Hi, I got some basic knowledge about how pneumatic brake system work on modern trains. But they are still some mysteries for me. If someone smart enough could explain me why …. 1) why does manometer which shows pressure in brake cylinders [1b) I guess in cab manometer shows those pressures on locomotives bogies, but that value should logicaly corresponds to all brake cylinders of coaches connected to system, right?] drops to zero when Electric brake (braking with traction motors on locomotive bogies) starts aplying it’s braking force? 2) when uncoupling coaches from locomotive, what pressure should be in main pipe line? I mean full train brake applied or full release. I can image that when full train brake is aplied, the pressure in brake pipe is around 3 bars. 3) And as far as the brake pipe line is deatached in one point, the whole train gots full brake becouse of pressure drop, right? 4) any short brief about Brakes overcharge reason and situation example?
1) It can only show the bogie cylinder pressure, as they are connected to the gauge. Cyl pressures throughout a train (if not electropneumatically braked, meaning cylinders are triggered electronically) will change with a delay as air travels slowly. Electric braking is most effective when it can transform all kinetic rotational energy into current, that's why brakes are being released until electrical braking isn't sufficient (too low / high speeds) 2) I'd say full service. Really depends on the situation and TOC rules though (bottling the air in the US). For the game, it's best to make a full service before uncoupling. 3) Yes. As brakepipe pressure immediately drops, brake cylinders get filled from the reservoirs which open due to no pressure from the brakepipe keeping them closed. (In case of a consist split when hoses are disconnected, the train will come to a halt.) 4) Cylinders react on BP pressure difference. Not all locos operate at exactly 5.000000 bar. So you're overcharging it a little to make sure all cylinders will respond equally after changing locos / to cab car). A bit similar to when your ears are "shut", you're squeezing your nose and "pump" a little air in your head to free your ears again...
1) The electric brake works like a dynamo, converting the kinetic energy from the wheels rotating into electrical energy which is then dissipated. In order for the electric brakes to be effective, the wheels need to be turning, so the brake cylinders on the locomotive only are released. If this did not happen, the electric brake and brake cylinder would be fighting each other and the brakes would be less effective. The brakes on the wagons are not released, since there is no electric brake on them. You are correct, the manometer only shows locomotive brakes. 2) I don't know what official procedures are, but I like to apply full service brakes and apply the parking brake on at least one wagon before leaving them. 3) Yes. 4) Mainly use for faults as I understand it. If a wagon is not properly releasing brakes at 5 bar, or if the locomotive is struggling to build up pressure, you use overcharge to help things out until the problem can be sorted in the depot. EDIT: Ooooh someone beat me to it!
