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Look Ma, no valve!

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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Look Ma, no valve!

Unread postAuthor: LeMaudit » Sun May 17, 2009 6:50 pm

Hi,

While working on the internal design of my handgun, I had an idea. I am sure many had it before, but anyway here it is (couldn't find anything relevant in the search, sorry...)

Why not using the ammo as a plug for the chamber? That way, there’s no more delay for opening the valve, because there’s no valve at all! No seat reduction, the air pressure if at full blow in the barrel. Of course it would only work for relative small size and perfectly round ammo… hmmm… yeah! Ball bearings ;-)

The design is simplified for the sake of clarity, and that’s no novelty either. Quick Connect works like that. It feels safe too, as a failure in the O-ring or a leak or a break will never allow the ball to fly, as it is positively prevented by the smaller ball.
It seems to me it would also be a smooth trigger, no much force needed there and it would even go by itself at the end (pushing the 45 degree side)

The only difficulty would be a very precise adjustment I guess, that I am not afraid of. But also I wonder if a O-ring could properly seal a curved surface, or if you guys see a better solution for the seal.

Any comments?

BTW: The drawing is to scale, with a 9/16 ball bearing (185grain) that nicely fit a cooper tubing (I know, I have them right in front of me) and a modest 1.7 inch3 chamber and a 9” short barrel, GGDT says for 400psi it will propel the little devil at a wooping 300fps with an energy of 35 tf*lb. :shock: My 400psi chock pump is ordered, and so are a couple of high-pressure schrader valves… more to come in a near future :-)
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Unread postAuthor: keep_it_real » Sun May 17, 2009 7:07 pm

The ball detent is around spudfiles in a couple different places. I'm pretty sure JSR used one in a bbmg to slow down the rof. I haven't seen one with a trigger like that though. Looks cool.

I think the design would work with a couple changes:

I would get the ball detent as close as possible to the o-ring. From the first picture, the pressure behind the ball is working against you by making the seal worse. If the ball detent is close enough to the o-ring, it might be able to stop the widest part of the ammo from getting through the o-ring. If this works out, the pressure will make the seal better. You might consider using a different detent (something with a 45 degree angle instead of a ball). This might allow you to get the detent closer to the o-ring.

Also, I would flip the trigger around so you can pull it like a trigger but you might have a different design in mind.
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Unread postAuthor: LeMaudit » Sun May 17, 2009 7:35 pm

ball detent :D

Somehow I lack the proper vocabulary for the search to be useful!
Thanks! I am going to search again...

And for the advices, too! I was afraid the O-ring would have too much stress being fully compressed when the ball goes through, but having it on the other side sure is a better seal!
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Unread postAuthor: JDP12 » Sun May 17, 2009 7:42 pm

odd...but interesting design.... I'm fascinated however
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Unread postAuthor: Hotwired » Sun May 17, 2009 7:53 pm

It seems it would be easier to make if you had it fire cylindrical rounds.

With the bearings you need to have the ball rather carefully positioned for the o-ring to work properly, a cylinder which actually went through the o-ring would have no issue at all, the o-ring would be pushed down the gap between cylinder and barrel wall until it reached the end of its groove and sealed.

Something like plastic rod would be a decent stock material for that.

Always nice to see lateral thinking turning up. Practically everything already exists, it just has to be discovered by a spudgunner in the right frame of mind ^^
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Unread postAuthor: LeMaudit » Sun May 17, 2009 7:59 pm

I agree a rod would be a easier seal to do. But would not be of the greatest accuracy I guess. Also those ball bearing are available easily. But I do keep in mind the idea. I must say that for me, precise positioning would be a great part of the fun, being a wanabe machinist ;-)
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Unread postAuthor: pizlo » Sun May 17, 2009 9:00 pm

Some bloke did this with a potato sealing and a nail in front of it witch he pulled out to fire, not efficient but it worked.
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Unread postAuthor: Hawkeye » Sun May 17, 2009 9:27 pm

I think you'll find that JSR's "valveless prototype" is pretty much what you show here.
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Unread postAuthor: LeMaudit » Sun May 17, 2009 10:35 pm

I think you'll find that JSR's "valveless prototype" is pretty much what you show here.


Absolutely !
It seems I am slowly following the steps of JSR :-D
Now I know what to search, I'll be very interested to search again the forum and look at the previous experiments. Thanks!
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Unread postAuthor: LeMaudit » Sun May 17, 2009 11:52 pm

A few adjustment in the design and the ball is now less sensible to positioning I think, and better sealed. And as a bonus the positive lock is now twice as high.

Thanks for the suggestions! I do intend to build this big bore gun 8)
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Unread postAuthor: Moonbogg » Mon May 18, 2009 12:12 am

Heres another way. It would be automatic and could be made to auto release at any desired chamber pressure by choosing spring force and adjusting lever distance. Or perhaps it could be used in a hybrid. The combustion would build until the ball frees itself. Either way, you actually would probably need a lever handle to depress it to allow the ball to load. I bet it would work as well as the original idea.

Image

You could also replace the spring with a spring plunger and have it catch the right side of the pivot block. It would be very easy to reset compared to this method.
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Unread postAuthor: LeMaudit » Mon May 18, 2009 7:30 am

That's an interesting variant.

What I had in mind was not an auto release, but quite the opposite,
Something that will keep the positive lock whatever happen (drop on the floor, mechanical failure like O-ring or your spring, sudden Armageddon, etc...)

One thing that may not be very clear in the drawing it that the ball release piece with the groove is in fact a cylinder. Very like the moveable part of a quick connect. The 2nd drawing shows that more clearly. On the opposite side of the push, a simple weak spring can bring back the cylinder in position. I draw a push by lazyness, but in fact it will be more a pull as the trigger will most certainly be in front of it.
It has also the advantage of being easy to machine (well, not difficult) with a metal lathe and I always have that in mind for the design. If there’s an experienced machinist here I am sure he will agree (or say I’m a fool ;-) !)

About reloading. With my design, loading is a matter of pressing the trigger with an empty chamber (no force to counteract), drop a ammo ball in the barrel, and release the trigger. Then the ammo is lock positively and pressure can by build.

With you design, I am not sure, as you will have a very strong force to counteract to pass the lock ball for muzzle loading. With a 400psi pressure at the scale I draw, you spring must counteract a 100 pound force. That is quite a spring! You may need a kind of breach loading instead. But there’s not much room there.
:idea:
But I am thinking air pressure! I read again your text, and with a pressure build by explosion your auto release would make perfect sense, to have a large pressure that build before the ammo is fire. I am not bold enough to build that though… not yet ;-) But I'd love to see a damage video :lol:
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Unread postAuthor: JDP12 » Mon May 18, 2009 10:15 am

that's similar to JSR's ball detent in my opinion...
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Unread postAuthor: LeMaudit » Mon May 18, 2009 10:33 am

that's similar to JSR's ball detent in my opinion...


You're absolutely right. I just discovered it on my own... I did try to search before posting to seek a similar design, but my English vocabulary lack of subtlety, and I couldn't find anything. Now that I have the proper words to search I can find it :-D
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Unread postAuthor: Davidvaini » Mon May 18, 2009 12:46 pm

ilovetoblowthingsup wrote:that's similar to JSR's ball detent in my opinion...


and JSR's ball detent is similar to a hopup in my opinion.

All great ideas come from somewhere, sometimes people think of the same ideas.
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