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Im Confused........just got ma pvc pipe for my 1st cannon of which is about to be build and i was woundering weather or not with the barrel being 5ft long should i have a long conbustion chamber or a short one ? or does it even matter
thanks guys
My first thought is that I dearly hope English isn't your first language, and my second is that your question (if I am in fact interpreting it correctly) doesn't make any sense.
Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
Should you have a long or short Combustion chamber?
Answer: it depends. you have a vast ammount more research to do prior to building your cannon. Not to mention since its a combustion chamber your posting in the wrong forum.
C:B Ratio problemhey guys,
Im 100% stuck on working out the c:b Ratio thing in terms of how long my air chamber should be with a 1" by 5FT barrel ! Would someone be kind enough to work it out quickly for me i its not too much trouble ? And by the way the dimater of the chamber is 3" . thanks guys and i'll be sure too post info and pictures of my cannon when finished . Thanks Noobyspud
Yep, more research please.
However, if you're just throwing together a spray n pray and you want a 1.5" dia.  5' barrel, I would use an 18" piece of 4" dia pipe for your chamber. Your C:B ratio would be respectable at a little over 2:1. You will have a beefy, energetic chamber....and a cannon you can still handhold.
You need to calculate the volume of the barrel first? Then, decide on what ratio you want. .8:1 ratio means your chamber volume should be 80% that of your barrel. Work the volume formula backwards to find your chamber length.
Your chamber should be 13.33" in length for a 2:1 ratio, my personal favourite.
You really shuld learn these calculations yourself, you'll need them to get through high school math, and it's better to practise on something interesting. Heck, you may want to practise by rechecking my calculations, I always goof up somewhere
Last edited by TurboSuper on Fri Jul 25, 2008 10:03 am, edited 1 time in total.
"If at first you dont succeed, then skydiving is not for you"  Darwin Awards
C:B ratio is the ratio of barrel volume to chamber volume.
The volume of a cylinder can be found by: (pi)(r<sup>2</sup>)(length).
Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
c:b ratio refers to the volumes. Calculate the volumes of your pipe. V = radius * radius * pi * length. Everything you need is in this formula...assuming of course you have round pipes for your barrel and chamber.
Please don't ask us to do your calculations for you. It tends to indicate that you are in over your head and need to research and understand better what you are doing. Edit: Be sure you use the radius and not the diameter in your calculations.
May I ask why you're using a combustion chamber in a cannon posted in the pneumatic cannons section?
"If at first you dont succeed, then skydiving is not for you"  Darwin Awards
Looks like he's all over the place. He just posted a related question over in C:B Ratio Problem.
noobyspud, browse around the Spudfiles Wiki. In particular, read the Chamber to barrel ratio page.
I don't know how old you are but this is why you've been taking math in schools for the last XX years. Math really does have useful applications and it really is a good thing to learn. I suggest you actually pay attention in math class. Starman, actually you don't have to use the pipe radius for the CB calculation, diameters work fine. You do have to use either both radiuses or both diameters and the calculation must involve the ratio of the two volumes, as it does in a CB calculation. Volume<sub>chamber</sub> = (CB ratio)(Volume<sub>barrel</sub>) converting from chamber volume to chamber length for a given CB ratio and barrel diameter and length; Length<sub>chamber</sub> = (CB ratio)(L<sub>barrel</sub>)(D<sub>barrel</sub><sup>2</sup>) / (D<sub>chamber</sub><sup>2</sup>) Since (D<sub>barrel</sub><sup>2</sup>) / (D<sub>chamber</sub><sup>2</sup>) = (r<sub>barrel</sub><sup>2</sup>) / (r<sub>chamber</sub><sup>2</sup>) it doesn't matter if you use diameters or radiuses.
In simple terms. Block one end of your barrel and pour water in it. Get the stuff your using for your chamber and however much is filled with water, mark it and cut it. Voila pefect 1:1 c:b ratio. Or if your like me you have an eye for the right lengths and sizes
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