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It's not often that I have a disagreement with Michael Sol, and granted I'm in over my head on this subject, but here goes.....[quote user="MichaelSol"] The idea of a dual-source locomotive makes little sense. EMD pitched a specific design to the Milwaukee Road in 1972, converting SD40 locomotives to alternative 3kV DC by the addition of a pantograph and related control equipment. Naturally, it cost more than either the straight Diesel or the straight Electric. This meant, when being used in the Diesel mode, it cost more per horsepower than a comparable Diesel-electric. When used in the electric mode, it cost more per horsepower than a comparable straight Electric. On 600-800 miles runs, there just wasn't a cost savings compared to simply switching motive power.[/quote]In this analysis, you're continuing to maintain two separate fleets.  But what if the dual mode locomotive allowed for a 1 for 2 replacement, aka 1 dual mode locomotive replaces 1 straight electric and 1 diesel?BTW - what was the proposed cost of the dual mode locomotive, at least relative to the costs of the electrics and diesels?  In other words, was the cost of 1 dual mode less than the cost of 1 electric and 1 diesel?  Same as?  More than?In the context of Milwaukee's decision to end electrification due to the expense of catenary rebuild, wouldn't the dual mode have allowed for some limited sections of catenary to be removed (aka Deer Lodge to Haugen), with the subsequent useful parts redistributed to the remaining sections of catenary?[quote]Too, combining a subsystem with a 92% availbility (the Electric) with a subsystem with 84% availability (the Diesel-electric), the resulting availability of the dual-mode machine was 76%, requiring more such machines to haul the targeted tonnage.[/quote]Where did these numbers come from?  Were they drawn from spec analysis, or did EMD actually provide a dual mode prototype(s) for testing?Again, in the modern context, is it necessarily true that a dual mode loco would have less availability than either straight electrics or diesels?[quote]Too, the concept undercut a key advantage of a straight electric locomotive -- the one-third cost of maintenance and the 30-40 year economic service life. Each dual mode locomotive gave up all of the mechanical and service life advantages of the straight electric -- key reasons for electrifying in the first place.[/quote]The FL9 had a useful service life running 50 years, didn't it?  What were some of the differences between the FL9 and the dual mode SD's that would account for the SD's having a lesser service life?[quote]Finally, every time one was used in its diesel-electric mode, crucial electric horsepower was unavailable under the wire -- and that was what the fleet investment was for in the first place, and also the limiting factor. It was a poor use of electric horsepower if the whole idea was to get the maximum utilization of system horsepower out of the high cost overhead instead of the high cost Diesel-electric. [/quote]I'm a bit confused on this statement - Did the Milwaukee try and run these locomotives in diesel mode while under active catenary?[quote]Again, the railroad had to look at a significantly larger and more expensive overall fleet to meet its needs, at a significantly higher cost per unit, in order to ensure maximization of the use of the catenary, if there was any likelihood at all that a portion of the fleet would be out "somewhere" burning up diesel fuel. And the numbers worked the wrong way there as well: for every diesel horsepower being used in the diesel-electric mode, the company gave up 2 electric horsepower. It made no sense to ever do that.They cost more, they were in the shop more, and the railroad would have needed more of them.It truly was a lose-lose proposition.[/quote]It seems to me the Milwaukee just had a crappy example of the dual mode concept compared to NH's experience with the FL9.  Granted, if the Milwaukee had no intention of reducing the number of electrified sections to preserve and extend the useful service life of more critical sections of catenary, then the dual mode locomotive concept probably didn't make a whole lot of sense.  It seems Milwaukee's attitude toward overhead wires was to either extend the catenary through the gap between Avery and Othello and thus have a premium electrified railroad from Harlowtown to Puget Sound, or get rid of it altogether.  Would this be a correct assumption?
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