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Crank Powered Semi Auto Idea

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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Unread postAuthor: jackssmirkingrevenge » Thu Mar 06, 2008 7:52 am

psycix wrote:Wouldnt that make a cloud JSR??


As it is, it would be a version of my ball valve strafer - if you replaced the ball valve handle with a crank, you'd have a dakka-dakka-dakka-dakka machinegun :D
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Unread postAuthor: Jared Haehnel » Thu Mar 06, 2008 8:43 am

Hey I like the idea of a back pack of compressed air and duel wielding bb (or pellet) pistols I bet something like that wouldn't be that hard to design or build if you use a conventional vortex block or a spool valve...

Having never built a machine bb gun you guys could do it better. 8)

But it would be a fun idea...
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Unread postAuthor: kablooie » Thu Mar 06, 2008 10:39 am

Yeah, I like that ball valve idea a lot, maybe that should be what I make. Now for some uniform spherical ammo, paintballs are too messy...marbles?

Would a plastic ball valve work? At least the smaller diameter valves aren't too hard to open and close. I am guessing this gun would need a mount, because of all cranking that could throw my aim off. I will think about this. Thanks!
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 06, 2008 11:02 am

Marbles would be just about perfect :) but I hope you have a big compressor ;)

A plastic ball valve would be ideal as it's easier to make a hole in for the magazine. A bit of lube will help it rotate better but a reasonably long crank handle should make it easy work of it anyway.

Some sort of tripod would definitely be in order, suits the look :wink:
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Unread postAuthor: SPG » Thu Mar 06, 2008 12:36 pm

psycix wrote:Wouldnt that make a cloud JSR??


Yes, but also, no. It'd be "cloudy" in the sense that the ammo is going to move around not just sit there, but it'd be much more efficient as it only releases air when the valve is open.

We've had this idea floating round for years though, and I can't remember why no-one's built one, perhaps just because they can't be bothered. But it would be very very simple and waste very little air.
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 06, 2008 1:56 pm

SPG wrote:We've had this idea floating round for years though, and I can't remember why no-one's built one, perhaps just because they can't be bothered. But it would be very very simple and waste very little air.


I "sort of" built one, remember?

Image

The excess torque needed to rotate the ball valve is what put me off, you'd need a pretty powerful motor and gearbox to make it work - but if you're hand-cranking it shouldn't be that much of an issue.
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Unread postAuthor: pizlo » Thu Mar 06, 2008 4:18 pm

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Hehe JSR is starting his own comic books, nice to see someone make a bit more than black and white lined :)
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Unread postAuthor: kablooie » Thu Mar 06, 2008 7:42 pm

Are you saying something about my diagram?? lol. Marbles would work, although I need to buy some. I do have a few lying around, and the 1/2" ball valve I have only fits the smallest diameter marble, one that has a significant gap around it while in the actual barrel. Should I try drilling out the valve a little bit? Or should I find another brand of ball valve? Thanks.
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 06, 2008 10:44 pm

kablooie wrote:Should I try drilling out the valve a little bit? Or should I find another brand of ball valve? Thanks.


It's more advisable to buy a slighly larger ball valve, then epoxy a piece of barrel tubing inside the rotating bit - that way the air losses between shots (assuming a tight barrel) will be minimal.
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Unread postAuthor: kablooie » Fri Mar 07, 2008 12:04 am

Alright, I'll do that then. Thanks for the help.
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Unread postAuthor: ghostman01 » Fri Mar 07, 2008 12:10 am

not if you open a close the valve with a crank or something a cloud is just opening a valve once and letting a heap of ammo out with a lot of air which i think doesnt make them very efficient this however is one burst of air for one piece of ammo like an auto or semi i guess, but with what you said :a cloud: imagine having a cloud marble gun....... yike !
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Unread postAuthor: Solar » Fri Mar 07, 2008 4:17 am

haha, you guys are going to get a kick out of my launcher when I show you how complex the machined mechanism is even though the operation is simple in the end. I think the cog idea is cool, but agree with the complexity if you aqree using only round ammo. Indexers of any sort are tricky even though they may appear simple. Adding pressure and projectiles always warrants precise manufacture and adds unexpected results on even the simplest designs. small parts tend to loosen up and binding is always an issue if you are doing any sort of direction change.

I have as book I will dig out called mechanisms and mechanical devices that has a GREAT section on simples AND complex indexing methods you you will all love to gander at.
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 07, 2008 4:33 am

Adding pressure and projectiles always warrants precise manufacture and adds unexpected results on even the simplest designs


In this case (my design), the use of a ball valve takes this headache out of the equation.
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Unread postAuthor: ghostman01 » Fri Mar 07, 2008 6:43 am

ok solar lets see it post it somewhere and let me know
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Unread postAuthor: Solar » Sat Mar 08, 2008 3:48 am

I'll try and dig it out by monday and scan it. It's in storage, but it will be worth the wait.
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