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full auto electric drive revisited

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full auto electric drive revisited

Unread postAuthor: jackssmirkingrevenge » Wed Nov 28, 2007 4:24 am

I was pondering turning again to the idea of a bolt worked by an external electric source in order to achieve semi/full auto fire for a small calibre. I had already thought up something similar or spudtech (that was reposted on this forum here), but I'm considering a new variation as per the attached diagram.

One of the main problems with the other prototype was too much friction in the bolt when it sealed well - to counter this, I've removed all rubber seals, relying on a tight fit of the bolt in the epoxy (there will be some leaks of course but nothing too drastic) and a separate (ball valve?) inlet for the air. Also, the retun spring now returns the bolt to the open instead of the closed position, meaning effectively faster valve opening.

The idea of course adds the complexity of bulding a separate solenoid or geared motor setup, but at least like this none of the air is diverted for feeding.

Ideas, comments?

edit:

Image
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bolt is shown in the "closed" position with the return spring under tension
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Last edited by jackssmirkingrevenge on Thu Nov 29, 2007 12:40 am, edited 1 time in total.
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Unread postAuthor: Novacastrian » Wed Nov 28, 2007 4:50 am

Can't see why it won't work, to counter any friction just use a stronger motor, i like the cam idea.
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Unread postAuthor: Infernal Maveric » Wed Nov 28, 2007 5:21 am

Looks like it would work, but tuning the motor/solenoid speeds would be required to reduce the chamces of jamming.

Can't wait to see it working
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 28, 2007 7:03 am

Infernal Maveric wrote:Looks like it would work, but tuning the motor/solenoid speeds would be required to reduce the chamces of jamming.

Can't wait to see it working


The appeal of having the mechanism motor driven is that you can easily control the rate of fire. Also, since it's the spring that moves the bolt forward that means that you'll get a consistent opening time not related to the revs per minute.

I reckon I can build it within a week or two, and the best thing is that you can build the diagram as is (without the electric mechansim) to test performance before commiting yourself to the drive system.
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Unread postAuthor: FeLeX » Wed Nov 28, 2007 8:47 am

That looks like a type of a hammer valve. Maybe a motor is not even needed? Or do you want it just to be able to controll the ROF?
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 28, 2007 8:59 am

I guess you can say that. If the air pressure alone is enough to drive the bolt back enough to feed another round into the chamber then the motor won't be necessary, but I doubt it will be sufficient - guess I'll just have to build it ;)

edit: modified the design a little for practical considerations in a similar manner to the previous idea along these lines, this way the seal will stop projectiles rolling out of the barrel prematurely and prevent a bit of air loss.
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Unread postAuthor: Hotwired » Wed Nov 28, 2007 12:25 pm

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Unread postAuthor: jackssmirkingrevenge » Wed Nov 28, 2007 1:02 pm

That's pretty much what I had in mind when I referred to an "eccentric cam" ;)
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Unread postAuthor: Hotwired » Wed Nov 28, 2007 1:11 pm

I was thinking more of the partially toothless gear pulling back the toothed and sprung rack and allowing it to fly back when the rack reached the toothless section.
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 28, 2007 1:42 pm

What I though of was more along the lines of the mechanism which loads BBs into the breech as opposed to the one that reloads the piston. It's simpler to make and will still allow the bolt to fly back propelled by the spring.
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Unread postAuthor: CpTn_lAw » Wed Nov 28, 2007 2:34 pm

To prevent bad flow, i would suggest you make the bolt diameter way bigger than the barrel's. that would give you some venturi effect to the rescue lol. :D
As for the mechanism....you know you complicate yourself way too much? a simple blowgun with a side slide-connector that closes when you actuate the blowgun, linked to a solenoid. simple, and yet effective. i have one major rule qhen building a new setup, think, build, see, improve. This has never failed me. (well....except for the capacitos in my chest lol :shock: )
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 28, 2007 2:43 pm

As for the mechanism....you know you complicate yourself way too much? a simple blowgun with a side slide-connector that closes when you actuate the blowgun, linked to a solenoid.


If I understood that correctly, it would only give semi-auto fire. I already made a successful blowgun actuated semi auto, now I'm going for dakka-dakka-dakka ;)

To prevent bad flow, i would suggest you make the bolt diameter way bigger than the barrel's. that would give you some venturi effect to the rescue lol.


Not only that, but it would increase the area available for the air to act on the bolt... hmmm...
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Unread postAuthor: iknowmy3tables » Wed Nov 28, 2007 3:31 pm

i this concept reminds me of speedball guns that operate on electric solinoid valves and hammer valves
http://www.ultratwistedpaintball.biz/mm ... mation.gif
http://www.ultratwistedpaintball.biz/mm ... mation.gif
I really don't like this no rubber seal thing the leaking air might blow the bbs from the breech, I think you just got to cope with the friction I think basic solinoids just aren't fit for this job especially if its homemade, get something stronger

why don't you try the design that has been partially brought up before add a pneumatic drive push the bolt forward and a spring return
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Unread postAuthor: Tom » Wed Nov 28, 2007 3:42 pm

Maybe if you at one rubber seal lubricate it and weight how much it takes to open the valve/close the breech. Then buy your solenoid on the information.
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Unread postAuthor: Hawkeye » Wed Nov 28, 2007 3:56 pm

Perhaps a spring mounted behind rather than on the side would decrease the likelihood of the mechanism being bent slightly to the side and increasing the friction.
You could just sleeve a larger pipe around the back portion of the epoxy block and cap it so you can tweak the spring type and tension.
I would think it would work fine on just air pressure. Really it is just the opposite of your blow forward breech prototype.
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