valveless pellet gun

Miniature guns are novelty custom, unique, and sometime downright crude! Common construction materials often include pill bottles or pens. Show us your work!
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jackssmirkingrevenge
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Thu Jun 21, 2007 11:19 pm

This is an idea I had a while back, which was to dispense with the valve altogether and use the projectile to seal the air chamber, locked in place until it was ready to fire. This would be to all intents and purposes the most effective "valve" happy red? :p I could think of.

The prototype I actually made had a bolt as a projectile stopper and used 0.22 airgun pellets which gave a good seal on the barrel. The performance however wasn't any better than my mini-piston designs so I shelved the idea as not offering sufficient benefits to warrant the awkward method of operation.

The disadvantage is that you need a projectile that's a 100% airtight fit in the breech, which also has to be of strong enough construction to retain the pressure behind it without collapsing. Still, for those seeking ultimate performance, it might be a workable idea.

For more detailed information on using epoxy, check out the how-tos here and here.
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concept drawing with a sliding lock
concept drawing with a sliding lock
valvelessbb.JPG (30.76 KiB) Viewed 3656 times
views of the actual prototype, from top to bottom:<br /><br />1)rear view of breech and barrel assembly<br />2)view down the barrel, you can make out the end of the bolt sticking out - note that it only has to enter the barrel a tiny amount to jam the projectile in place.<br />3)breech threaded to a blowgun for low pressure testing<br />4)High pressure chamber for 300 psi+ testing.
views of the actual prototype, from top to bottom:

1)rear view of breech and barrel assembly
2)view down the barrel, you can make out the end of the bolt sticking out - note that it only has to enter the barrel a tiny amount to jam the projectile in place.
3)breech threaded to a blowgun for low pressure testing
4)High pressure chamber for 300 psi+ testing.
valveless strafer concept
valveless strafer concept
valveless.JPG (27.2 KiB) Viewed 3640 times
prototype breech construction
prototype breech construction
valveless breech.JPG (33.73 KiB) Viewed 3640 times
breech concept closeup
breech concept closeup
valvelessclose.JPG (26.43 KiB) Viewed 3640 times
Last edited by jackssmirkingrevenge on Sun Sep 09, 2007 12:04 pm, edited 4 times in total.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Redcoat
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Thu Jun 21, 2007 11:24 pm

bravo jack, your ideas keep on comng and there always good.I never would have thought of that.That is a good idea maybe for a sniper?

A one shot pistol is pretty annoying (in my books).
Poo.
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rednecktatertosser
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Thu Jun 21, 2007 11:25 pm

So a valveless gun with the most effective valve you could think of? That made me laugh.

But in all seriousness that is a really good idea. I might just make one this weekend... Providing I find money.
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noname
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Thu Jun 21, 2007 11:26 pm

Knowing you and your epoxy skillz, I think you could make it. Good luck. What kind of projectiles do you have in mind, seeing as they need to seal?
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hi
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Thu Jun 21, 2007 11:26 pm

i think you would have to pull the trigger fairly fast, but it should work, if you can ge it to seal.
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jackssmirkingrevenge
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Thu Jun 21, 2007 11:37 pm

sorry guys but I pressed the "submit" button too early (d'oh!) I actually made a prototype of this, check the edited post :)
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Velocity
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Thu Jun 21, 2007 11:39 pm

Its like a burst disk on steroids! (not really?)

Nice design here... I am surprised that you were able to get it to seal.

It would be interesting to compare this to a burst disk gun of similar size.
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rednecktatertosser
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Thu Jun 21, 2007 11:40 pm

well another one of your wonderful innovations has been put into my "stuff to build" file in my favorites. once again good job jack, like usual.
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jackssmirkingrevenge
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Thu Jun 21, 2007 11:40 pm

rmich732 wrote:Nice design here... I am surprised that you were able to get it to seal.
It sealed easily without any rubber because the soft lead skirt of the pellet "inflates" and seals agaisnt the barrel. This is after all the same way that brass cartridges seal the propellant casses inside firearms.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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rednecktatertosser
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Thu Jun 21, 2007 11:44 pm

AH so it works off the pricipal of grease seals on a car axle, where its cupped to one side, the side it seals so that it helps hold pressure. thats ingenious.
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shud_b_rite
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Fri Jun 22, 2007 1:36 am

I like your chamber. Where did you get it? Or how did you make it?
Airbeds... so many different uses
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FreakyShotGlass
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Fri Jun 22, 2007 1:51 am

You could use a solenoid to hold back the projectile and then apply a current and the solenoid would activate and release the projectile.
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jackssmirkingrevenge
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Fri Jun 22, 2007 2:16 am

shud_b_rite wrote:I like your chamber. Where did you get it? Or how did you make it?
I made it myself, as per attached diagram.
You could use a solenoid to hold back the projectile and then apply a current and the solenoid would activate and release the projectile.
You'll need a pretty hefty solenoid to achieve that, for a 3/4" barrel at 100 psi it'll have to hold a force of 44 lbs.
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chamber diagram
chamber diagram
untitled.jpg (18.44 KiB) Viewed 3608 times
hectmarr wrote:You have to make many weapons, because this field is long and short life
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potatoflinger
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Fri Jun 22, 2007 8:11 am

That's a great idea, but wouldn't the pellets wear down the barrel after a while, since they expand to fit the barrel perfectly? It seems like they would scrape the sides the whole way down the barrel.
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lukemc
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Fri Jun 22, 2007 8:34 am

jackssmirkingrevenge wrote:
You could use a solenoid to hold back the projectile and then apply a current and the solenoid would activate and release the projectile.
You'll need a pretty hefty solenoid to achieve that, for a 3/4" barrel at 100 psi it'll have to hold a force of 44 lbs.


what if you made it like this the solenoid wouldnt have to direcly hold back the pressure
Image
Last edited by lukemc on Fri Jun 22, 2007 8:35 am, edited 1 time in total.
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