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[quote user="wsherrick"] [quote user="wholelephant"] Does anyone know, then, 1) how big a train the A could haul at 60 mph? What happened to N&W fast freights after dieselization? Figure this is the more critical figure today than the decade of dieselization, when the diesel's advantages on slow, heavy trains and fast light trains were more decisive. The speed limit today comes from the expense of fuel on fast freights. It is well documented in the pages of TRAINS if little realized that diesels are very, very expensive on fast, heavy trains, 5 hp/ton being about the economic limit. July 1970, January 1974, May 1986, April 1990. The Niagara was both more powerful at 60 mph than a 6000 hp E7 and cost less to operate, on the other hand, per March 1984 article. Too bad one was never tried on a Flexi-Van. 2) How fast could a 2400 hp SD24 or 2500 hp SD35 haul 5,000 tons? [/quote]The average time freight tonnage for an A Class was 5600 tons.  Their maximum tonnage ratings for that speed was 7500 tons.  That's not a mis-print.  This was determined in testing and in actual practice could take a few more tons at that speed if required.The fate of the N&W's fast time freights was the same as most other railroads after dieselization.  They vanished.  The era of "drag freights" returned as railroads tried to cut costs buy piling as many cars into a train as they could which as a management decision, reduced levels of service with the result that time sensitive merchandise, etc. only went over to the truckers all the faster. A single SD double digit anything can't haul 5,000 tons.  It takes several of them to do it.[/quote]Time freight, 60 mph? 7500 tons? On straight, level track? This is not an urban legend? The bumblebee flies anyway?My figures are taken from LeMassena's Turntable, January 1974, that a single 3600 hp SD45 can haul 5000 tons on straight, level track at 35 mph, two at 51 mph, three at 62 mph, and four at 70 mph, these taken from an EMD publication. By these figures, then, the Class A was indeed doing the work of 4 1/2 SD45s at 60 mph.Three SD9s hauled 18,000 ton trains on the DMIR, at somewhat less than 30 mph.It is not a question of steam or diesel being better, but which is better for which task. The misbegotten ACE 3000 was a GP40 equivalent sent to do the diesel's job. Withuhn's otherwise superb June 1974 article barely mentioned steam's advantage at speed, but not divided drive's, and was oriented only toward drag freight performance, the diesel's forte.There is a crying need today to increase freight train speed. Diesels can do it physically but not economically. As James McClellan was quoted in May 1986, they "crapped out" at speed.After reading those 1945 Railway Mechanical Engineer pieces on the Pennsy steam turbine, it does seem to me that is the way to pull a 5000 ton train at 80 mph. Put a Q2/Class A size boiler, with the Porta/Wardale improvements, on 4-10-4 running gear, with a proper booster for under 20 mph, and we have it, the Q-3. Also in that 1945 RME is an editorial on boilers having the greatest room for improvement.
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