Last night I got the DC motor attached to the record player / drawing surface of my harmonograph table, allowing me to finally christen it “The Three Pendulum Spiraling Harmonograph”.

It has been a long time coming and I already know of some pertinent adjustments that need to be made but nevertheless it was a good feeling to finally give it a test run in it’s final form. It’s pretty cool to see it in action (see the video below).

I sent through multiple sheets of paper, testing out different kinds of pens, swinging one pendulum and not the other, with drawing surface spin and without.  It was an interesting experience to get to know how it all worked.

I came to realize two flaws.  One which is simple and one not so simple.  The simple one is that my drawing surface was too small.  I need to expand it out about two inches in all directions.  I would get everything swinging and the pen would move beyond the surface boundaries pretty regularly.

The not so simple one is the motor.  The motor is not good enough for this function (either the motor or my variable power source).  I found that the speed of the motor was very irregular.  It would speed up and slow down seemingly randomly.  I’m sure part of it was due to the weight of the swinging and the resistance of the pen on the paper.  That’s why I think I need a slower motor with more torque.  If I can find a motor that will run at a constant speed the symmetry of these drawings will truly be apparent.

Anyways, back to research.  In the meantime, enjoy my little demo video below.