Tennis Ball Gun

Date: May 2017
I had big plans of putting a lidar detector in this thing to allow for fully-automated kinematics. Real life stinks. Someday I will go back and make this tennis ball cannon automatically adjust its angle to accommodate different distances. In the mean time, I’ll have to let this idea ferment on the back burner and learn my Taylor series like a good boy. Oh the joys of being an engineering student!

Just a tip or two for people building tennis ball guns for an engineering class (or otherwisee).

1) We used a 4″ PVC Schedule 40 pipe for the air tank. I forget the length. Feel free to look at our AutoCAD design. After a shot, there was always about 15 PSI left in the tank. I don’t know “air physics”, but my hunch is that we had an excessive air supply at 80 PSI but not that excessive.

2) There is quite a bit talk online about the speed of the switch. We used a sprinkler valve to kick this booger on. The story on the streets is you need a valve that will open insanely fast to allow a full-on attack on the tennis ball. This makes some sense. If the trickle were spread out over 30 seconds, the tennis ball may fall out the other side… best. With that said, there were other humans in the competition that used a hand valve and they had absolutely no problem applying monstrous force to their tennis balls. In short, you dont’t necessarily need a sprinkler valve for high transient pressure.

3) When it came to the actual competition, our professor was a little ticked that a few teams (ours included) did not use the required parabolic trajectory. (You don’t get to type “parabolic trajectory” with your clothes on very often.) We want with a fixed-pressure design which meant we varied the angle to hit our targets. For extremely-low-angle shots, this meant we basically shot the cone as if we were shooting a bad guy in a Clint Eastwood movie. If we missed by a inch, we actually missed by a mile as we were judged by the distance from the cone to where our tennis ball hit the ground. You may want to test variable-pressure designs.

Download: AutoCAD PDF Export Files

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