Here's a 3.5 minute YouTube video with a brief history of the Shay including a nifty photo of the very first one.
It looks like something waiting to be modeled by someone here.
https://www.youtube.com/watch?v=8G7mHfIaWjE
The Shay salesman even managed to sell one over here in the UK, it went to a steelworks in Wolverhampton, West Midlands (only lasted 4 years though, I guess the fitters didn't understand this wierd machine!). One of the highlights in my life was "footplating" a working Shay at a sugar factory in the Philippines back in 1978.
Les
Thanks for the info ' Bill very nice and useful
Barney