Alco "RSD-12" Locomotives: Data Sheet, Roster, Photos

Last revised: August 26, 2024

The RSD12 was one of the final six-axle designs produced in the Road Switcher (RS) series. The locomotive sold relatively well for the American Locomotive Company (Alco) considering most six-axle models were lucky to see more than 50 sales.

The RSD12 was essentially an extension of the RS11, which was Alco's attempt to compete with EMD's four-axle GP9. Unfortunately, once again the builder was late to the game as EMD's SD9 (the six axle version of its GP9) had already been in production for two years.

As such, despite railroads continued reluctance to purchase six-axle locomotives in large numbers EMD sold three times the SD9s in comparison to Alco's RSD12. Today, there are at least three preserved although it is unknown whether any are currently operational.

Photos

Utah Railway RSD-12 #600 (ex-Chesapeake & Ohio #6707) at Martin, Utah, circa 1977. American-Rails.com collection.

Overview

With the woefully unsuccessful RSD7, which attempted to compete against Fairbanks Morse's H24-66 "Train Master" the Schenectady builder switched directions back to a more traditional model with the RSD12.

The road-switcher began production in the spring of 1956 and was one of the few RS models to utilize Alco's newer (and more reliable) 251B prime mover capable of producing 1,800 horsepower (the same as the RS11).

The locomotive remained in the company's catalog until 1963 and while it ultimately sold more than 150 units less than half of those sales went to domestic (American) railroads including the Pennsylvania, Southern Pacific, Chesapeake & Ohio, and Nickel Plate Road (the small Lake Superior & Ishpeming also purchased a few).

Tractive Effort

The RSD12 featured the highest continuous tractive effort of any Alco diesel locomotive it had offered up until that time; 78,500 pounds (continuous) that included dynamic braking.

In comparison, EMD's SD9 provided just 75,000 pounds. The high tractive effort was actually an Alco trademark; its locomotives had gained quite a reputation for pulling more tonnage far above what the builder would rate its products and many railroads used this to their advantage employing their units in heavy-haul service (coal, ore, etc.).

Despite the fact that General Electric was just a few years away from releasing its own line of diesels, a result of Alco's continual loss of market share to EMD, the RSD12 still used traction motors and generators built by them.

A former Pennsylvania RSD12, #6858, is seen here in Syracuse, New York during the very early Penn Central era on April 7, 1968. Fred Byerly photo. American-Rails.com collection.

Design

The road-switcher was one of Alco's first to offer a low, short nose as an option although only the Southern Pacific ultimately purchased the model with such.

In general, the builder's six axle models were meant to provide a sizable increase in traction and used on light branch/secondary lines allowing the locomotive's weight to be distributed more evenly over additional axles.

While most railroads that went on to purchase the RSD12 retired their fleets within a decade or so these unique beasts were beloved by the Lake Superior & Ishpeming for their amazing ability to pull just about anything.

Data Sheet and Specifications

Alco Class	606-DL-360
Entered Production	4/1956 (Chesapeake & Ohio #6700)
Years Produced	4/1956-4/1963
Model Specification	DL702
Engine	251B, V-12
Horsepower	1,800
RPM	1,000
Carbody Styling	Alco
Length (Between Coupler Pulling Faces)	58' 1.75"
Weight	360,000 Lbs.
Dynamic Brakes	Optional
Trucks	C-C
Truck Type	Trimount
Truck Wheelbase	12' 6"
Wheel Size	40"
Traction Motors	GE 752 (6)
Traction Generator	GT586
Steam Generator	-
Gear Ratio	65:18
Tractive Effort Rating	78,750 Lbs. at 5.5 MPH
Top Speed	75 MPH

Production Roster

Alco

Total Built = 161

Owner	Road Number(s)	Serial Number(s)	Completion Date
Chesapeake & Ohio	6700-6709	81943-81952	4/1956 - 5/1956
Companhia Siderúrgica Nacional (Brazil)	3501	82477	12/1961
Companhia Siderúrgica Nacional (Brazil)	3502-3510	83947-83955	10/1962
Ferrocarril del Pacifico (Mexico)	1502, 1503	82921, 82922	8/1958
Ferrocarril del Pacifico (Mexico)	1504-1508	83339-83343	2/1959 - 10/1959
Ferrocarril del Pacifico (Mexico)	509, 510	83545, 83546	10/1959
Ferrocarril del Pacifico (Mexico)	511-514	83636-83639	10/1960
Ferrocarril del Pacifico (Mexico)	515-517	83968-83970	2/1961
Ferrocarril del Pacifico (Mexico)	518-520	84080-84082	3/1962
Ferrocarriles Nacionales de México (Mexico)	7400, 7401	82919, 82920	8/1958
Ferrocarriles Nacionales de México (Mexico)	7402-7408	83548-83554	12/1959 - 3/1960
Ferrocarriles Nacionales de México (Mexico)	7409-7418	83626-83635	3/1960 - 6/1960
Ferrocarriles Nacionales de México (Mexico)	7419-7423	83851-83855	3/1961
Ferrocarriles Nacionales de México (Mexico)	7424-7428	83806-83810	4/1961
Ferrocarriles Nacionales de México (Mexico)	7429-7440	83956-83967	4/1961
Ferrocarriles Nacionales de México (Mexico)	7441-7457	84083-84099	8/1962
Ferrocarriles Nacionales de México (Mexico)	7458-7472	84278-84292	8/1962 - 9/1962
Lake Superior & Ishpeming	1801, 1802	81953, 81954	4/1956
Lake Superior & Ishpeming	1803, 1804	83547, 84293	11/1959, 4/1963
New York, Chicago & St. Louis (Nickel Plate Road)	325-332	81955-81962	2/1957 - 6/1957
New York, Chicago & St. Louis (Nickel Plate Road)	333	82378	6/1957
Pennsylvania Railroad	8655-8663	82379-82387	12/1957 - 1/1958
Pennsylvania Railroad	8664-8678	82066-82080	2/1958 - 3/1958
Pennsylvania Railroad	8679	82918	4/1958
Southern Pacific	7000-7005	83640-83645	2/1961
Southern Pacific	7006-7020	83836-83850	2/1961 - 4/1961

Montreal Locomotive Works

Total Built = 10

Owner	Road Number(s)	Serial Number(s)	Completion Date
Companhia Siderúrgica Nacional (Brazil)	3501	82477	12/1961
Companhia Siderúrgica Nacional (Brazil)	3502-3510	83947-83955	10/1962

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.

Solomon, Brian. Alco Locomotives. Minneapolis: Voyageur Press, 2009.

After receiving their batch of four from Alco between 1956 and 1963 the LS&I later acquired six, second-hand RSD15 Alligators from the Santa Fe.

During the 1960s Alco released its Century line to replace the floundering RS series. Unfortunately, it saw no rebound in sales or recovering interest in its products and left the market entirely before 1970.