Alco "RS-27" Locomotives

The Alco RS27 was a late model of the Road Switcher (RS) series that produced more than 2,000 horsepower. However, the model was unsuccessful along with the fact that by the time it was debuted the American Locomotive Company (Alco) was already working on its next generation of road switcher, the Century series. As such, the RS27 looked very much like Alco's later models and was the first to receive the builder's new styling. By the late 1950s Alco was slipping further behind the Electro-Motive Division in the locomotive market and before the decade was over it would also be competing with one-time ally General Electric. Interestingly, examples of this rare Alco model can still be found, in service on shortline Minnesota Commercial (a haven for Alcos). 

The locomotives were purchased from the Green Bay & Western, which had purchased them from the Chicago & North Western (#901 and #903).  Aside from RS27's, their roster over the years has included RS3's, C424's, and even Montreal builds (RS18's, RS23's, M630's, and M636's).

A pair of Alco's RS27 demonstrators, #640-2 and #640-1, circa 1959. The lead unit (#640-2) became Union Pacific #675 while the trailing unit (#640-1) was sold to the Pennsylvania and became #2415. The three other demonstrators (#640-3 - #640-5) were also acquired by UP becoming #676-678. George Hockaday photo.

The Alco RS27 began production in 1959 using a B-B format (two axles per truck) and producing a hefty 2,400 horsepower for a somewhat small, four-axle unit. As with other late-model RS designs the RS27 came in a standard low-nose setup using Alco's much more reliable 251B prime mover. In terms of the company's history as a locomotive builder, the RS27 offered the first glimpse of its Century series, which began production in 1963. The model retained the flush, long hood with the cab and the classic notched corners on the carbody remained. However, the cab featured a slight design change with raised number boards and headlights, and the nose was shorter giving the locomotive a more blunted appearance.

An American Locomotive builder's photo at its Schenectady plant featuring one of the Soo Line's two RS27's (#415) it purchased in 1962.

From an exterior standpoint the RS27 began the common look of second-generation designs, as GE used a similar setup with its U25B, and EMD did the same beginning with its GP18, GP20,and GP30 models. Perhaps it was due to Alco's earlier troublesome engine designs that kept railroads away but whatever the case the builder found little success with the RS27 selling less than thirty units with the Pennsyvlania Railroad purchasing the most (15). The year 1959 was not a particularly good one for Alco.   It was increasingly losing market share to EMD, had not cataloged a successful locomotive since the RS3 finished production in 1956 (although its RS11 design did sell relatively well). 

Additionally, that year GE ended its five decade partnership with the company when it released its own line of diesels beginning with the U25B (which ironically far outsold the RS27).   From an operational standpoint, the RS27 varied little from the RS11 aside from the additional horsepower. It actually offered less continuous tractive effort (42,000 pounds) but more starting effort (66,000 pounds). As had been the case for nearly two decades when the RS27 was produced, internal components like traction motors, generators, and air brakes/compressors came in from GE and Westinghouse.  For more information about the RS27 please click here.  

Precision Engineering Company (PECo) RS-27 #901, built new for the Chicago & North Western carrying the same number, is seen here on lease to the Canadian Pacific at Ste Luc Yard in Montreal, Quebec on March 22, 1970. Roger Puta photo.

Production Roster Of Alco RS27s

Owner Road Number(s) Quantity Date Built
Alco Demonstrator640-1, 640-2, 640-3, 640-4, 640-551959-1960
Chicago & North Western900-90341962
Green Bay & Western31011960
Pennsylvania2400-2414151962
Soo Line415-41621962


Former Pennsylvania Railroad RS27 #2404 surprisingly made it into the early Conrail era before it was retired.

In the end the model proved another abysmal failure for Alco as just four Class I railroads ultimately purchased the RS27; the aforementioned Pennsylvania, Soo Line, Chicago & North Western, and Green Bay & Western.  Of note, however, Union Pacific did purchase two of the demonstrators, #640-2 and #640-3. Somewhat unsatisfied, UP returned them to the Montreal Locomotive Works where they were later resold.  Today, the Minnesota Commercial is apparently quite happy with its two RS27s as the railroad has kept them on its roster for nearly three decades now.  To read more about other Alco Road-Switcher (RS) models please visit the Diesel Locomotives section of the site, which can be reached from the top of this page.




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Header Photo: Drew Jacksich




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