Is the cost of the addition al weight of a heavy locomotive really worth the cost? From what I have read the added weight adds only about 9000 pounds of added tractive effort. I believe that they use heavier steel frame work and does it make economic sense for so little a gain in tractive effort?
On my carrier's most severe grage a 'Heavy' is rated 200 tons more than a regular AC. On a more level territory a 'Heavy' is good for 1350 tons more than the regular AC. More tonnage = more revenue. Additional revenue tonnage per trip adds up over time.
Never too old to have a happy childhood!
A cost-benefit analysis of increased weight in AC-traction locomotives isn't meaningful unless it considers the increased adhesion that results from the advanced control features that leaverage the increased weight into increased tractive effort. Using CSXT as an example. . .
If the weight of a conventional AC4400CW, which could probably be relied upon to maintain about 35% adhesion, were increased from 412,000 pounds to 432,000 pounds, the increased 20,000 pounds of weight would result in a tractive effort increase of about 7,000 pounds. That TE increase would not be worth the cost of the increased weight -- which is why CSXT has never increased the weight of an AC-traction locomotive without making adhesion-control improvements to it.
The adhesion control systems that are installed on CSXT's 432,000-pound AC-traction locomotives are capable of maintaining adhesion levels of from about 42% to slightly above 46%. That, in conjuction with the additional 20,000 pounds of weight, results in estimated TE increases of more than 37,000 pounds and 54,000 pounds, respectively, in comparison to the railroad's conventional AC4400CWs. TE increases of those magnitudes do justify the cost of the additional weight (as well as the cost of the adhesion control enhancements).
JayPotterThe adhesion control systems that are installed on CSXT's 432,000-pound AC-traction locomotives are capable of maintaining adhesion levels of from about 42% to slightly above 46%.
Does coal still go up Cranberry? With four ACs to 13000 tons?
CSXT rates one of its high-tractive-effort GEs for 2,900 tons eastbound on Cranberry Grade; and tonnage trains dispatched east out of Grafton are generally sized for somewhat less than 11,600 tons. Moving a train of that size by four HTE units would require each unit to maintain only slightly more than 32% adhesion on Cranberry Grade; however not all tonnage trains dispatched east out of Grafton are headed by HTE units. The most common scenario in which an HTE unit would attain 42% or greater adhesion on Cranberry Grade would be when the head-end consist loses adhesion and the helper (which always consists of HTE units) must produce an increased amount of tractive effort in order to avoid a stall.
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