Designing a low technology flamethrower with limited resources

Question

This is an extention of these question: Using dead bodies for material 4: ammunition and Arming all untrained people with firearms, which weapon would do?

The world is suffering from the creatures of fantasy and nightmares which can appear with just a few minutes of warning anywhere, regardless of it being the middle of the street or on top of your bed while you are asleep. It can be a single one, or millions that swarm the area. The world's infrastructure has been degrading, food and supplies are harder and harder to come by. While firearms work well against these creatures the bodies left behind attract and breed both insects and disease. It is not feasible to hold on to area's with low populations as a sudden appearance of many nightmares can wipe them out.

In some settings there are some expectations that almost always feature, like airships in steampunk and dwarves with axes. In this case some of the nightmarish creatures require the ministrations of Hans and his Flamethrower.

While I could hand-wave that flamethrowers are simply produced and available I would prefer for flamethrowers to be build and maintained with the limited resources at hand, mainly dead bodies.

The question: what is the most capable flamethrower possible with a limited amount of supplies?

Conditions that apply:

• the flamethrower is portable by one person.
• approximately more than 75% of the flamethrower has to be of non-metals since those are in short supply. If that isn't possible, explain where and why your version uses more.
• the most abundant materials are from dead bodies. Any material you can get from them in large quantities is allowed.

To select the most capable flamethrower it is graded on the following, in order of importance:

• it needs to be safe enough not to burn the user in normal operation (someone bursting your tanks is not normal operation)
• it needs to significantly burn the opponent rather than leave a few scorch marks. Opponents are assumed to not wear armor.
• for the above point a type of fuel needs to be chosen, potential available fuel types can be found here: Using dead bodies for material 3: fuel
• it needs to reach at minimum 5m in distance.
• an approximate idea of the duration of one burst. Longer is better. Exception: a flamethrower like the Russian LPO-50 could not stop its burst of flame which makes extended bursts a potential problem.
• the amount of bursts
• the amount of times the flamethrower is expected to be re-used or as an alternative the rarer to obtain parts to be recycled.

I understand that a full and exact list of capabilities is nigh on impossible without building one. That is why I will be satisfied with approximate values.

Answer 1

Carve bones into a pump system, use a flab of leather for the suction.

Carve a leg bone into a hollow cane and use it to aim the fluid. Melt fat from the dead bodies and use the oils as fuel.

Use guts and penises as flexible tubes to move the fuel.

Guts are longer and need to be treated to gain resistance, penises are shorter and more resistant but can be knitted together to make a longer tube.

Use leather to make a bag for the fuel to sit in.

Results will look like a flamethrowing bagpipe made from people.

Answer 2

Metal isn't necessary at all, and bodies provide almost all the materials you need.

Most practical flame throwers operate by applying air pressure inside a tank of liquid fuel to propel the liquid fuel out and aerosolize it as it passes an ignition source. Often this means a metal tank with a either a piston or forced air blower to provide pressure, but there's other ways.

If you can harvest a few meters of skin and tan it into leather, you can build an air bladder that can be squeezed to provide pressure. Think bagpipes. With a bit of practice you can produce sustained, steady pressure for minutes at a time!

With the source of pressure solved, the next concern is the fuel. Worst case scenario you could pour gasoline directly into your leather bladder, but it won't take long for it to draw all the moisture out of the leather and render it stiff and brittle. If you treat the bladder as disposable then it's fine. A separate fuel tank would be much more practical. Metal would be good but a glass jug would work equally well. Heck, a ceramic pot or dried gourd would work too. If glass or ceramic or too fragile for your needs, wrap them in rawhide strips for protection. It'd also be a good idea to mount the tank on the user's back.

The sprayer sounds like a tough problem. Because the flame can easily work its way back along the fuel stream the sprayer needs to be long enough to give the operator a safety margin while also be fire resistant. Fortunately, dead bodies solve this too: Femurs. An adult femur bone, hollowed out to for a tube that's narrow at one end, would be sufficiently long and fire resistant. Bones will burn, of course, but won't ignite by themselves and require a lot of heat for a long period of time.

The real challenge is the hose that connects the fuel to the sprayer. It needs to be about 1m long and flexible enough to give the user freedom of movement, but also resistant to the fuel. In this case, there's not many good options aside from a rubber hose (nitrile or some other plastic that doesn't react with your chosen fuel). A rubber hose wrapped in fiberglass would be ideal.

This only leaves the ignition source. It could be as simple as a twig dipped in pitch or splinter of sappy heartwood lashed to the end of your bone nozzle, lit with a match prior to the action, but if it goes out or burns away entirely then you're in trouble. A small butane lighter would work better, but that might be hard to come by. A small ceramic pot full of fuel with a neck stuffed with fiberglass wick would stay lit for a very long time.

Answer 3

The Byzantine Empire managed to create a flamethrower with only 7th Century AD technology. It was a major tool that was instrumental in several important victories against Arabs and rebels. The formula isn't known but it probably isn't too different from napalm and you could have the people in your world recreate it by accident.