That's a good way to show standing waves, but did they understand what they were looking at, or did they just think it was some sort of a trick?
Well I think the "ninkompoops" invested about $10M in the 60's so they must have thought he had something going on.
I guess it was that era's version of a dog/pony show.
What were they investing in?
Gramp's machine was called "Big George". It vibrated stuff at insane frequencies and amplitudes. At various times he claimed it
1) Made paper stronger
2) Aged wine
3) Could filter industrial smokestack pollution
But after many years working with engineers, I finally realized that gramps just wanted to make the loudest, highest frequency sound possible.
His patent (one of many, no he wasn't a troll, he built everything he patented) http://patent.ipexl.com/US/3708033.html
At one end he had a geared down variable-speed motor that pushed the slinky with a sine wave motion. I believe the other end was fixed. In between, he had painted various parts of the slinky blue. The blue parts seemed to be completely still, even as the areas between the blue pulsated back and forth.
He said it was a demonstration he built "to show my ninkompoop investors about standing waves".