We use electricity to move things with the help of motors and magnets all the time. But if you have enough voltage, you can move things with voltage alone. As [James] found out, though, it works best if your objects — ping pong balls, in his case — are conductive.
He wanted to add a Van de Graaff generator to add to his “great ball machine” which already has some cool ways to move ping pong balls. However, to get the electrostatic motion, [James] had to resort to spraying the balls with RF shielding spray.
We liked that he did some experiments to see how the balls would work before spending a lot of time 3D printing the final project. We did wonder, though, if there were cheaper options to make the balls conductive such as graphite or conductive ink.
The end result is a 3D printed low-energy ping pong rail gun, more or less. The design is pretty clever and you might find some ideas even if you don’t want to actually accelerate ping pong balls. An Arduino, of course, controls the whole affair. If you do want to replicate it, you can find the CAD files and the software on GitHub.