Alco "RSD4" Locomotives: Data Sheet, Roster, Specs

Last revised: December 27, 2024

The RSD4 was Alco's fourth installment of its six-axle Road Switcher (RS) series built at the same time as the RS3. Essentially, the design was a C-C version of that model (Alco had also produced an A1A-A1A RSC3).

Unfortunately, it was one of the least successful with fewer than 50 produced by the time production had ended during its two year production run. Perhaps most notable was the incredible tractive effort it offered, by far the most of any RS model produced up until that time.

Overview

Alas, railroads still had yet to embrace the six-axle concept, another reason for the design's poor sales. If one wanted to catch these rare locomotives in action by the 1980's, a good place to start was the Chicago & North Western.

Also known as the "Cheap & Nothing Wasted," C&NW was really pinching pennies in those days; they rebuilt older locomotives, purchased used first-generation power, and continued operating Alco's long after most other Class I's had sold or scrapped theirs.

The RSD4's could be found working the railroad's famous "Alco Line," a secondary corridor which stretched from Winona, Minnesota to Rapid City, South Dakota.

Photos

Utah Railway RSD-4's #300, #301, and #304, along with RSD-5 #306, burble and belch away as they work the loadout at Mohrland, Utah during the 1970s. American-Rails.com collection.

Remaining first-generation Alco's were sent here to streamline maintenance and it was a railfan's paradise. One could find RS11's, RS3's, RSD4's, RSD5's, C425's, RS36's, and others pulling freights that creaked and weaved along decaying trackage.

The RSD4 line was built for two years, between 1951 and 1952 at the same time as the RS3. The locomotive featured Alco's standard, but troublesome, 244 model prime mover allowing for 1,600 horsepower.

As with the original six-axle model (RSD1) the RSD4 was meant to provide a sizable increase in tractive effort. The model had a slight design flaw as there was insufficient space for the unit's main generator, which was corrected with the RSD5 featuring a longer hood and carbody.

As a result of this change the RSD5 sold much better than the RSD4 with nearly six times more units produced during the time Alco cataloged the locomotive, from 1952 through 1956.

Significance

One important historical note about; from a technical standpoint, the model was the very first C-C design (meaning all six axles were powered) that Alco offered standard in its catalog.

The RSD1 was merely a specialty order for the US Army and the RSC2 and RSC3 locomotive were A1A-A1A designs whereby the center axle was not powered (i.e., lacking traction motors).

Jersey Central RSD4 #1603 was photographed here at the road's terminal in Jersey City, New Jersey in 1964. American-Rails.com collection.

With the RSD4's six motors the model could produce a starting tractive effort rating of 89,000 pounds and 78,750 continuous. This was nearly a 33% increase over the RSC3 which could produce 60,100 pounds starting tractive effort and 52,500 continuous.

Data Sheet and Specifications

Alco Class	606-DL-360
Entered Production	3/1951 (Chicago & North Western #1515)
Years Produced	5/16/1950-8/1956
Model Specification	E1663/A
Engine	244, V-12
Horsepower	1,600
RPM	1,000
Carbody Styling	Alco
Length (Between Coupler Pulling Faces)	55' 11.75"
Weight	360,000 Lbs. (Optionally reduced to 270,000 Lbs.)
Dynamic Brakes	Optional
Trucks	C-C
Truck Type	Trimount
Truck Wheelbase	12' 6"
Wheel Size	40"
Traction Motors	GE 752 (6)
Traction Generator	GT581
Steam Generator	-
Gear Ratio	74:18
Tractive Effort Rating	78,750 Lbs. at 5.5 MPH
Top Speed	60 MPH

Production Roster

Total Built = 36

Owner	Road Number(s)	Serial Number(s)	Date Built
Santa Fe	2100	78218	6/1951
Santa Fe	2101 - 2105	78386-78390	6/1951 - 9/1951
Santa Fe	2106 - 2109	78741-78744	9/1951 - 10/1951
Chicago & North Western	1515 - 1517	78214-78216	3/1951 - 4/1951
Chicago & North Western	1619, 1620	80445, 80446	8/1952
Central Railroad of New Jersey	1601 - 1606	78745-78750	11/1951 - 1/1952
Central Railroad of New Jersey	1607, 1608	78946, 78947	1/1952
Central Railroad of New Jersey	1609 - 1614	78949-78954	1/1952 - 2/1952
Kennecott Copper Corporation	201	78217	5/1951
Utah Railway	300	78948	1/1952
Utah Railway	301, 302	78955, 78956	2, 3/1952
Utah Railway	303, 304	80284, 80285	7/1952, 8/1952
Utah Railway	305	80444	8/1952

Santa Fe RSD4 #2105 and a cow-calf set (TR4 #2418/#2418A) work yard service in Argentine, Kansas at the east end of Argentine Yard along the Kansas River on October 17, 1954. Mac Owen photo.

Internally, the RSD4 was supplied with parts from General Electric (its model 752 traction motor) and Westinghouse (air brakes and compressors). It kept the same frame as the RS3, remaining at a length of 55 feet, 11 inches.

However, the one striking difference aside from its six axles was the weight; at 180 tons the RSD4 weighed nearly 70 tons more than the RS3 (of course, this weight also added to its increased tractive effort).

Use

The five railroads that ultimately did purchase the model used them as intended, in heavy freight service. This include the Atchison, Topeka & Santa Fe, Utah Railway, Central Railroad of New Jersey, Kennecott Copper Corporation, and the Chicago & North Western.

Today at least one RSD4 remains preserved, and operational, Kennecott Copper Corporation #201 (the only RSD4 the company ever owned).