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Those evil , evil squirt guns. sheeeesh heyNeeds a bayonet lug, too..... Don't tell Diane. |
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That's what always stop me from making home-made flamethrowers, fear of the fire traveling up into the tank and the thing blowing up in my hands. Any science/engineering types out there have any input on preventing this in homemade designs? Like some hard numbers for common substances like gasoline/wd40/alcohol on minimum velocity and volume limitations in order to gaurantee the flame can't back up into the tank? Also, is there some ingenious valve design out there that will allow a flammable liquid to go in one direction but won't let fire go back the other way? Inquiring minds want to know... |
Checkvalve? There'll be a lot of trouble if these kids ever figure out you can buy WD40 in a bottle.  Or that Kerosene would probably work as well.
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Well, a checkvalve would prevent backflow of the liquid itself, but not the flame. It is possible for the liquid to be flowing outwards at some speed while the flame moves "up" the stream of liquid in the reverse direction, if your flow speed is slow enough. The problem is I don't know what "slow enough" is for various flammable liquids. |
THAT IS AWESOME!! gonna have to try that some day! lol jk
Check Valves like stated above will work. The link above has the best directions, but substitute the PVC with an old fire extinguisher(SP?) if you want it to last forever. I followed the directions in that link to make a "super soaker" for shop-fair at school, all you need to make it into a flamethrower is denatured alcohol, and a the torch. |
As long as your source tank has no "air" in it, the flame can not travel back up the "hose" to the source container. My propane flame thrower:  (If you want a 100ft stream, just flip the propane tank upside down so liquid propane comes out. It over exposed my camera every time, so no pics.) The propane bottle only contains propane as a liquid and a gas, nothing to let it burn. I figured this out the hard way by putting a sparkplug into a propane tank and trying to blow it up, lots of spark, no explosion. Filled it with 1/2 propane and 1/2 air, big boom. |
Ah yes I forgot about the oxygen part, doh. So assuming your fuel needs oxygen to burn, and most I would use do, all I need to do is put in a check valve and make sure there's a decent length of narrow tubing between the checkvalve/nozzle and the tank (which would of course have air in it). If you really wanted to get fancy with the safety features, you could even pressurize it with some other nonflammable gas instead of regular air, just in case somehow bubbles went through the line or something. |
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