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Propane Semi Auto Spud Cannon Design 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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Propane Semi Auto Spud Cannon Design Help!

Unread postAuthor: spudnutbutthut » Wed Aug 05, 2009 6:42 pm

Image

1. 2 inch barrel

2. 2 to 1 in. reduction for sprinkler valve

3. blow gun

4. propane hooked up to chamber with hose

5. 1 inch sprinkler valve

6. 3 inch chamber

7. 1 inch to 3 inch increase for chamber


Will this design work? I want to have a semi auto bazooka that will shoot at leat a round every 2 min without pumping!

First of all how does a sprinkler valve work? I wanna buy a modified 1 inch valve but how do you attach the blowgun?

Is it ok to have the 3 in chamber flow into the 1 inch valave out into the 2 in barrel?

Will the propane hookup fill the tank? And once the tank is at 120 psi will the propane stop filling? Cause thats the pressure of propane. It wont be able to go over 120 and explode right?

IUl be shooting nerf rockets! For airsoft ;)
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Unread postAuthor: hi » Wed Aug 05, 2009 7:04 pm

not. if you ignite propane into a sealed chamber, it will expand, then it will go back the pressure it was at. it will not expand and stay pressurized.

even if it did, you would only get one shot because a sprinkler valve would release all the pressure and you would have to vent it out before you were able to ignite more propane.

a sprinkler valve is just a diaphragm valve that works off of pressure differences. the top side has more pressure than the bottom because the bottom has a part that is not pressurized. when you release the air from the top via either with a solenoid valve or a pneumatic valve, you change that pressure difference and the bottom has more pressure than the top, which causes it to open.

it it were that easy everyone would make one... :roll:
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Re: Propane Semi Auto Spud Cannon Design Help!

Unread postAuthor: Technician1002 » Wed Aug 05, 2009 7:09 pm

spudnutbutthut wrote:Image

1. 2 inch barrel

2. 2 to 1 in. reduction for sprinkler valve

3. blow gun

4. propane hooked up to chamber with hose

5. 1 inch sprinkler valve

6. 3 inch chamber

7. 1 inch to 3 inch increase for chamber


Will this design work? I want to have a semi auto bazooka that will shoot at leat a round every 2 min without pumping!

First of all how does a sprinkler valve work? I wanna buy a modified 1 inch valve but how do you attach the blowgun?

Is it ok to have the 3 in chamber flow into the 1 inch valave out into the 2 in barrel?

Will the propane hookup fill the tank? And once the tank is at 120 psi will the propane stop filling? Cause thats the pressure of propane. It wont be able to go over 120 and explode right?

IUl be shooting nerf rockets! For airsoft ;)


Safety first; not last..

Safety first.. Then work on design.

Propane vapor pressure is directly related to the pressure for a liquid.

If you are assuming 120PSI, then you are thinking dangerously.
Please do some research.. Start with a Google search for Propane Vapor Pressure.
The pressure is close for a 72 degree F tank. Holding it in a warm hand or a warmer day may spell disaster.
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Unread postAuthor: hi » Wed Aug 05, 2009 7:19 pm

i didnt realize you were using a charged propane tank. i thought you were trying to make a semi auto combustion. in that case, yes, it would probably work, but you would be breathing a lot of propane.what tehcnition1002 said is important.
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"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
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Unread postAuthor: spudnutbutthut » Wed Aug 05, 2009 8:03 pm

i wont light the propane with my hand lol, and no its not a combustion haha, or else thatd be a verrrrry bad design !

Will the propane go over 120psi? Or does it stop filling the chamber at that pressure?
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Unread postAuthor: Moonbogg » Wed Aug 05, 2009 8:34 pm

I haven't made a pneumatic myself, but just by looking at your general idea I don't see why it wouldn't work at least to a reasonable extent. It looks like you just want to make a typical pneumatic and use propane tanks as your pressure source rather than a pump. I don't know how many times the chamber will fill at a decent pressure though. Maybe someone with all those crazy math/chemistry/pressure stuff skills can tell you that.
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Unread postAuthor: spudnutbutthut » Wed Aug 05, 2009 8:44 pm

cool, is it ok to go from a 3in chamba to a 1 inch valve and hoe does a sprinkler valve with a blogun work!
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Unread postAuthor: irisher » Wed Aug 05, 2009 8:51 pm

I have used propane to power pneumatics before and you most likely will not get 120 psi out of a small tank.I also would like to remind you that unburned propane reeks.
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Unread postAuthor: spudnutbutthut » Wed Aug 05, 2009 9:05 pm

i know the smell is part of the fun lol, tell me more bout your design please, I dont need 120 ps im just asking if the gun wont pressurize of the pressure of the propane bottle!?
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Unread postAuthor: irisher » Wed Aug 05, 2009 9:09 pm

The tank will fill your chamber but I usually got 60-90 psi.My fill method was a propane torch head with the nozzle cut off and 1/4 hose clamped on it.
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Unread postAuthor: deathbyDWV » Wed Aug 05, 2009 9:10 pm

Your design will work. I have seen other cannons like this that work. Look in the help section and there is a thread on how to modify a sprinkler valve. You're only problem will be that as propane expands it cools and produces less pressure. Taking shots 2 minutes apart will probably be fine. Just make sure thaty there are no sparks or flames nearby. Even if all goes wrong and it does ignite, It should not explode as long as you use all pressure rated parts. Also this is the link to the propane vapor pressure: http://www.spudfiles.com/spud_wiki/index.php/Propane
Hope this helps and good luck!!! :D
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Unread postAuthor: irisher » Wed Aug 05, 2009 9:13 pm

If you don't want a cloud of propane hanging about you then you might want to consider a ignition source on the muzzle.It also looks sweet :twisted:
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Unread postAuthor: deathbyDWV » Wed Aug 05, 2009 9:18 pm

I had never thought about lighting the muzzle blast. That is a good idea and might be safer than having the cloud of propane that could light accidentally. :shock: And it would look sweet!!! :twisted:
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Unread postAuthor: irisher » Wed Aug 05, 2009 9:21 pm

You have to be careful when lighting it because the flames will sometimes light your muzzle on fire.
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Unread postAuthor: spudnutbutthut » Wed Aug 05, 2009 9:27 pm

no way am i lighting anything close to the propane tank, it seems safe in theory but its more risky than running around in a cloud of propane, in airsoft not many people cause firstion fires etc. This will be sooooo cool if it works!

If i shoot once every 2 min how many shots you think i could get off?
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