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mk 5
Posted: Sat Mar 05, 2011 9:09 am
by domino
barrel is 29" long and 1.5" wide
chamber is 18" long and 3" wide
Could the chamber be too long? its unreliable to say the least. But when it does work, it really does bang!
Ive tried several different ignitors but found an AA battery operated rapid spark thing works best
ive made several others in the past (electrical tape specials that lasted 5 minutes) and they all worked fine, just cant figure out why this ones so unreliable
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Posted: Sat Mar 05, 2011 10:35 am
by Gaderelguitarist
So I'm guessing that this is a combustion. The chamber includes that strange yellow corrugated tube.
You can shorten the chamber without any noticeable performance drop. Larger chamber/ barrel ratios make for louder cannons.
Unreliability can be caused by many factors, induvidual or coinciding. The most common problem with combustions is getting an ideal fuel mixture for combustion to occur. Do you have a way of metering your fuel, or are you simply using a can of aeresol propellant?
Looks like a unique build. Welcome to Spudfiles.
Posted: Sat Mar 05, 2011 11:12 am
by Crna Legija
do you have a fan? its the #1 upgrade for a combustion cannon. that think looks mean as hell
Posted: Sat Mar 05, 2011 11:51 am
by saefroch
Are you metering fuel? If you're not, changes in temperature will throw off spray 'n' pray fueling by a huge margin (personal experience), which will become very significant with such a large chamber (personal experience).
Posted: Sat Mar 05, 2011 12:02 pm
by Technician1002
Getting fuel to properly mix the length of a long chamber is difficult. Adding some kind of spray paint agitator ball and then shaking thoroughly to mix the contents helps in long chambers without a fan. A 1 inch bouncy ball may do the trick. Proper venting (completely) between shots is a must. Adding fuel to an oxygen free chamber of spent gas won't work well.
Posted: Sat Mar 05, 2011 12:07 pm
by jackssmirkingrevenge
two objections if I may:
1) feet
2) What is that tubing connecting the chamber to the barrel.
Have you tried
syringe fuel metering 
Posted: Sat Mar 05, 2011 2:10 pm
by Fnord
Is that...
a vacuum cleaner hose??
Posted: Sun Mar 06, 2011 7:57 am
by domino
The hose is just some thick rubber tubing i found lying around. Theres no fuel meter or fan, just spray and prey.
Would shortening the chamber do the trick?
i have a pc fan but its just too big
Posted: Sun Mar 06, 2011 9:11 am
by mark.f
domino wrote:spray and prey
I like the way you think.
Posted: Sun Mar 06, 2011 10:15 am
by Crna Legija
As tech said, put something in the chamber and shake it around. Cutting down the chamber may help but if it doesn't then you will have a less powerfu,l unreliable cannon. So your better off trying to mix the full better and use a bit less/more fuel
