a question for the trainmen:
is it an operational problem putting motive power units together that have different gearing?
A scenario I am considering has a F unit with 62:15 gearing coupled to another F unit with 65:12 gearing.
other than a limit on top speed with the lower geared unit, is this a non-issue or does it bring about a significant operating challenge?
Replies sorted oldest to newest
No problems at all. The 65:12 gear ration equipped unit/units have a lower "minimum continuous speed" than the so called standard, for freight, 62:15 gear ratio. When mixing units, the top speed is NOT as important as the minimum continuous speed, i.e. get a unit with "passenger gearing" and lug it way down slow, and you will most likely do damage to the traction motors AND the main generator.
great, thank you.
Now, you really have to be careful if you have a consist of AC and DC units...and the AC is lead!
Now, you really have to be careful if you have a consist of AC and DC units...and the AC is lead!
Why do you say that?
A few years ago, we were sent down the Creek with an SD80AC and a GP40-2 on 60 loads. The SD80 was fine marching up the hill, but I had to sit back in the GP40-2 and keep an eye on the ammeter. We got down to it in the last pull, but made it over. But I tell ya, that GP40-2 smelled like a backyard-BBQ. It was wonderful.
Why do you say that?
Because the AC unit will constantly go back and forth and the DC unit will only pull in one direction. 
Actually, Dominic, I ran many a train with an AC on the point and one or more DCs trailing. No problemo. All computer DC locos (which is pretty much everything after the EMD 50 series or the GE dash 7's) will automatically cut their power back if their traction motors, alternator, or engine gets too hot. The train drivers of today don't have to do anything. (Except maybe double the hill when those units do cut back. Been there done that). Now if the trailing DC unit(s) are say a 40 series or earlier then the engineer needs to be aware of those units' short time ratings and operate accordingly. Of course if it is 25 below zero outside you can stretch the time quite a lot. Even in warmer weather if you don't mind the smell of traction motor smoke you can go over the hill. 
That is the concern I was thinking about.
>>Because the AC unit will constantly go back and forth...
Sixty times a second?
Access to this requires an OGR Forum Supporting Membership
