There was recent interest in the specifications for the new diesels going to the White Pass & Yukon and the Durango & Silverton.
These are from two different builders, using two different core designs converted from existing models. What seems to be fairly solid is that they are both built around the EMD 16-645 turbocharged engine at 3,000 traction hp and GE764 traction motor, two long established and reputable components. Weight should be around 125 tons, and I know the WP&Y units will be 6-axle (similar truck to the 114 and USG units?) and the D&S units likely the same.
Based on the limited information that is available and long established diesel-electric practice, it is my belief that these will approximate the performance of a similar 4-axle standard gauge model. Continuous tractive effort should be around 54,000 pounds at about 12 mph. 500 horsepower per axle was the limit for a standard gauge traction motors, so at lower speeds (below 20 mph or so) they will have to derate to around 2,000 hp to stay within the GE764's working limits. Another factor is that they are approaching the adhesion limits based on the weight per axle, though modern wheel slip systems have pushed it higher in my experience for a DC drive design this is still severely under poor rail conditions. Personally I believe these are too big and it would have been better, but far more expensive, to plan on pairs of smaller locomotives rather than continuing to think like steam and put all your eggs in one basket.
I have made my living for many years in the shortline and railroad industry, as a manager in the last few years. I recently had to convince the owner of the railroad I work for that he can't load up his high power locomotives with heavy tonnage where they are limited to 5 mph. He couldn't understand why since they were under the color coded limits on the ammeter and the badge plate for the short time rating. He can't understand why speed makes any difference, yet there are few DC locomotive designs that are capable of full tonnage operation below 10 mph (and I have run a few of them). At my suggestion, we're looking into a retrofit system which will calculate the traction motor heating and reduce excitation at low speeds to stay within the limits and keep from toasting the traction motors.
The White Pass units for sure, and likely the D&S units will have micro-processor controls. Because these are custom designs from builders not experienced with 36" gauge designs, it will take some effort to work the bugs out and fine tune the mechanical, electrical and control software to get a consistent maximum performance out of them. I don't think anyone will know really what either design will do until they have done it for at least 90 days. It may take only 30 days to determine they are a failure, or it may take a couple years. I doubt the builders or the railroads will be able to afford them to fail and will do whatever to make them work.
