Can someone explain something to me about all this. I always understood that the Westinghouse air brake system was a fail safe system, and that springs held the brakes in the "brake" position until such time as a loco began to build up air pressure in the system
The springs are only used to release the brake because the air only travels in one direction and that's into the brake cylinder, springs aren't very strong either, one person can compress the springs with their hands while air can give 45~50PSI pressure which is allot of force, to release the brake you charge the brake pipe and the triple valve closes the aux res to brake cylinder port and opens the brake cylinder vent port which the spring now moves the piston to the release position.
Cheers.