Propane Semi Auto Spud Cannon Design Help!

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
spudnutbutthut
Private 4
Private 4
Posts: 85
Joined: Thu Jan 22, 2009 4:00 pm

Thu Aug 06, 2009 1:36 pm

ummm, i like your ideas but the torch isnt convincing me, id rather just get a propane adaptor its 7 bucks and il connect it straight to the chamber, plus the thing does have a valave that you unscrew so the propane wont just hiss out non stop.

And why is it bad to have liquid propane in the chamber at such relatively safe pressures?
User avatar
Technician1002
Captain
Captain
Posts: 5189
Joined: Sat Apr 04, 2009 11:10 am

Thu Aug 06, 2009 2:24 pm

spudnutbutthut wrote: And why is it bad to have liquid propane in the chamber at such relatively safe pressures?
Put a piece of PVC in the deep freeze. Then pull it out the next day and drop it on concrete..

Cold PVC is brittle. Propane boils near -44F at atmospheric pressure.
Safety first.
User avatar
dewey-1
Sergeant 3
Sergeant 3
Posts: 1298
Joined: Wed Mar 28, 2007 10:24 am
Location: NE Wisconsin USA

Thu Aug 06, 2009 2:44 pm

spudnutbutthut wrote: Id be launching a nerf rocket, around 150 - 200grams i think
A Nerf Pocket Vortex football weighs 30 grams to be a little more accurate!
spudnutbutthut
Private 4
Private 4
Posts: 85
Joined: Thu Jan 22, 2009 4:00 pm

Thu Aug 06, 2009 2:59 pm

how much of a chance do i have of getting liquid propane in ther?
jimmy101
Sergeant Major
Sergeant Major
United States of America
Posts: 3197
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Has thanked: 5 times
Been thanked: 15 times
Contact:

Thu Aug 06, 2009 3:14 pm

spudnutbutthut wrote:how much of a chance do i have of getting liquid propane in ther?
Based on the valve you intend to use, somewhere between 0% and 100%, inclusive.

If you invert the propane tank then it's 100%. If the propane tank is upright then it is near zero.
Image
spudnutbutthut
Private 4
Private 4
Posts: 85
Joined: Thu Jan 22, 2009 4:00 pm

Thu Aug 06, 2009 4:05 pm

will it kill the gun right away?

and me...
User avatar
pat123
Corporal
Corporal
Posts: 514
Joined: Sat Dec 23, 2006 10:08 pm
Location: S.C.
Contact:

Thu Aug 06, 2009 4:17 pm

will it kill the gun right away?

and me...
The gun- most likely

You- probably not, you would just have shrapnel lodged in you. probably not killed but it wouldn't feel good.
spudnutbutthut
Private 4
Private 4
Posts: 85
Joined: Thu Jan 22, 2009 4:00 pm

Thu Aug 06, 2009 4:43 pm

should i build this god dammit?
User avatar
POLAND_SPUD
Captain
Captain
Posts: 5402
Joined: Sat Oct 13, 2007 4:43 pm
Been thanked: 1 time

Thu Aug 06, 2009 6:07 pm

yeah go for it... just take some basic steps to build a safe launcher...

Normally I would advise to use metal chamber but I am aware that weight might be an issue here so you would have to find something relatively light, preferably aluminium... if you can find something suitable it would be a good idea to use metal on all the parts apart from barrel and the valve... threaded fittings should speed the building process a lot and let you mod the gun in the future


but I suppose you can use pressure rated PVC if you couldn't find suitable metal chamber... however, with PVC you have take into consideration what tech said about cold temperatures


generally the design is rather simple and proven I suppose you shouldn't have too many problems with it
I don't really know why this discussion in on 4 pages already... some people just make you think it's more difficult than it is... safety is an important issue but you can solve almost every problem you face with this gun with the use of a metal chamber

ohh BTW it isn't a semi auto at all... to be a semi it would have to have a loading mechanism... it isn't a crime that you labelled it in the wrong way but it confuses those who want to help you
Children are the future

unless we stop them now
spudnutbutthut
Private 4
Private 4
Posts: 85
Joined: Thu Jan 22, 2009 4:00 pm

Thu Aug 06, 2009 6:46 pm

ah. actually thanks to everyone I was verrry confused at the often very different views on the matter but i have figured it all out. Im gonna use a benzomatic valve with a hose etc. And i thougt about making a magazin. The magazine would be an open top box that gravity feeds rocket into the barrel as the loaded rocket leaves the barrel. It would have a trap door as not to get in the way of the loded shell. The first shell would fall into the barrel, then the door would snap back on a spring until the rocket left!

Im prolly not gonna do that though haha!


THANKS AGAIN!
User avatar
ramses
Staff Sergeant 2
Staff Sergeant 2
United States of America
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm

Fri Aug 07, 2009 9:31 am

just make a bolt action breech

granted that one has to be scaled up a little, but just replace all of the 1" pipe with 2" and all the 1 1/2" with 2 1/2".
same with all fittings
so for things besides pipe, you would need:

Small hose clamp for 2" Pipe
Screw and wooden dowel for lock
2 1/2" -2" Bushing x2
2 1/2"-2" Coupling x2
2" to Male thread
Washer, ideally rubber, just under 2.445" OD, ~2" ID
POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
spudnutbutthut
Private 4
Private 4
Posts: 85
Joined: Thu Jan 22, 2009 4:00 pm

Fri Aug 07, 2009 12:44 pm

il think about, muzzle losdingbis fun though :]
Post Reply