When two or more modern North American locos are lashed together, how is the speed of the followers controlled? I’m looking for specifics, not “they have a thingy called a jumper and some hoses”. Maybe a loco Electrician or Electrical Engineer (GE/GM) is out there?
Where may I obtain schematics and/or specs. which describe the connections?
Thanks,
TOE
WELL FIRST OF ALL YOU HAVE TO START WITH THE JUMPER CABLES. THE CONNECT THE" ELECTRICAL BRAIN" OF 1 LOCO TO THE OTHER. BASICALLY WHEN YOU HAVE A LOCO WITH THE REVERSER IN NEAUTRAL, AND THE GENERATOR FIELD SHUT OFF IT IS IN “OPEN MODE”. THAT MEANS IT IS BASICALLY LOOKING FOR A CONROL INPUT. WETHER IT BE FROM THE CONTROL STAND FROM THAT OR ANOTHER LOCOMOTIVE. ID DOES NOT MATTER FROM WHICH END THE CONTROLLING UNIT IS CONNECTED EITHER. THIS IS ONE OF THE UNIVERSAL FEATURES OF ALL LOCOMOTIVES. SO IF YOU WANT YOU COULD HOOK UP A 1950’S SWITCHER WITH A BRAND NEW AC4400. YOU ACCOMPLI***HIS WITH LOCOMOTIVES WITH OR WITHOUT -2 ELECTRICALS OR MICROPROCESSORS
Perhaps it will be a little clearer if one remembers that the throttle – whether on one locomotive or a dozen – does NOT control the speed at which the locomotive wants to go, but controls only the POWER which the traction motors will deliver to the rails. In a MU lashup, what the engineer does is ask, using the lead engine’s throttle, his engine and all the trailing units to deliver a certain amount of power – let’s say notch 6, for discussion. Which, if all goes well, they all do. This is true regardless of the horsepower of each unit. So if the lead is, let’s say, and elderly RS11, and notch 6 produces perhaps 1,000 horsepower, and the two trailing units are SD80MACs (I did say discussion, guys) and 6 on them produces, say 3,000 horsepower, you have a total of 7,000 horsepower trying to move your train – and it is that total horsepower which determines how fast she’ll go.
So the various MU links control the throttle setting, reverser selection, independent brake, dynamic brake… I’ve forgotten something… train brake is lead engine only.
And speed is determined by the total power of the engines.
That help?
THANX JAMIE THAT MADE MORE SENSE THAN MINE. I KNOW WHAT HAPPENS BUT I AM NOT ARTICULATE ENOUGH. AS LONG AS I SIT DOWN IN THE RIGHT HAND SEAT AND I KNOW WHAT IS SUPPOSED TO BE WHERE AND WHAT IS SUPPOSED TO HAPPEN.
Jaime - is it fair to say that we non-railroaders should think of this as notch 4 means power rather than speed? As opposed to a car, which you step on the accelerator and we get speed. You can’t compare the two at all - they work very differently? I think I am getting there! Slowly!
Mookie
Actually it doesn’t control the power, it controls a series of valves which controls the prime mover speed (the governor). That’s why the engine revs when the throttle is increased. The engine will rev when the throttle is increased regardless of how much power is being produced. If you “turn off” the main generator, the engine will rev up in the steps, even though zero power is being produced.
The prime mover is directly connected to the main generator, so when the main generator excitation field is on, the higher the engine RPM, the more power produced by the main generator.
Dave H.
Mookie – you got it. Also, dehusman’s got it – the throttle on most engines (not all – F40s are a notable exception) does determine prime mover speed, and that controls power delivered to the traction motors. The only engines I recall where the prime mover speed and the actual speed of the train were closely related were the late (un)lamented RDCs and the diesel-hydraulics Krauss-Maffei units which SP and, I think Rio Grande, had years ago. Which were a back shop nightmare.
Amtrak’s F40s are perhaps the best example of the complete lack of relationship between prime mover speed and train speed – they run at the same prime mover speed (900 rpm I think, somebody correct me if I’m wrong!) all the time, so that the train gets the proper 60 cycle current. This is whether the train is standing still in the station, or going along at 79 mph. Fascinating…
I’m curious why anybody would want the electrical specs on a locomotive control system, since the original question wasn’t “how does it work”, but a request for the technical specs and schematics. Its not something a er could use, since no system (small or large scale) uses that system to control the operation of the “motor”.
Dave H.
dehusman,
I want the details because they will help me understand what is really going on inside. I’m in the industrial electrical/electronic business and have a pretty good grasp on the technology. I’m also a bit of a train nut.
Thanks,
TOE