I just found a nifty little track plan in the data base called the Appalachian Central, published in Jan '02 MR and in 102 Track Plans. It’s a pretty neat little island layout with what I’m assuming is a coal mine as the focul point of the layout. It has a nice small yard with an interchange track on it that I think would be better made as a small yard in an urban setting where helper locomotives are switched in/out of consists to help an the grade (as written 2%). As far as I can tell the mine tracks could fit a total of 24 50-55T hoppers.
My question is would that small of a consist (25 loaded 55T hoppers) even need a helper engine? What engines could be used? F-units? 1st gen geeps? 1st gen seeds?
Is your question more prototypically based or model based? If prototype, then probably no helpers needed, 1st generation SDs would fit well since the extra axle helps spread the weight and tractive effort over track that is not that well maintained.
If model, then I would use helpers since our train lengths are usually representative. Few of us have large layouts running prototype length trains. Many layouts I’ve run on limit train lengths to 20-25 cars to represent full length trains so using helpers would help foster that illusion and add some operational interest.
What kind of grades are on the layout, and, since you’re modelling an interchange, what kind of grades would be just off the edges? In practice, if the line is mostly flat but has a steep grade at one point, it might be more economical to add a helper just for the grade, and then cut it out. This is particularly true of a cargo like coal, which is not particularly time-critical, so the delay to add and remove the helper would not cost the railroad much.
The only track plans in the Jan 02 MR are the “Rock Ridge Central” a 4x8 HO layout, the “The Western Coal Hauler in N Scale” a 3x16 N scale layout and 2 very large layouts.
Oops, found it, its in the Jan 2000 MR. I wouldn’t make the yard “urban”, unless you consider 3 or 4 two story brick buildigns an “urban” setting. I would keep it a small town. I only see about 27" of room at the mine (remember each track should only be HALF full or else you’ll never load any cars.) At about 4 in per car, that’s about 9 cars, 3 per track.
Engines sould be a AA set of F’s or more likely a road switcher or two.
I also think the staging is bass ackwards because any train coming out of staging has to run around itself someplace to get back into staging. Part of the lower staging needs to be reversed.