C:B ratio

[stevenarroyo]

am planing on making a new Combustion Cannon with all the good stiff propane metering/ camber fan. the cannon is going to be a over/under design.

my question is i have a C:B ratio of 1.22:1 is that good??
i did not add the 2 elbows that are 1 1/2in size.

so if some1 can help me?!?!

i was never good with math... lol

[brogdenlaxmiddie]

i was never good with math... lol

Apparently you weren't pretty good with grammar either!

EDIT- Also, why is this in the showcase section

[stevenarroyo]

that too

and i would like for people to help me not make fun of me.

[brogdenlaxmiddie]

Fair enough, I think that your C:B is pretty good, but I think that an important thing would be the space inside of the elbows. I'm not an expert on the whole C:B thing but I personally try to go for almost a 2:1 just because I don't look for performance in my combustions, but noise

[stevenarroyo]

i hear that a good C:B is around 1.6 or 1.5 i think?

[brogdenlaxmiddie]

It very possibly is, but are you going for sound, or performance?

[stevenarroyo]

i want to get more performance then sound

sound would not hurt too lol

[mark.f]

If you're using metered propane and a chamber fan, then a CB ratio of about 0.8:1 is desired. Are you holding your chamber size or barrel size constant in your design, though?

[stevenarroyo]

my chamber volume is 87.21 cu in without the (2) 1 1/2inch elbows

and my barrel volume is 71.44 cu in

my chamber size is 3" x 12" long
and barrel is 1 1/2" x 36" long

[jimmy101]

1. Read the Wiki page on CB ratio.

2. Get a copy of HGDT (search for it in the Wiki). It'll answer your questions about how changing the CB affects the gun's performance. The difference in performance between CB 0.8 and 1.2 isn't going to be huge, something like 10-20% in muzzle velocity (20-30% in kinetic energy).

[stevenarroyo]

ok thanks

[nickz]

My current gun has a 8.something to one ratio, it is a 30" by 1 1/2" chamber with a 24" by 1/2" barrel because that all I had laying around.And it shoots very good. According to EVBEC I would need a 158" by 1/2" barrel to make 1.2 to 1, and it would almost double the velocity.

I would need an 20 foot barrel to get .8 to 1, and it would shoot at over 560 fps.

[Hotwired]

Possibly.

Or then again such a long barrel could give the gases behind the projectile time to cool enough to cause a vacuum and make the projectile lose energy/not exit at all.