ive always been wondering how locomotives push and pull evenly when latched in multiples? i suppose its all computer based nowadays. but how did the steam guys do it? its easy on a model train set with DCC but what about real life?
MU Diesel and Electric Locomotives use a Multiple Unit (MU) cable system connecting to each other for mu operation. The AAR standard is one big 27 pin cable for the electrics then there is 3 air hoses to connect the resivoir and such. The 27 pin connecter was the most important as it directed electricity to certain relays to change engine speed, direction, dynamics, etc. This standard wasn't around from the beginning of the diesel era so early ALCOs and EMDs aren't compatible and some didn't even have MU capability. This is also how Cab-Cars operate except the cables run through the cars to the tail end cab-car. Steam locomotive didn't have a way to MU so they used double heading. Each locomotive was operated by its own crew so they kept in visual communication and worked together to move the train.
ah so thats what the MU cables are for. without them it seems like it was a precision job to keep the locomotives in sync (i.e. steam). i get a knot in my stomach just watching my locos running in DC coupeled to each other and one running harder than the other since they arent in sync
Years ago I read an essay posted by Al Krug (Tales From The Krug) about how he started a double-headed steam train. Multiple steam locomotives used whistle signals from the lead locomotive to communicate required actions. When starting a double-headed train, the lead engineer would whistle two short, then wait for a response. The second engineer would then open his throttle, but the engine could not move against the stopped lead locomotive. The second engineer would then whistle two shorts to indicate that he was ready to move. The lead engineer would then release his brakes, open the throttle, and start to move which would allow the second locomotive to start moving, and thus the whole train. I hope some engineers with steam experience will chime in to correct me, and fill in other actions such as stopping, changing speed, etc. LEW or Jerry (DeBene), have you ever run double-headed steam?
its just all fascinating to me to know just how they balance it all (esp for steam). seems like its a precision job to do without computers.
