Re: Need help with Vacuum Brake Equipment

Eames was a predeccesor to the New York Air Brake Co., still based in Watertown, NY. NYAB seems to have dropped all the older designs in favor of new owner Knorr's.

The vacuum brake was actually a spring vs. vacuum design. A spring applied the brakes, the vacuum released it. It did have the advantage of having a built in emergency function, and graduated application or release, and no chance of "pissing away" your brakes.

Simple physics proves the biggest drawback to a vacuum system. Atmospheric pressure is around 14.7 psi, and gets less the higher in elevation you go. You will actually get somewhat less than 14.7 psi in force due to leakage and resistance.

A 70 pound brake pipe has a normal service brake cylinder pressure of 50 psi. The current FRA standard of 90 psi results in a 64 psi service brake ylinder pressure. To equal the force developed by a air brake cylinder, a vacuum diaphragm would have to be at least twice the diameter, even bigger to meet today's requirements.