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My push rods are cut from a white Acetal Copolymer Rod, 1/8" Diameter that I ordered from McMaster's Carr.
Acetal Copolymer Rod 1/8" Diameter, White  McMaster Carr Part Number 8497K11  $ 0.32 per Ft. This item is only sold in lengths of 4 Ft. 

Craig Reinbrecht had recommended that I use White Delrin Rod, but this is unavailable in the 1/8" Diameter size that I needed. I doubt that there is any practical difference between Acetal Copolymer and Delrin.

I snipped the rod to the desired length and then sanded the top of the rod to a smooth rounded head. It is important to create a smooth round head in order to eliminate any friction between the top of the push rod and the brain cam. The brain cam was created by Scott Sanderson.

One has a bit of flexibility in determining the length of the push rod. The longer the rod, the higher the light rod will rise. The shorter the push rod, the lower the light rod will descend. The only logical travel limits are the top of the brain and the bottom plate of the bubble. The push rods can be of any length as long as the light rods avoid hitting either of these objects. I made my light rods of various lengths in order to create more random and varied light rod movements. To my mind, this better replicates the movement of the light rods of the original robot.


Decreasing the length of the rod is simple because Acetal Copolymer Rod is so easily sanded. I deliberately cut the rod a bit longer than it needed to be. Inserting the push rod into place and turning the brain cam over it revealed how much more material needed to be removed. I then extracted the push rod from its shaft and sanded down the bottom of the rod with a piece of 180 grit sand paper. It only took a few swipes with the sand paper to remove the requisite amount of material.

After the entire brain mechanism was in place, I tested it by connecting the hankscraft motor to a battery. I was stunned by the beauty of it. The spinning crown and the moving light rods were deeply impressive. It is so amazing that these complex motions are created by a single motor. It is a simple system that produces a complex and eye-catching display.