Pneumatic Potato Cannon

- Under construction -

When finished, Mark II will be 43 feet long. The goal is to break the sound barrier. I recently had the idea of using three valves that open simultaneously in order to minimize the pressure drop across each valve. This requires a complete redesign of the rear half of the cannon compared to the photos below, but the front half stays the same. Three valves means air only needs to go through each valve at 1/3 the speed of sound, which is critical since I’m sure it would be next to impossible to get supersonic air to bend 180 degrees and flow through a relatively turbulent passageway.

Stats

Type: Pneumatic, rated to 220 psi
Length (overall): 43 feet
Length (barrel): 40 feet
Barrel diameter: 2 inches
Air chamber: 2.5 cubic feet
Velocity (theoretical): Mach 1.1 (840 ft/s)

Construction Pictures

Plans

Top and side view shown. Total length is 43 feet.

On the left is a side view, right is top view. Clear polygons are pieces that will be cut out of expanded PVC sheet and glued together to make casting forms for alluminum parts.

The cut paths for each piece of expanded PVC. My friend Ben has access to a CNC router, which will cut these pieces with computer-guided precision.

An overview of Spudcannon mk II. Top view is shown on the right, side view on the left. Red is PVC fittings, black is 2" or 4" PVC tube.