andegold wrote: ↑Sat Jul 11, 2020 9:48 am
Weren't the ALP45-DPs created for the concept of using the pans as the primary source and the diesel for last mile? If true, that would mean fuel efficiency was secondary, almost immaterial. Yes, I understand "last mile" here is a bit of a misnomer particularly on the Raritan Valley line or for future service on West of Hudson lines if a loop was ever built. However, whether on those lines or on the NJCL where there is more electric mileage than diesel the point is that electric power needed to be either the primary focus or equal to diesel power. Amtrak, MetroNorth, and LIRR only need electric for true "last mile" service and, therefore, much lower power requirements and, presumably, weight.
Could a pan-equipped motor make sense for Amtrak and LIRR? It would need enough power for a slow slog through the tunnels and for HEP, not for any type of high speed acceleration (other than to clear out of the station in a timely fashion and not become a bottle neck). What are the speed limits within the electric only zones of Penn and Sunnyside?
Metro North would be much more difficult because of different clearance issues and lack of AC catenary to begin with. Since that would make a single spec joint purchase impossible perhaps it is either (A) not worth it at all or, (B) more worth it to examine routing all MN diesel trains via West Side or Hell Gate to Penn and require a transfer somewhere for NYG.
The ALP-45DP was designed as an equal parts diesel and AC electric. Neither mode was intended to be last-mile. NJ Transit uses them on diesel-exclusive trains as well as electric-exclusive trains, and they perform decently well on both. This is why they are so heavy - they have full AC gear as well as dual CAT diesels for 4200hp. They are allowed 90mph in either mode, unlike the P32ACDM which is allowed only 60mph in DC electric mode, down from 110mph in diesel. I believe the DM30AC is good for 80 in DC electric mode but it may also be restricted to 60. Similarly, the ALP-45DP is designed for 125 in electric mode and 100 in diesel mode, but has been restricted to 90 by Amtrak as a side effect of their weight.
Ruling grade for the dual mode diesels is under the East River. This is also where they reach their highest speed in electric mode, as track speed in the tunnels is 60mph. Performance criteria for a DC dual mode should be derived from this area.
I would say the current method of DC third rail for last mile and diesel otherwise works fine. No need to reinvent the wheel where it doesn't need to be reinvented, especially if you are introducing new issues like maintaining two units or dragging around a lot more dead weight. There isn't really anywhere that a dual cab design would save any time, as Amtrak trains have to run around the loop at Sunnyside to reach the yard and LIRR/MN trains are push-pull.