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[quote]QUOTE: Originally posted by Murphy Siding Dave: I'm not saying your premise is incorrect-that it might be cheaper to change all the heavy axle-load railcars than to change all the track structure to carry the heavier axle loads. I am suggesting that you're doing sort of a mixed-math-metaphor type of trying to quantify a number. If the engine in my car was made 15% lighter, the whole car wouldn't cost 15% less. It seems to me, that the railroads would have had to have this axle-loading vs. rail structure problem worked out in the 1960's, when they went to 286,000#. It's too late now. [/quote] First, a few corrections: 1. Someone emailed me that the 115#, 136#, etc. rail is per yard, not per foot. That would make more sense, and does change the calculations dramatically, albeit in favor of lighter rail. 2. As to that "one million a mile comes out to $20 million....", well, I have no idea where I came up with that. On reflection, it makes no sense, so on that one I am way off. All I can say is put it in the [%-)] file along with "conical driving wheels". Well, nobody bats 1.000! Now, I'd like to comment further on something mudchicken brought up - the "track modulus" effect, wherein (if I am correct) the rail will bend down vertically as a bogey passes over. He stated that the effect is greater with the lighter rail than the heavier rail, presumably because of less vertical rise in the rail itself, or that lighter rail is a few inches shorter than the heavier rail. And it makes sense, since the effect is the same whether it be 80 tons on a two axle truck or 80 tons on a three axle truck, 80 tons pushing down is 80 tons. Since the lighter rail would have more "bend" the supporting components underneath the rail would experience greater wear. What I have observed today is that from a trackside standpoint a 264k car running over both lighter branch line rail and heavier mainline rail, there is no observable difference in the degree of "bend" when a loaded 264k car passes over (and they were presumably loaded because both were outbound and/or westbound), therefore is there really a significant difference in rail support component wear? The relative degree of movement in the rail looks to be the same, so where's the gain attributed to heavier rail for this particular dynamic? Are there any studies available with measurable variables to support the notion that heavier rail will cause less wear on support components? Although the heavier rail is "taller" and therefore would spread the impact more longitudinally, is that really enough to offset the 2 inch height difference?
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