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 74 users online :: 7 registered, 0 hidden and 67 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Im Confused........

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
Sponsored 
  • Author
    Message

Im Confused........

Unread postAuthor: noobyspud » Fri Jul 25, 2008 8:25 am

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

:?
  • 0


noobyspud
Private
Private
 
Posts: 23
Joined: Fri Jul 18, 2008 11:21 am
Reputation: 0

Unread postAuthor: Hubb » Fri Jul 25, 2008 8:36 am

C:B ratio
  • 0

User avatar
Hubb
Major General
Major General
 
Posts: 2390
Joined: Mon May 28, 2007 8:39 am
Location: South Georgia
Reputation: 2

Unread postAuthor: DYI » Fri Jul 25, 2008 8:39 am

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.
  • 0

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.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: noobyspud » Fri Jul 25, 2008 8:55 am

it makes perfect sence
  • 0


noobyspud
Private
Private
 
Posts: 23
Joined: Fri Jul 18, 2008 11:21 am
Reputation: 0

Unread postAuthor: socoj2 » Fri Jul 25, 2008 9:25 am

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.
  • 0


socoj2
Master Sergeant
Master Sergeant
 
Posts: 169
Joined: Fri Jun 29, 2007 9:17 am
Reputation: 0

C:B Ratio problem

Unread postAuthor: noobyspud » Fri Jul 25, 2008 9:43 am

hey 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

:?
  • 0


noobyspud
Private
Private
 
Posts: 23
Joined: Fri Jul 18, 2008 11:21 am
Reputation: 0

Unread postAuthor: starman » Fri Jul 25, 2008 9:53 am

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.
  • 0

User avatar
starman
Donating Moderator
Donating Moderator
 
Posts: 3041
Joined: Wed Dec 12, 2007 12:45 am
Location: Simpsonville, SC
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: Hubb » Fri Jul 25, 2008 9:54 am

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.
  • 0

User avatar
Hubb
Major General
Major General
 
Posts: 2390
Joined: Mon May 28, 2007 8:39 am
Location: South Georgia
Reputation: 2

Unread postAuthor: TurboSuper » Fri Jul 25, 2008 10:02 am

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 :D
  • 0

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

TurboSuper
Brigadier General
Brigadier General
 
Posts: 986
Joined: Thu Jun 16, 2005 1:44 pm
Reputation: 0

Unread postAuthor: DYI » Fri Jul 25, 2008 10:03 am

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).
  • 0

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.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: starman » Fri Jul 25, 2008 10:04 am

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.
  • 0

User avatar
starman
Donating Moderator
Donating Moderator
 
Posts: 3041
Joined: Wed Dec 12, 2007 12:45 am
Location: Simpsonville, SC
Reputation: 0

Unread postAuthor: TurboSuper » Fri Jul 25, 2008 10:04 am

May I ask why you're using a combustion chamber in a cannon posted in the pneumatic cannons section?
  • 0

"If at first you dont succeed, then skydiving is not for you" - Darwin Awards

TurboSuper
Brigadier General
Brigadier General
 
Posts: 986
Joined: Thu Jun 16, 2005 1:44 pm
Reputation: 0

Unread postAuthor: starman » Fri Jul 25, 2008 10:12 am

TurboSuper wrote:May I ask why you're using a combustion chamber in a cannon posted in the pneumatic cannons section?


Looks like he's all over the place. He just posted a related question over in C:B Ratio Problem.
  • 0

User avatar
starman
Donating Moderator
Donating Moderator
 
Posts: 3041
Joined: Wed Dec 12, 2007 12:45 am
Location: Simpsonville, SC
Reputation: 0

Unread postAuthor: jimmy101 » Fri Jul 25, 2008 2:11 pm

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.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3130
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: TwitchTheAussie » Sun Jul 27, 2008 2:12 am

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 :wink:
  • 0

Raise your horns if you love metal.
spudgunning is like sex, once you've tasted, you can't wait til next time.
-
CpTn_lAw
User avatar
TwitchTheAussie
Brigadier General
Brigadier General
 
Posts: 980
Joined: Tue Feb 06, 2007 3:23 am
Reputation: 0

Next

Return to Combustion Cannon Discussion

Who is online

Registered users: Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], Majestic-12 [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'