[Brian] from 24 Hour Engineer has a friend with arthritis who can’t easily play ball with his new puppy — so [Brian] stepped in and built him this awesome tennis ball launcher.
You see, most tennis ball launchers require a solid flick of the wrist, and since just plain old throwing it is out of the question too, [Brian] had to make him something powerful and easy to use. After sketching out some designs he came up with the basic concept that eventually became what is pictured above.
The frame is made of 2″ PVC pipe, which serves two purposes, support, and safety. The bungee cord launching system is actually contained within the pipe, keeping it out of the way, and free from catching on anything during firing. A pair of pulleys mounted at the cord opening ensure the cord doesn’t wear out.
What we really like is the trigger mechanism [Brian] made out of some carefully cut wood, a steel corner brace and a few nuts and bolts. It’s a simple mechanism that provides leverage and an easy way to release the bungee cord.
Now we know what you’re all thinking — how is a guy with arthritis suppose to load this thing? Well, it’s actually foot loaded: stand it up straight, put your foot on the ball harness, and step down until it clicks into the trigger mechanism. It’s similar to loading a crossbow backwards… which you would never do for obvious reasons. Still, we feel the tennis ball has rather low risk associated with it compared to a sharpened steel bolt…
If you want to build your own, [Brian’s] laid out everything you need to know on his site, with plans to turn it into an Instructable at some point — there’s even more info via his build log.
You could also build an electric version if you’re feeling particularly lazy.