MK III Cannon

The Mk III (read "Mark Three") Cannon is just another step in a much larger H.E.A.T. Air Cannon project. Long before the actual cannon was sketched, its goals were determined. To fit into our grander cannon development plans, the Mk III Cannon's firing mechanism needed to be actuated from a VEX Robotics Cortex. This characteristic would define the third generation air cannon, while acting as a significant milestone towards our ultimate goal - the Mk IV.
After determining the overarching goals for the Mk III, we then turned our attention to details that were targeted to this particular build. It was decided early on that the new cannon would be large... really large. At this point, it seemed somewhat clear that this may be a single-construction generation, as it would require a great deal of materials and time.
To make this large cannon more interesting, it was decided that the cannon would utilize two fully-independent systems, allowing a second shot before reloading. It also needed to be somewhat mobile - fit through doors, in the back of pickups, have at least two wheels for easy movement/repositioning, etc... Initially, it was thought that the cannon barrels might have two axis motion, but this was simplified to a single axis. From these fundamental design goals, design began.

The Mk III Cannon was based on all we'd learned in construction and testing of the first two generations of cannons.
The Mk III barrel systems are immense - each barrel is 5' long with over 10' of 2" reservoir fixed behind its valve. Each system is equipped with a Schrader-style filling valve and pressure guage.

The cannon's carriage was of somewhat simplistic design.

Carriage began to take shape, but did look a little boring at first.
Barrel mounting system we settled on                     Desert camo with burned barrel tips.

Early test-fitting of the barrel-mount and single-axis movement, some "plating" in place
The barrel mount became a bit complicated...           and required some carriage modifications.

Here's a closer look at the counter-weight lobe that also acts as an anchor point to lock the barrels at a range of angles.

The barrel assembly is ready to mount!

The carriage ended up looking pretty good; note the Skunkworks logos.

Somewhat assembled...
Relays allow for VEX Cortex control.                             Again, the BHE Skunkworks logo...

Each system has its own LED-lit arming switch and firing button. Very fun.

Ultimately, the MkIII Cannon has been a great success. Construction of the cannon took roughly three weeks. Since its initial construction, H.E.A.T. members have worked to give the cannon new capabilities -
- The cannon can now fire most anything that will fit down the barrel thanks to design and construction of clever "plugs" or wadding that provide a perfect seal and minimal friction during the firing process.
- It has fired a tennis ball over 80 yards.
- T-shirts can be fired over 70 yards.
- It will soon be fired over the internet... from literally anywhere on the planet.

Our most frequently asked questions are, naturally, about the safety of this unit. Our designed safety measures follow:
Schedule 40 PVC is used throughout the cannon.
Everything on the high-pressure side of the valves is rated to an operating pressure of 280psi (burst pressure is likely twice that).
Pressure gauges on each reservoir are clearly marked with a 125psi max pressure warning.
Air compressors used to pressurize reservoirs have a maximum pressure of 125-150psi.
The control panel has a two-step firing procedure, and insists on two-handed operation.
Arming switches have spring-loaded covers (much like the missile switches you see in movies).
Our artillery division students are trained in safe use of all equipment involved.