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.

The 2003 Power System

We acquired this generator on Ebay. It was originally someone's home backup unit, which they never used. It generates around 5800 watts.

Our hydraulic power unit was designed and built by Jeff. The engine is off an old snowblower, and has a handy electric start. The pump and other hydraulic parts were bought new, designed for a log splitter. The Punkin Chunkin association requires that hydraulic hoses and parts are "like new", and not of junked tools, so this was important.

The frame is welded up bits of exhaust tubing.

In 2005, we started using an auxiliary trailer to haul our power units onto the field. This saved lots of grunting and lifting of these heavy items as we could just leave them on the trailer. It also helps keep our pit tidy.

The 2007 all-in-one Power Pak

In 2006, we purchased a 35 Hp diesel engine off a refrigeration truck. Sadly, the guys selling it thought they'd do us a favor by just cutting all the hoses and electric bits to extract the motor thinking we were going to part it out. So we had to piece quite a bit of it back together. Oh well.

We acquired an old welder/generator unit with a defunct gasoline engine. We measured up the flywheel interface on the diesel engine, and Jeff fabricated an adapter shaft so we could attach our welding head to it.

Once the adapter shaft was bolted onto the flywheel, the bell housing for the welder/generator head was fitted to an adapter plate, and then to the housing around the flywheel. To weld the generator housing onto the new adapter plate, we spent a bunch of time measuring the wobble to make sure everything was perfectly centered.

A really big wrench was used to spin the main shaft on the engine so that we could do the indicator measurements on the other side.

Once that was welded together, we were able to mount the welder/generator head onto the engine. There were lots of random dangling bits of wire and do-dads that enables the welder and provides AC power. Quite a bit of time is being spent building mounting brackets so all this stuff can be bolted down to something.

We bought two 19 gallon hydraulic tanks because they were on sale, cheaper than one 25 gallon tank, and fit into the footprint of the powerpak nicely. Sadly, we then had to plumb together a new monstrosity.

Once the tanks were mounted, the upper frame was built. The top of this frame is removable so we can get inside. In this picture, Kevin and Dave are laying out the location of where the radiator will hang.

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	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 (This Page)	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.