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Proposed Carburated Bolt Action Cannon (Need Feedback)

Built a combustion 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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What is the probability of this design working?

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6
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Low
7
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Total votes : 13
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Unread postAuthor: starman » Sat Jan 26, 2008 12:10 am

rcman50166 wrote:
starman wrote:Another thought... if you could somehow harness some of the combustion power enough to "auto pump" the chamber...you could automatically evacuate and aspirate the chamber...potentially setting up an auto-fire capability. Of course, PVC would never hold up to the heat build up of an automatic gun...have to do it with steel or aluminum.

Something to think about....


Well congratulations you just thought up the internal combustion engine in a sense.


Sarcasm noted and appreciated....:-)

Actually this very idea with air/propane has been floating around in my head for a couple of weeks so when i saw someone had actually put it down on paper and thought out a reasonable working solution, I got excited. Thanks for sharing your work.

The animation looks great. I see no reason the concept shouldn't work. What are you waiting for....:-) My only reservation is the big check valve in the middle, if it will act as too much of a blast restricter and operate fast enough. BTW, the overcome pressure of the check valve in the flow direction is on the order of 2 PSI. Also, the gas setup may be tricky but I'm sure it's ultimately doable.
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Unread postAuthor: rcman50166 » Sat Jan 26, 2008 11:49 am

ugh... always with the propane. I dont have the mony to buy that stuff. My personal income is less than a thousand a year. However if I had the money I would.

Ooo. I found a flaw in my design the back side of the piston doesn't have a pressure release port!
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Unread postAuthor: rcman50166 » Sat Jan 26, 2008 12:35 pm

Novacastrian wrote:
rcman50166 wrote:
thespeedycicada wrote:im just worried about the check valve choking flow


If I need to I'll just make the barrel longer allowing more time for acceleration.


And more time to choke the flow. sorry i could not resist.


That is true but the amount of energy loss due to the valve is greater influenced by exaust velocity. Allowing for longer periods of acceleration lowers the exaust velocity by adding more mass to the projectile. This allow the exaust gases to escape less impeded than the original setup would. Assuming that is an actual factorable problem that occurs.
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Unread postAuthor: starman » Sun Jan 27, 2008 3:08 am

rcman50166 wrote:ugh... always with the propane. I dont have the mony to buy that stuff. My personal income is less than a thousand a year. However if I had the money I would.

Ooo. I found a flaw in my design the back side of the piston doesn't have a pressure release port!


A standard 14 oz canister of propane is only $3.00 or so at Home Depot and lasts for many shots in an average cannon. A 17 lb refillable propane tank is only $15 (if you have a return) at Walmart and would more than likely support a lifetime's worth of spudding. The propane is actually LOTS cheaper than the potatos you'll shoot into oblivion. It's clean and ready to fire with good energy....lots of reasons it's become the standard advanced combustion fuel.
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Unread postAuthor: rcman50166 » Sun Jan 27, 2008 12:32 pm

What about all the valving and high pressure tubing that would be needed. Is there an estimate that you could give me on that?
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Unread postAuthor: starman » Sun Jan 27, 2008 1:28 pm

rcman50166 wrote:What about all the valving and high pressure tubing that would be needed. Is there an estimate that you could give me on that?


$40-45 or so for an unregulated meter setup, parts all available in the plumbing or compressor dept at Home Depot or Lowes. Throw in extra $15-20 if you want a basic regulator. Pre-built meters can be purchased online, our very own BCarms would be happy to set you up with one... http://www.bcarms.com/product_info.php? ... 0f659d5698
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Unread postAuthor: rcman50166 » Sun Feb 03, 2008 3:00 pm

I've seen the check valves before but have never used them in any design. I know now they are meant to alieviate any built up pressure in the system that it is attached to. (Before I thought they were a failsafe design feature to keep the fluid/gas flowing in a designated direction.) Does anyone know the max flow rate for these valves and whether their fully open position will maximize or reduce flow?
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Unread postAuthor: thespeedycicada » Sun Feb 03, 2008 4:22 pm

check valves dont have alot of flow i think this is the only thing really hindering this design.Why not take the fueling and venting and give it a separate place? like taking a homemade pump but put a carb on the intake? you elimanate the check valve choking flow and still have the pump action alot like the tippman C3.
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Unread postAuthor: jrrdw » Sun Feb 03, 2008 5:24 pm

These little pulse type carburetors take mutable pulses to pull fuel through. The primer bulb only circulates the fuel through the carburetor for easier starting, you still need multi pulses for the diaphragms to pump the fuel.

The check valve isn't the only restriction, the piston it's self will restrict the fuel from atomizing in the firing chamber. If you put check valves in the piston for fuel to pass through, the fuel will hit the valves and from drops causing puddling in the chamber.

The throttle body injector idea is all most ideal, except they need constant fuel pressure and circulation in order to inject a mist instead of a stream. Thats not mentioning the size of them, usually 5 1/2" in diameter, and kinda bulky.

Keep your eye on Briggs and Stratton, they are now useing fuel injection on some of their 25HP vertical shaft engines. If you feel like looking, they have all ready been used on Bobcat zero turn commerical mowers.
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Unread postAuthor: dongfang » Sun Mar 02, 2008 3:35 pm

Hi,

That´s a beautiful idea there.

I´m concerned too that the check valve may lose too much pressure. How about

1) Inventing a way of making the projectile act as a check valve? If you use, say, golf balls, maybe with a little precision you could make a surface that it will be sucked against when pumping the gun (refilling the chamber)

2) If that fails, just use a big PVC ball valve. It´s manual anyway..

Regards
Soren
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Unread postAuthor: rcman50166 » Wed Mar 12, 2008 2:29 pm

Well thanks. Making a carburetor work requires a near flawless seal. The ammo, to work as a valve, would need to be consistent. The intended ammo was supposed to be paintballs, so there's no promise there. The ball valve would solve the problem, but the "It's manual anyway.." statements suggests that you know what I'm about to say. The design was intened to work in a practical single action loading mechanism. The only solution is to make the valve larger I'm afraid.
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 14, 2008 1:40 am

Why not the blow-forward breech?

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You could have the piston hit a switch on the return stroke to close the spark plug circuit...
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Unread postAuthor: Jared Haehnel » Fri Mar 14, 2008 8:19 am

check valves dont have alot of flow


They make large check valves for sump pumps that won't have a huge impact on your flow...
You could look at using small carburetors like say for a model airplane engine that cost very little, weigh very little and are more accurate then lawn mower engine carburetors. They have to be since they measure out lower increments of fuel... they have a lot of adjustment too. And you don't need an air filter or a high pressure line. Gravity feed is just fine. You would have to use a reed valve...
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Unread postAuthor: Cosmic Muffin » Fri Mar 14, 2008 7:55 pm

just remember that the petrol itself doesnt combust, its the vapours that explode. so you will need to use gas (propane etc.) otherwise you will just flood the chamber. and also i would advise creating this beast from metal. i like the design, good luck :D
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Unread postAuthor: tpcaudill » Mon Apr 21, 2008 2:33 pm

i know im kinda late but keep in mind that gasoline engines must have the fuel/air mixture compressed to achieve combustion.
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