Brake Light Question

It's the pull out and twist style like a Toyota pickup.

 

George Westinghouse.
The brake system for trains also kept a part of the train from rolling back down a grade if it broke off from the part with the loco (which has the air compressor).
Always thought the system was used on early semi-coupled setups to stop the trailer if it broke loose from the tractor.

 

It completes an electronic circuit, but do you think there might be a reason they’re installed on ports on the treadle valve?

Whaaaaaat?
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This to me doesn’t even look close to what you describe.

 

When you push in the yellow knob, air flows through it and to a valve… it may be a Quick Release (QR-1 or QR-1C) valve or a relay valve (R12).

With a QR-1 valve, the air will push down a rubber diaphragm over the exhaust port and air will flow to the spring brake chambers.

If it uses a relay valve, the air will push down a plunger which covers the exhaust port and opens up the inlet port, which runs directly to the primary air tank.

Air then flows to the spring brake chambers, filling diaphragms in those chambers and pressing against a large spring to compress it.

When you pull the yellow knob out and cut off air flow to the Quick Release or relay valve…

With a QR-1 valve, the rubber diaphragm will pop back up, and that opens the exhaust port. With a relay valve, a return spring pushes the plunger back up and opens the exhaust port. The air is vented out through those exhaust ports, aided by the pressure of the spring.

 

Air does in fact work the brake light switch. It's a normally open switch that when the pedal is depressed and air flows to the brake cans the pressure closes the switch thus turning on the brake lights

 

Would it be better to make it complicated? LOL

 

The effect is the same but the mechanism is different. Trains don't have spring brakes and rely on a pressure differential valve to apply brakes in either service or emergency modes depending on the differential and rate of change. The air applied is stored on the car itself, in that football shaped thing under the car which is the air two tanks siamesed together.

Cars can run away after a break and cause destruction, either by intention or error. I worked with someone who was hit by runaway loaded cars in a downtown area, they knocked his locomotives off the track. It happened at a grade crossing during rush hour.

Events like that are the reason I sit far back from crossings while the gates are down, why I look up and down the tracks when I cross, because stuff fails.

Couplers and air brakes were not enough to prevent railroad deaths and injuries. At one particular hump yard there was still an average of one fatality a day into the 40's.