Homemade Flamethrower - Page 2 - Tilted Forum Project Discussion Community

ForgottenKnight · 04-17-2005, 02:51 PM

That's impressive!

But definately a "don't try this at home" thing.

blahblah454 · 04-17-2005, 08:08 PM

Wow great video, that thing is just mean! I especially liked the backing track for that video, very classy.

dashdot · 04-19-2005, 02:30 PM

Quote:

Originally Posted by MooseMan3000

Now, unless I'm mistaken (which I may be - don't take my word for it) the gas tank can't simply "combust." If you fuck up a seal, the most you'll have is unintentional discharge, in the wrong direction. Now that could be pretty bad too - imagine, if you will, being shot in the back by your own tank. However, the ball of death described as above shouldn't happen. Gas doesn't work like that - it has to be misted into a piston chamber to explode correctly, and that doesn't change if it's in a backpack.

The problem is, when the fuel runs low, the tank is almost *exactly* like an engine cylinder, only with MUCH more fuel, and under MUCH more pressure.

Whenever the fuel level gets to a point where air is escaping along with the (now) atomized gasoline, flashback is quite easy. And once it reaches the tank, well, someone gets injured. Badly. And since that someone would be me, its double bad

The reason military flamethrowers didn't have this problem is because they used a flammable gas, usually butane, to pressurize the fuel tank. Seems counterintuitive, but it works because while the butane will burn, it can't trace back very easily without oxygen. So when they ran out of fuel, their flame characteristics changed because it was shooting burning butane rather than burning gasoline.

Now, my worries would be greatly reduced if I got a tank of Argon or something inert that doesn't allow things to burn (no oxygen). Or, I could just say to hell with it, hook up a 100lb tank of propane to the sucker, and be done with it.

Regarding flamethrowers made out of squirtguns and pvc pipe: Bad idea.

I wish those videos had never been made. Somebody HAS to have hurt themselves trying to imitate that. While I can't say that what I've done is safe, or sane, I did know the dangers before I built it. Also, I've never used it indoors, or near anything living that didn't agree to be there after I told them about the possibility of it blowing up.

Bagezio2 · 04-22-2005, 07:32 PM

hmm.. i feel bad for anyone who tries to rob your house!!! lol.. that sure is a story to tell in jail...
''damn man what happened to you!!"
"i was robbing a guy's house and he pulled out a dam flamethrower on my ass!!"

dfings · 04-23-2005, 06:40 PM

dam, i want one of those

Blackthorn · 08-31-2005, 07:24 PM

I mentioned this to a friend last night so I had to come back here and do a search for "flame thrower"

This is still amazing...

Daniel_ · 09-01-2005, 01:27 AM

Gulp - I'll keep out of your yard, Sir!

aquinzani · 09-02-2005, 11:32 AM

It looks like fun, but I think I'll stick with Molotov cocktails. I can throw them far enough so the burst is away from me !
flame

Quote:

Originally Posted by dashdot

I've been lurking around here for quite some time, but haven't posted anything becuase I didn't have anything to say. Well, I made something I could talk about.

<a href="http://dotd.net/fire/flame.wmv">flamethrower!</a>

Note: I don't know how well my host can hold up. They're pretty pathetic at times.

The fuel tank is a 20lb tank, not 30 as the video says (typo, too lazy to correct it).

I've fueled and fired this thing 5 times so far. It is quite a sight to see in person. I usually fill the tank a little over halfway, to maintain pressure. With the compressor attached to it, it can maintain pressure for the full burn time. That video only shows the tank pressurized to about 90psi tops though. Maximum is 135psi.

The hose is a Buna-n hydraulic hose and all connections have gas-safe (as I was told, and as experiments in a bucket of gas have proven) threadlocker on them. Everything is rated for at least twice the pressure it is under.

The fuel tank has an air inlet and gas outlet at its top. A pipe internally extends down to the bottom of the tank to siphon the gas out.

The gun assembly is a pressure washer gun with about 12" of brass pipe that terminates in a check valve, then the nozzle (1/4" nozzle in this video). The gun was also left partially open in a bucket of gas for 24 hours and the seals did not degrade at all.

Since this thing is essentially a fuel air bomb, flashback is a huge concern. I haven't been able to find a flashback arrestor for use with a liquid like gasoline. Any suggestions on where to get one?

Total cost: Under $160.

Beyond that, any ideas for improvement?

Disclaimer: This is probably one of the most dangerous things you could ever make. Don't make one, don't try to make one, don't think about making one.

EXTRA DISCLAIMER!!

If ANYONE of you is stupid enough to try this, don't come crying back here.

