EMD DD35
Encyclopedia
The EMD DD35 was a 5000 hp 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 3-unit locomotive set to replace the turbines
then in use. The DD35 was a cabless booster (B unit
) locomotive that basically consisted of two GP35
locomotives on a common frame, riding on a pair of long 4-axle Flexicoil trucks. The 4-axle truck was considered too harsh on the track to be in the lead, and thus EMD's response to the UP 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.
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 the UP and the Southern Pacific Railroad
. The 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.
Three demonstration units were built for the Southern Pacific, which tested them, kept them, but ordered no more. They were numbered 8400-8402, later 9500-9502 and still later 9900-9902. They saw only light use, being among the first locomotives sidelined whenever there was a downturn in traffic. The SP scrapped them all in the 1970s.
The DD35s were initially quite unreliable; some of this was blamed on sand from the internal sandbox
es getting in electrical gear, so new sandboxes were fitted on the walkways in 1969. The DD35s were among the last EMD road units to be built with DC generators and old-fashioned switchgear, which were more maintenance intensive than the later AC/DC equipment.
Once teething troubles had been overcome, the DD35s were reasonably successful, but they were less flexible than smaller units and thus all of the original B units were withdrawn by 1977 as the railroads fell on harder times. The DD35A
s survived a little longer, until 1981. There are no survivors of either the DD35 or DD35A models.
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...
of D-D wheel arrangement
Wheel arrangement
In rail transport, a wheel arrangement is a system of classifying the way in which wheels are distributed beneath a locomotive.. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country...
built by General Motors Electro-Motive Division for the Union Pacific Railroad
Union Pacific Railroad
The Union Pacific Railroad , headquartered in Omaha, Nebraska, is the largest railroad network in the United States. James R. Young is president, CEO and Chairman....
and Southern Pacific Railroad
Southern Pacific Railroad
The Southern Pacific Transportation Company , earlier Southern Pacific Railroad and Southern Pacific Company, and usually simply called the Southern Pacific or Espee, was an American railroad....
. In the early 1960s Union Pacific started asking for a 15,000 hp 3-unit locomotive set to replace the turbines
Union Pacific GTELs
Union Pacific operated the largest fleet of gas turbine-electric locomotives of any railroad in the world. The prototype, UP 50 was the first in a series built by General Electric for Union Pacific's long-haul cargo services. The prototype was introduced in 1948 and was followed by three series...
then in use. The DD35 was a cabless booster (B unit
B unit
A "B" unit, in railroad terminology, is a locomotive unit which does not have a driving cab, or crew compartment, and must therefore be controlled from another, coupled locomotive with a driving cab . The term booster unit is also used. The concept was largely confined to North America...
) locomotive that basically consisted of two GP35
EMD GP35
An EMD GP35 is a 4-axle diesel locomotive built by General Motors Electro-Motive Division between July 1963 and December 1965 and by General Motors Diesel between May 1964 and January 1966. Power was provided by an EMD 567D3A 16-cylinder engine which generated .Many railroads traded in Alco and...
locomotives on a common frame, riding on a pair of long 4-axle Flexicoil trucks. The 4-axle truck was considered too harsh on the track to be in the lead, and thus EMD's response to the UP 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.
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 the UP and the Southern Pacific Railroad
Southern Pacific Railroad
The Southern Pacific Transportation Company , earlier Southern Pacific Railroad and Southern Pacific Company, and usually simply called the Southern Pacific or Espee, was an American railroad....
. The 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.
Three demonstration units were built for the Southern Pacific, which tested them, kept them, but ordered no more. They were numbered 8400-8402, later 9500-9502 and still later 9900-9902. They saw only light use, being among the first locomotives sidelined whenever there was a downturn in traffic. The SP scrapped them all in the 1970s.
The DD35s were initially quite unreliable; some of this was blamed on sand from the internal sandbox
Sandbox (railways)
A sandbox is a container on most locomotives and self propelled multiple units, or trams, that run on tramways and adhesion railways...
es getting in electrical gear, so new sandboxes were fitted on the walkways in 1969. The DD35s were among the last EMD road units to be built with DC generators and old-fashioned switchgear, which were more maintenance intensive than the later AC/DC equipment.
Once teething troubles had been overcome, the DD35s were reasonably successful, but they were less flexible than smaller units and thus all of the original B units were withdrawn by 1977 as the railroads fell on harder times. The DD35A
EMD DD35A
The EMD DD35A was a 5,000 hp diesel locomotive of D-D wheel arrangement built by General Motors Electro-Motive Division exclusively for the Union Pacific Railroad. They were a cab-equipped variant of the previous, cabless booster EMD DD35...
s survived a little longer, until 1981. There are no survivors of either the DD35 or DD35A models.
Original Buyers
| Owner | Quantity | Numbers | Notes |
|---|---|---|---|
| Southern Pacific Railroad | 3 | 8400-8402 | |
| Union Pacific Railroad | 27 | 72B-98B | 72B and 73B ex EMD (demonstrators) 5653 and 5655 |