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Surface differential piston test result

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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Surface differential piston test result

Unread postAuthor: Solar » Fri Aug 08, 2008 12:26 am

The test showed that the valve trigger on the Eclipse launcher could be regulated down to 150psi and fire a shot of 275psi. The valve is rated at 300psi. I am going to see if I can fire a shot using 300psi in the trigger and 550psi in the ballast chamber. Not sure if the results are scalable. The safety burst hose in the grip is rated at 265psi with a 3:1 burst ratio. Should be good to 795psi. Will have to cap off the 1200psi rated tank for the test since my safety pop off is a 350psi one. Recently had to add a piece of rubber hosing to act as a bumper in the piston assembly since the shoulder that was put in to prevent the main spring from bottoming out was pounding it's way through the main valve. New spring and bumper seem to work well so far. Took some pics, but this computer does not have a USB for my card. Will post soon with new videos.
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Unread postAuthor: Hotwired » Fri Aug 08, 2008 6:46 am

Sounds reasonable, significant surface area difference between the two sides.

You can do the same thing with a QEV after you've filled it - the trigger side can have the pressure drop well below the chamber pressure but because of the larger trigger side area it stays shut.

I thought you were using chamber gas to trigger the piston, are you now using a separately regulated supply?

If it's a separate supply, how are you getting the trigger gas to vent afterwards?

Also, completely unrelated but it's been nagging me for a while... are all the connections on your cannon either threaded or bolted?
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Unread postAuthor: Solar » Tue Aug 12, 2008 2:43 am

Gas for firing is from the main chamber still, but regulated down before it reaches the trigger with a palmer regulator. The used trigger gas always vents from the stem of the trigger. The regulator does trap air between it and the trigger that would need to be exhausted by pushing the trigger after de-gassing I would assume.

Yes, everything is threaded or bolted except for a few hose fittings in the trigger system. Using 265psi rated hose over brass barbs. I will replace with braided line if need be.
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Unread postAuthor: rna_duelers » Tue Aug 12, 2008 4:20 am

This valve looks an alot like a Blow Of Valve from a car with forced induction,did you get some design characteristics from one of them?
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Unread postAuthor: CasinoVanart » Tue Aug 12, 2008 4:44 am

The only thing i can think of is that they must be able to take extreme pressure looking at the design (maybe soup the threads up), looks like a very nice representation of the manufacturing process there Solar, well done. :)
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Unread postAuthor: Solar » Tue Aug 12, 2008 7:25 pm

Tested the launcher with the trigger at 280psi and the main ballast at 520psi. Worked awesome and blasted two of the fins from the foam rocket nearly clean off.

The design is based on a humphrey piston valve that uses the same principle. I designed mine to take advantage of the differential triggering.

The o-rings should be good to 1200psi. I would need about a 650psi trigger and a possible death wish to fire that with the volumes I am using in a hand held launcher. I actually trembled after the first shot and then sat the launcher down to take pause before resuming tests.
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Unread postAuthor: Hotwired » Wed Aug 13, 2008 5:32 am

Have faith in your engineering skills :)

No but seriously I'm always nervous when I crank up the pressure significantly on a launcher, I'm 90% certain its perfectly fine, it's just out of what I was comfortable with.

Still didn't help the nerves when I pumped up my below launder to 400psi instead of the usual 240psi :o
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Unread postAuthor: Solar » Thu Aug 14, 2008 3:33 am

Yeah, served me right for listening to the store where I purchased the tank and reg who told me that it would put out 450psi instead of the 520 I registered on a gauge. It was rather comical after I fired the round and realized that there was a lot of power in that blast, and it having just recharge itself compelled me to sit the launcher down while I speculated on the concept of exactly how much different it was. 200psi more power was no small step. Very confident now though in the launchers overall design and potential for sending aloft heavier objects. The military is going to be getting their looks by summers end. More fun videos soon. These ones are really sweet. oh, and check out this pic.

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