Combustion powered weapon

[maddox10]

Simplest point. The build rules allow for it.

Event organisers, venue owners and HS&E have another idea

[Daniel Vernall]

Indeed, I'll keep my designs and try and see if any event guys allow it in future thanks guys

[RoboLibre]

A list of food for thought...

fit it with a thick walled plastic fuel tank.
encase the fuel tank in 10-20mm of silicone for impact resistance. also flame resistant.
locate the tank in a well protected part of the robot, preferably with steel armour.
if using a vapour vent on the fuel tank, use a double baffled vent with flash back retarder, in-case vented vapors ignite. you could also use an expansion chamber instead.
use armoured fuel line, or run a heavy duty fuel line through a stainless steel home shower flexihose. firmly secured along entire route.
vent exhaust fumes through a catalytic converter. xD

being a tad more serious, I do see a bit of a potential issue with flammable liquids escaping and catching fire.
but I do agree this would be an interesting avenue to explore, and that "technically" it does fall within the guidelines.
If there are robots using petrol as a fuel, then there should be no reason why it should not be allowed in a static weapon at those same events.

I'd definitely hang onto your designs, and personally, I'd build the damn thing anyway, just out of interest, haha