On that thought,
I worked on and drove (just a test drive) a 1932 Marmon car with the aluminum V16, a very fancy car.
It had vacuum assisted mechanical brakes, and they worked really well, better than I would have ever guessed.
All the linkage was mechanical, similar to a Model A ford, but on the cross shaft that then pulled the linkage for each weel it also had an arm for a vacuum diaphragm to pull on. To control it was a vacuum valve in the rod from brake pedal to the cross shaft.
The way the vacuum part was controlled and operated was similar to air assist power steering, or similar to the early Chevy PS. Otherwise all mechanical, but with a sensing valve and then a cylinder to help the mechanical stuff.
Grigg
