GLRX12 wrote:Thats because the natural position of the piston is retracted. It has a spring that forces the piston closed (and the brakes released) when there is no air pressure. Also, unknown to many people, car's operate the same way, but in a more complicated way. Its only the air pressure (on a straight air system like locomotive brakes, and certain freight and passenger equipment also equipped with straight air) that forces against the spring, and apply the brake. So when its retracting, it has to work against the escaping air pressure. And thats more powerful a force then the action of the spring.
I get it now, thanks!
GLRX12 wrote:In case anyone was wondering about car brakes, the triple valve turns a reduction of air pressure into an application of pressure from the car's reservoir. FourEightFour knows more about car brakes and brakes in general then I do.
I had to learn about triple valves when I was doing the air brake system for the Consolidation, to get it to simulate "peeing away your air". It made for fascinating reading. It really helps to see a cutaway diagram of the car braking system, to be able to understand how the change in air pressure in the train brake line, versus pressure in the auxiliary reservoir, changes the position of a piston in the valve so that different openings are opened, letting air from the auxiliary into the brake cylinder to move the piston and apply the brakes, or shutting that off and instead allowing air to escape from the brake cylinder and release the brakes, and seeing how it recharges the auxiliary reservoir from the train line. Then there's the emergency reservoir to take into account too (which I couldn't do properly in the Connie because of limitations of the core programme ... same story with bail off). Very clever stuff.