@rplst8 posted:I don’t know a ton about train brakes, but it’s sort of interesting that the emergency failsafe on railroad cars isn’t more like those in tractor-trailers. There a spring applies the brakes until enough air pressure is generated to lift the “parking brake” off of the actuating rod.
Any rapid loss of air pressure results in the spring returning and applying pressure to to the control rod, which rotates the S-cam through an actuating rod. The design of the cam allows the brakes to be held on with almost no effort by the spring.
That would have been my guess as well
