When Amtrak was formed in 1971, the passenger railroad inherited locomotives (F and E units) and cars from the freight railroads who abandoned passenger operations. The locomotives were poorly maintained and often broke down en route of Amtrak trains. In 1973, Amtrak bought the first of their new locomotives, the SDP40F, an interim solution to their locomotive requirements, before cars with electrically heated arrived. As the name suggested, the SDP40F was a full car body passenger version of the 6-axle SD40 freight locomotive. It had the same 16 cylinder EMD 645 engine as the SD40 and the same 500 hp traction motors, but was geared for a top speed of 100 mph. Steam generators were equipped on these units to provide heating to the old passenger cars.

SDP40F (2nd and 3rd units) on the San Francisco Zephyr

The SDP40F was a reliable locomotive like her freight cousin, but had several high speed derailments. The cause were unclear but was believed to be the uneven weight distribution caused by the addition of the steam generator and water tanks on board. Eventually the SDP40F was withdrawn from service. Amtrak was able to trade these units in for credit towards the newer Head End Power equipped F40PH and 18 units were traded with the Santa Fe Railroad for 43 switchers. The SDP40F made her last appearance on Amtrak in 1985.


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