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World Championship Chunk 2009: Mista Ballista
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Mista Ballista returned to Delaware for the 2009 Punkin Chunk. Unlike Last Year, our bundles were not only ready to go, we pretensioned every strand with a goal of 1000 lbs per strand.
You can see one cribbing here in the foreground. The rear cribbing are already installed in this picture.
Notice the Science Channel cameras in the foreground. Getting a good photo without them being in frame was a bit of a challenge this year.
Our analysis was that this bowstring had been made for our old Carbon fiber arms, which were 30" longer. That meant the cross piece in our pouch was too long, and took a full force impact after triggering. We shortened that, and remade the left side of the bowline and were then good to go for our second shot at the end of the day. Here Eric fits our next pumpkin into the newly revised pumpkin pouch.
A big Huzzah to the hard work the spotters and Pit Boss put in to getting through the remainder of Day 1, and all of the Day 2 lineup in one day.
We analyzed this problem as well, and eventually discovered that our throwing pouch was uneven and allowing the pumpkin to slide out the sides during early acceleration. Eric then rigged up some edges to the pouch which we tried out in a practice throw.
Here is a highspeed video of the same shot.
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Contact: Team Tormentum Copyright © 2000-2022 Eric M. Ludlam All rights reserved. Twas' brillig, and the slithy toves did gyre and gimble in the wabe... | Last Modified: 05/10/09 |
Basic assembly ran late into the night. Here, 
Sadly, our hydraulic setup, which had been giving us trouble at home, ceased to function at the chunk. We had use carb cleaner at home, and it started running well there. Sadly, the trip had dislodged some detritus which was now clogging up the fuel lines. Here 
With our rope bundles now pre-tensioned, inserting the arms is not a simple task. Two specialized bundle wedges are used to separate the two sides of the 
Here 
Once the arms were in, winding begins (see the red hydraulic cylinder) and ended almost as quickly. After only 1/4 twist on all sides, the arms are locked in place by the bundle and we no longer need the arm stands. Another 1/4 twist after that, and 
Once that was done, we did a test lift to make sure our new lift system worked. Notice in this picture how high off the ground the trailer wheels are. With no hole at all, we reached a 40 degree angle. Not bad. New chunk rules disallow the digging of holes in the farm grounds. No question that digging the hole was faster than installing all the foot cribbing though.
We then looped 1" nylon rope over the arm for our new arm stops. We sighted along the rope to make sure it would clear all the trailer obstructions, and removed some interfering bits from the back of our trailer foot assemblies. This rope will help stop the arms during a launch to prevent the arms from breaking. The rope is tied to the rear of the machine with giant cleats, and there are aluminum pins welded to the arms to keep the rope from sliding out on the arms. Who needs springs when you're using nylon rope?
To keep the 1" rope in place, long "whiskers" were added to suspend the rope in the air. During out test pullback, everything worked well, and the new arm stops were considered good to go.
We never did get a test shot off that day, but we did discover that the distance between arm tips became much shorter, and the bowline needed to be adjusted. Here 
With the Day 1 chunk incomplete, our first shot was early in the morning. With the revised bowstring length ready to go, the bundles goosed up with another 1/4 twist, we had high hopes of a grand shot. Unfortunately, the bowstring broke when we triggered the machine and the pumpkin rolled off the side.
Well, 
Our final shot prepares to launch as 
One of our concerns from analyzing video from last year was that pulling on the Seacatch lanyard caused a slight rise in the bowline, which caused the machine to launch the pumpkin slightly downward. We designed a new triggering pole to use in conjunction with the trigger line. The trigger pole has a flat bit of metal on the end that wedges between the Seacatch and its trigger lever. Pulling straight back wedges up on the triggering lever causing launch without lifting upward on the trigger.
Not satisfied with our pullback numbers, the team decides to add a last 1/4 twist to the machine, for a total of one full twist.
Our previous days worth of shooting resulted in our arm tips slowly sinking downward. This is a problem that has always plagued us, but with pretensioning, it was more challenging that usual to overcome. A car jack was used to force the issue.
Bob Carbo broke Onager's winch yesterday. We offered up our hydraulic setup which was moved between our machines. Unfortunately some testing suggests that the root of the problem appeared to be his hydraulic motor, and not the engine and pump setup. Using our hydraulic system, a giant come along, and 2 hours of patience, he was eventually able to get Onager cocked and ready for his 3rd shot of the show.
With the revised shorter bowstring, it caused our right arm (on the right in this picture) to scoot in, and rub against the inner regulae. We pried on it till it got past, and then continued on for our final launch of the day.
And a new personal best was set for 
After removing the arms, all the pretensioning work we did remained! Everything was nice and tight. We beat our previous best with 3/4 less twist, and the fact that the bundle was still tight indicates that we had removed all the mechanical stretch from the rope. So we have high confidence in future work to improve our pretensioning. Good stuff!
The torsion class had a tough year filled with broken and incomplete machines. As a division, however, we all pooled our resources and helped each other out.