EMD SDP35

Seaboard’s SDP35: Dual Service Locomotives

By Justin May

Photos by Warren Calloway unless otherwise noted

Seaboard Air Line’s Silver fleet was an amazing example of how passenger service was to be operated. In the 1950s, SAL would constantly update the ranks of passenger equipment to keep demand with increased ridership and the increasing demand for larger, spacious accommodations thus requiring additional equipment. Seaboard capably powered the Silver fleet with ranks of EMD E units, but as ridership increased, SAL did not update their passenger locomotive fleet in kind after the last E8A unit purchase in 1952.

Seaboard Air Line’s passenger fleet consisted of aging pre-War cab units that ranged from the first EMC E4 cab units constructed in 1938 to their newest cab unit, an E9A, constructed in 1963. Though needed, Seaboard Air Line was not likely to purchase an all-new passenger locomotive given decreased ridership numbers in the looming future.

In 1964, as passenger service was beginning to decline, Seaboard Air Line was faced with maintaining an elderly fleet of cab units, or to replace those units with an all-new Special Duty Passenger dual service locomotive. Locomotive builder, General Motors’ Electro-Motive Division, was specifically offering a new SDP35 for railroads facing similar circumstances wherein the need to replace old pre-War cab units existed.

The use of the dual service locomotive permitted the railroad to use it in both passenger and freight service as needed. When the need to power passenger trains ceased, the unit could then be used in freight service exclusively. The dual service concept was successful for not only EMD, but for many other railroads which rostered the SDP35.

Production:

EMD produced only 35 examples of the SDP35, with Seaboard Air Line becoming the first and largest owner of the locomotive. Additional examples were built for competitor Atlantic Coast Line, as well as Louisville and Nashville, and Union Pacific. 

Seaboard Air Line used the SDP35 in both high-speed freight and passenger service unlike other railroads who found them either ill suited or surplus for their intended role upon delivery. Atlantic Coast Line used their single 1965 delivered SDP35 in dual service roles, however, preferred the freight only model, the SD35. ACL 500, would later become ACL 1099 and ultimately join the SAL SDP35s under the SCL umbrella as SCL 600.

Similarly, L&N purchased four of the units in 1965, in anticipation of use as passenger locomotives, however, prior to delivery, L&N discontinued several passenger trains. All four SDP35s, initially numbered as L&N 1701-1703, lacked steam generators. The L&N examples would become freight locomotives, however, outwardly resembled later production SDP35s.

The fourth purchaser of the SDP35, was western power, Union Pacific, who sought to use the dual purpose SDP35 on its passenger and special trains as protection power. UP purchased ten units in 1965, numbered as 1400-1409, to supplement a fleet boiler equipped GP9s and GP30Bs, however, it was determined due to electrical problems that plagued the EMD 35-line, the reliability of the E9 was preferred. The UP SDP35 fleet was assigned to the Eastern District, keeping them close to Omaha, NE shop forces. Ultimately, the UP SDP35s would become relegated to special passenger train moves, and pilot duty for use on the C&NW. In mid-1980, the UP fleet was stored and eventually retired in 1985.

Unlike the UP, Seaboard experienced a much different path that would ultimately lead to decades of successful service albeit in a varied form. The SDP35 was powered by EMD’s turbocharged 16-cylinder 567D3A prime mover that enabled the locomotive to run at a top speed of 89 mph, though three additional gear ratios were available.

The SDP35 is described by EMD as, “essentially an SD locomotive with the long hood and rear walkway extended to accommodate a steam generator. The fuel tank is divided into a combination fuel tank and water tank and the gear ratio at the traction motor pinion is suitable for high-speed operation. This equipment enables the locomotive to perform as a passenger locomotive and as a freight locomotive at low minimum continuous speeds comparable to GP locomotives equipped with the usual freight gearing.”

Seaboard Air Line SDP35 variants:

The SDP35 was built for Seaboard in two orders consisting of units 1100-1113 being built to Phase 1a and 1b specifications. The initial order, EMD builder numbers 29339-29352, was constructed in July through September 1964. These units were denoted by spotting features to include three latched engine room doors, a flat topped fuel tank profile, a bulge beneath the upper headlight housing for the use of a Gyralight, and Flexicoil FC1C type truck side frames.

 The second order consisted of units 1114-1119 which were constructed in November 1964. In the interim months between the first and second order of SDP35s, several phase changes occurred to include the use of seven latched engine room doors, and a change to the louvers on the fireman’s side battery box doors. These were reduced from three sets of three louvers to two sets of a single louver. The second order, like the first order, used EMD Flexicoil FC1C type truck side frames, however, is denoted as Phase Ic2.

