Mista Ballista returned to Delaware for the 2007 Punkin Chunk. We didn't get everything done that we wanted, but we had high-hopes to improve over last year.
We started to do the master list checking and last minute packing after work. One of the tasks involved filling tires with the correct air pressure, but the regulator on the air-compressor was broken at only 40psi and Mr. B wanted 115 psi in the tires. Getting that fixed with a regulator that happened to be around took a long time, and we didn't end up leaving till just after 11 PM.
At about 3 AM, the rear driver-side tire blew out on the highway at about 50 mph. Fortunately Mr. B is a dual axle machine, and survived just fine. As we had just fixed the air compressor, we pulled out the impact wrench, and started making Garage noises in a small neighborhood just off the highway. We soon had the spare on and were on our way.
Hey, what's that cruising down the highway? Every year I try to take a picture of the ballista cruising the highway and they rarely come out well. We don't seem to travel by daylight anymore so options are limited. We left so late, however, that we drove straight through till morning and I managed to get this shot.
Each time we put this Ballista together, it's a little easier and faster. This time we had to finish making our strengthened torsion arms by doing the final fit to the modiolii. The rope bundles are gettiing loose, we were able to put 270 degrees in using just the 2 ton come-along.
Here is the obligatory "pre setup" picture I take every year. Our trailer keeps getting neater as we find better ways to store stuff on the trailer.
Once we slid the rope-bundles forward, it was time to bolt on all the support beams. We've gotten much better at this, and we were done fairly early in the morning, and were ready for winding.
While on the field, Jeff Frankensteined our hydraulic setup with a 24volt hydraulic solenoid valve, with a 30ft cable hooked up to an Altoids box with a small switch in it. Flipping the switch caused the valve to force hydraulic flow to extend or retract a hydraulic cylinder.
Next, we stuffed the arms in. The wooden structure on the bottom of this picture is the "Arm Centering Tool". It supports the arm at the center of the rope-bundles, and the metal pin that sticks straight up positions the arm so that it won't bump into the framework of the ballista.
Bolt on the torsioning arm. You can clearly see the three pins that hold the arm into the holes on the modiolus in this picture, and the one bolt with washer that holds the arm onto the modiolus with a threaded hole. The other torsioning arm is in frame down on the bottom of the machine.
Test fit the back of the machine in our Ballista hole. You can see the support trailer was rained on by hydraulic fluid when a change to the valving leaked while Jeff tested it.
Roger tries out the electric switch to control the new ram in its trunnion mount. The Altoids box had a short in it, so we ran off to Lowes to pick up something more appropriate as a junction box.
Google Video Service|
2007 - Adding Torsion to Mista Ballista
Using hydraulics with an electric valve on a long lead, Roger can tighten our rope bundles and get a good view of when the holes line up.
9 sec - Nov 5, 2007
Today early we looked at our setup from the previous day, and it looked like the arms had drifted in. When that happens, there's a chance the arm butt will bump a frame member during pullback. See the 2005 chunk when we broke our arms due in part to this problem. So we unwound both sides (one at a time) and rewound with a little bit more twist than we started with.
Mr. B waiting for his turn to shoot a Cheese Pumpkin.
Mr. B fully pulled back and ready to fire!
When the time came to fire everything worked well, and we shot 582 feet. Our new trunnions, and the fancy electric-hydraulic valve really saved a lot of time for us. Huzzah!
Saturday started for Mr B. with a new round of bundle tightening. We were still 90 degrees off last years maximum twist. We started by putting 90 into both bottoms modiolii, and we put 90 more on the top left, then after an extra 30 or so degrees, the noises made us decide to stop there.
We then started to torsion up the other side and after the first 30 degrees, we noted that we bent a pin in our new "stronger" torsion arm.
We swapped it out for the backup torsion arm, and sheared 1 of 3 of the 1" pins. Thankfully, the shear did not cause the bundle to completely unwind.
We then started asking around, and Wayne Wallace of team "Lets Bounce" helped us out big-time with use of an acetylene torch and welder to bend our first torsioning arm back into shape, then strengthen it. We returned and found the machine badly unbalanced, so we went for it and put in 30 more degrees of twist.
About 20 minutes later, it was time to fire. We pulled half way back, and the safety officer had us stop due to cracking noises, so we fired from there, and the pumpkin exploded. Inspection showed that the rope had cracked through the carbon-fiber shell where a thin layer of pine was collapsing inside. We thought this wouldn't affect the arms much, but the safety guys wanted to watch us throw during the free-for-all.
During the free-for-all, we did a full pull, and everything was fine. In this picture, Roger is hooking up the lanyard to our trigger while the machine creaks slightly in the breeze.
We fired, pied the shot, and our right arm buckled in recoil, putting us out of the game for the rest of the weekend. It was a sad moment for the team as our precious arms were now trash. Pullback had measured 4000 lbs at the trigger, which equals 43,650 ft lbs of torque for both bundles combined.
After the arm broke, the team packed up the machine so part of the team could head home a little early. Naturally we all stayed long enough to see the torsion division fire on Sunday. We may be broken, but we are all still a Torsion Team!