C:B ratio or power to weight ratio?

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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Rambo
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Sun Feb 12, 2006 3:58 pm

Why for so many people it is important the C:B ratio?In bulgaria the alkohol is cheap(2lv=1.25$ for L) and I don't want to get the absoliut maximum from it.I think that the 'volume to power ratio' is much more inportant then the C:B ratio.I prefere a small powerfull and uneficient gun then a big, long very eficient and not so powerfull gun. :shock:
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drac
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Sun Feb 12, 2006 5:13 pm

But there's your problem. More efficient guns provide more power. And efficient guns don't have to be big, infact, they can be pretty powerful. i recently made a mini combustion that will shoot a nail through 4 sheets of computer paper.

I'll post pics as soon as i get them, my camera's on the fritz.
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Shrimphead
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Sun Feb 12, 2006 6:07 pm

When you have the right c:b ration, your gun is using all of the energy from the combustion, making it quieter, and more powerful. If you have too short of a barrel for how big the chamber is, then you are wasting energy. In that case, lengthening the barrel would make it more powerful.
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boilingleadbath
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Sun Feb 12, 2006 7:04 pm

I don't get the obsesion with utilizing all the energy possible, either. The cost of the propelent is very low, about .001$/shot, so the waste doesn't really matter. Sure, an efficient launcher is quiet, but that's a bit special-purpose, isn't it?

However, of what use is the launcher that has the most power per volume? Most power per length is more important, in my opinion - a portable launcher can only be so long and still be portable, so it makes most sence to optimize for power/length.

Either way, you can optimize the preformance of the launcher by using EVBEC, available in our "tools" sub-forum.
Interestingly, a launcher constructed from all one diameter of pipe which, (other than freaks with a smaller diameter chamber than barrel) would want the smallest C:B ratio, optimizes for power/length at roughly a 1.2:1 ratio.
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Rambo
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Mon Feb 13, 2006 2:39 am

I agree that power to length ratio is more inportant.I think that the comb. canons are better for light projectails(like a funnel) and the pneumatics are better for hevy projectais.For light projectail is inportant the volume of the chanber and if it is too long twin spark will be good.The light pr. will have the speed of the gasess befoure it is out of the barrel.If we have a gun with a huge chamber and very short berrel, then with hevy projectail the kenetic energy will be proportianl to the lenght of the barrel. :shock: sorry for the speling
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