wsherrick wrote:Now, this is basically how the Westinghouse Brake works. You have an air compressor on the Locomotive and a large tank called the main reservoir. The air for the brake system is stored in the main reservoir. Then it is connected to all the cars on the train by the brake pipe. On each car or coach you have an auxiliary reservoir which also stores air. The brake pipe and the auxiliary reservoirs are kept at the same pressure. On a freight train that is 90 lbs psi.
To apply the brakes, the engineer releases a measured amount of air out of the brake pipe. This air escapes to the atmosphere. You have gauges which tells you what pressures are in each part of the system and how much you release during an application of the brakes.
What happens then is that the difference in pressure between the auxiliary reservoir and the brake pipe causes a valve to move under each car which opens a port which directs air FROM the auxiliary reservoir to the brake cylinders on the car and applies the brakes at the exact same corresponding pressure that the engineer released from the brake pipe. You can only reduce the brake pipe so much. On a freight train it is twenty six pounds. After that you get no more braking pressure.
You can't modify the application. Once you have taken it out, that is how much braking effort you get. If you apply to much brake, you have to release the brakes and re apply. You also have to closely monitor the pressure in the Main Reservoir. It is easily possible to over use the brakes and run yourself out of air. In that case you must release the brakes and allow the compressor to recharge the main reservoir and brake pipe.
The system works by REMOVING AIR from the system, that was designed to make it fail safe. If the train brakes in two or there is any disruption in the pressure in the brake pipe then the rapid loss of air causes the brakes to be applied on every wheel at an emergency rate. The engineer also has the ability to place the brake system in emergency. This is called, "dumping the train." Even in emergency, it takes a long time for a speeding train to stop.
The Hand Brakes referred to here are manual brakes that are applied on each car individually. These are only used when cars are placed in sidings or other such times. The hand brakes are never used while the train is in operation.
There is a whole lot more to it than I have explained here. If you have any questions, I will try to explain it to you.
Very good write up, I learned some from that. I run a trackmobile at work, we move rail cars full of cement around ( about 100 ton of cement in a car ) I usally have anywhere from 10 cars to 15 on the trackmobile. I"am not a railroad person and I really don't know much about there procedure, but I was told when I air the cars up to release the brakes I should go by a simple rule,,, 7 minutes for the first car then 1 minute per car after that. Also when applying the brakes for a emeragancy stop I was told that that is called "dynamiting" the brakes. Like I say, i'am no train expert.