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6mm First Attempt.

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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6mm First Attempt.

Unread postAuthor: Someone89 » Wed Oct 24, 2012 7:12 pm

Hey all, so I happened across this site while trying to find out how the CO2 cannons on RC naval combat ships work and got a bit hooked.

Hefty dose of forum searching and trying to avoid posting noobish questions and I've made this thing out of an Airsoft barrel off ebay, 1/4" QEV, slide valve, and a 1" Tee with adaptors for a chamber. Couldn't find any schrader valves with bsp threads (I'm in the UK) so just drilled a hole in an end cap for a bolt in tyre valve.


Image

Made a blow forward bolt out of some 15mm copper, 6mm aluminium tube, and 2 compression stop ends. (Wanted it to be dismantlable)

Image


Was using a cheap CO2 tyre inflator to fill it but that blew up so I'm waiting for an aquarium regulator for disposable cartridges to arrive to give that a go. Using a shock pump in the mean time but it takes too long and I want a constant supply.

I cut a slot for a O ring detent but I think the bolt chopped that to bits in about 4 shots, + its not very effective and allows double feeds so that needs some work. BBs feed from a vitamin pill box hopper that pushes onto a 10mm Tee.

Pretty sure the chamber doesn't need to be that big and it could also do with being parallel to the barrel for ergonomics....bit underwhelmed by the power at 10 Bar as well (particularly with steel bbs) so tempted to get a 1/2" QEV but er...yeah...there it is. Many improvements are necessary I reckon!

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Unread postAuthor: Lockednloaded » Wed Oct 24, 2012 7:19 pm

Great first! Not many people just show up on the scene with a nicely functioning semi auto, so kudos to you.

As for your problems, it'd probably be better to implement a tiny ball detent with a spring; that way your bolt won't chop it up because it can retract. Secondly, as far as power and efficiency are concerned, your chamber is waaaay too big and you're using far to low of pressure. All you need is to ditch the 1" fittings, put about 2" of 1/2" pipe on there, and then up the pressure with that shockpump
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Unread postAuthor: jackssmirkingrevenge » Wed Oct 24, 2012 11:49 pm

Lockednloaded wrote:Great first! Not many people just show up on the scene with a nicely functioning semi auto, so kudos to you.


hear hear, well done!

Some ideas for implementing a detent without complex tooling:

Image

If you're using steel BBs though, a small neodymium magnet strategically places should suffice.

bit underwhelmed by the power at 10 Bar as well (particularly with steel bbs) so tempted to get a 1/2" QEV


You won's see much of a difference in power by using a larger valve, what you want is more pressure. Consider purchasing a paintball tank ;)
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Unread postAuthor: archie370 » Thu Oct 25, 2012 12:32 am

Wow this puts me to shame haha :) , about JSR's plan ... How tight should the ball bearing be in the chamber ... (or is it the case of how long is a piece of string) ... if you had the springy metal bit close to steel you weld it on, therefore not needing the epoxy resin ... (probs wont work but its a thought)
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Unread postAuthor: jackssmirkingrevenge » Thu Oct 25, 2012 12:35 am

archie370 wrote:(or is it the case of how long is a piece of string)


You said it before I did ;) doesn't need to be too tight, just enough to stop the pressure blowing it out on firing.

... if you had the springy metal bit close to steel you weld it on, therefore not needing the epoxy resin


Could be done, but I always assume someone has only basic tools to work with, therefore - epoxy!
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Unread postAuthor: archie370 » Thu Oct 25, 2012 2:09 am

Oh Very good then :)

Good saying to go by as well ;)

"Could be done, but I always assume someone has only basic tools to work with, therefore - epoxy!"
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Unread postAuthor: jakethebeast » Thu Oct 25, 2012 7:24 am

Haha nice! Now just make it high-mix hybrid :D

Looks like a nice plinker, but when you basically use 1/4" ammo with 1/4" valve its sufficient enough. But when you reduce the chamber volume and up the pressure youll see a BIG difference!

Somekind of detent is eesential though, also makes a diffenrence in velocity ;)
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Unread postAuthor: Someone89 » Fri Oct 26, 2012 10:48 am

Cheers people! I've got a couple of magnets from a harddrive but am using airsoft ammo as well as steel bbs so I think a ball detent is the way forwards.

It's not as compact as I wanted so I'm thinking of pointing the QEV upwards and adding a couple of elbows so the chamber (which will be drastically shrunk) and slide valve are parallel to the barrel. Then devising something involving springs and a lever on the slide valve so it feels more like a proper trigger. And making some kind of stock/casing out of wood.

Got access to a drill press, dremel and blowtorch for soldering but that's about it, never really built anything that didn't come in a kit before haha

:)
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Unread postAuthor: archie370 » Fri Oct 26, 2012 4:21 pm

Haha Yeah most of the stuff on here doesn't come from a kit :) .... With the metal bb... do you reakon it will have the same effect as a bb which is a magnet which would hold your ammo in place not risking it would role down your barrel? (food for thought)

At the moment the stock im building for my airgun is made out of aluminum strips ... in the shape of a m16 stock but much lighter ... How are you going to make a stock out of wood, you might need to aquire some new tools such as chissels, router (for the middle part to hollow it out ...) and some other stuff, i wouldn't mind making one myself but somehow i'd probably stuff it up.
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