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!

One of Dave's great finds, the articulated part of a 12 foot long dump truck bed. The base attachment frame, the 12 foot lifting frame, plus a hydraulic cylinder and pump. The cylinder is about 1 foot across, and is very heavy. We plan on assembling the ballista on the 12 foot frame, and using the hydraulics to lift the ballista to a 45 degree angle for firing. We welded extensions to the bottom of the dump frame to improve support around the center of gravity. Best of all, it was very cheap.

Fitting adapters between the regulae and the bottom scutulas of the rope bundles. Here you can see the new adapter plates temporarily bolted in place.

We finished building our regulae frame for holding the rope bundles together. We also fitted brackets for bolting our rope bundles to the frame. Here Kevin and Roger fit the units together. While each metal rope bundle unit weighs in at about 700 pounds, sliding them together proves a bit of a challenge. Getting small bolt holes to line up also requires some finesse. Fortunately, Roger found some Grade 8 bolts which can be persuaded into position without destroying their threads. Nifty.

The regulae frame is then bolted to the transverse regulae, and our scapus climacidos. (The long ladder/runway along which the pumpkin will travel.) To get enough pieces of the proper length, we found a lot of disparate pieces of box and welded them end to end. We also added lots of extra strengtheners not in the original ancient designs for fear of the forces we intend to generate.

Additional Pages
Mista Ballista : Modiolus and Epizygis	The Modiolus and Epizygis used in Mista Ballista account for a majority of the time spent. The size and detail needed to construct these items in a way that could reliably contain the force of so much rope worried us, and we over engineered them.
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 (This Page)	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 : Arms	Building an arm for a torsion machine this large has been very challenging. A list of our failures in this area might provide some hints on what not to do.
Mista Ballista : Trailer	One of our goals for the 2003 season is to acquire a dedicated trailer for Mista Ballista.
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 : 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 : Torsion	Mista Ballista's engine operates with 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 alternate means of twisting is needed.
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 : 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.