Advanced Combustion FPS And Foot Pounds Of Energy?

Boom! The classic potato gun harnesses the combustion of flammable vapor.
spudkilla224
Private 4
Private 4
Posts: 65
Joined: Wed Mar 19, 2008 8:04 pm

Hello, i am in the process of making a Advanced combustion with a 30" long 3 inch diameter pipe, and a 2" diameter by 5 foot long barrel. I am using metered propane at 35 psi.

I was wondering how many fps i could shoot a 100 gram slug, and how many Foot Pounds Of Energy My Cannon Should Have?
User avatar
starman
Sergeant Major
Sergeant Major
United States of America
Posts: 3027
Joined: Wed Dec 12, 2007 12:45 am
Location: Simpsonville, SC

Have you tried HGDT? It makes these kinds of calculations rather trivial.

If you used a 65 psi burst disk and 3 spark gaps, 3.5 oz projectile, 2" inch bore, it looks like you would be at 834 ft*lbs and velocity of 493 ft/sec. Rather nice c:b ratio of 1.12:1 as well.
User avatar
jackssmirkingrevenge
Five Star General
Five Star General
Posts: 26219
Joined: Thu Mar 15, 2007 11:28 pm
Has thanked: 581 times
Been thanked: 347 times

starman wrote:it looks like you would be at 834 ft*lbs
That's almost the same as a three round burst from one of these, so be careful ;)
User avatar
starman
Sergeant Major
Sergeant Major
United States of America
Posts: 3027
Joined: Wed Dec 12, 2007 12:45 am
Location: Simpsonville, SC

jackssmirkingrevenge wrote:
starman wrote:it looks like you would be at 834 ft*lbs
That's almost the same as a three round burst from one of these, so be careful ;)
That's also the range of force on one of my trip thunder golfball shots.

Image
User avatar
trigun
Specialist
Specialist
Posts: 161
Joined: Mon Jan 26, 2009 11:21 pm
Location: Illinois

starman i thought you used propane ?
User avatar
starman
Sergeant Major
Sergeant Major
United States of America
Posts: 3027
Joined: Wed Dec 12, 2007 12:45 am
Location: Simpsonville, SC

trigun wrote:starman i thought you used propane ?
I've used them both equally successfully. I switched to MAPP at the Christmas shootings and it offers a small but slightly noticable performance thump. You need a little more MAPP than propane...I just upped my regulator setting from 68 to 75 psi and that was about right.
User avatar
trigun
Specialist
Specialist
Posts: 161
Joined: Mon Jan 26, 2009 11:21 pm
Location: Illinois

so the mapp is better maybe i'll upgrade. I inspected your cannons farther and saw what you were talking about with the male to 4-2 reducer it looks so clean !
Post Reply

Create an account or sign in to join the discussion

You need to be a member in order to post a reply

Create an account

Not a member? register to join our community
Members can start their own topics & subscribe to topics
It’s free and only takes a minute

Register

Sign in

  • Similar Topics
    Replies
    Views
    Last post