The first power assist brakes I remember hearing about on the family's trucks were on 1934 and 35 Chevy single-drive tractors towing trailers from Milwaukee to Nashville hauling beer. They had vacuum-assisted mechanical brakes! I wish a few pictures of those rigs had survived! My grandparents' primary business was selling coal and ice, and they had a fleet of about 15 delivery trucks, but they also did over-the-road trucking of beer and dynamite.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!