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Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: MrCrowley » Sat Feb 23, 2008 3:13 pm

TurboSuper wrote:I find the whole concept of a combustion a bit unwieldy for launching a ball for a dog. I'd just rig up some sort of spring piston pneumatic sort of deal.

If you bothered to read, you would realise pneumatics are out of the question.
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Unread postAuthor: D_Hall » Sat Feb 23, 2008 3:27 pm

Pumping was listed as out of the question.

I've made a few pneumatics. I've never pumped.

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Unread postAuthor: MrCrowley » Sat Feb 23, 2008 3:31 pm

Yes, though I stated in a post on the other page, CO2 was going over-board for what is needed cost wise for the relative performance.
Then Singularity seemed to dismiss Pneumatics all together. (Not sure if he was only referring to hand pumps though)

MrCrowley wrote:If he's done his back in, I doubt he wants to pump up a pneumatic, so that leaves him with CO2, which is overkill.



Singularity wrote:I already built it, it the size of a standard cannon. It runs off propane so he doesn't have to worry about it not firing and because he can't use a hand pump (so pneumatic isn't even an option).


If he wants to use CO2, so be it, I was just going off what I read.
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Last edited by MrCrowley on Sat Feb 23, 2008 3:33 pm, edited 1 time in total.
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Unread postAuthor: TurboSuper » Sat Feb 23, 2008 3:32 pm

MrCrowley wrote:
TurboSuper wrote:I find the whole concept of a combustion a bit unwieldy for launching a ball for a dog. I'd just rig up some sort of spring piston pneumatic sort of deal.

If you bothered to read, you would realise pneumatics are out of the question.


Because he doesn't have a pump...that's the beauty of a spring :D

Just a straight tube, place some check valves behind the tennis ball and a piston behind that. When you draw the piston back against some sort of spring, it will pull air in through the check valves and then just release to fire.

It won't go very far...but my understanding is that you don't want to send it into space anyways.

On that note, you could just make a slingshot...
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Unread postAuthor: MrCrowley » Sat Feb 23, 2008 3:34 pm

What? Like an air rifle, that would be huge :shock: :)

Edit: Just saw your edit, nevermind.
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Unread postAuthor: D_Hall » Sat Feb 23, 2008 3:38 pm

Yeah, if he can't pump, I doubt he can cock a springer.

As for the OP's dimissal of pneumatics in general... I can't save people from themselves. I can only offer realistic solutions given rational constraints. His constraint is not listed with a real world reason so I can only assume that it is due to an uneducated bias. Thus, I can attempt to educate him. ;)


(And that little bottle I use? It will also take 12 gram CO2 cartridges.)
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Unread postAuthor: MrCrowley » Sat Feb 23, 2008 3:40 pm

I 'spose he could always go for 12gm CO2 cartridges if the guy doesn't mind paying for them, they run out pretty quick.
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Unread postAuthor: D_Hall » Sat Feb 23, 2008 3:56 pm

Of course, the obvious solution that's been neglected in this thread....

BUY a dog trainer. You don't get to throw tennis balls (instead get a bean bag of sorts), but....

http://www.gundogsupply.com/-970-.html
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Unread postAuthor: MrCrowley » Sat Feb 23, 2008 4:20 pm

Only in America... :D
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Unread postAuthor: jackssmirkingrevenge » Sat Feb 23, 2008 4:36 pm

D_Hall wrote:Of course, the obvious solution that's been neglected in this thread....

BUY a dog trainer. You don't get to throw tennis balls (instead get a bean bag of sorts), but....


Note: The Retriev-R-Trainer should only be used with dogs which have already been satisfactorily conditioned to gunfire.


I believe noise is an issue in this case, a long barreled combustion would certainly be quiter than a rimfire blank.
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Unread postAuthor: jimmy101 » Sat Feb 23, 2008 6:45 pm

Boosting the propane to ~8% will still fire but the change in performance is going to be pretty negliable. (And it'll get finicky as you get too close to the flammability limits.) The same applies to lowering the % propane, it really won't change the perforamnce all that much.

Cutting the barrel down will make it too loud.

Porting the barrel is a possibility.

A ball valve is a possibility, but there are probably other was to accomplish the same thing.

Use undersized ammo, that'll drop the velocity because of the increased blowby around the shell. It'll also quite the gun a bit.

Heck, maybe just drill a 1/2" or so hole clean through the tennis balls. That'll both quite the gun and drop the muzzle velocity.

You might be able to just insert a couple of fine metal mesh screens (like bug screen) lengthwise inside the chamber. The high surface area and heat capacity of the mesh should rob the gun of a heck of a lot of it's power. Of course, you have to keep the screens away from the spark gap.

You could insert some hunks of stryofoam (or wood, or ...) in the chamber to decrease the chamber volume.

Does the gun have a cleanout plug? Perhaps bolt a hunk of wood to the cleanout plug so that when it is installed it significantly reduces the volume of the chamber.
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Unread postAuthor: singularity » Sun Feb 24, 2008 11:10 am

im thinking the best plan of action here is just to reduce chamber size by cutting off the old clean out and buying a new one for what like $5 and putting it back on after shortening the chamber about 6 inches. then i suppose i should port the barrel toward the end of it.

the 12gram co2 cartridge was considered but decided it was unsafe after considering the following fact/situation...

lets assume the guy i sold this thing is sitting in his back yard with his friends then somehow he brings up the topic of this cannon i made for him. so he goes inside and gets he cannon and shows his friends how cool it is. they fire off a few shots after charging it with one cartridge a shot. they are all equally impressed but then one of them gets a brilliant idea, what if they charged one shot would two cartridges... eventually they are up to like 4 or 5 cartridges per shot and by now the PVC is ice cold due to the expanding CO2 and eventually it explodes. then one of the neighbors calls the cops because there was a loud noise (note that the neighbor wouldn't have even checked to see if anyone was injured they just don't like loud noises, this is crucial to understanding how assholic people in this town are), they freak out and make some huge deal about it and tell everyone (by everyone i mean the dozens of bystanders who have gathered by now cause this town is so boring theres nothing better to do) how dangerous spud guns are (disregarding the fact that you need to be atleast a level 23 moron to make one explode) then somehow the mayor of whoever runs this terrible place hears of the event and make it his/her duty to rid the town of spud guns in some pathetic and desperate attempt to gain the support of paranoid moms... basically a bunch of dumbasses freak out and run around like chickens with there heads chopped off

... thats is why i didn't use 12grams, and the guy im building this for didn't have a air compressor and buying one for this single purpose probably wouldn't be worth it in his mind.

i do wonder how effective the screen idea would be might jut have to try it on a smaller scale
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Unread postAuthor: jimmy101 » Sun Feb 24, 2008 6:02 pm

Singularity

Give the metal screen a try before you chop the gun up.
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