Re: Need help with Vacuum Brake Equipment

Dan, If the brakes are applied by springs and vacuum holds the brakes off, then altitude would have nothing to do with max brake force. With this system, braking force would be determined by the force exerted by the springs and the lever lengths, and brake shoe surface area? To increase braking force to meet a higher max std. one would have to increase the spring pressure available, redesign lever lengths, or increase the size of brake shoe contact area.
On the other hand, it would seem that it might not be impossible to release brakes unless the brake cyl or diaphragm size was designed to adequately pull off the brakes with reduced atmospheric pressure at high elevations.
When I visited the NG mining rr at Kimberly, B.C, the builder of their equipment explained to me how he had designed the brakes for the cars around the emergency system that truck brakes use. The brakes are spring applied, but use air pressure to release. Sounds much like the vacuum system in reverse.