Why?

[dave9999]

John,
Thanks again. Dave

[jwar]

Hi Dave
Im degressing back a few years ago F7 GP 7-9-20-35 and 40s. I worked for a road that used EMD and GEs. They were connected by the MU electrical connector between the unit that had possably twentiy or so wires in them. As the engineer set the throttle up a notch in the lead unit a signal was sent to the following units electrical systems and all the engine govenors would go up a notch. There were only eight speeds the engines ran 1 to 8. The govenors were compinsated to altitude and delivered the same horsepower at sea level as at the top of the summit. The engeneer ( I was a locomotive machinist (mechanic) mind you not the engeeneer) could then set another selector with four settings which were electrical loading to the traction motors. If one traction motor of any of the units had wheel slippage the engeeneers wheel slip light would inform him to either reduce power or apply the sanders for better traction and he also used the amp meter help him make control adjustments.

Being the wheels were driven by electrical motors it dident matter if the following wheels were the same size in dia. as long as they were all a freight ratio, as passenger units had a higher gear ratio. If I remember correctley we had problems running GP35's with F7s due to the difference in traction motors and overall weight.

I had a sign over my desk that stated " It wasent my job the blow the whistle, nor even clang the bell, but if the damn thing jumped the tracks, guess who catches hell.

Im useing only DC on my layout. I cheated a tad MUing units, glued the knuckles shut. May not be the proper way to run a railroad...but it works for me LOL. Take care...John

[Anonymous]

Dave - the diesel engiens are just generators that power the electric motors for the power... they run a computer type control cable to get them all rotating at the sane rpm's.

[dave9999]

John,
Great explanation. Now, maybe you can explain how they get three or four different
locos to operate together. In other words, match speeds, acceleration and such.
It would seem like locos from different manufacturers, most of them with different horsepower and traction motors, would be impossible to match up.

It sometimes takes me a couple of hours of tweaking CV's to get two model locos to run together in sync. Thanks Dave

[jwar]

First of all Welcome to the forum michaeli.

Locomotives have control swiches in the cab to desiginate which end ( long end or cab end ) the unit is to power in a foward direction.. If the lead engine is cab to the front it will be set to "lead cab end forward". It will be the control unit and the following units will respond as if one, in unison.

The second following units electrical selector switch will be placed in "Trail long end forward" and air brakes set to trail, if the engine as you say is running backwards.

The third unit may be cab to the front and will be placed in "Trail cab forward".

The forth unit may have engine problems as the engine died, it would then be placed in 'dead in trinsit' and would be in a since as if it was just a box car.

Now all units are electricaly set to pull in the same direction by the lead units control stand, however if any of the following units selector switch is set wrong, they could pull or push against each other. this MUed (mulitipal units ) consist would be set usualy buy the shop crew, electricians, machinist and inspectors from point of origin. Perhaps even by the train crew if any unit is added on latter.

Most roads run with the cab forward for the crews visability and saftey. Its easier to have two units with the cabs facing away from each other, to make the return trip home, with having to turn them on a wye or turntable.

Wi***o welcome you again, however it would be very helpfull if you could state what type of info you desire as the word "why" is all inclusive and there are some of us that wont enter a post if its not a tad more specific.

This is a great forum and you will find some good info and great people here, Take care and have a great day...John

[Anonymous]

Thank You! I thought that might be the case, but I wasn't sure.

[andrechapelon]

QUOTE: Originally posted by michaeli

Help me out here please? I am wondering why on long trains some of the locos are running backwards. Are they actually working or what? Why do they do that?

They're bi-directional. From a power output standpoint, it doesn't matter which way they're facing. All the locomotives in a consist are under the control of the engineer in the lead locomotive as they are connected electrically.

Andre

[Anonymous]

Help me out here please? I am wondering why on long trains some of the locos are running backwards. Are they actually working or what? Why do they do that?