World Championship Chunk 2012: Mista Ballista
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Mista Ballista returned to Delaware for the 2012 Punkin Chunk. After our big success with bundle pre-tensioning last year allowing us to break the 1000ft mark, we opted to leave good things alone, and instead focus on torquing up the bundles to the max, and compounding the machine to see what it could do! Our drive to Delaware was hindered by Superstorm Sandy, causing us to arrive late. We planned ahead, and Mr. B left it's field before the storm hit and the field got soft. On the way down, however, the ballista tow vehicle started to run out of gas in Jersey, and the lines were incredibly long. Later we learned many people were in line for 4 or more hours! Fortunately, we had a spare 14 gallon tank for use with our small engines, and we used that to keep going to southern Jersey where the lines were shorter, only a 1/2 hour! In addition, the storm caused the Chunkin' field to flood, and the WCPCA decided it was not possible to get the field ready for competition on Friday, so Friday was cancelled. Here's a short news spot including Eric Ludlam for Mista Ballista telling some of the story: WMDT on Punkin Chunkin.
Due to pre-tensioning the the bundles, we can no longer just 'put' the arms into the bundles. We must first drive wedges between the two halves of the bundles. Once in place, the arms will slide between the two wedges, and we knock the wedges back out of the bundles.
And with that, we called it a day.
Well, that just meant the whole team was there getting the Ballista ready bright and early, and then we got to relax!
Here you can see our seacatch, our velcro/nylon pouch, the punkin' seat-belt, and bowline separators. The separators ended up being pretty dangerous. Check out the video below and you can see one getting launched backward into the crowd. Good thing there is a giant net back there.
This picture is also interesting in that you can see how the arms are crushing our wooden inner arm stops. These stops had been working well for several years, but they are starting to give up structural integrity with the new more intense bundle winding techniques we're using.
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Bright and early on Friday we started removing travel bolts holding 
After lifting the machine, the gray jack stands are placed underneath, the feet are raised back up, and the large cribbing are placed under the landing gear, and the landing gear is bolted to the cribbing.
In this image, junior team member Trevor cranks on the big foot after the cribbing was installed. You can see the jack stands behind 
Last year during winding, the frames we torque the bundles from flexed dangerously, so this year we welded on some strengthening bars in diagonals across the front. This made everything safer, and we didn't have to invent ways to hold things down.
Next, we drag the bundles to the front of the machine using our winch. We drag it forward to marks we've painted on the machine, and then use a 3-ton come along to tip the bundles up into place. In this picture, you can see the faint orange triangle on the scapus underneath the bundles that mark the tipping point.
After bolting the bundles into place, we installed the arms.
Once the arms are in position, it is time to crank up torsion engine! We use a big hydraulic cylinder attached to a mega-sized bicycle chain. The chain wraps around a big gear that makes up
the 
Once everything was twisted up and ready, we put on the bowstring, and then tighten up the arm arrestors, which are the 1" rope that prevents the arms from pushing all the way forward.
We use the bowstring to pull back on the arms. while the arms are partially cocked, we use cleats on the back of the machine to tighten up the arm arrestors so that they can slow the arms down gently.
We arrived bright and early on Saturday morning. On Friday night an email went out requesting that the youth and Torsion lines bring pumpkins to the captains meeting since we'd both be firing first. Turns out that was a typo. It was supposed to be youth and Trebuchets.
Loading the punkin'! Saturday's punkin color was blue, and we had to write our pit number all over it. When fitting a punkin into a ballista pouch, we have to pull back slightly to get everything under tension. We then need to find a punkin shaped just like our last shot of 2011, as we can't adjust the pouch anymore since sewing it all together. I always place the bowline over a ridge to help hold the pumpkin in, and then add a blue seatbelt.
Lock and load! The pumpkin is ready to be shot.
Waiting for the pit-boss to give us permission to fire.
Naturally the thing you do immediately after a successful shot where nothing broke is to start cranking it up even more! We twisted until the hydraulics could do no more. We tightened up the hydraulic pressure limiter until the pump engine stalled. Naturally we then reached into the motor and goosed it to get a few extra HP and PSI and put more into 
Sunday dawned, and it was an awesome day, partly because daylight savings time gave us a whole extra hour of sleep before the captain's meeting.
To prevent hurling the bowline separator off into the crowd again, 
The first Sunday shot color was orange. Naturally we had orange paint on a white punkin. After yesterdays shot, I noticed here that the bit of rope whipped around the pullback lines had melted. When I pulled it off, I discovered that the heat from the friction of firing was so great, the nylon also melted inside the twist. Fortunately the bowline is made of vectran which is very heat tolerant and was not affected. I had to replace the protective rope after only one shot.
Another great picture by 
Launching our pumpkin 1213 feet was pretty cool, but it did a number on our nice throwing pouch. Unlike previous years, we had two shots due today, which meant if we were going to do shot 3, AND try compounding the machine for the first time ever, we had a lot of work to do in a short period of time!
Fortunately, 
While 
This diagram shows the basic idea behind compounding 
After starting to pull back, 
After 2 days of intense work, here's the end result. Traditional bowstring provided the greatest distance (1213 ft) with our current Scapus length. Once compounded, using the short amount of pullback distance we hindered performance resulting in the shortest shot (813 ft).
The torsion class had a great year with every machine throwing over 1000ft, Chucky III broke 3000 ft again, and spectacular failures on almost every machine on the field.