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The EMD (Electro-Motive Division) SDP40F is a type of six-axle, 16-cylinder, 3,000hp (3,200hp in some cases) diesel locomotive built from 1973 to 1974 with 150 built and delivered specially for Amtrak.
Although they are regarded as being the first new diesel locomotives built for the transportation agency, the EMD F40PH and GE P30CH tend to take most of the credit, for the SDP40F was essentially a cowl-bodied SD40-2; essentially the 16-cylinder equivalent to the 20-cylinder F45 and more specifically, FP45.
The locomotives had an otherwise short-lived career, for they proved to be prone to a number of derailments that led to its demise, resulting in retirement from 1977 to 1984. In an unusual move, during September 1984, the ATSF (Santa Fe) traded 25 CF7 units and 18 SSB1200's in exchange for 18 SDP40F's from Amtrak. Upon delivery, they were rebuilt to freight specifications (amid several exterior modifications), and were reclassed as SDF40-2's. These units were essentially used as companions to their existing six-axle "40" and "45" series units built from EMD.
All but three have since been scrapped. Two heavily modified units: EMDX 169 and 218 (ex-AMTK 509 and 609), currently serve as part of EMD's test fleet as test units at the Transportation Technology Center in Pueblo, CO. Another unit, the former BNSF-Maersk Sealand-sponsored unit (DYRX 644) has since been preserved, and is currently owned by Dynamic Rail Preservation Inc. in Ogden, UT and is awaiting restoration to be rebuilt into its previous (pre-ATSF/BNSF) state when it was first delivered to Amtrak (minus several interior components, such as the steam generator).
Upon the formation of Amtrak in 1971, the newly-established public passenger rail transportation agency enacted by the US Congress received nothing more but hand-me-down locomotives and rolling stock
to transport passengers to and from destinations. Among their vast, colorful fleet, were various aged passenger diesels acquired from various railroads under varied ancestry. From E and F units built by EMD for the Great Northern (GN) and Union Pacific (UP), to the RDC railcars built by Budd for the Pennsylvania Railroad (PRR), Amtrak not only had a lack of power to meet increasing demands, but also had trouble keeping maintenance up-to-date, while further keeping maintenance costs lowered and reduced. To solve these issues, after receiving increased funding while further gaining more profit, the organization contracted EMD with a delivery of 150 SDP40F units to replace the aging E units, while further replacing a number of F units as well. Starting June 1973, EMD began delivering the first few batches of SDP40F units to Amtrak.
The 396,000 pound full-cowl steam-generator-equipped SDP40F bore a strong outward resemblance to the FP45 delivered to the ATSF years prior, but internally, the locomotive was mechanically similar to an SD40-2 (save for the HTC trucks).
Although mechanically flawless upon debut, the locomotive was prone to a number of derailments which ultimately led to the end of its short-lived career. The derailments ultimately lead to a series of in-depth investigations and otherwise exhaustive tests conducted by the AAR and FRA concerning the locomotive's performance when turning on a sharp curve or navigating a steep bend. Despite having speculated that these derailments were attributed to the design of the HTC truck, the weight and sloshing of the water stored inside the on-board water tanks for the steam generator soon proved to be the official culprit. Although EMD offered a solution to the problem, Amtrak denied, and instead took delivery of more F40PH units to replace the existing SDP40F units on long-distance passenger service.
The F40C was essentially the HEP-equipped variant of the original model built specially for the Milwaukee Road under two seperate transportation agencies split into two entities: North West Suburban Mass Transit District and the North Suburban Mass Transit District (the latter of whom, ultimately became Metra). Only 15 were built between March and May of 1974, and remained in primary service with Metra until 2003-2004, when all but two (METX #611 and 614) were retired and sold to Helm Leasing (HLCX) and National Rail Equipment (NRE).
Unlike the SDP40F, the F40C units were built with louvered stainless-steel carbody panels. While the HEP generator could demand up to 700hp, the locomotive's compactness allowed the F40C to be built on an SD40-2 frame rather than the longer FP45 frame needed to accomodate the SDP40F.
AMTK 500-539 were built with a pointed nose similar to what was present on the existing F45/FP45, while the other units were built with flattened noses.