Just as the comment that a Mike could pull 100 cars is true on level track, once you start adding grades on par with what model railroads use you end up with things like B&O using three EM-1s on a 75 car drag or DRG&W using two L-131 type 2-8-8-2s on 58 cars. In the case of the EM-1s the minimum speed got down to around ten miles an hour and in the case of the L-131s two engines were used so that speed could be held above 25 mph throughout the run.
Given the fact that both curves and grades increase resistance (and sharp curves are speed limited as well), most layouts should be looking at what heavy power they need to pull twenty or thirty cars rather than worrying about getting their average single engine to pull more than ten or twelve cars and possibly 15 or so with some of the more powerful modern engines.
When I had a fairly large layout I had a scale for engines such that when a train came in with a Mike but needed greater speed on the next leg of its journey it would have a Mohawk replace the Mike. When several trains were combined, an even larger engine would replace the others. I'm not afraid to weight an engine when I need to, shoot, I have a couple of brass articulateds that weight in at 4 1/2 pounds each. That's enough weight with the motors they have to combine three other trains for the next leg of the route and fit into the scale car limits very well. It's also enough weight to pull 120 hoppers with various flavors of trucks in a test run on someone else's layout. Do my Connies or Mikes need to do that even on straight and level track? Not unless I want it to look like the RR management is stupid for buying the larger engines. When it comes to diesels, the dynamic brakes sold them to RR management as much as anything else and it takes several engines to hold the train back with dynamic braking and limit the brake applications. The savings in brake shoes must be incredible if you think about it and if it takes an extra engine to go up the grade, it probably takes at least that much to hold the train back going down it.
JMHO, but unless you're planning a layout with no grades and twelve to fifteen foot radius curves you shouldn't be pulling much more than a ten or twelve cars without using multiple diesels, something made extremely easy using DCC consisting.
Given the fact that both curves and grades increase resistance (and sharp curves are speed limited as well), most layouts should be looking at what heavy power they need to pull twenty or thirty cars rather than worrying about getting their average single engine to pull more than ten or twelve cars and possibly 15 or so with some of the more powerful modern engines.
When I had a fairly large layout I had a scale for engines such that when a train came in with a Mike but needed greater speed on the next leg of its journey it would have a Mohawk replace the Mike. When several trains were combined, an even larger engine would replace the others. I'm not afraid to weight an engine when I need to, shoot, I have a couple of brass articulateds that weight in at 4 1/2 pounds each. That's enough weight with the motors they have to combine three other trains for the next leg of the route and fit into the scale car limits very well. It's also enough weight to pull 120 hoppers with various flavors of trucks in a test run on someone else's layout. Do my Connies or Mikes need to do that even on straight and level track? Not unless I want it to look like the RR management is stupid for buying the larger engines. When it comes to diesels, the dynamic brakes sold them to RR management as much as anything else and it takes several engines to hold the train back with dynamic braking and limit the brake applications. The savings in brake shoes must be incredible if you think about it and if it takes an extra engine to go up the grade, it probably takes at least that much to hold the train back going down it.
JMHO, but unless you're planning a layout with no grades and twelve to fifteen foot radius curves you shouldn't be pulling much more than a ten or twelve cars without using multiple diesels, something made extremely easy using DCC consisting.