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Check it out, lucky no one was hurt.
https://www.youtube.com/watch?v=v7cQ9yE ... e=youtu.be
Careful sir, our coffee is extra hot today!
That's a nice well ventilated area you have there sir.
My point is that is styrofoam! i tried and tried and i couldnt even crack it.
I really figured the first shot would blow it apart and water would fly everywhere so i first tried it in the sink. 3 times nothing.
Ill try taping 2 cups open end to open end and then cut the bottom one out of the top one to increase the velocity and see if i can get it to split but the pressure of the explosion wont even damage these cheap cups.
1 The cup is not styrofoam. It is a drink cup, but not foam. It is a lot stronger than styrafoam.
2 The gas air mix was quite rich. It was a flammable mix, but short on Oxygen. This is noted by the length of the burn and color of the flame. The heated gas exited the cup and then burned above the cup as the gas mixed with more air. Note the location of the flame in the still.
A leaner mix would have more bang to it.
Watch someone light a welding torch sometime. Without oxygen turned on the flame is large, yellow and sooty. Add Oxygen and that all changes.
In summary, he was lucky.
Tech's #2 point is key.
Your probably generating the Acetylene gas by letting the calcium carbide sit in water for "a while" then attempting to light it? The probability of hitting a "sweet spot" for fast burn this way is pretty slim unless you practice a good bit. Look up oxygen acetylene trash bag if you want to see an example of what a stoichiometric mixture combusting looks like I've had some fun in the past using welding torches and baloons with this, but you have to be careful because the mixture can quickly transition to a detonation, and seriously injure your hearing...
Its a very thin weak styrofoam you can poke your finger threw it if your not careful. Very weak some of the weakest styrofoam you can get.
I tried several different mixes agree some were rich but if you watch the video half were also very lean and there was little to no flame.
Its the design of the containment.
Ive done other tests. I bought a weed sprayer from walmart and put the same amount of carbide into the bottle i use for my cannons figuring for the volume. Then i filled small balloons with the air and gas mix from the sprayer.
If i light the balloons just holding them in the free air they pop make a little flash but there is little to no noise.
If i take that same balloon size, air and gas mix amount and put it into a tube closed on one end then i get a very loud bang. If i put a reducer on the end of that 3" pipe it gets even louder.
To be technical, "Styrofoam" is a trademark for closed-cell extruded polystyrene foam held by The Dow Chemical Company.
It is not the same stuff as the expanded polystyrene foam (expanded this time, not extruded) that people often refer to as Styrofoam.
Does that thing kinda look like a big cat to you?
Re: Calcium carbide is so dangerous!
A 50/50 mix with oxygen is quite dangerous. a 20/80 mix with air burns slower with less energy. You won't get the same bang with air as you will with pure Oxygen. Not sure if you will get detonation with an air mix as you can with 50/50 Oxygen mix.
Its pretty cheap stuff.
New design more testing https://www.youtube.com/watch?v=cGuxNe0 ... e=youtu.be
With carbide it will never be a 50/50 mix without adding in pure oxygen im not doing that its to much work and hassle i want it easy. I dont think its a 20/80 mix either i think it only produces 80% acetylene from the carbide but these test i dont think im getting 80% acetylene maybe like 20/20 if im lucky
I changed the design but it can still be better, the opening is still to large for this volume of air. I took 2 foam mcdonalds cups, styrofoam, styrene, what ever it is and used paper tape to connect them. Then i cut the bottom off the second one the opening or muzzle end is about 2-1/4"
A .22LR shell holds about 5 grains by volume so im going to use that as the measuring guide for the powder. I think its 5 grains of water by volume.
The bang was the best when i covered the muzzle with cardboard, so the opening could be smaller for a better bang.
The part that i find amazing is that the cup has held up to the pressure, pressure enough to produce a VERY loud bang.
I wonder if i cover the muzzle and add weight slowly till the cup cracks? will this tell the pressure in pounds? It will propel small weight but it will get to a point that it cant push away the weight and the container will give and split?
Foam shrapnel seems pretty harmless
So much for that, i taped the bottom back on and cut a smaller hole, didnt help much then put the carboard over top and then it cracked. I tired some hairspray in it also to see if i could tell any difference i swear the hairspray just seems slightly less energetic.
I need a new cup now my fun is over for the day.
It is pretty hard to get a chamber to rupture when it has that big an opening and nothing significant retarding gas flow. The press on cup lid probably pops off at a fraction of one PSI above atmospheric. In other words, your peak pressure is probably less than 1 PSIG.
Heck chemistry prof's routinely ignite natural gas + air mixtures in 5 gallon water bottles. There is little risk of rupturing the bottle since the one to two inch bottle neck vents gas too fast for the pressure to build up all that much.
But why is the bang so effective?
My largest cannon has a 4" chamber about 12" long to a 3" that is also 18"
Today i shot one of them over and over about 8 times in about 15 minutes. The outside of the chamber got warm, i never shot any of them that much that quickly.
A couple things if the pipe is all one size from chamber to muzzle its loud and deep doesnt really hurt your ears like the same size does when its reduced. The pitch of the boom increases in tone when its reduced. I normally wear ear protection but a few times i shot them without it.
There is a guy on youtube who built a replica 6 pounder cannon and his chamber is 6" down to 3" the barrel is long like a potatoe gun. Ill bet his is loud with a high pitched crack but not deep like mine seem to be.
Didn't feel very safe while watching these videos... Plus you make me want to go to McDonald's
I didnt either at first, those were the few shots over the sink. After i knew the cup wasnt going to blow up i then moved infront of the camera.
This is the one i shot over and over yesterday
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