Railway air brake test rig

This is a traditional railway air brake. A drop in train line pressure engages the brake, drop in reservoir line pressure does not.

In the modern day, systems with a triple valve have been replaced or augmented by systems with distributors. Even on trains with rheostatic or regenerative braking, such systems are still used for redundancy.

The main reservoir line doesn’t need to charge aux reservoir, since pressure in train line will also charge it. Some trains may not need to use more than a single line across carriages anyway.

I do not recommend using an analogue lever as the driver’s valve. Use a counter to make a lever with five positions if it’s possible in your use case.

Do not leave the driver’s valve connected in a train. Use valves to disconnect it from the braking and reservoir lines in all units except the controlling unit.

In the release position, train line pressure will be charged quickly to that of the main reservoir. Pressure in the brake cylinder will be very quickly released by the triple valve. Aux reservoir will be fully charged from the train line.

In the running position, train line pressure will be slightly lower than that of the reservoir and pressure in brake cylinder will still be released by the triple valve. Aux reservoir won’t be fully charged from the train line.

In the lap position, train line pressure will be lower than that of the running position. The triple valve will not charge nor discharge the brake cylinder or the auxiliary reservoir. If your system has no leaks, pressures will sit still.

In the application position, train line pressure will be significantly lower than the pressure of any reservoirs and the reservoirs will charge the brake cylinder. Brake is applied.

In the emergency position, train line pressure will be exhausted. Brake cylinders will be charged by the auxiliary reservoirs due to the drop in pressure. Brake is applied.

Dark red: main reservoir line pipe (charging train line and optionally aux reservoirs)
Blue: train line pipe (brake control. drop in pressure = brake engages)
Orange: driver’s valve (charge/discharge train line)
Bright red: triple valve, aux reservoir and brake cylinder (charge/discharge brake cylinder, actually engage brake)
Pink: reservoir pipe cutoff (cut off the reservoir pipe if you do not wish to charge the auxiliary reservoir from the main reservoir)
Lime green: output function for train wheel assembly

(warning: off steam) railway technical website’s complete overview. good diagrams[www.railway-technical.com]
(warning: off steam) integrail’s description of the driver’s valve. text only[www.integrail.info]

You’re free to use the air brake in part or in full on your creation or take inspiration from it. Attribution advised but not enforced.