I thought of this  while making my large copper rolling ball sculpture. I had a round tin to keep the ball bearings in and when I was thinking about what to do next with it I absent mindedly tilted it to make the balls go round the outer wall. It consists of a track that can be tilted by a servo.

There are two operation modes. The first is manual mode where you can control the degree of tilt with a potentiometer. The second is automatic mode which consists of about 4 different sets of pre-determined routines which can be selected by the potentiometer. The final routine is random mode which selects a random routine every so often.

Code for Perpetual Ball Roller



Thanks to Hack-A-Day for posting Perpetual Ball Roller!

Here are some responses to comments made on that blog.

Electromagnets instead of servos

Electromagnets would probably work. I think it would be trickier to get so many different positions accurately. The simplicity to MAKE the project would decrease even if the viewing of it was not. If anyone tries it then send me a link to the video and I’ll put it on this page. It is not something I am personally going to try.

The need for sensors

I originally thought they would be needed but the ball just finds it’s way into the rotation. The speed could be changed through the potentiometer and that was the original idea. I would not be particularly exciting though and I prefer the erratic routines.

It’s not perpetual (motion)!

The track is a circle, there is no start and no end. It just keeps going round and round. “Perpetual” was the best word I could think of to describe this. You can think of it being used in an arty sense instead of scientific terminology.

I did not claim perpetual motion. I am an undergraduate Mechanical Engineer and probably know more about the laws of thermodynamics than a random person on the internet. Apologies if this sounds rude but I tire of being accused of  making false claims. 🙂

If the name really gets under your skin… you may want to disconnect your computer from the internet.

[Lisa] In this house, we obey the laws of thermodynamics!

Final Comments

The metal loop that connects the servo to the track is important. This connection allows a wide range of tilting. Ideally the the servo horn should be placed directly under the bolt so there is an equal range of tilting on both sides.

It is a completely useless desktop toy but so far people that have seen it have liked it. There is something in its simplicity that makes it easy to understand once you have seen it but it is unlikely to be anything you’ve thought of or seen before. If you have seen it done before or you’ve made one yourself then please let me know!