C:B 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.
User avatar
Mattmp36
Private
Private
Posts: 7
Joined: Sun Jun 17, 2007 11:14 am
Location: Acworth, GA

Thu Feb 28, 2008 12:19 pm

I have been trying to develop plans for a new spud gun. I am a little unsure if my calculations are right though. I thought of a 4 x 12" CC and a 1.5 x 60" barrel. I tried to do the math and I came up with a ratio of about 1.5:1. Am I close or way off?
-Matt
User avatar
jimmy101
Sergeant Major
Sergeant Major
United States of America
Posts: 3199
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Has thanked: 5 times
Been thanked: 17 times
Contact:

Thu Feb 28, 2008 2:01 pm

The simplest equation to calc CB ratio of your guns is just:
(4*4*12)/(1.5*1.5*60) = 1.4222
Or
(2*2*12)/(0.75*0.75*60) = 1.4222

Or
V<sub>chamber</sub> = (Pi)(r<sub>chamber</sub><sup>2</sup>)(L<sub>chamber</sub>)
V<sub>barrel</sub> = (Pi)(r<sub>barrel</sub><sup>2</sup>)(L<sub>barrel</sub>)
Where r is the radius and L the length.

The CB is V<sub>chamber</sub>/V<sub>barrel</sub>
Image
Post Reply