Alco "RSD-1" Locomotives: Specs, Roster, Photos, History

Last revised: December 27, 2024

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.

Photos

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

Overview

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.

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.

Data Sheet and Specifications

(Original 13, #8000-#8012)

Alco Class	606-DL-319
Entered Production	11/1942
Years Produced	11/1942-2/1943
Model Specification	E1640
Engine	539T, 6-Cylinder In-Line, Turbocharged
Engine Builder	McIntosh & Seymour
Horsepower	1,000
Carbody Styling	Alco/U.S. Army
Length (Between Coupler Faces)	55' 11.75"
Weight	257,000 Lbs.
Dynamic Brakes	Yes
Trucks	C-C
Truck Type	Trimount*
Wheelbase	11' 3"
Wheel Size	40"
Traction Motors	GE 731 (6)
Traction Generator	GT533
Gear Ratio	16:75
Tractive Effort Rating	34,000 Lbs. at 8 MPH; up to 43,000 Lbs. at 5.5 MPH.
Top Speed	60 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.

(#8013-#8056), Construction Numbers 70634-70677

Alco Class	606-DL-319
Entered Production	11/1942
Years Produced	11/1942-2/1943
Model Specification	E1645
Engine	539T, 6-Cylinder In-Line, Turbocharged
Engine Builder	McIntosh & Seymour
Horsepower	1,000
Carbody Styling	Alco/U.S. Army
Length (Between Coupler Faces)	55' 11.75"
Weight	261,000 Lbs.
Dynamic Brakes	Yes
Trucks	C-C
Truck Type	Trimount*
Wheelbase	11' 3"
Wheel Size	40"
Traction Motors	GE 731 (6)
Traction Generator	GT533
Gear Ratio	16:75
Tractive Effort Rating	34,000 Lbs. at 8 MPH; up to 43,000 Lbs. at 5.5 MPH.
Top Speed	60 MPH

(#8000-#8099), Construction Numbers 72073-72172

Alco Class	606-DL-319
Entered Production	10/1944
Years Produced	10/1944-8/1945
Model Specification	E1646
Engine	539T, 6-Cylinder In-Line, Turbocharged
Engine Builder	McIntosh & Seymour
Horsepower	1,000
Carbody Styling	Alco/U.S. Army
Length (Between Coupler Faces)	55' 11.75"
Weight	286,000 Lbs.
Dynamic Brakes	Yes
Trucks	C-C
Truck Type	Trimount*
Wheelbase	11' 3"
Wheel Size	40"
Traction Motors	GE 731 (6)
Traction Generator	GT533
Gear Ratio	16:75
Tractive Effort Rating	34,000 Lbs. at 8 MPH; up to 43,000 Lbs. at 5.5 MPH.
Top Speed	60 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.

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 (Requisitioned By U.S. Army)

Railroad	Road Number	Construction Number	Date Built	Date Rebuilt	U.S. War Department Number	Replacement Construction Number
Rock Island	748	69424	3/1941	11/1942	8005	70816
Rock Island	749	69425	3/1941	12/1942	8006	70817
Atlanta & St. Andrews Bay	901	69426	3/1941	1/1943	8010	70810
Atlanta & St. Andrews Bay	902	69427	3/1941	1/1943	8011	70811
Tennessee Coal, Iron & Railroad	600	69428	4/1941	12/1942	8008	75203
Tennessee Coal, Iron & Railroad	601	69566	4/1941	1/1943	8009	75204
Milwaukee Road	1678	69567	6/1941	11/1942	8002	70814
Milwaukee Road	1679	69568	6/1941	11/1942	8003	70815
Rock Island	746	69569	8/1941	12/1942	8007	70818
Rock Island	747	69570	8/1941	11/1942	8004	70819
Atlanta & St. Andrews Bay	903	69800	6/1942	1/1943	8012	70821
New York, Susquehanna & Western	231	69992	6/1942	11/1942	8000	70812
New York, Susquehanna & Western	233	69993	6/1942	11/1942	8001	70813

