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Folding stock idea... HELP!!

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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Folding stock idea... HELP!!

Unread postAuthor: williamfeldmann » Tue Sep 18, 2007 9:44 pm

So after seeing Goat's Gun I finally figured out how to make my break action on my golf ball cannon work. See it here, http://www.spudfiles.com/forums/goats-gun-t7859.html.

In the past, I built a cannon that had a PVC folding stock. It worked out well except because of the size of the chamber it only folded say 150 degrees so it stuck out cockeyed from the gun. Not a huge deal but I want to make this one a bit more professional looking.

These pics show both the top view and the side view as planned. The two bend points are the red Tees that are sanded out so they slide all the way around the various pipes. There is no air inside the stock system.

My problem with this and the previous design was that I have no way of "locking" the stock in the open or closed positions so that it doesn't fold the wrong way or too far and can be changed quickly or for storage. Also the kick of the cannons would cause the stock to fold a bit when I fired.

The black is barrel and tank and what not, blue is valve. These parts make up the actual gun. The red is two tees both around their corresponding pipes that provide the bend points for the stock. The green is a fixed portion of the stock. Size and what not are not to scale and the design is just to show what is happening. Any thoughts about the design or any suggestions as to the locking situation would be greatly appreciated.

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Unread postAuthor: f.c » Tue Sep 18, 2007 10:00 pm

sounds like a very interesting idea. if i make another bbmg i will have to try this.
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Unread postAuthor: williamfeldmann » Wed Sep 19, 2007 8:07 am

Does anyone know of a gun that had something similar? I spent some time searching both on here and on google and can't really find out anything.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 19, 2007 8:26 am

have you considered installing an item made for airsoft? It removes the DIY buzz but saves a lot of hassle and i'm sure you can get cheaper prices if you look around.

Edit: for $65 you can get this which is the same style of stock used in the new Brügger & Thomet GL-09 grenade launcher.
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Unread postAuthor: mega_swordman » Wed Sep 19, 2007 9:56 am

I see a potential problem with the folding of the fact that the t-joints are not glued. I simply see that as a bit of a problem with leaking as well as safety. I could be wrong though, and by all means prove me wrong.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 19, 2007 10:10 am

The easiest way to lock your design would be to drill a hole through the T that attaches to the launcher (and the tube inside it) and put a bolt or similar through to lock it when the stock is extended.
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Unread postAuthor: williamfeldmann » Wed Sep 19, 2007 10:27 am

@Mega_swordsman

There is no leak, the tee that is attached to the vertical pipe is sanded/dremmeled out so it basically sleeves the actual gun. There is no air in the stock system.

@ Jack

That would work on the second joint attached to green part of the stock, but how could I do that with the first joint without punching a hole through a part of the gun carrying air?

Also seeing that stock you linked gave me some thought on a side-hinge for this thing. It would not only get the stock far enough over to fold up square with the tank and barrel but also give me one joint which is easier to lock. I will draw up some plans and post them on here to see what you and the others think.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 19, 2007 10:48 am

williamfeldmann wrote:That would work on the second joint attached to green part of the stock, but how could I do that with the first joint without punching a hole through a part of the gun carrying air?


Cut down another Tee glued permanently to the chamber section and drill through that.
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Unread postAuthor: mega_swordman » Wed Sep 19, 2007 11:24 am

Ah, well then. I see no problem with the stock. I think Jack's idea would be the best for your needs, although the cannon would be a bit tall. Ah well.
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Unread postAuthor: williamfeldmann » Thu Sep 20, 2007 1:06 pm

Based on discussion earlier with Jack, you can see that we found a good way to lock one of the joints in the original design. Unfortunately, that doesn't help much with the second joint.

Remembering my good old days in the USAF, the most effective folding stock went to LEFT of the gun. It makes sense if you are right handed, your right never leaves the trigger even when flipping the stock around.

My major problem was that because of the diameter of the tank and barrel I had to get the stock a couple inches (I was thinking either 2 or 3 inch chamber, typical over-under or abit off center to the left to make room for the trigger) out from the center axis of the gun to make it fold all the way out of the way. The side hinge appears to do that.

These two drawings show a side hinge idea. The side view would be basically the same as the side view from earlier posts, but the top view changes dramatically. You can see that Instead of a single line up to the valve I used two. That is not neccesary, but if I wanted to add on another 45 degree elbow to the stock, I could make a bumber for the other upright to stop the stock from over-swinging, thus possibly eliminating the need for Jack's locking mechanism.
ImageImage

The red part is again a tee that is sanded out to fit around the pipe carrying air. If I was to to do the bumber idea I could make the right side of the system so it is blocked off with no air movement and create a lock with a pin similar to Jack's idea there. Let me know what you think or if you have any ideas on making this work better.
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Unread postAuthor: dongfang » Thu Sep 20, 2007 3:10 pm

Hi,

How about this: Split a pipe in half, but leave the last 10 cm or so. It must fit rather snugly around the stock pipe, but still clear the elbow fittings. Maybe you need to glue a smaller pipe inside the uncut section.

EDIT: Or just glue in a reducer in each end. Easy.

Aluminum would be really nice.

Somewhere on the gun, insert a sliding (or fixed) ring that the split pipe can jam into and stay in place. Or use zip ties, a hose clamp, or a band with one of those brackets for holding lids on containers, or whatever....

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Unread postAuthor: jackssmirkingrevenge » Thu Sep 20, 2007 3:21 pm

Very valid ideas guys but personally I'd just buy one, much simpler and saves the result from looking like it was yanked off from below a sink.
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Unread postAuthor: dongfang » Thu Sep 20, 2007 3:36 pm

HiJack,

Come on, we have seen dozens of examples of people having made really cool things themselves - with skill, care, and from learning from each other.

I left amateur radio when 95% of people just bought their equipment and never tinkered with it :lol: (just my taste, of course)

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Unread postAuthor: jackssmirkingrevenge » Thu Sep 20, 2007 3:48 pm

Fair enough, but hey - some people make their own piston valves, some people buy sprinkler valves or QEVs. I'm all for "rolling your own", but I see the stock as an accessory, in my book it's allowed :) besides, grafting a stock made for airsoft to PVC pipe is going to be a bit of a DIY challenge in itself hehe
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