I don't know of anyone who works on them but I have a pdf that I downloaded from the net. It has a lot of Info. I just don't know how to post it here. Google Truckstill and Tip-Toe Matic. There is a mention of them on the HAMB and also the Stovebolt BB I think.

Beater

"I wonder if God created man because he was disappointed in the monkey?" Mark Twain