The "Punkin' Chunkin" contest -- some thoughts about the hardware, etc.

[tallguy]

I've been a big fan of this contest for a long time, and have been fascinated by catapults
of all kinds for many years.

I recently saw a video where one of the contestant teams modified their pneumatic cannon
to give some backspin to the pumpkin.  I thought that was a great idea -- and it apparently
helped, by providing lift to the pumpkin.

Here are some other thoughts I have about the pneumatic cannon hardware.  If I could
find a forum where the contestants go, I'd post it there.  But land speed racers, to me,
are of a similar mindset, so I thought I'd post here, to see what you think of my ideas.

(And if you could point me to a punkin' chunkin' forum, I'd appreciate it.)

One of the issues with the pneumatic cannons is that sometimes a pumpkin can't withstand
the forces of launch.  Here are some thing's I'd do if I could, and were a contestant:

1.  Use an extremely long barrel.  I don't know how long is permissible within the rules.

2.  Have the bore teflon-coated.  I think this is permissible.

3.  Design the plumbing for smoother fluid flow (i.e., no small-radius edges or turns in the pathway) from the reservoir tank.

4.  Evacuate the barrel ahead of the pumpkin.  This could certainly present a challenge, but we can discuss it.  I saw a very
     impressive live demonstration of how this principle could help.  In this demonstration, a regular ping-pong ball was blasted
     from a long barrel, and went through both sides of an aluminum can that wasn't restrained.  It was just in the path of the
     ball!

5.  Add additional fluid (gas, not liquid) flow along the launch path just ahead of the muzzle, so the pumpkin doesn't hit "still
     air" as suddenly.

6.  Use gas (that is less dense than air) to propel the pumpkin.  I don't know whether nitrogen or helium or hydrogen are permitted
     for this.

7.  Preheat the launch gas and the barrel before launch.

8.  Use the largest permissible pneumatic reservoir.

9.  Use a very large and fast solenoid valve to release the gas.  Perhaps use a manifold of several branches that feed into the
    launch tube.  Each branch would have a very large and fast solenoid valve.


Thanks for all your comments on this.

[Peter Jack]

Google potato gun or potato cannon and go from there. Some of those guys have done some pretty amazing things. Stand clear!  
You may want to try substituting spud for potato in your search as well.

Pete

[Milwaukee Midget]

Call me a Luddite, but I prefer traditional siege weapons such as a catapults and trebuchets to dispose of surplus pumpkins.

[WOODY@DDLLC]

Trebuchets were the ICBM's of their day! 

Even today 2800+ft for a punkin' toss: http://punkinchunkin.com

[maj]

I suppose you cant freeze the pumpkin

[Crackerman]

Dont they use air over 300psi? Some of the knes i saw had 6" pressure piping. Punkins cant be frozen, but they use a gourd with extra thick skin to keep it together. Unfortunately a pumpkin is oval, barrels are round, is a sabot of sorts ok?

[WhizzbangK.C.]

They can't put a frozen pumpkin down the barrel, as I believe that the pumpkins are provided by the organizers. They are allowed to hand pick the pumpkins from those available for best fit to the barrel. I don't believe that any wadding is allowed.

If one was to build a really large reservoir, and have a "slow leak" into the barrel right at the pumpkin's location, could you possibly cool the pumpkin at the same time as you were charging your reservoir, resulting in a frozen pumpkin leaving the barrel??? 

Another thing that I haven't seen anyone do is to pipe some of the air into the barrel near the muzzle end, prior to launch. By using a venturi effect to create a partial vacuum in the barrel you would be able to get better muzzle velocity, and the air stream flowing away from the muzzle should also help prevent "pie".

[Crackerman]

Depending on the quantity of that airmentioned above, it could also be used to backspin the gourd.

[floydjer]

That has to be a fascinating rule book to peruse.

[redhotracing]

I love the power and sound of the air cannons...
That being said, the trebuchets, especially those
with 4 or more counterweight mechanisms
are just plain cool. 1300's technology in action!

http://youtu.be/dg4hboje3VE?t=1m36

Also a bike powered machine for you, SteveM.

http://youtu.be/dg4hboje3VE?t=54s

[donpearsall]

The 'chunkin website says there will be no contest this year. They had to move the site at the last minute and could not reschedule until next year.

Hmmm, remind you of certain landspeed events this year...?

[Joe Timney]

It's just down the road from here...one big 'Drunk-a-thon'!!! You can't even see the punkins coming out of the guns.

[floydjer]

I imagine their rule book saying things like.." Thou shant not loiter down field of yon chunker lest thine widow be consoled by thou`s friends in a manner thee might find un-savory"

[WOODY@DDLLC]

You have to give an email and answer some questions but this it what the champion chunkers are doing: [Hope it works for you! ]
http://mkt.solidworks.com/emarketing_enu/start.swe?CID=1-36U6IUE&SSId=1-35TIBI6&SWEMethod=StartSS&SWECmd=InvokeMethod&PRO=1-NKZ7N&OID=1-35SVS62&SWENargs=SSId%3D1-35TIBI6%2CSSName%3DREP+SW+Pumpkin+Chunkin+American+Chunker%2CSSLC%3D%2CSSCC%3D%2CCID%3D1-36U6IUE%2COID%3D1-35SVS62%2CCOID%3D1-36U6IUF%2CPRO%3D1-NKZ7N&COID=1-36U6IUF&_sn=ONkiqmRSPoKrH2WWmbX5qZ36WOEzQW9g15Wn2yEdoc9naTMpmr9mQ00nYVrevuSH1uftF-FnWiotxpUlchxGdNiRKWE0fJkcY0JZviohM7Ifp0qxpADHLde81SUMCOgM-u9FgybqYnqtbYMGVjhkq4YTBQEicgB1SCnuVvBAT3hQ2VinBH3YuezmBnki5ecs0huU5hn-jPk_&SWEView=URLRouter&SRN=&SWEHo=mkt.solidworks.com&SWETS=1417731479&SWEApplet=SSRoute&SSName=REP+SW+Pumpkin+Chunkin+American+Chunker

[ONEBADBUG]

I built a 10% scale model trebuche with some innovations I thought could get me the world record. But then, some guy showed up with an enormous thing that took cranes to assemble, I couldn't compete with that.