EMD DD35

EMD DD35

Two Union Pacific Railroad EMD DD35s sandwiched between a lead SD45 (#3638) and an unidentified trailing unit.

Type and origin Power type Diesel-electric Builder General Motors Electro-Motive Division (EMD) Model DD35 Build date 1963–1964 Total produced 30

Specifications AAR wheel arr. D-D Gauge 4 ft 8 1⁄2 in (1,435 mm) Prime mover Dual EMD 16-567D3A Engine type 2 stroke diesel Aspiration Turbocharged Generator DC generator Traction motors DC traction motors Cylinder size 8 1⁄2 in × 10 in (216 mm × 254 mm) Transmission diesel electric Loco brake Straight air, Dynamic Train brakes Air

Performance figures Power output 5,000 horsepower (3,730 kW)

Career Locale North America Retired 1981 Disposition No surviving units

The EMD DD35 was a 5,000 horsepower (3,700 kW) diesel-electric locomotive of D-D wheel arrangement built by General Motors Electro-Motive Division for the Union Pacific Railroad and Southern Pacific Railroad. In the early 1960s, Union Pacific started asking for a 15,000 hp (11,200 kW) 3-unit locomotive set to not only replace their turbine locomotives, but to bring new generation of diesel locomotives to the states, and then put them into use. This request also led to the introduction of the ALCO Century 855 and GE U50. The DD35 was a cabless booster (B unit) locomotive that consisted of two GP35 locomotives prime movers (engines) and electrical systems, mounted on a common frame and covered with a single cowling, riding on a pair of 4-axle Flexicoil trucks, so each prime mover was powering a single set of 4 axles instead of two sets of 2 axles, as in the GP35. Being a "B-unit", the DD35 lacked any sort of cab, and could only be run on the main line when connected with another "A-unit" to control it. The 4-axle truck was considered too harsh on the trackwork to be in the lead, and thus EMD's response to UP's request was a 4-unit (instead of the requested 3-unit set) locomotive set, consisting of a pair of 2,500 hp GP35s sandwiching a pair of DD35s, to make one 15,000 hp locomotive set (basically six GP35's in four units)

EMD produced a demonstrator set like this in September 1963, painted in striking red and white (similar to the Frisco's livery). It was demonstrated on a number of railroads, but the only interest came from Union Pacific and Southern Pacific. UP bought the entire 4-unit demonstrator set, and followed up with an order for 25 more, which were delivered from May through September 1964. The two demonstrator locomotives were numbered 72B and 73B; the 25 production locomotives were assigned 74B through 98B.