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The Zener article that this demonstration is based on assumes we will use normal engineering materials, such as steel or glass, but ball bearings and marbles aren't the bounciest balls we know of and may not be the most fun for a hobbyist to play with. So, I decided to try to make a flat plate per the Zener article that would make a Super Ball©, or a generic version of one, stop with no perceptible bounce. This type of ball will be referred to as a "bouncy ball" and the thing that stops it as a "dead" stop if there is no perceptible bounce. In physics or engineering, this would be known as a coefficient of restitution approaching zero.The bouncy balls we wanted to stop are basically rubber so we had to get a little bit creative to find a flat plate material with a similar softness. First of all, we had to be able to solve the non-linear differential equation from the article. That actually was pretty easy to do using a common, and pretty old, spreadsheet application. The results indicated that we would need a plate material with a very low density and that it couldn't be very rigid.
We got several bouncy balls to try and the bounciest one was thrown to us during a Fourth of July parade in Ely, Minnesota. The ball was 1.45 inches in diameter and bounced back to 84% of the height it was dropped from. We concentrated on finding a bounceless stop for this ball.
The plate material that worked the best was a 4 foot by 4 foot sheet of extruded polystyrene insulation. Ours was pink, not the white stuff made of little beads more or less bonded together. The pink insulation comes with a thin skin of material that made it too rigid for our purposes. Besides, we needed to thin down the material to make it work right, so we sanded it from both sides to get the thickness down from 1 inch to about .82 inches. It isn't easy to measure the somewhat variable thickness of a sheet this big, so we drilled holes thru the thickness about every 6 inches and measured the thickness at each of 64 places with a caliper.
The plate material was soft enough that the ball, dropped from heights of 15" to 72", would leave dents so we bonded on a 2" diameter disk of fiberboard. This did the trick and we were able to stop the ball with no perceptible bounce.
If you're thinking that there's nothing patentable here and it doesn't seem like a useful engineering device, you're absolutely right. But, it was fun to play with and makes me appreciate good engineering materials, like steel, even more.
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