ideal chamber/barrel ratio. please help

[Nertzor]

ok i just typed up a long post and i accidentally closed the wrong tab, fml.

I need to know the best measurements for a 4' chamber 2' barrel spud gun, I know the optimal ratio is 1.5:1 but i never really bothered with it,


My current cannon is a 1:1 gun I think, has a 1" 4'combustion chamber and a 2" 2' barrel. Launches like clockwork about 100 yards.


would that mean for the 1.5:1 ratio i would need an 18' chamber? or is my understanding all jacked up. and would this yield me better distance.


attached is the picture of my current cannon (and its switchable barrels)

[Gun Freak]

1" 4'combustion chamber and a 2" 2' barrel

You're getting your units mixed up. Feet is ' and inches is ".

Nice cannon, the attached barrel looks way too big for the current chamber though. It doesn't look like it's even 1:1.

[Nertzor]

With that barrel. No lol. That was just for if I wanted to shoot anything bigger. The cannon was built around The smaller 2' barrel at it's side

[evanmcorleytv]

There are 2 ideal ratios, 1.5 to 1, and 2 to 1. a TON of people go inbetween with a 1.75 to 1, or a 1.8 to 1.

Sometimes this is meaningless.. I have an old combustion with a 10 inch by 3 inch chamber, and a 3 foot by 2 inch barrel, and it's a better ratio that ANY other combustion that I've made, it shoots probably 250 yards, and was ghetto chronographed at about 300 FPS.

[pneumaticcannons]

it shoots probably 25 yards, and was ghetto chronographed at about 300 FPS.

......?

[velocity3x]

it shoots probably 25 yards, and was ghetto chronographed at about 300 FPS.

How can a projectile possible fly at 300 fps, yet travel only 25 yards?

[MrCrowley]

I assume he meant 250 yards.

[Nertzor]

Uh back to the subject at hand. With a 2ft 2"pipe barrel I would need a 1.5 foot, or 18 inch 4" chamber for a 1.5:1 ratio? Or is my formula wrong

[Technician1002]

To answer the question, but not spoon feed, the ratio is based on volume. Use math to calculate the volume of the chamber and the volume of the barrel.

I'm mentioning this because of the 1:1 cannon measurements don't work out.

My current cannon is a 1:1 gun I think, has a 1" 4'combustion chamber and a 2" 2' barrel.

Volume of a cylinder is area times length. Area is Pi X Radius squared.

The 4 inch combustion chamber is;
3.14159 X 2 squared. 2 squared is 4. 4 X pi is 12.56636 square inches of area. Area times 12 inches length is about 150 cubic inches.

The barrel is 24 inches of 2 inch pipe. Radius of 2 inch pipe is 1. 1 squared is 1. 1 X pi is 3.14159 square inches. Area times length = volume. Pi X 24 = about 75 Cubic inches. Your 1:1 is really a 2:1 ratio. I'll let you do the math following the example.

Learn the math.

[evanmcorleytv]

I assume he meant 250 yards.

Indeed.. Sorry about that..

[jimmy101]

Download a copy of HGDT and play with the dimensions.

The question really isn't "efficiency", it is how much extra chamber volume are you willing to lug around for a 10% increase in muzzle velocity? (Given that most combustion guns have shot to shot variations of 10% or more.)

There are other things that'll do more to boost performance than diddling with CB ratios > 1. A fuel meter (or syringe) will have a much larger affect on muzzle velocity (and significantly reduce shot to shot variability). A chamber fan will do a lot also.

[Essohbe]

What size chamber do I need for about a 4foot long, 3inch pipe barrel?

[battlelava]

What size chamber do I need for about a 4foot long, 3inch pipe barrel?

Like what was just said get hdgt its free and play with the numbers there is a guide on the site were you download it from