Alaska Railroad's SD70MAC-HEPs predate the Metra SD70MACHs by nearly 2 decades. In the early 2000s, Alaska Railroad was handling oil trains from the Flint Hills refinery at North Pole, Alaska to Anchorage, coal trains from the Usibelli mine near Healy to the port of Seward, and interchange cars from their barge operation in Whittier, and three trainsets of SD70MACs with hopper cars were moving aggregate from quarries in the Palmer-Wasilla area for construction in Anchorage all summer long. Cruise ships were also driving tremendous growth on the passenger trains.
HEP for the passenger trains was first handled by 2 parallel 150-kW generator sets slung underneath the baggage car. Then, later in 2000 and 2001, six GP40s were rebuilt into HEP-equipped units for passenger service, with #3009, #3010 and #3011 equipped with 300kW Detroit Diesel generator sets and #3013, #3014 and #3015 with ex-Amtrak 800kW gear-driven generators. Each had their disadvantages though. The baggage car gen sets had limited capacity and were susceptible to clogging with cottonwood lint, the 300kW Geeps were noisy and again had limited capacity, the 800kW Geeps were VERY noisy, had very small fuel tanks and were not at all fuel-efficient, and all the equipment, though recently rebuilt, were getting old. And since Alaska Railroad is in, well, Alaska and not connected to any outside rail network, leasing equipment was not an option.
Alaska Railroad reached out to EMD for suggestions, and EMD recommended the F59PH, basically a cowl-body passenger variant of the GP59, but Alaska Railroad wasn't keen on the idea of expensive new locomotives that could only be used for summertime passenger service. Robert Stout, Alaska Railroad CMO at the time, basically said to EMD, “We like what the SD70MAC does for us, what’s the possibility of putting HEP on one?” Such a dual-purpose unit would be flexible for both the short passenger season and then useful the rest of the year as a freight locomotive.
The request wound its way to EMD Engineering, where they realized that one of the two Siemens-supplied Traction Converter Cabinet of a SD70MAC might be modified to provide HEP, leaving the other TCC and truck to propel the unit, and one truck just coasting. Consultations with Siemens confirmed that Siemens could adapt the HEP transformer previously designed for the LIRR DE/DM30AC locomotive with the inverter of the SD70MAC to provide 480V 3-phase HEP. As the original SD70MAC had no room in its carbody for the additional needed HEP equipment, several different ideas were proposed, including using the locomotive roof and running board. The only realistic hope was to dramatically shorten the fuel tank and sling the HEP equipment underneath the underframe. As the LIRR DE30AC HEP transformer was hung similarly under its structural carbody, this didn’t seem too bad of a situation, and the real challenge would be designing cabinets for the HEP switchgear for the underslung application. Design, cost and manpower estimates were made at EMD, but then, ARR decided not to buy locos for that calendar year
In the fall of 2002, CSX enters into this story. They came looking for new units; more SD70MACs like they already had but with 3 important differences:
- The engines were hopped up from 4000hp to 4300hp.
- By EPA regulations, they would be required to meet Tier-1 emissions and thus needed a new split cooling system (first applied to UP SD70DC units but never applied to a SD70MAC.)
- CSX requested space be designed in the rear of the unit for an Eco-Trans APU (keeps cab lights and HVAC powered up and circulates fluids with main engine shut down)
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By some creative re-arranging of components, a volume of 3’6”x6’x5’9” was created for the APU by replacing the 4-cylinder electric drive air compressor with a shorter direct-drive 3-cylinder compressor, rotating the #2 TCC 180 degrees so that its “blind side” faced aft (the Siemens TCC has one face with no access doors for maintenance), and moving the battery box from the conductor’s side to engineer’s side of the long hood. The design was finalized in December of 2003 and construction for 130 SD70MAC Tier 1s for CSX began. With the design complete, EMD realized that the CSX APU space could easily morph into a location for an Alaska HEP system without shortening the fuel tank and without hanging transformers and equipment underneath the loco. This proposal was offered up to Alaska in the spring of 2003, and Alaska liked the design but had one requirement; the locomotives had to be delivered before the May 2004 passenger season kicked off. Unfortunately the lead time wouldn't make it possible to meet that requirement, so EMD made a deal to deliver the locomotives before then, sans HEP, and then retrofit the HEP equipment as it became available. Alaska RR accepted the offer, bumping the order from 4 to 8 units as well.
The results of this project were eight versatile passenger/freight locomotives, ARR #4317 through #4324. When the HEP system is off, the unit is a 4300HP C-C locomotive. With HEP on, it is a 2400HP C-3 locomotive with 730kW HEP generation. Moreover, it can deliver that HEP load in Run 3 (490 rpm) and up to 270kW HEP in Run 2 (370 rpm). An F40PH or GP40-H in contrast would run at a constant 900 rpm to deliver the same HEP. The system has turned out to be very reliable. If the 710 engine starts, then HEP is available. There is no pony engine to service and thus no pony engine cooling system, fuel system or lube system to deal with. The only filter to change is the HEP blower filter and the cottonwood lint at 15 feet off the rail has been very manageable. On paper having one truck unpowered would seem less than favorable, but again, modern controls, AC traction, and the HTC-R truck still give decent tractive effort. Since the Denali Star is often in excess of twenty cars, one SD70MAC HEP is used with another SD70MAC or SD70MAC HEP with HEP disengaged, are often paired up.








