Optimizing a Flamethrower Battlebot

>>1086071
pressure is really the only thing, more pressure and you'll see less spread, more focused combustion

you could try adding oxygen and shaping the explosion against a target surface, but it wouldn't be a flamethrower at that point

you could also try using liquid combustibles for a napalm effect

>>1086089
Liquid combustibles/napalm are illegal.
I'm new to combustibles, is oxygen added by just exposing the gas to outside air before igniting? Or would it need to be mixed via an oxygen tank?

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41KB, 1250x403px

>>1086071

I very much doubt a servo will have sufficient force.

Any way, you'll need a venturi behind the nozzle to get a hotter flame.

>>1086103
Ah ok. I'd have to make sure that's legal. But assuming it is, at what point is the gas ignited? Is it inside of the cylinder? Or right as it exits?

>>1086127

At the exit of the venturi tube, the tube pulls in air together with the fast moving gas flow and mixes them.

>>1086071
Go watch a video about Bunsen burners, haven't you used one at school?

Yellow flame is because of incomplete combustion, there isn't enough oxygen (air) in the chemical reaction during combustion. There is a little hole at the bottom that you open that lets air in that mixes in the tube bit meaning there is enough oxygen to burn completely. The air is sucked in thanks to venturi effect.

If you look at the burner on a blowtorch you see exactly the same thing, there are little breather holes that let air in to mix before it burns out the end. If you cover them up it will start burning yellow sooty flame from incomplete combustion.

You don't want to pump oxygen in because 1) it's over complicated 2) it's dangerous. Butane burns right? If the flame somehow burned back into the tank it would go boom right? Well no you need oxygen for fire, consider the fire triangle you need fuel heat and oxygen. There is no oxygen in the butane cannister so it won't blow up because there isn't oxygen. But a tank of oxygen does have oxygen. A flame will propagate down an oxygen line and the tank will explode and you will die.

That's why if you want to build a liquid flamethrower and you need to pressurize it to make it flow you don't use air like a water gun because then it has oxygen in the tank to support combustion in the tank and that's exactly what you don't want, so you use something inert like nitrogen or carbon monoxide to pressurize the fuel. But we aren't doing that so forget it.

So what you want is a small nozzle to mix oxygen like a bumsen burner or a blowtorch. The important question you .

>>1086150
should be wondering is if the fuel and air mixture is mixed in the nozzle then why doesn't the flame propagate into the nozzle? Well I'm not exactly an elemental physicist or chemist so I don't know for sure. I heard a few people say that the pressure keeps the velocity of the gas higher than the speed of the flame. That to me is stupid because the flame doesn't stay where you light it, it travels down to the mouth of the nozzle doesn't it? So I guess that thinking back to the fire triangle the metal nozzle is able to dissipate enough heat from the flame that combustion can't be supported inside the nozzle because its not hot enough. Pretty sure that's the principal that Davey safety lamps and certain flame arrestors work on anyway.

If you want something small and relatively harmless to experiment with get some of those bbq gas lighters with the long nozzles and try making a venturi mixer for it, is small enough that you won't be picking bits of your house out of your face if it goes wrong.

>>1086071
spiral tip

>>1086156
Thanks for the tips. But yeah it's just a 3lb not so hopefully not too much death.

>>1086156

> should be wondering is if the fuel and air mixture is mixed in the nozzle then why doesn't the flame propagate into the nozzle?

The speed of the flow and the heatsinking from the metal tube prevents the flame-front to get into the venturi tube, the gas simply can't get hot enough to burn.

>>1086200
I did mention the speed of the flow but I think its a red herring otherwise you could light the gas an inch above the opening and the flame would stay there instead of burning down to the opening.
But yeah the heat thing I think its onto a winner. I do have two blow torches somewhere but I'm not suicidal enough to try heating the nozzle of one with the other to see if I can force it to propagate

Or forget safety (its on a remote system wear some goggles) and make a thermal lance. Look up "bacon thermal lance", i think pepperoni sticks would work good.

>>1086103
>I very much doubt a servo will have sufficient force.
servos can push 20 kgs... they are strong enough