Siege Mista Ballista : Trailer

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Mista Ballista : Trailer
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One of our goals for the 2003 season is to acquire a dedicated trailer for Mista Ballista.

Last year our borrowed car trailer was barely able to carry it, and it worried us. This custom trailer was built for our length and weight requirements, and for multiple stabilizing feet.

In a previous life, the scrounged wheels and axles hauled homes from Pennsylvania to New Hampshire, and were abandoned, but not for long. So cheap, we bought an entire axle with wheels instead of one spare tire. They are supposedly rated as 6000 lb axles, so a pair of these guys should easily carry the ballista around the country.

Found these at a scrap yard while scrounging for structural steel. At 20 cents a pound, quite a bargain. The front of the trailer will bear the majority of the mass of the ballista while operating, so they will be mounted on the front beams.

Once all our structural steel was cut to length, we carefully positioned the wheels and cross members so that everything was square. The very first beam took two tries to install correctly. We had already positioned the spring mounting brackets so it was important to make them even. The straps held everything together before the weld, and kept the entire system level.

Dave put the weld in, making Roger's measurements permanent. Or so we thought. It didn't meet our exacting standards of squareness (over a 20 foot length) so we took it apart, and did it a second time until it was perfect.

We purchased a hitch system that needed to be welded on. The only new structural steel in the whole trailer was the triangular piece at the front of the trailer.

Once the frame was together, we flipped it over, and had to actually bolt in the two axles. Given the wobbliness of Dave's driveway, this was a significant challenge. Fortunately, everything fit perfectly. Amazing!

Dave is trying to sell his house, so the trailer had to be made road worthy that same day we assembled it. On went the trailer accouterments for minimal safety such as chains and jack.

Off it goes to Eric's house. We followed as many back roads as we could, and safely made it to the driveway it will call home until the trailer is fully registered and plated. Next up, paint, lights, and brakes.

After painting the trailer, and getting all the lights hooked up, adding decking, and getting it registered as a home built, it was time to put the ballista on it. As Mista Ballista had final assembly done at the 2002 Chunk by a friendly forklift, we had to somehow lift the whole thing up and plunk it down on top with nothing but a few floor jacks and chunks of lumber. In this picture you can see the trailer behind Jeff.

Eventually, the ballista was raised up on three rather precarious cribbing piles, and the trailer was pushed under it via a hand truck. (We didn't trust anyone's ability to drive the thing under there with only 6 inches of clearance on either side.) We only had about 2 inches of height clearance getting it under the cross bar. It is amazing how much weight a 6x6 pressure treated beam can carry. It is also quite impressive that it deflected about 6 inches under the ballista without exploding.

Last year, the ballista sat on a car trailer. To work properly, we had welded on long extensions to the dump frame. With a dedicated trailer, we needed to remove these old extensions. The old dump frame will now be bolted directly to the trailer which will provide the stability needed to raise our rope bundles 16 feet into the air.

After getting things bolted down, the Big Feet were augmented, and then bolted onto the trailer. Already, these feet proved vital to the usage of the machine making it noticeably more stable once they were lowered into place. We couldn't put the feet on the very front of the machine because they would get in the way of the rope bundles during deployment. Currently they are located in such a way to avoid the rope bundles sliding past, and also avoid them when they are in the firing position. In this picture the feet are fully retracted. (The flash makes it hard to see that the toes are a foot off the ground.) You can see a hitch pin holding the toes onto the big feet. We need to travel with the toes removed in order to have enough ground clearance to make it over speed bumps. Eventually we added a second set of big feet to the back half of the trailer as well. Stability is our friend.

For 2009, new rules indicated that we could no longer dig holes in the ground. Instead we built 4 new cribbing blocks which are bolted onto the landing plates of our big feet. This let us raise the entire machine off the ground by about 2 more feet, giving us a launch angle of 40 degrees with no hole.

Additional Pages for Mista Ballista
Mista Ballista Mista Ballista is _Team Tormentum's_ *Torsion Division* competition catapult.
Mista Ballista : Modiolus and Epizygis In 2008, Dave devised a new system for managing the torsion in Mista Ballista with his friends Karl Hamm and Kevin Cheney. This represents a large investment in our machine in these custom parts.
Mista Ballista : Bowstring The bowstring has been one of the most challenging pieces of our torsion engine. It is the last piece to get right, and has been the most likely part to fail in any given year.
Mista Ballista : Rope Bundles The rope bundles are the main engine of the machine. The framework that holds everything together is about 24 ft long, and 6 feet tall.
Mista Ballista : 2005 Rope bundle Upgrade At the 2004 chunk the main stanchions for the torsion frames were bent by the impact of the arms. You can see the animation of when this happened on the Mista Ballista Arms page.
Mista Ballista : 2006 Rope Bundle Reconfiguration In 2005 we broke our fancy fiberglass arms. In 2006 we got the new carbon fiber arms and video taped them in action in the summer at our 2006 History Chunk. This led us to discover how much they bounced around the outer stanchions. We were getting multiple recoils after every shot, sometimes back at least 30 degrees. That was also just with 2000 lbs of pullback, which is much less than we expect to use in competition.
Mista Ballista : Frame The framework for the Ballista had to be built strong enough to resist the pullback, and to hold up the 2500 pounds we currently estimate of our engine. It must also push it up 16 feet in the air!
Mista Ballista : Trailer One of our goals for the 2003 season is to acquire a dedicated trailer for Mista Ballista.
Mista Ballista : Torsion Mista Ballista's engine operates on torsion from twisted rope bundles. One of the biggest challenges of torsion for this machine has been adding the twist. An onager is pretty straight forward in that a large lever and gravity can be used. With our ballista, the direction of twist is sideways, so an alternate means of twisting is needed.
Mista Ballista : Arms After the failure of our arms in 2007, a new tactic was needed. Dave contacted his friends Karl Hamm and Kevin Cheney about designing and building a set of ballista arms out of aluminum. Aluminum was chosen for its strength and light weight.
Mista Ballista : Deployment To travel to different chunkin' locations, we need to pack the system down onto our trailer. Deploying from the folded up position is challenging and time consuming, taking a day and a half at the 2002 chunk. This year at the 2003 Punkin Chunk, we were done in about 4 hours.
Mista Ballista : Hydraulic and Electric Power Mista Ballista uses hydraulics for lifting the engine to a 45 degree angle for firing, and also for winding the cord bundles. We also like having electricity on hand since Mr. B has a tendency to break, and need on-field repairs. This page describes what we are using to power up the system.
Mista Ballista : Mystery Parts All winter during 2003 we have been collecting the parts we need to accomplish our 2003 chunk goals. Here are a bunch of pictures of these random parts. Can you guess what they are for?
Mista Ballista : Modiolus and Epizygis 2007 This page describes the Modiolus and Epizygis system we used from 2002 through 2007. In 2008 we developed a new system for twisting up Mista Ballista.
Mista Ballista : Torsion 2007 All torsion catapults depend on twisting the rope bundles to create the engine to drive the catapult. Mista Ballista went through many phases as we attempted to add more power every year to our throw. This page describes the obsolete systems we'd used in the past.
Mista Ballista : Arms 2006 - 2007 This page describes the construction of our dearly departed Carbon Fiber composite arms. We miss them.
Mista Ballista : Failed Arms Building an arm for a torsion machine this large has proven to be very challenging. Based on the experiences of our competitors, who also keep breaking arms, we find that we are not alone in this dilemma.

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