3/4" exhaust valve cannon

[jackssmirkingrevenge]

Some damage pics using a saboted 0.5" steel bearing:



Standard issue laboratory safety glasses...




...and the 1" thick pine board that was behind them. This was the entry hole.



Exit hole

[wannabie]

thats a very nice hole you got going there jack. what PSI what that at?

[jackssmirkingrevenge]

all shots were done at 110 psi

[spudthug]

sweet.. this gun is awesome.. but why did u call it 3/4 exhaust valve cannon? shouldnt it be piston cannon?

[jackssmirkingrevenge]

A piston valve is technically a quick exhaust valve

[spudthug]

oh yea i guess it is.. but woudlnt it be the other way around?? a quick exhaust valve is a pisotn valve??

[wannabie]

all shots were done at 110 psi

wow i just took my ball valve gun up to 120 and it didnt even get close to any of that kind of dammage.

[integral]

Even if you modded your ball valve, you can't open it anyway near as fast as actuating a piston valve.
Last time I feel safe wearing those lab glasses...

[spud yeti]

That is a cool gun. I am building paintball gun with similar valve, so its nice to see it might work. Mine is quite different actually. Does it have 100% seal and no leaks?

Merged:
Sorry didnt see above post on leaking! my bad! How much pressure is lost though?

Nice gun, but how much does the leak with the piston decrease the pressure because I have built a paint ball gun with similar valve and could perhaps mod it but want to know how much it leaks pls??

[jackssmirkingrevenge]

oh yea i guess it is.. but woudlnt it be the other way around?? a quick exhaust valve is a pisotn valve??

The both use the quick exhaust of a pilot chamber to move a piston to operate, so technically both terms are true.

Last time I feel safe wearing those lab glasses...

Well, it was a direct hit, and they shattered as opposed to being penetrated - I've tried direct hits from 12 ft/lb air rifles in 0.177 and 0.22 that only dimpled the perspex, and my friends tell me they will survive a load of birdshot from a 12 bore too

wow i just took my ball valve gun up to 120 and it didnt even get close to any of that kind of dammage

.

Now do you understand the benefits of a QEV? you can't beat good valve opening time

[wannabie]

LOL i was just stating that mine was at a higher psi and yet yours did more damage.

[rna_duelers]

Can't believe I never noticed this little cannon before,well I think this is classed as huge for you JSR.

A nice report on some of those shots,like really nice crisp crack.Have you GGDT this thing for its estimated muzzle velocity?

You need to step up into the larger bore guns and this is a good start!

[jackssmirkingrevenge]

Yep, by my standards this is massive - in fact it's the biggest pneumatic I ever built

Re the estimated velocity, it's on the first page:

I don't have the facility to chrono projectiles over 6mm in diameter, however according to GGDT when pressurised to 110 psi it fires a 10 gram glass marble at approximately 480 feet per second.

I have a large bore pneumatic in the pipeline for that ball bearing, but I have other projects (spudding and otherwise) before I can start it.

[DYI]

If you make something to fire that ball bearing, please get it to at least 300 fps. Anything less would be a waste of money. Maybe you could do something with that SCUBA tank (unregulated of course) and some hydraulic pipe + fittings?

[jackssmirkingrevenge]

I don't really have a velocity target as the ball bearing is so massive you could break something just by dropping it, but of course I'll want optimum performance meaning considerable barrel length and chamber size and efficient valve, though I think I'll stick to compressor pressures.