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[quote user="MichaelSol"][quote user="Murphy Siding"]      I would think that being able to make the cars lighter, with higher capacity, would mean the trains would/could be the same length, but with a higher total tonnage.     I've always wondered, about coal mines and coal receivers that use dedicated equipment.  It would seem that developing equipment that would allow you to haul more tonnage, in the same length of train, yet still fit through the receiver's dumper would pay some handsome returns.[/quote]How?Equipment that is railroad owned but shipper specific carries inherent economic risks, including a negotiated price risk: the railroad is the hostage to the equipment, not the shipper. Further, car weight and capacity, for an econometric analysis, measures averages -- the average of loaded and empty, for which the economic impact is most strongly influenced by the overall empty return ratio, not the difference between the tare and loaded weight. The second most important influence is the interest rate on the equipment purchase. The third most important factor is productivity or utilization. Specialized equipment is especially sensitive, in all the wrong ways, to railroad congestion and variations in shipper demands. The fourth most important factor is route specific. Required drawbar force is the sum of several resistance forces which vary in extent and proportion with the operating conditions of the particular lines of railroad. These include grade resistance, curve resistance, train resistance, and acceleration resistance. Which drawbar strength need is that 110th car designed for, aside from the fact that it is the 110th car? Where do you put the DPU?Normally, experienced people talk in terms of economies of scale. This discussion seems designed to try and figure out just how to make production of railcars as specialized and customized, and expensive, as possible, with car specs and inventory needs multiplying like rabbits. [/quote]I understand your points about specialized equipment.  I am only pointing out the inherent tare weight penalty on all cars in a loose-car system, and how a fixed car train-set can overcome that penalty as well as the penalty of slack.  It is not my idea, and it is not even a new idea.  I am not advocating it, and I am not even in a position to see all of the pros and cons of it in any application.  However, it is one direction that the evolution of freight cars could take.  To your question about the 110th car:I assume you are asking about the 110th car in a conventional loose-car train.  As such, its design strength must be adequate to be the first car in any train, and be strong enough to pull what has generally become established as the longest practical train length, say around 200 cars.  In short, that drawbar needs to be as strong as all drawbars are today.  In a dedicated train-set of say 120 cars, where cars are permanently coupled, the 110th car's drawbar only needs to be strong enough to pull 10 cars because that 110th car will always have ten cars behind it.
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