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auto-piston prototype

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: qbnbountyhunter » Thu Dec 20, 2007 9:04 pm

Very complicated and sophisticated. that take salot of skill and craftmanship, I hope it functions as good as it looks!
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Unread postAuthor: clide » Thu Dec 20, 2007 11:37 pm

Looking good.

Besides the flow rate into the pilot the only other thing I can think of that could cause problems is the relief valve design.

I think the commercial pop-off valves have some sort of mechanism that makes them "pop" open when a certain pressure is reached and stay open until there is a significantly lower pressure. I haven't taken one apart to look, but it may be a larger surface area that makes them pop, much like a piston valve.

I'm not sure if yours will actually pop or if it will just release the pressure when it reaches a certain level. If it only ends up releasing pressure at a certain level then I think you can still get the gun to work, but not in the way you are probably expecting. It would fire based on the rising pressure in the chamber rather than falling pressure in the pilot, and your relief valve would just be acting to maintain a constant pressure in the pilot.

My point is that if your relief valve is only maintaining a constant pressure, then it could be eliminated completely and just make a fairly large pilot volume that would remain somewhat constant in pressure even as the piston moved back. This would require a perfect sealing piston, but it would make an efficient full auto piston by eliminating the need to exhaust the pilot.
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Unread postAuthor: jackssmirkingrevenge » Thu Dec 20, 2007 11:54 pm

Sorry to disappoint you guys but I have it a go this morning, and... well, nothing, the *profanities* thing doesn't even seal!

*BLASPHEMY*

I was fairly sure I got the piston alignment right, clearly my confidence was ill deserved.

Valid points clide, I think an airtight piston (for which read a syrigne plunger :) ) would definitely help my cause - of course now everything's all sealed up in bulletproof epoxy, so it's hacksaw time :roll: :evil:
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Unread postAuthor: LikimysCrotchus5 » Fri Dec 21, 2007 1:25 am

Well thats depressing, all that epoxy, tsk tsk tsk. But i believe the educational value of the concept learned here is far beyond comparison to the failure of it :D

P.S. Have fun hack.
*The crowd begins to chant* "HACK, HACK, HACK, HACK, WOOO!
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Unread postAuthor: jackssmirkingrevenge » Fri Dec 21, 2007 2:19 am

I'll do some hacking this afternoon, provided I'm not too affected by the ridiculous stock of whisky we intend to demolish as part of the last-day-of-work-of-the-year celebrations :D It will only require one pouring of epoxy so you can expect results before the weekend is through.
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Unread postAuthor: Antonio » Fri Dec 21, 2007 5:51 pm

looks interesting! Coming very close to the automag design here. With an equilibrium gas system. I think it is a bit tidious though (not to be offencive). I have working on my guns for a while, and I have always tried to make them more simple so it easily can be made into bigger numbers. But yeah impressive stuff here. Plz post a video once u got it all working; I am curious! Anton
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Unread postAuthor: jackssmirkingrevenge » Sat Dec 22, 2007 4:45 am

ant wrote:I have always tried to make them more simple so it easily can be made into bigger numbers. But yeah impressive stuff here. Plz post a video once u got it all working; I am curious! Anton


Bigger numbers? Will you be supplying an army :)

Well, this prototype is heading straight towards the failure bin, I agree that things should be kept as simple as possible which is why I'm trying to cook up a different design :)

I know I said I'd be trying to fix this one but i think all that whisky gave me a rare moment of clarity :D
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 18, 2008 12:36 am

As part of the ongoing saga that is my quest for full auto, this design hasn't died yet, but is currently being modified as follows:
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Unread postAuthor: ALIHISGREAT » Fri Jan 18, 2008 2:41 am

so its basically a BtB style pop-off stuck onto a barrel sealer that fills from the chamber. as long as you get the construction right it will work and i hope it does, i'm starting to get bored with all your auto-piston topics :roll: hey look i just noticed this could probably be made with off the shelf parts :P maybe you wouldn't have all the construction problems if you did that :wink:
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 18, 2008 3:00 am

BtB style pop-off


He might have built it first but in all fairness we had arrived to the same design independently, and anyway, it's basically how commercial pop-off valves work.

i hope it does, i'm starting to get bored with all your auto-piston topics


You and me both :P

hey look i just noticed this could probably be made with off the shelf parts


Naturally, but would it be as compact and, more importantly, as cheap?
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Unread postAuthor: Antonio » Fri Jan 18, 2008 4:49 am

jackssmirkingrevenge wrote:
ant wrote:I have always tried to make them more simple so it easily can be made into bigger numbers. But yeah impressive stuff here. Plz post a video once u got it all working; I am curious! Anton


Bigger numbers? Will you be supplying an army :)


Well I am not trying to supply or make an army lol. Its just that some of these airguns here are so complex. The stacked tube airgun I made is already fairly complex and it doesnt even shoot auto. I tried to reproduce trigger parts for it, but I cant seem to get the same things over again. So yeah at these small scale highprecision'' projects it is difficult to produce a simple and good working airgun. So thats why I have this goal in mind. I think its an achievement of making a good working airgun but think about what an achievement it would be if u could reproduce it:)
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Unread postAuthor: VH_man » Fri Jan 18, 2008 6:13 am

you know JSR, i actually tried your whole epoxy construction method, and I AGREE it is extremely unforgiving.

however, it turns out SO GOOD LOOKING its worth the effort. and things are so much more compact.

Also, Making your pistons sit inside a syringe tube is also a great idea......

i tell you JSR, you are truly an innovator............

anyway, that prototype looks prettyyyyyy good. If you construct it succesfully i will attempt at making the same, except with off-the-shelf parts for reliablitity...........

either that or ill start work on my GBB airsoft rifle. it has a blowback mechanism that replicates the blowback mechanism in a GBB airsoft pistol. Ill post animations eventually, when i finally get the time to make them. the thing has so many parts!!!!!!
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 18, 2008 6:38 am

I think what people don't appreciate is the amount of possibilites that this form of construction offers.

It's the difference between making something out of lego or out of clay, it might be a bit more challenging to work with but it opens up your horizons, and what you spend in time and patience you save on $$$ and since many members here are youngsters with low income, sounds like a good deal to me :)
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Unread postAuthor: Brian the brain » Fri Jan 18, 2008 1:13 pm

He might have built it first but in all fairness we had arrived to the same design independently, and anyway, it's basically how commercial pop-off valves work.


True.I had not yet read the full-auto threads, and I built It without telling anybody about this in advance.
It's different to a commercial pop-off however.

THe snapvalve would be one crappy safety pop-off..

Imagine your compressor is overfilling..bbzzzz

BANG!! :shock: ( scaring the sh** out of you)

And you are left with an empty(!!) reservoir.. :roll:

Safetyvalves are made to relieve just a small portion of the pressure without the typical BANG of the Snapvalve.
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: ALIHISGREAT » Fri Jan 18, 2008 4:54 pm

Naturally, but would it be as compact and, more importantly, as cheap?


no and no... but it would work :wink:
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