Combustion Competition

[xXunderXcoverXx]

So this is my first post and new to spudfiles but I'm not new to spudding. Ive built a pneumatic gun that will be on here soon and as human male instinct It has to get bigger and better. I made a bet with my girlfriend and her dad that I could a better spud gun then they could and so the competition began. Her father owns a hardware store and I figured If I better win. I'm thinking about a 96" 2" sch. 40 barrel and a 36" 6" sch. 40 Chamber with metered propane and chamber fan. which give the c:b ration about 3.2-1. Please questions or comment would help a lot Thanks

[bigbob12345]

Make it a pneumatic they are a lot more powerful

[xXunderXcoverXx]

Ive done some research and Ive found that pneumatics are a lot more powerful but part of the bet was it has to be a combustion gun

[cwazy1]

you definitly dont want a c:b ratio of 3.2:1, you want .8:1 for a combustion to yeild the most efficiency.3.2:1 would be more of a ratio for a pneumatic. why are you using 6" sch40?? why not just 4"?and you understand that with a chamber your size, 1017cu-in you will need alot of propane per shot? i recommend that you go with a more reasonable chamber volume like along the lines of 300-500 cu-in.

and i would hope that you know the mix for propane to air is a 4.2%. and the way to find out how much propane you need in a meter of "x" size, you should use burntelakte's calculators.

[octane89]

Like cwazy said, the best ratio for combustion is an .8:1 ratio. You will have faster muzzle velocity and distance too.

[xXunderXcoverXx]

Yes Ive been to burntlakte and read all their stuff. I know the c:b ratio is High but I'm not really looking for efficiency. I guess it could be alot lower like 1:1 but I figued if I waste a little potential energy then the potato would be at maximum kinetic energy by the end of the barrel.

[octane89]

With 3.2:1, it will just be loud and have plenty of kick. Thats why .8:1 delivers a perfect match because your combustion is complete when it leaves the barrel, and the potato will be at "max kinetic energy" like you said.
If you wanted to boost performance, use MAPP instead of propane but the mix is 4.6%

[cwazy1]

yeah as octane said, 3.2:1 would be loud.

mapp gsa does boost preformance, but it is alot more expensive and you get alot less of it per bottle. over where i live, its 3$ for a small tank of propane, while 9$ for a small tank of mapp and it has less mass. it all reall depends on what you perfer, if you like loud, well then, you can stick with your 1000cu-in chamber and a 3.2:1 ratio (make sure to wear hearing protection.)

[octane89]

Mapp here is $5, and propane is $3. I just like it because I get a bit better muzzle velocity.

[cwazy1]

oh lucky, i've been reluctant to try mapp cuz of its price. ahahha im a cheapo

[BC Pneumatics]

His planned ratio will preform better with a 96" barrel than a .8:1 ratio with the same size barrel. Lowering your C:B ratio will only help if you do it by lengthening the barrel.

Of course, you are paying a lot for the relatively small increase in power that the oversized chamber gives you.

[SpudBlaster15]

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[cwazy1]

^^ you dont have to have a burst disk

[SpudUke5]

Yea he knows it isnt neccesary but the benfit of having one is that it locks the pressure up until it bursts at a specific point and all of that pressure shoots out at once, therefore giving better overall performance.

[MrCrowley]

Golfball barrel.

If your competition is on distance, golfball should win it, if it's on power or destruction golfball should win it.

I believe you can buy them from BC Pneumatics website BCARMS, just click the link in his signature.