Both orders of the SDP35 featured a 1500-gallon fuel tank and a 1500-gallon water tank, which were contained within a flat-top profile tank. Upon delivery to Seaboard, the SDP35s all received Hancock air whistles in place of the typical Leslie 3 chime horn used on other Seaboard Air Line locomotives.

In-Service:

With the arrival of the SDP35s, the aging E4 and E6 units were retired in 1964, bringing an end to the pre-War cab unit era. The SDP35 was used in a variety of service throughout the Seaboard Air Line system that typically included handling secondary passenger trains, mail trains, hotshot TOFC trains, as well as powering general freights in concert with other EMD General Purpose locomotives or with other SDP35s. The units were based on the northern end of the SAL system being serviced frequently in the Hamlet, North Carolina shops.

In passenger service, the SDP35s, “went to work on several secondary and local passenger runs, starting with the Richmond-Miami Palmland and the Hamlet-Atlanta/Birmingham locals. Later assignments included the Sunland, winter season Trains 15-16, and the Atlanta-Birmingham section of the Silver Comet. They eventually turned up on almost any train in the Seaboard lineup except for the Silver Meteor and Silver Star. True to their dual-purpose design, the SDP35s were also placed on piggyback trains or other fast freights where their moderately high speed could be put to good use. A single SDP35 could handle an average-size local run, but longer trains found them mixed in with one or two E units. The Palmland often drew a back-to-back pair of the SDPs.”

With the formation of Seaboard Coast Line on July 1, 1967, the SDP35s were renumbered into the 601-620 series and were hastily repainted using the original SAL Pullman Green to paint over the existing Seaboard lettering. Atop the fresh paint, a new green SCL herald was applied to the nose, new yellow cab numerals, and yellow ‘SEABOARD COAST LINE’ lettering were placed atop the yellow band along the long hood. When repainted, the original rear end numbers were eliminated. This scheme has come to be known as the Split Image scheme that many units wore in the

immediate years after the merger.

The units were repainted in no certain order with many of the units receiving the black and yellow ‘Bumble Bee’ scheme between 1967 and 1971. During 1971, the SDP35s were de-boilered removing the long hood bulge and installing a flat steel plate in their place. The deactivation of the boilers meant an end to passenger service capabilities; however, the units would continue to serve SCL for many years. During the boiler removal process, the units were again renumbered as SCL 1951-1970. 

The once front running SDP35s became another 2,500 horsepower to their new owner and were often tasked with handling various freight jobs. On July 31, 1977, nine of the former Seaboard SDP35s would be sent to power short Louisville and Nashville as a stopgap measure due to increased coal traffic. The SDP35s joined the ranks of former SAL Alco RS11s, C420s, Alco Demonstrator C430s, and former ACL C628s and C630s, along with former ACL GP30s, SD35s, and the former ACL SDP35.

Upon reassignment to L&N, the former SDP35s remained in their as built appearance replete with the raised steam generator area, as delivered rear step wells, and steam generator stacks intact. The units were initially numbered in the 7000 series upon delivery and in April 1979 were renumbered into the 1200 series to conform to the existing L&N roster.

Four SDP35s were held in reserve for rebuilding into H15 hump yard switchers in 1981. The conversion took place at the Waycross, Georgia shops and involved SAL 1100, renumbered to SCL 5, SAL 1104 renumbered to SCL 2, SAL 1106 renumbered to SCL 1, and SAL 1113 renumbered to SCL 6. The conversion involved replacing the turbocharged EMD 16-567D3A prime mover with that of a non-turbocharged 16-567BC. This replacement reduced the available horsepower to 1,500. 

Additional changes included simplifying the electrical system, eliminating the dynamic brake equipment, fitting a paper air filter atop the long hood for normal aspiration, converting the FC1C Flexicoil trucks to a two brake cylinder arrangement, installation of a 3,000 gallon fuel tank, and rebuilding the rear of the unit with standard EMD step wells and shortening the long hood end.

The intended role of the H15 was to operate in pairs with that of former ACL SD35s as hump pushing units at the large Rice and Hamlet hump yard terminals, a role they served in until retirement in 1991 by CSX Transportation.

Equally at home on an express mail train or lugging freight in consist with GP30s, GP35s and GP40s, the SDP35 was truly a dual purpose locomotive well suited for the needs of both Seaboard Air Line or Seaboard Coast Line.

Sources:

I would like to thank Warren Calloway for the use of his photographs. Additionally, the works of both Larry Goolsby, author of Seaboard Air Line Passenger Service The Streamlined Era and Doug Strack’s excellent website, UtahRails.net were referenced in this article.