn't.
On a side note captain, I'm listening to Digitally imported now. Its great, I owe you one.
Once I get the leaky valve problem (hehe) sorted out Ill make one of my darts fit in the half inch barrel and see how far a gun designed for potatos can shoot a weighted dart.

[CaptainSlug]

What page are you looking at? Most Q-E valves are $50-$300

I also recommend http://www.somafm.com which has a lounge station aside from just some really awesome chillout and down beat stations.

Edited by CaptainSlug, 19 January 2008 - 08:05 PM.

[pizlo]

I'll check that site out, thanks.

Actually Mcmaster doesn't list these with the rest if the QEV, and they call them quick exhaust AIR valves, under the section compressed air control valves. Its near the bottom of page 957.
product number 6646K23.

Edited by pizlo, 19 January 2008 - 08:25 PM.

[CaptainSlug]

Those aren't really control valves. You would need another valve to control its actuation.
See: http://www.about-air...ck-exhaust.html
Or for a diagram: http://www.ascovalve...ick_Exhaust.pdf

Edited by CaptainSlug, 19 January 2008 - 08:42 PM.

[pizlo]

I'm aware of that, but I didn't realize that that was the difference. I think a modded husky blowgun would do just fine, they can pilot one inch sprinklers, and there only like 3 bucks. and the other upside is you get a trigger like feel. is the performance worse?