This is probably one of the MOST dangerous things I've seen posted, because one simple mistake or screw up and you've made a full air bomb that can demolish a house or you've set yourself on [b]fire[b], which as I understand, is a particulary painful way to die (I hear that survivors actually wish they had died).

So please, don't make TFP the next example of "Guy does something stupid he read about on the internet, so lets censor the internet".

-lebell

EXTRA, EXTRA DISCLAIMER!

Original poster here. Once I saw the above disclaimer, I thought it prudent to add this bit extra:

If something went wrong with this device, it WOULD explode. And the above disclaimer's statement about a house being demolished is entirely true, and maybe even conservative about this thing's destructive power.

Taken from http://home.earthlink.net/~jimlux/energies.htm:

Gasoline has an combustion energy of about 47.4 MJ/kg, so a simple calculation will show that the cup (170g) will release about 8MJ when burned. When vaporized and mixed with air at the optimum ratio (stoichiometric), the mixture will occupy about 2100 liters, or a sphere some 0.80 m in radius. Assuming the mixture is ignited at the center of the sphere, it will take about 2.5 milliseconds for the flame front to propagate to the outer edge. This makes the assumptions that the flame front moves at the speed of sound (probably reasonable), and that the sphere of mixture doesn't expand appreciably due to the heating in the middle (probably very optimistic). So, 8 MJ in .0025 seconds is 3200 MW, or 3.2 GW

3.2 GIGAWATTS. That site states that a 3000lb car hitting a concrete wall is only 2.1 MEGAWATTS. This fuel tank exploding will incinerate you.

DO NOT DUPLICATE THIS PROJECT!!

wdevauld · 09-02-2005, 01:21 PM

That is fucking awsome!

handsolow · 09-05-2005, 06:38 PM

I think I -need- one of those!

Mr Honest · 09-09-2005, 01:34 PM

Pah, coward wearing that suit

Looks cool though.

I once set fire to a small forest when I was a kid. Didn't need a flamethrower. A match isn't classy enough though. Home made bow and arrow, arrow head in turps, light and fire quickly. Ouch! I was only 10 so forgive me

I'm sure if there's a hell then I'm going to the green one where trees stamp on me forever like our of LOTR

04-17-2005, 02:51 PM	#41 (permalink)
ForgottenKnight Jesus Freak Location: Following the light...	That's impressive! But definately a "don't try this at home" thing. __________________ "People say I'm strange, does that make me a stranger?"

08-31-2005, 07:24 PM	#46 (permalink)
Blackthorn Beware the Mad Irish Location: Wish I was on the N17...	I mentioned this to a friend last night so I had to come back here and do a search for "flame thrower" This is still amazing... __________________ What are you willing to give up in order to get what you want?

09-01-2005, 01:27 AM	#47 (permalink)
Daniel_ Evil Priest: The Devil Made Me Do It! Location: Southern England	Gulp - I'll keep out of your yard, Sir! __________________ ╔═════════════════════════════════════════╗ Overhead, the Albatross hangs motionless upon the air, And deep beneath the rolling waves, In labyrinths of Coral Caves, The Echo of a distant time Comes willowing across the sand; And everthing is Green and Submarine ╚═════════════════════════════════════════╝

09-02-2005, 01:21 PM	#49 (permalink)
wdevauld Tilted Location: Calgary, AB	That is fucking awsome! __________________ As soon as you stop living, you start dying....

09-09-2005, 01:34 PM	#51 (permalink)
Mr Honest Crazy	Pah, coward wearing that suit Looks cool though. I once set fire to a small forest when I was a kid. Didn't need a flamethrower. A match isn't classy enough though. Home made bow and arrow, arrow head in turps, light and fire quickly. Ouch! I was only 10 so forgive me I'm sure if there's a hell then I'm going to the green one where trees stamp on me forever like our of LOTR __________________ Human beings : who could ever claim to like them all?

04-17-2005, 08:08 PM	#42 (permalink)
blahblah454 Let's put a smile on that face Location: On the road...	Wow great video, that thing is just mean! I especially liked the backing track for that video, very classy.

04-22-2005, 07:32 PM	#44 (permalink)
Bagezio2 Tilted Location: Astoria, Queens, NY	hmm.. i feel bad for anyone who tries to rob your house!!! lol.. that sure is a story to tell in jail... ''damn man what happened to you!!" "i was robbing a guy's house and he pulled out a dam flamethrower on my ass!!"

04-23-2005, 06:40 PM	#45 (permalink)
dfings Upright	dam, i want one of those

09-05-2005, 06:38 PM	#50 (permalink)
handsolow Upright	I think I -need- one of those!