Alco "RSD-1" Locomotives

Last Revised: December 19, 2021

By: Adam Burns

The RSD-1 was the first road switcher of its kind to feature six-axles. However, when the model debuted railroads had yet to embrace the diesel locomotive for main line service, let alone show interest in a six-axle curiosity whose benefits had yet to be understood.

The American Locomotive Company's six-axle RS1 came in two variations, the six-motored RSD-1 (C-C) and six-axled RSC-1 (A1A-A1A).

While the RSD-1 saw roughly half the sales of its four-axle counterpart it was beloved by the US Army, who interestingly ended up as Alco's only customer for the model. 

Today, nearly a dozen RSD-1s are preserved around the country while a few are still operational including U.S. Army #8652 at the North Alabama Railway Museum (Huntsville) and former Tennessee Coal & Iron Railroad #601 (built as U.S. Army #8009) at the Orange Empire Railway Museum in Perris, California.


A former U.S. Army RSD-1, #8653, in service; March 17, 1973. Location not listed. Vincent Porreca photo. American-Rails.com collection.


RSD-1 History And Background

It should be noted that while historians and railfans often index the six-axle RS-1 model as either an RSD-1 or RSC-1, Alco itself made no such distinction. The builder cataloged them all as RS-1s and only differentiated the three by their designation numbers.

This is further reinforced in John Kirkland's book, "The Diesel Builder's: Volume Two."  It appears railfans came up with the separate designations on their own after studying Alco construction files.  Ironically, this work was even provided to Alco department heads in 1965, for reference use only.

According to Brian Solomon's "The American Diesel Locomotive" the three were classified as follows:

  • RS-1's as E1640, E1641, E1641A

  • RSD-1's as E1645, E1646, E1647

  • RSC-1's as E1651

Alco's use of only designation numbers can likely be explained by the fact that the builder never really intended to develop a six-axle RS-1 and did so only upon request from the Department of Defense.

The Army liked the RS-1 for its light weight and sufficient horsepower, allowing it to be used in switching applications on bases while handling heavy loads.


Alco's Other Six-Axle Road-Switcher Models

RSC-2

RSD-4

RSD-5

RSD-7

RS-11

RSD-12

RSD-15 "Alligator"

With World War II's onset, the Army wondered if a six-motored design would not only offer more tractive effort but could also handle Europe's lighter rails more effectively as the locomotive's axle loading would be reduced.



RSD-1 Data Sheet (Original 13, #8000-#8012)

Alco Class606-DL-319
Entered Production11/1942
Years Produced11/1942-2/1943
Model SpecificationE1640
Engine539T, 6-Cylinder In-Line, Turbocharged
Engine BuilderMcIntosh & Seymour
Horsepower1,000
Carbody StylingAlco/U.S. Army
Length (Between Coupler Faces)55' 11.75"
Weight257,000 Lbs.
Dynamic BrakesYes
TrucksC-C
Truck TypeTrimount*
Wheelbase11' 3"
Wheel Size40"
Traction MotorsGE 731 (6)
Traction GeneratorGT533
Gear Ratio16:75
Tractive Effort Rating34,000 Lbs. at 8 MPH; up to 43,000 Lbs. at 5.5 MPH.
Top Speed60 MPH

* These appear to be a version of the Trimount and probably developed by James G. Blunt based on the large journals utilized.  This truck was never replicated, even on standard production RSD-1's.

It was used solely on the original thirteen RS-1's requisitioned by the War Department since Alco had to retrofit C-C trucks on a frame designed for only four-axles.

RSD-1 Data Sheet (#8013-#8056), Construction Numbers 70634-70677

Alco Class606-DL-319
Entered Production11/1942
Years Produced11/1942-2/1943
Model SpecificationE1645
Engine539T, 6-Cylinder In-Line, Turbocharged
Engine BuilderMcIntosh & Seymour
Horsepower1,000
Carbody StylingAlco/U.S. Army
Length (Between Coupler Faces)55' 11.75"
Weight261,000 Lbs.
Dynamic BrakesYes
TrucksC-C
Truck TypeTrimount*
Wheelbase11' 3"
Wheel Size40"
Traction MotorsGE 731 (6)
Traction GeneratorGT533
Gear Ratio16:75
Tractive Effort Rating34,000 Lbs. at 8 MPH; up to 43,000 Lbs. at 5.5 MPH.
Top Speed60 MPH

