Ball Balancing Beam




Introduction: Ball Balancing Beam

About: I am an American teaching English at Shangluo University, Shaanxi. I like making machines that do interesting but fairly useless things - I call them Quixotic Machines.
This is a video of a ball balancing beam mechanism I constructed. Fun little experiment that didn't work as expected but did return some useful information for further modifications that might make it work.

Mechanism is a simple geared motor connected to a balance beam. The ball serves as a  switch to connect two electrical contacts that will provide voltage to turn the motor in one direction or the other. The electrical contacts were initially pieces of aluminum can, then I used 4 stainless steel rulers which conducted better as I had to sand a non-conductive coating off the aluminum strips. I used two adjustable power supplies. For just allowing the ball to roll back and forth, a single supply would be sufficient and also both switches could run the motor in the same direction. It is slightly more efficient to have the motor run in two directions based on which switch is turned on by the ball.

For future work, I need to build a servo driver which I believe will execute fast enough to make the mechanism actually balance the ball. As it stands now, the geared motor responds too slowly to allow the beam to react quickly enough to actually balance the ball. Also, the motor sometimes has to complete a cycle in the opposite direction of the desired beam movement - a servo would always turn in the correct direction and respond more quickly.



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6 Discussions

Hi JimRD,

I have looked at a couple of your projects and have been inspired by their simplicity and use of commonly available materials. One thing which I though of since this is labeled as a ball balancing beam was maybe using a potentiometer as used in your balancing Gyro robots. In one of them, you used a Pot on the Gyro to control a servo with a weight on it.

What about using a similar setup and have a servo on one side of the fulcrum and a Pot on the other so that when the ball rolls past the center of the fulcrum and makes it tip down, this change is registered by the Pot so that the servo moves in the opposite direction to try and return the Pot back to zero and level? This way, the ball is kept as close to the middle as possible to maintain the balance. What do you think?

Thank you! It is fun playing with electric motors.
I really have to build a servo driver with a 555 chip and see if I can't make this better.

Hi JimRD,

I wonder if the "screw drive" motor (and assembly) that controls a CD tray would work? Like, the switch on one side of the balance beam runs the motor clockwise which pushes up one side, then the switch on the other side of the beam turns the motor counter-clockwise and it pulls back down. Maybe just vary the length of the metal contacts so the motor runs just long enough to achieve a steep enough angle for the marble to change direction. Might simplify the up/down part? Of course a much smaller marble(/bearing?) would probably be necessary because the CD motors aren't that beefy... dang, now I wanna build one!

Take care,


Also it would be a make for a great reuse of the CD tray mechanism which is pretty cool in itself.

I agree completely, hope someone does that as it would make a fantastic tabletop gizmo, which I love.