Comments on: Why Do Some Lash-Up Engines Face Backwards?

By: Frank B

Frank B — Wed, 22 Nov 2017 20:54:44 +0000

For long freight trains, multiple locos will be needed to provide sufficient force to pull the train.

For convenience, the power consist (the set of locos) will be assembled with a cab at each end to avoid having to turn them all round at each end of the line. A siding can then be used to easily run the loco set from one end of a freight train to the other, and the engineer just gets in the other cab.

“A” locos have a cab. “B” locos don’t, but (with the trailing “A”s) are all controlled from the cab of the leading “A” unit.
So a power consist of four locos might be A-B-B-A, to have a cab at each end.

By: WES

WES — Fri, 10 Nov 2017 20:37:42 +0000

Tim Morlok’s answer about engine facings is a good one.

Regarding whether they are all used or not, sometimes one or more diesel will be powered, producing power (AC or DC, depending on the particular manufacturer) to applied to traction motors on various axles. This way, the power can be energizing many wheels to provide better pulling power (think of the physics of a Shay engine).

To help determine how many and which diesels are actually operating, watch for heat waves above each loco’s stack. These are the units providing the electricity.

By: Tim Morlok

Tim Morlok — Fri, 10 Nov 2017 00:39:13 +0000

As a former Union Pacific trainman/conductor, I can say that each engine in the multi-unit consist is controlled from the lead unit via the MU cables between each unit. Some of the units can be on line and some can be just in tow ( transferring power to a location where they are needed). Some times the power of the whole consist is not needed. Depending on the tonnage and grades in the part of the run the train is on, the dispatcher and the engineer will determine the number of units on line at any given time. The engineer must manually isolate or shut down each unit that is not needed. Except in cold weather conditions, the units are usually shut down (to save fuel) for the part of the run that they are not in use. The direction that each unit faces does not matter except in the case as stated in the reply above.

By: John Mauro

John Mauro — Thu, 09 Nov 2017 13:25:12 +0000

I don’t know

By: Larry

Larry — Thu, 09 Nov 2017 01:57:01 +0000

If I am understanding the question, it is for the return trip. Say the Main line is an East-West route, the
Engines are mated together, facing opposite directions. The Locomotives do not use a transmission that a personal Vehicle does. So the traction and gearing mirror each other. (Work the same in both directions). Rotating Turntables are not used much in my area.