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 49 users online :: 4 registered, 0 hidden and 45 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Firing problems HELP!

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

Firing problems HELP!

Unread postAuthor: blaineanator » Sat Feb 04, 2012 7:36 pm

Hey guys so i built my first cannon its 4 inch combustion with 3 inch barrel. a BBQ grill sparker and a PVC screw back pretty basic. i tried metering propane and butane multiple times with all failures. the dimensions of the combustion chamber are
16" tall 4" wide so pie radius squared times 16 is 201 inches converted to cm is 508 cm. 3% of that is 15.5 which equates to about 16ml. i bought a syringe at Kroger used for cooking and tried filling it to 16 i pumped it in screwed the cap on and waited a few minutes for it to diffuse. no boom tried 5 times with pro and butane..... whats going on :idea: :(
  • 0


blaineanator
Private
Private
 
Posts: 12
Joined: Sat Feb 04, 2012 7:29 pm
Reputation: 0

Unread postAuthor: jimmy101 » Sat Feb 04, 2012 7:56 pm

I think your math is off.

A cylinder that has 4" diameter and 16" long has volume pi*(2^2)*16=201 cubic inches. For propane you want 4% of the chamber volume, which is 8 cubic inches = 131 ml.

For butane you want 3% of the chamber volume, 98 ml.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3129
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: Fnord » Sat Feb 04, 2012 9:01 pm

508 cm^3 is half a liter... Just by looking at it, do you really think your chamber is that small?

Off the top of my head I'd say your chamber is probably closer to 3.5.
  • 0

Image
User avatar
Fnord
Major General
Major General
 
Posts: 2244
Joined: Tue Feb 13, 2007 9:20 pm
Location: Pripyat
Reputation: 7

Unread postAuthor: blaineanator » Sat Feb 04, 2012 9:08 pm

well i know that inch to cm conversion is 2.54 so 200 X 2.54= 508...
  • 0


blaineanator
Private
Private
 
Posts: 12
Joined: Sat Feb 04, 2012 7:29 pm
Reputation: 0

Unread postAuthor: blaineanator » Sat Feb 04, 2012 9:09 pm

a cc equals a ml
  • 0


blaineanator
Private
Private
 
Posts: 12
Joined: Sat Feb 04, 2012 7:29 pm
Reputation: 0

Unread postAuthor: blaineanator » Sat Feb 04, 2012 9:24 pm

ok i added roughly 100 ml of butane and it shot surprisingly but not near as far as axe would propel it....
  • 0


blaineanator
Private
Private
 
Posts: 12
Joined: Sat Feb 04, 2012 7:29 pm
Reputation: 0

Unread postAuthor: pneumaticcannons » Sat Feb 04, 2012 10:01 pm

blaineanator wrote:well i know that inch to cm conversion is 2.54 so 200 X 2.54= 508...


This is a common mistake.... we are talking about volume not length. so if you want to convert 200 cubic inches then you would have to multiply 200 by (2.54^3) or about 16.4..... about 3,277.4 mL. Online Conversion is useful tool :wink:

But before you redo your math, re-measure. A sch 40 pvc pipe that has a "4 inch diameter" is not going to have a 4 inch inner diameter.
  • 0

ramicaza <- My Youtube Channel
User avatar
pneumaticcannons
Major
Major
 
Posts: 392
Joined: Sat Oct 30, 2010 9:45 am
Location: shite country in asia
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: jimmy101 » Sun Feb 05, 2012 3:03 pm

What pneumaticcannons said ...

You have to check your units.
well i know that inch to cm conversion is 2.54 so 200 X 2.54= 508...

Add units and see if it still makes sense;
(2.54cm/inch)*(200inch<sup>3</sup>)=508inch<sup>2</sup>*cm
which is a not a very useful unit, though it is a unit of volume (length cubed).

The conversion factor's units have to work out.
(2.54cm/inch)<sup>3</sup>*(200inch<sup>3</sup>)=508cm<sup>3</sup> = 508ml (since 1ml=1cm<sup>3</sup>)

Length: 2.54cm/inch
Area: 2.54<sup>2</sup>cm<sup>2</sup>/inch<sup>2</sup>
Volume:2.54<sup>3</sup>cm<sup>3</sup>/inch<sup>3</sup>
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3129
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: jimmy101 » Sun Feb 05, 2012 3:06 pm

blaineanator wrote:ok i added roughly 100 ml of butane and it shot surprisingly but not near as far as axe would propel it....
Meter them both and they will perform exactly the same. The only advantage Axe has is that since it is injected has a fairly high velocity stream it tends to mix better. Use propane (or butane) and wait a couple minutes for mixing (or better yet, use a chamber fan which will mix almost instantly) and the propane (butane) will not only work the same it is cheaper and won't muck up your spark gap.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3129
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: blaineanator » Sun Feb 05, 2012 3:58 pm

Ok so i measured some more its ACTUALLY 17.5 inches tall and 4 inches wide (diameter) so can someone tell me what 3% would be in ml. I have propane and butane in my garage.

And if i meter it right by simply waiting a few mins allowing it to mix will cause the projectile to fly much further??
  • 0


blaineanator
Private
Private
 
Posts: 12
Joined: Sat Feb 04, 2012 7:29 pm
Reputation: 0

Unread postAuthor: jimmy101 » Sun Feb 05, 2012 4:36 pm

It will make the projectile fly as far as possible with that particular gun and ammo.
(17.5in)(3.14)(2^2in^2)(2.54^3/in^3)(0.03)(ml/cm^3)= 108 ml for 3% mix
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3129
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: blaineanator » Sun Feb 05, 2012 4:47 pm

thanks so i have a 35 ml cooking syringe all i do is fill it up 3 times and pour that in then cap it off and wait? like..... 2 mins or 10-20?
  • 0


blaineanator
Private
Private
 
Posts: 12
Joined: Sat Feb 04, 2012 7:29 pm
Reputation: 0

Unread postAuthor: Crna Legija » Mon Feb 06, 2012 4:11 am

Put a ball of foil in the chamber when you meter fuel close it up and shake for a minute then fire at will.
  • 0

'' To alcohol... The cause of, and solution to, all of life's problems.”
--Homer Simpson

Add me on ps3: wannafuk, 8/11/11 cant wait
User avatar
Crna Legija
Major General
Major General
 
Posts: 2333
Joined: Sun Jul 20, 2008 5:14 am
Location: australia
Reputation: 0

Unread postAuthor: blaineanator » Mon Feb 06, 2012 9:15 am

thanks! ill try that
  • 0


blaineanator
Private
Private
 
Posts: 12
Joined: Sat Feb 04, 2012 7:29 pm
Reputation: 0

Unread postAuthor: blaineanator » Mon Feb 06, 2012 9:41 pm

it worked but still only launched my orange about 50 yards how do i achieve the magical 100+????
  • 0


blaineanator
Private
Private
 
Posts: 12
Joined: Sat Feb 04, 2012 7:29 pm
Reputation: 0

Next

Return to Combustion Cannon Discussion

Who is online

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

Reputation System ©'