The Prof is here.
First, there is no way that LL was trying to "build in" the pulling capabilities of the Y3 vs the Y6b as I don't believe they were that much different. I have some books and will do a little research but believe all the improvements that the N&W was trying to accomplish and did so in a great many respects was in the effiency field. Less coal burnt, less water used, fewer stops for service etc all added to the operating ratio which affected the bottom line. That is why they were the last to dieselize. Their modern steam power was very efficient compared to older steam power and they were basically newer engines with a lot of life left in them. An empty freight car weighs somewhere around the 30,000 pound range. A big steam loco weighed somewhere around 1,000,000 pounds plus. If an N scale car weighs X number of ounces how many pounds would the N scale engine have to weigh to be camparable.
Yes a real locomotive can pull way more then a model loco just due to the weight factor. I assume that all railroads are basically the same when it comes to tonnage, after all a ton is a ton is a ton right. The difference is in the geographics of the territory being traversed. The NS figures its' tonnage ratings based on maximum grade on a district based on being able to maintain track speed. Sandusky, Oh to Portsmouth, Oh is relatively flat with any grades being of the downhill type.and an old SD40 is rated at 10,200 tons. A modern SD70 is rated at a little over 15,000 tons. We would send a 225 car empty hopper train out of Sandusky with one SD70 or the equivilent GE brand. All though the engine could have pulled way more we were limited on the length of train the district could handle (length of sidings mostly). Coming North out of Portsmouth towards Sandusky the grades were against them and the ratings dropped dramatically to almost 7,000 tons for an SD70 which meant a 150 car coal train weighing 18,000 tons would take 3 engines of this type. If one broke down enroute it did not necessarily mean the train could not make it, it just could not make it at track speed (45 mph max for a loaded coal train)
All NS engines were placed in to groups. Group1 was GP40, GP38 B23's etc. Group 2 GP 50's etc, Group 3 SD40, C37's etc, and so on up to the big ones in group 5. The Division Timetable would list the tonnage rating for each group across every district in both directions. The tonnage for a train was computor generated based on the weight of the car and the weight of contents either by actual weight or declared weight by the shipper. A 100 ton car of coal would actually be around the 130 135 ton mark when the weight of the car itself was figured in.
back to steam vs diesel. A single Y6b would handle a 200 car coal train from Roanoke to Norfolk with an assist from a pusher up the grades. Today it takes 3 new wide bodies and they still need the assist up the west side of the mountains.
I do not believe the story about the UP using steam in pusher service. They did at one time before becoming completely dieselized but not since then. The N&W, during the first oil crises, made serious studies about going back to steam but found the initial cost prohibitive. Now wouldn't that have been something!!
Mike