RSD-1 Data Sheet (#8000-#8099), Construction Numbers 72073-72172

Alco Class606-DL-319
Entered Production10/1944
Years Produced10/1944-8/1945
Model SpecificationE1646
Engine539T, 6-Cylinder In-Line, Turbocharged
Engine BuilderMcIntosh & Seymour
Horsepower1,000
Carbody StylingAlco/U.S. Army
Length (Between Coupler Faces)55' 11.75"
Weight286,000 Lbs.
Dynamic BrakesYes
TrucksC-C
Truck TypeTrimount*
Wheelbase11' 3"
Wheel Size40"
Traction MotorsGE 731 (6)
Traction GeneratorGT533
Gear Ratio16:75
Tractive Effort Rating34,000 Lbs. at 8 MPH; up to 43,000 Lbs. at 5.5 MPH.
Top Speed60 MPH

The first 70 locomotives in this batch, #8600-8669, were built to a broad, 5-foot gauge for operation in Russia.  In all, there were 144 RSD-1's built new, in addition to the 13 RS-1's requisitioned and converted into RSD-1's, for a total of 157 units built domestically.

Sources:

  • Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.

  • Kirkland, John F. Diesel Builders, The:  Volume Two, American Locomotive Company And Montreal Locomotive Works. Glendale: Interurban Press, 1989.

  • Pinkepank, Jerry A. Diesel Spotter's Guide.  Milwaukee: Kalmbach Publishing Company, 1967.

It proved quite successful and the Army ordered several batches of RSD-1's beginning in 1942. Interestingly, with World War II ongoing and in desperate need of locomotives, the Army requisitioned the first 13 RS-1s built for the Rock Island, Milwaukee Road, New York, Susquehanna & Western, Atlanta & St. Andrews Bay, and Tennessee Coal, Iron & Railroad and had Alco convert them all into RSD-1's.

Internally, the RSD1 was identical to the RS1 featuring the turbocharged McIntosh & Seymore model 539T prime mover and the same length.

Alco went on to produce several version of its Road Switcher models in either six axles or six motors, such as the RSC-2, RSD-5, RSD-7, RSD-12, and RSD-15.


Prior to the start of World War II there were thirteen RS1's produced for five different railroads.  Please refer to the table below.  These locomotives were later requisitioned by the U.S. Army for use on the Trans-Iranian Railway to supply Russia with war materiel during the conflict.  

New locomotives were later built for the original railroads (paid for by the U.S. government) to replace those requisitioned, in April and May of 1943 (1946 for the Tennessee Coal, Iron & Railroad).


Original 13 RSD-1's Requisitioned By U.S. Army

Railroad Road Number Construction Number Date Built Date Rebuilt U.S. War Department Number Replacement Construction Number
Rock Island748694243/194111/1942800570816
Rock Island749694253/194112/1942800670817
Atlanta & St. Andrews Bay901694263/19411/1943801070810
Atlanta & St. Andrews Bay902694273/19411/1943801170811
Tennessee Coal, Iron & Railroad600694284/194112/1942800875203
Tennessee Coal, Iron & Railroad601695664/19411/1943800975204
Milwaukee Road1678695676/194111/1942800270814
Milwaukee Road1679695686/194111/1942800370815
Rock Island746695698/194112/1942800770818
Rock Island747695708/194111/1942800470819
Atlanta & St. Andrews Bay903698006/19421/1943801270821
New York, Susquehanna & Western231699926/194211/1942800070812
New York, Susquehanna & Western233699936/194211/1942800170813

Total Production Of Alco RSD-1s

Owner Road Number(s) Quantity Date Built
U.S. Army8000-8012, 8013-8056, 8600-86991571942-1946
National de Mexico5700-570561946

Total Production Roster Of MRS-1s

Owner Road Number(s) Quantity Date Built
U.S. ArmyB2041-B2084, 2085-2123831953

Total Production Roster Of RSC-1s

Owner Road Number(s) Quantity Date Built
Sao Paulo Railway (Brazil)500-50341946


Department of Transportation RSD-1 #012 is seen here on the test track in Pueblo, Colorado on April 18, 1980. This unit was built as Tennessee Coal & Iron #801, circa 1941, and later became U.S. Army #8009. Robert Harmen photo.

In all, over 250 six-axle RS-1's were produced; 253 for the US Army (including the 83 MRS-1s the Army purchased in 1953 along with the thirteen RS-1 units requisitioned), 4 for Sao Paulo Railway of Brazil (which purchased the A1A-A1A RSC-1), and 6 for National de Mexico. 

More information about these locomotives can be found in the production roster listed above.  Of the dozen units preserved four are known to be operational:

  • U.S. Army #8018 at the Orange Empire Railway Museum

  • U.S. Army RSD-1 #8652 at the North Alabama Railroad Museum 

  • U.S. Army #8669 and #8677 at the Tennessee Valley Railroad Museum.  
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