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[quote user="MichaelSol"] Futuremodal has expressed his interest in dual-service locomotives, and while I happen to think the idea can't fly from a strictly economic perspective, ideas like that offer a challenge to think about.This was the Electrical Engineer's perspective, and he was interested...Office of the Electrical Engineer Chicago, Milwaukee, St. Paul & Pacific Railroad Co. 1100 East Milwaukee Way Tacoma, Washington 98421September 7, 1972Mr. R.B. Wallis ElectroMotive Division La Grange, Ill. 60525Dear Mr. Wallis,You asked my opinion as to the merit in augmentation of diesel output by separate electrical supply on the Milwaukee Road.To give some current perspective, TE curves of an SD40 and SD45 have been added to the curve you prepared (attached). The general conclusion indicated is that augmentation essentially doubles the SD40 output horsepower in the mid range speed using a double drive motor from the separate electrical supply. Such conclusion would suggest further exploration of the scheme.This system, which presents a new management alternative to resolution of the electrification status, would not require wiring the gap or upgrading substations or feeder. It would allow through operation of power on the Idaho. It would utilize standard diesel parts as used throughout the country. It would allow continued use of the EF-4 engines.The added engine complexity would be countered by fewer units required and reliability and flexibility added by two power sources.Such a flexible system suggests that time could be bought during a transitional period of uncertainty on railroads as regards mergers, coordination, motive power technological development, fuel-energy concern and possible Federal government encouragement of electrification.Recognizing that our trolley efficiency varies as the square of the voltage and that the boosted conversion introduces a loss, the desireability that the unit accept 3000 Vdc becomes evident.The augmented diesel could serve as a transition by other railroads to full electrification and give incentive to hardware development.The hard fact of life-weight on drivers must still be faced. This suggests the possibility of developing a solid state module that could go in parallel with an individual traction motor. This could supply additional controlled energy to each axle modulated to result in the 25% adhesion which ASEA has attained (see schematic).With individual controlled added power to each axle, rapid dropping of this power to prevent slipping would tend to throw the load over to the diesel generator I believe.This alternative would have to be justified on the basis of reduced engine maintenance and ownership cost.Further feasibility requires estimating cost for such a unit and projected maintenance cost.A chopper controlled electric engine that could achieve 25% adhesion is still the most promising possibility.Very truly yours,/s/George R. Frazier Elecrical Engineer The Milwaukee Road[/quote]I'm not clear on the whole "weight on drivers/25% adhesion" discussion.  Was this an attempt to improve the adhesion of the SD's to 25%?  What was the rated adhesion of the SD's on the Milwaukee mountain grades?  If it was simply a matter of increasing weight on the SD's drivers, wouldn't the necessary added equipment provide this increased weight, aka that would be a net positive, not a net negative?It is interesting that with the dual mode concept there is a recognition of the possibility of maintaining the 3kv system as it was while also improving the intra-industry standardization possibilities if a future merger was in order.  Mr. Frazier also seems to suggest that dual mode engines would improve relative reliability of the engine fleet.
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