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Propane powered bbmg has no power

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 powered bbmg has no power

Unread postAuthor: c19o » Thu Oct 18, 2007 7:12 pm

Today I bought a propane adapter and mounted one of those disposable propane canisters on my bbmg. It had one very short powerful burst but then
it was just coming out very slowly. I turned it upside down and it shot pretty good for a second but the liquid propane froze my blowgun :( . Does anyone know how I could fix this so it actually works? I made the hole in the adapter slightly bigger with no effect. Oh and it says 120psi when i pressure tested it.

<O>_<O>
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Unread postAuthor: HaiThar » Thu Oct 18, 2007 7:17 pm

I'm guessing that it got too cold, condensated, and your pressure got eated by the physics monster, so work in a warmer environment? Like when the sun is shining maybe?
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Unread postAuthor: c19o » Thu Oct 18, 2007 7:20 pm

it got cold when i turned it upside down, right side up it has no power except for 1 second and it stays the same temp.
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Unread postAuthor: Dornep » Thu Oct 18, 2007 7:20 pm

What happens if you wait a few seconds between bursts?

I've also tried propane on my MP5 bbmg but it didn't work too well. Does the adapter go straight from the propane bottle to your blow gun or?

Edit.. It sounds like when you let it set the pressure builds behind the blowgun and gives a nice shot or two until the pressure starts to equalize.. I don't think the propane bottle can feed enough pressure fast enough to make a rapid firing bbmg work efficiently .....

Then again I may be wrong.
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Unread postAuthor: c19o » Thu Oct 18, 2007 7:25 pm

It goes straight to the blowgun, I also tried a pressure washer handle and it didnt seem to freeze up.

EDIT: Hmm ill go try and see if waiting like you said will work
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Unread postAuthor: Dornep » Thu Oct 18, 2007 7:38 pm

If you look at your adapter it's basically the same thing as a torch head. Your propane has to flow through that teeny tiny hole, through your blow gun and then push a BB down your barrel.

I may be way off (as I said in my last post) but I just don't think it's possible to make a bbmg perform as you would expect, with bottled propane. It might work fine in semi auto airsoft guns but full auto is another story.


I've thought about using propane in a mini-ish semi auto cannon. Instead of the propane running directly through the blow gun and into the barrel, make a small chamber about the same size as the propane bottle. Let the propane pressurize the chamber and then each squeeze of the blow gun you let a bb/marble/battery rip.


EDIT.. I would really like to see you figure this out and get it working well. I would like to use this same setup on my MP5, it would be a really cheap alternative to Co2.
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Last edited by Dornep on Thu Oct 18, 2007 7:39 pm, edited 1 time in total.
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Unread postAuthor: Fnord » Thu Oct 18, 2007 7:39 pm

Edit: looks like you beat me to this Dornep :/

The propane is not evaporating fast enough to maintain the pressure you need.

Things you can try:
Make a "buffer tank" between the main tank and the valve(It should be a couple liters).
Paint the propane tank black
Make a water jacket for the tank and fill it with warm water.
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Unread postAuthor: Dornep » Thu Oct 18, 2007 7:47 pm

_Fnord wrote:The propane is not evaporating fast enough to maintain the pressure you need.

Things you can try:
Make a "buffer tank" between the main tank and the valve(It should be a couple liters).
Paint the propane tank black
Make a water jacket for the tank and fill it with warm water.


WOW! You obviously know a lot more about propane then I do Fnord! I really like the water jacket idea. I kind of thought of the buffer tank, but not in the way you describe.. I will have to try that.
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Unread postAuthor: c19o » Thu Oct 18, 2007 7:49 pm

Tomorrow I'll see about the buffer tank and water jacket, maybe even putting the tank on a heat pad. When I get this all figured out I'll post the results and some damage pics!
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Unread postAuthor: noname » Thu Oct 18, 2007 10:53 pm

Seemed to work for me with my sidestrafer... But then again, the thing empties so damn fast you don't really have time for the tank to freeze up.
Spraying propane out of a blowgun I can spray for around 10 seconds before the flow slows a bunch.

Then again, maybe my propane's just better than yours. :lol:
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Unread postAuthor: c19o » Thu Oct 18, 2007 11:43 pm

Haha, all I need is short burst fire for my application.
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Unread postAuthor: experament-u2 » Fri Oct 19, 2007 12:45 am

adding a long hose between the propane and ur blow gun would help or adding an expansion chamber/buffer tank ether way i dont think you can get a constant stream but burst fire would be fine
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Unread postAuthor: c19o » Fri Oct 19, 2007 1:11 am

would a 3ft long 1/4" hose work?
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Unread postAuthor: Acdcmonkey1991 » Fri Oct 19, 2007 9:44 am

Yes that should work but you still might want to ad a 6 in. length of 2 in. pvc in the middle, as that would help a lot.
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Unread postAuthor: williamfeldmann » Fri Oct 19, 2007 11:05 am

First off, are we talking about the little Coleman green camping stove propane tanks? If we aren't, I am crazy confused.

Why would adding the hose help compared to adding a buffer pressure chamber? I would think the tank, once charged would provide better flow than a hose.

And why would adding a small piece of pvc in the middle of the hose help the hose method? I don't understand the purpose of this, please explain.

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