A MAKE Reader Builds the Solar Pendulum from Volume 28

Tom Buchanan, a retired teacher, emailed to let us know he successfully built Owen Tanner’s solar pendulum, as seen in MAKE Volume 28, Page 146. He writes:

I really liked both the look and the function of Owen Tanner’s solar pendulum. My box base was made from 1/4″ poplar and pine (4″x6″x2.5″) with box joints. I milled a 7/8″ depression for the coil done with a Forstner bit, and then stained it cherry.

I put some some ball feet on the bottom with removable screws so that the bottom panel could be removed to access the circuit and internal wiring in case I messed something up. I found an old brass plumbing tube for the upright (9″) and some thinner wall 1/4″ brass tubing for the horizontal beam (7.5″). The solar panels are supported by an angled brass music-stand shaped piece attached to some 9/32″ brass tubing that just slipped over the 1/4″ tube, and I found an old lamp bulb-base for the support base which is bolted to the box. The beam, upright tubes, and solar panel assembly were soldered with a low temperature hard solder and then the solar panel holder and 9/32″ pendulum support rings were super-glued to the horizontal beam.

Mr. Tanner’s pictorial circuit diagram was both clear and easy to follow. And, as he indicated, getting the wiring through the soldered upright and horizontal tubing was a little tricky; I used a length of thin, strong wire bent into a elongated V-shape to fish the wiring through the tubes and then checked the fished wiring with a meter to make sure I hadn’t stripped and shorted the wires when I pulled them through.

After assembling everything, I was getting ready to check the pendulum’s function with a battery when I was happily surprised to see it start swinging all by itself under my shop work-light. We’ll see how long my bearing surfaces hold up (brass rings slightly lubricated).

All in all, I really enjoyed putting this together and was very pleased that everything worked just fine as soon as I finished…thanks to the very clear instructions provided.

Thanks again for this fun project.