Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 70 users online :: 5 registered, 0 hidden and 65 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Pneumatic CB Ration

A place to ask general spud cannon related questions.
Sponsored 
  • Author
    Message

Pneumatic CB Ration

Unread postAuthor: keep_it_real » Sun Dec 31, 2006 8:47 pm

Dunno if this has been said (well I know it's been said but maybe not this way) but here's how i calculated it. I'm not positive if it works like I think but the pressurized air in the chamber will expand until it reaches atmospheric pressure. After that, it seems the projectile will create a vacuum inside the barrel (if there is an ok fit/seal). This could slow it down. So there should be a point where the projectile (tater) gets pushed by the air but doesn't get sucked back in. This works best for a semi auto valve because the chambers are a lot smaller. If this was a one shot pneumatic, the barrel would be freakin' gigantic. Anyway, does that make sense...


p1 = average chamber pressure (psi)
v1 = chamber volume
p2 = atmospheric pressure (approx 14.7 psi at sea level)
v2 = barrel volume (including volume between valve and projectile) This is the variable we are finding

pv = pv (Charles law i think)
(p1 * v1) / p2 = v2

v2 - (space between valve & tater) - v1 = barrel volume

piR^2 * height = cylinder volume
so...
R = ID of PVC / 2
barrel volume / (piR^2) = BARREL LENGTH!!!

k now I'll find the actually CB Ratio for a gun with an average psi of 100 and a barrel with an ID of 3/4

p1 = 100
v1 = 3
p2 = 14.7
v2 = ???

(100 * 10) / 14.7 = 20.4

volume between valve and tater = 2

20.4 - 2 - 3 = 15.2 (barrel volume)

(pi * .375^2) = .4416

15.2 / .4416 = 34 inches.

You probably don't need all 34 inches because the last little bit of pressure inside the chamber isn't going to push the tater much faster. So call it 30

It seems kinda long but it makes sense.
  • 0


keep_it_real
Captain
Captain
 
Posts: 320
Joined: Sat Dec 23, 2006 4:41 pm
Location: Bend, Oregon
Reputation: 0

Return to General Spud Cannon Related

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'