Production Rosters

RSD-1

Total Built = 150

Owner	Road Numbers	Serial Numbers	Date Built
U.S. Army	8013-8033	70634-70654	11/1942 - 12/1942
U.S. Army	8034-8056	70655-70677	1/1943 - 2/1943
U.S. Army	8600-8649	72073-72122	10/1944 - 1/1945
U.S. Army	8650-8679	72123-72142	1/1945 - 2/1945
U.S. Army	8680-8699	72143-72172	2/1945 - 3/1945
Ferrocarriles Nacionales de México	5700-5705	74671-74676	1/1946, 4/1946, 5/1946

RSX-4 (MRS-1)

Total Built = 83

Owner	Road Number(s)	Serial Number(s)	Date Built
U.S. Army	B-2041, B-2042	80357-80358	4/1953
U.S. Army	B-2043	80359	4/1953
U.S. Army	B-2044	80360	4/1953
U.S. Army	B-2045 thru B-2047	80361-80363	4/1953
U.S. Army	B-2048	80364	4/1953
U.S. Army	B-2049, B-2050	80365-80366	4/1953
U.S. Army	B-2051	80367	4/1953
U.S. Army	B-2052	80368	4/1953
U.S. Army	B-2053 thru B-2055	80369-80371	4/1953
U.S. Army	B-2056	80372	4/1953
U.S. Army	B-2057	80373	4/1953
U.S. Army	B-2058	80374	4/1953
U.S. Army	B-2059	80375	4/1953
U.S. Army	B-2060	80376	4/1953
U.S. Army	B-2061	80377	4/1953
U.S. Army	B-2062	80378	4/1953
U.S. Army	B-2063	80379	4/1953
U.S. Army	B-2064	80380	4/1953
U.S. Army	B-2065	80381	4/1953
U.S. Army	B-2066	80382	4/1953
U.S. Army	B-2067	80383	4/1953
U.S. Army	B-2068	80384	4/1953
U.S. Army	B-2069	80385	4/1953
U.S. Army	B-2070	80386	4/1953
U.S. Army	B-2071 thru B-2072	80387-80388	4/1953
U.S. Army	B-2073	80389	4/1953
U.S. Army	B-2074	80390	4/1953
U.S. Army	B-2075	80391	4/1953
U.S. Army	B-2076	80392	4/1953
U.S. Army	B-2077	80393	4/1953
U.S. Army	B-2078	80394	4/1953
U.S. Army	B-2079	80395	4/1953
U.S. Army	B-2080	80396	4/1953
U.S. Army	B-2081	80397	4/1953
U.S. Army	B-2082 thru B-2084	80398-30400	4/1953
U.S. Army	B-2085	80401	10/1953
U.S. Army	B-2086	80402	10/1953
U.S. Army	B-2087 thru B-2090	80403-80406	10/1953
U.S. Army	2091	80324	10/1953
U.S. Army	2092 to 2094	80325-80327	4/1953
U.S. Army	2095	80328	4/1853
U.S. Army	2096	80329	4/1953
U.S. Army	2097	80330	4/1953
U.S. Army	2098	80331	3/1953
U.S. Army	2099	80332	6/1953
U.S. Army	2100	80333	4/1953
U.S. Army	2101	80334	4/1953
U.S. Army	2102	80335	4/1953
U.S. Army	2103	80336	4/1953
U.S. Army	2104	80336	4/1953
U.S. Army	2105	80337	4/1953
U.S. Army	2106 thru 2108	80335-80337	4/1953
U.S. Army	2109	80338	4/1953
U.S. Army	2107 thru 2116	80339-80349	4/1953
U.S. Army	2117	80350	4/1953
U.S. Army	2118	80351	4/1953
U.S. Army	2119	80352	6/1953
U.S. Army	2120	80353	6/1953
U.S. Army	2121	80354	6/1953
U.S. Army	2122	80355	6/1953
U.S. Army	2123	80356	6/1953

RSC-1

Total Built = 4

Owner	Road Numbers	Serial Numbers	Date Built
Sao Paulo Railway (Brazil)	500-503	75006-75009	9/1946

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 154 six-axle RS-1's were produced; 146 for the U.S. Army, six for National de Mexico, and four RSC-1s for Sao Paulo Railway of Brazil.

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.

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.