SpudFiles

I was watching some pumpkin chuking videos and noticed one of the air cannons is using something better than a traditional butterfly valve. By watching the video, I noticed the cannon has a piston valve that is operated by a pair of ball valves. One valve is used to close the piston. That valve remains open until just before the cannon is fired at which time it is closed. Next to fire it a second valve is opened to pilot the piston valve. This is the very first time I have seen a piston valve in a pumpkin cannon. Well done guys. Video is below.
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Awesome !!
Would like to know more details about it ..hmmm
Just curious, which chamber is the the air tank? or are they both air tanks? or is it a complicated design.......
Must of been a real head turner transporting that huge thing.

[quote="daniel0663"]
Just curious, which chamber is the the air tank? or are they both air tanks? or is it a complicated design.......
quote] I think they are both air tanks , or one of them is the piston valve
this thing make me remember the paris gun from the ww1

Did you reach space?

OMG a girl...

That aside, look at the low frequency resonance of the air in the barrel around 2:15. Based on it being a closed cylidrical pipe, a .65s period would give a length (at STP, which this is probably not) a 55 meter long barrel.

With the valve open, resonant frequency is lowered and not just the pipe length. The barrel is not 55 meters.

I found some data on the cannon on this page;
http://big10inch.org/story/media.html
Barrel is 100 feet of schedule 80 Aluminum. The world record attempt is 5,545.42 feet.

The cannon has two air chambers.

At these dimensions it seems pretty silly not to use a burst disk, simply bolting some frangible material between the barrel and chamber flanges will give much better performance than any mechanical valve.

May as well stick a spark plug on there and inject some MAPP gas while you're at it...

MrCrowley wrote:May as well stick a spark plug on there and inject some MAPP gas while you're at it...

Aren't there enough cryptic pumpkins around at Halloween ;P

All I have to say is WOW!! That is just over a mile that pumpkin took for a ride, however I do not see why they put beer on the pumpkin. In my opinion, that is definatly alcohol abuse!! A.K.A., a drunkin pumpkin!!

mattyzip77 wrote:however I do not see why they put beer on the pumpkin

I imagine the tradition started as a crude projectile lubricant.

MrCrowley wrote:I imagine the tradition started as a crude projectile lubricant.

It's good social lubricant, I can see the logic

You might find this link interesting

http://www.punkinchunkin.com/docs/punki ... lesv10.pdf

It explains why burst disks aren't used, they're against the rules.

The world championship is held every year about an hour from my house. I really should go sometime.

Secret Squirrel wrote:It explains why burst disks aren't used, they're against the rules.

I couldn't find any reference to burst disks, care to elaborate?

jackssmirkingrevenge wrote:

MrCrowley wrote:I imagine the tradition started as a crude projectile lubricant.

It's good social lubricant, I can see the logic

I second that!!