I participate every year in a huge water balloon battle. The clash happens between two universities so you can imagine that the commitment, at least for some people, is quite high. To give you an idea last year some 40000 (thats 40e3) water baloons were thrown, plus there were some home made war machines, namely a catapult, a trebuchet, some arquebuses running on compressed air and such. Safety is of course the primary concern and nothing more than water/water balloons has ever been thrown.
I want to build a water cannon and I would love some advice/ideas. What do I mean by water cannon? I mean a machine capable of throwing a lot of water, from 1 to 3 litres, at some 20 metres at least, in a shape like a cannonball rather than a stream.
Is it possible for a "blob" of water to maintain its shape after being shot in the air at some speed, at least for a limited range? I see two challenges: accelerating the water and "keeping it together" while in the air. The latter can be achieved with a plastic container (such as a balloon), while the first part may be trickier. Balloons tend to rip and explode if accelerated too much, while leaving the balloon out may make the second challenge impossible.
The design I am considering could have a huge tank connected to a smaller one that serves as the "firing chamber." You fill the firing chamber, then close the line between the tank and the firing chamber, then you open another line that launches the water out through a barrel. The idea is to use compressed air but my main concern is that the water will not maintain a "ball" form while in the air.
The best solution for me would be one that works within the constraints for the water balloon battle.
- About 100 € material cost.
- No fire is allowed in the propulsion system, compressed air is fine but no electric compressor is allowed so efficiency is a must. Our arquebus could fire a lemon sized balloon some 50 m away on about 2 atm.
- Safety is absolutely the primary concern. For no reason at all there can be risks for the operators or the opponents. We experimented with a firing shell with our arquebus because friction with the barrel would destroy the balloon, and the shell was secured to the barrel with many redundant wires to be sure not to fire it too.
Workforce and time are pretty unlimited if the project is cool. We have some very high manual skills and quite a lot of common and not so common tools.