SpudFiles

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:

Can't see why it won't work, to counter any friction just use a stronger motor, i like the cam idea.

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

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.

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?

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.

That's pretty much what I had in mind when I referred to an "eccentric cam"

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.

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.

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.
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 )

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...

i this concept reminds me of speedball guns that operate on electric solinoid valves and hammer valves
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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

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.
GR.Tom

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.