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A few questions..

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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A few questions..

Unread postAuthor: Mailbox12 » Sat Nov 08, 2014 4:50 pm

I am going to attempt to make a calcium carbide cannon, and have a few various questions.

1. Fuel - Air ratio
I have heard that Calcium carbide + water (Acetylene) has a wider range of percentages/ratios in which it will ignite. Is this true?
What would the most efficient ratio range be, and how would one go about measuring the reactants to obtain such ratios? I assume that the water would be the limiting react, and the calcium carbide would be the controlled / measured substance.

2. Force
Just how strong is calcium carbide? Say the cannon I make has a combustion chamber with a volume of roughly .5 gallons or 1.89 L, and a somewhat efficient fuel-air ratio is used. Would it be able to launch golf balls 100-300 feet?


3. Projectile
I have spent some time looking for what most use for their projectiles, but haven't found a great thread on it yet. Looking for something round, compact, and between 1 - 1.5 oz.


4. Loading
Say I was going to make a cannon to fire golf balls, and the build of the cannon was a single PVC pipe barrel directly connected to the combustion chamber with an adapter piece of some sort. In order to keep the golf ball from dropping into the combustion chamber when loading through the muzzle, could a wire of some sort be threaded across the barrel somewhere and glued on either side or pulled through the pipe via drilled holes then glued or filled?


5. Water Pump
Thinking about using a cheap ball pump hooked up to tubing and some one way ball valves to insert the water into the combustion chamber. Anyone ever done something similar to this? How did it work out? Maybe a syringe of some sort would be a more accurate way?


6. Operating
Between shots, will the gases need to be cleared out of the cannon in a calcium carbide cannon like Aerosol cannons?

Also, assuming water is the excess reactant when forming the Acetylene, will water be left inside of the combustion chamber after firing? Sort of a dumb question I guess, but just need to clarify.


Thanks in advance! :mrgreen:
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Re: A few questions..

Unread postAuthor: Mailbox12 » Sun Nov 09, 2014 4:13 pm

If you can answer just one of them that is fine as well..
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Re: A few questions..

Unread postAuthor: BowerR64 » Mon Nov 10, 2014 5:48 am

I started little, a friend of mine had one of those older pot metal cannons you can buy from amazon called big bang cannons. I just inspected its size and the amount of carbide used and built something similar. I then searched online and found all different sizes youtube is where i found the best plans 2 kids and their dad gave an awsome tutorial giving sizes, lengths and even demonstrated how it worked firng it several times after the build. I built one and i was shocked how loud it was scared the hell outta me to be honest. The smaller ones are no slouch they can be quite shocking as well

I then found some more links and articles where a few guys were building some way larger shooting tennis balls, a few used foam cut out to fit inside the barrel then cut out to fit the tennis ball. Im thinking they were using 4" or 6" and making these sort of plugs that split in half and they split apart after leaving the muzzle.

IMO the problem with using a golfball is the weight of the ball. The tennis ball is light enough that it doesnt need to be a perfect tight fit so you get some blow by which imo is better with this stuff. I dont really care to shoot anything from my cannons because the projectiles arnt cheap but they are louder shooting them and thats what im going for maximum noise. A heavy projectile will increase the pressure and i dont want to push this stuff.

I dont know of any way to measure the mix, its kinda like the hair spray cannons you just kind of guess. I will say this in my early testing i did notice that when i used to much carbide it left more black suit inside the cannon so if you just pay attention to the inside after you fire it how much smoke lingers inside you know how much to use.

I didnt find the water to be very critical on its power or noise, the more you use the more volume the water robs from the chamber, the more you use the more shots you get before you dry up, to much starts to spit out the barrel. This stuff stinks so you dont want it flying out.

My designs i used larger chambers with a taper, i found a taper also helped to generate more noise so i used a nail or a door hinge to block the barrel so the projectile didnt fall down into the chamber. I started with marshmallows light, cheap and they seem to be made in sizes that fit into the smaller pvc. They also didnt blow holes in my walls when i was testing them indoor. Nerf foam darts fit but the power of these cannons blew the foam apart the marshmallows held up way better.

So far ive yet to have a failure but im not saying it cant happen. The most ive shot one is a shorter 4" to 3" barrel thunder mug looking one i buit with a little handle ive put close to 30-40 shots threw it mostly shooting 3" tennis balls. I then gave it to a friend of my dads and im not sure now how many shots its had.

all of my larger ones 3" and up i used SCH40 but ive seen a few youtube videos where a few used DWV the thin green stuff. I wouldnt recomend that. They used a straight pipe though it had no taper so im sure the pressure is lower. A video of a group of people shooting cannons near a lake. It was setup on a golf caddie and had 2 holes drilled in 2 different spots to change the burn mix. They used to much carbide once and it wouldnt fire in the bottom hole using a BBQ point a flame so she moved up to the hole further up the barrel where the mix was leaner and it then fired. Idea i never thought of but will try on my next builds.

Ill admit there isnt alot of info about this stuff the US seems scared of it but if you search different spellings like karbid or karbit or something you will find videos where they use this stuff ALOT in other countries and they have it mastered. Shooting soccer balls from old milk jugs, launching trash cans and stuff there are more videos from their country then ive seen anywhere else.

Other questions, like i said with projectiles i chose tennis balls i found a 3" kid size at walmart rolls in and out easy not a tight fit in 3" PVC there is another smaller ball i found for small dogs called "Chuck it" they roll down a 2" the same as the 3" they are more firm and way more durable.

i usually leave the water in the cannon, i put say 1-2 cups into the chamber and just shoot it several times then replace it after a while.

the air is the limit just like other fuels your limited to the 20% oxygen in the air, the cleaner the air the better it burns so cleaning it out each shot is better but if you design it right just opening it to reload it is enough.

for a .5 gallon start with 1/8 tsp of carbide and about 10-20oz of water. Try half the 1/8tsp then try a full scoop, dump it into the water and give it a 15 second count to build the gas then fire. 15-20 seconds is what i like to use as a count down it gives others time to get back, plug their ears and to be aware of whats about to happen. If you lose count or have to stop dump the water, air it out and start over. Dumping the water doesnt make it safe though the gas can still linger in it. Also after a shot the gas can still continue to build so ALWAYS expect a second shot. Always consider it loaded and ready to fire

be safe

wow sorry this was so long, and sorry for my spelling and punctuation errors.
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