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Having trouble getting a tennis ball mortar to shoot

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Having trouble getting a tennis ball mortar to shoot

Unread postAuthor: Xenophile » Sun Jun 03, 2012 5:12 pm

Hey guys. I have recently constructed a tennis ball mortar out of 3" diameter PVC pipe with two pringles cans lining the inside to act as baffles as detailed in the tennis ball mortar plans of the book "Backyard Ballistics". I use lighter fluid as my propellant an a piezoelectric lighter or long handled fireplace matches as my ignition source. Unfortunately, I have failed to get the tennis ball to fly out of the barrel. I know I am achieving ignition as I here a "whoosh" sound when I ignite the lighter. I also know I have achieved combustion as the tennis ball has a ring of carbon deposit when I remove it from the barrel to try again. What am I doing wrong? Any help/input would be appreciated. Thanks, you guys.
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Unread postAuthor: Technician1002 » Sun Jun 03, 2012 6:51 pm

Too much fuel. Reduce it to go from whoosh or whump to bang.
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Re: Having trouble getting a tennis ball mortar to shoot

Unread postAuthor: jackssmirkingrevenge » Sun Jun 03, 2012 7:34 pm

Xenophile wrote:with two pringles cans lining the inside to act as baffles


Baffles? In a combustion chamber? Doesn't make sense to me...

If you want turbulence to encourage complete combustion, use a fan.
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Re: Having trouble getting a tennis ball mortar to shoot

Unread postAuthor: battlelava » Sun Jun 03, 2012 9:31 pm

jackssmirkingrevenge wrote:
Xenophile wrote:with two pringles cans lining the inside to act as baffles


Baffles? In a combustion chamber? Doesn't make sense to me...

If you want turbulence to encourage complete combustion, use a fan.


The baffles are to hold the tennis ball and prevent if from dropping all the way to the bottom
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Re: Having trouble getting a tennis ball mortar to shoot

Unread postAuthor: jackssmirkingrevenge » Tue Jun 05, 2012 1:40 am

battlelava wrote:The baffles are to hold the tennis ball and prevent if from dropping all the way to the bottom


One simple screw will do that without filling the chamber with rubbish :)
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Re: Having trouble getting a tennis ball mortar to shoot

Unread postAuthor: battlelava » Tue Jun 05, 2012 9:04 am

jackssmirkingrevenge wrote:
battlelava wrote:The baffles are to hold the tennis ball and prevent if from dropping all the way to the bottom


One simple screw will do that without filling the chamber with rubbish :)


Yea I wish I could find my copy of the book so I could post what its suppose to look like
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