Turbocharged Siblings

Amid the “Horsepower Race” of the late 1950s and early 1960s, Electro-Motive introduced its GP20 and SD24 siblings.

Words by Gary Dolzall

As the 1950s decade neared its end, America’s railroads, with a few notable exceptions, had fully traded steam for diesel power, and, in fact, the earliest generation of diesels were themselves coming due for replacement. Having dieselized in the 1940s and early 1950s with a primary diet of 1,500-horsepower diesels, the railroads were looking for more horsepower, and the competitive diesel builders were willing to oblige.

Aside from a few true oddities (such as Baldwin’s famed 3,000-horsepower Centipedes), the first builder to seriously toy with marketable main line high-horsepower diesels (and at the time, high horsepower could be generally defined as 2,000+ horses) was Fairbanks-Morse with its 2,400-horsepower H-24-66 “Train Master” of 1953. The handsome six-motor F-M met with only limited success and, alas, may have simply been before its time. By 1955-56, Alco (American Locomotive Works) was also pushing the power envelope with its new 251-series engine and the likes of its long-nosed, six-motor, 2,400-horsepower RSD-15 (DL-600B). General Electric, which traditionally partnered with Alco for main line locomotive production had, in 1954, quietly rolled out a set of its own testbed streamlined cab units, and by the late 1950s it was little secret that General Electric was soon to enter the U. S. main line diesel market on its own (and indeed, GE’s entry, in April 1959, was the landmark 2,500-horsepower U25B).

Electro-Motive, secure in its position as the dominant North American diesel builder, had, into the mid-1950s, been in no hurry to rock the boat, and EMD was hesitant to make the jump toward turbocharging its extraordinarily successful and reliable 567-series 2-cycle powerplant. But as the horsepower race heated up, EMD reconsidered. Electro-Motive began its own turbocharger development in 1956 and watched with interest (and then collaborated with) Union Pacific’s experimentation in turbocharging some of its existing GP9s (which eventually became nicknamed “Omaha GP20s”).

The result of Electro-Motive’s embrace of the turbocharger, making its debut in 1958 and 1959, was EMD’s new “20 Line” of road-switchers, the four-axle (B-B) 2,000-horsepower GP20 and six-axle (C-C) 2,400-horsepower SD24. Both of EMD’s new offerings were powered by turbocharged versions of the 567-series V-16 powerplant (for the GP20, the 567D2, and for the SD24, the 567D3.

Electro-Motive was typically as effective in marketing as it was in design and manufacture – and both the SD24 and GP20 garnered much press coverage. EMD, for example, promoted the GP20 to the railroads in several ways. The new model was positioned as a cost-effective replacement for first-generation diesels, and EMD offered what was effectively a price-attractive “trade-in” plan. In this plan, 41 specific components of old F-units or earlier Geeps – including components such as the truck frame, main generators, engine crankshafts, fuel pumps, etc. – would be reconditioned and used in the GP20s. As far as performance, EMD heavily promoted the GP20’s capability to haul equal or greater tonnage using fewer units. Based on the fact that three GP20s provided the same horsepower (6,000) as four F7s, EMD promoted this three-replaces-four capability.

Among the new turbocharged siblings, it was the SD24 that first rolled out of EMD’s LaGrange (Illinois) plant. EMD testbed demonstrator 5579 was introduced in July 1958, and eventually Electro-Motive would field an additional three demonstrators (all of which would later be sold to Union Pacific). The SD24 technically remained in production through 1963, although all units but one were constructed by 1960. Four big roads – Santa Fe, Southern Railway, Burlington Route (CB&Q), and Union Pacific – purchased a combined total of 223 SD24s, with mining company Kennecott Copper buying the sole unit built in 1963. Coming as it did just as railroads began changing their preference from “high-nose” to “low-nose” road-switchers, the SD24 was built in both variations. And Union Pacific, always to be counted on to make matters interesting, specified that 45 of its 79 SD24s be cabless boosters. Santa Fe proved to be the most prolific customer for the SD24, acquiring 80 units in 1959-60.

The SD24’s little sister – the GP20 – made its first appearance in November 1959, with the first order going to Western Pacific in the form of six high-nose GP20s dressed in the road’s orange-and-silver livery. In the summer of 1960, EMD rolled out a quartet of flashy blue-and-silver GP20 demonstrators that barnstormed much of the country (and were eventually sold to Southern Pacific). Through 1962, seven railroads acquired 260 GP20s. The GP20 proved to me very much a creature of the West, with six of its seven buyers being CB&Q, Santa Fe, Southern Pacific/Cotton Belt, Union Pacific, and Western Pacific. New York Central was the sole eastern buyer of the GP20. Like the SD24, the GP20 was built in both high-nose and low-nose configurations, and NYC’s 15 units were notable for being the only GP20s (or SD24s) built without dynamic brakes.

In retrospect, the production numbers of the SD24 and GP20 perhaps seem modest, but each had a relatively short production life-cycle (until being replaced by the SD35 and GP30, respectively). But regardless of numbers, the turbocharged siblings set the stage for the full bloom of EMD’s subsequent second-generation line of turbocharged locomotives and are viewed as the harbingers of dieseldom’s “second generation.”

Both the SD24 and GP20 journeyed forth to enjoy long service careers and, through mergers and resales, came to wear a rainbow of colors. Both types, too, were the subjects of major rebuilding programs that extended their lives, perhaps the most notable of which was Santa Fe’s conversion of its large fleet of SD24s to upgraded “SD26s.” And truly unusual was Illinois Central’s purchase of 35 aged Southern Railway and Union Pacific SD24s (including boosters), which IC ran through its legendary Paducah (Kentucky) shops to emerge as IC “SD20s” (yes, albeit without turbochargers). Chicago & North Western also acquired ex-UP and Southern SD24s, which it removed the turbochargers from and then reclassified as SD18s. Surely there was some irony in the fact that many SD24s and GP20s had their lives extended by the removal of their turbochargers. Another road always on the look-out for a bargain – Guilford’s Springfield Terminal – purchased a number of ex-Santa Fe SD26s.

The days of the SD24 and GP20 serving their original owners are past, but two ex-CB&Q SD24s are preserved – most notably, Burlington Route 504 was beautifully restored in CB&Q Chinese red and gray and is operational at the Illinois Railway Museum. Several private shippers still employ the ex-IC SD20s. Meanwhile, a number of GP20s still work for short line railroads such as New Jersey’s Raritan Central, and three GP20s are known to be preserved, including the restored Western Pacific 2001 – the first GP20 built – that is operational at the Western Pacific Railroad Museum located in Portola, California.

Most certainly, should you encounter one of the remaining SD24s or GP20s, take an extra moment to admire the locomotive, for it represents in steel a notable keystone in the evolution of the American diesel locomotive. – Gary Dolzall

A snow storm is descending on northern Illinois, but Santa Fe Electro-Motive GP20 1113 carries on powering a local freight through Joliet, Illinois. Santa Fe was the most prolific buyer of both the GP20 (75 units) and SD24 (80 units). In this January 1969 scene, AT&SF 1113 remains much as it was when it rolled out of EMD’s LaGrange (Illinois) plant a decade earlier. Photograph by Gary Dolzall.

Union Pacific acquired 79 SD24s and, as usual, the road had a penchant for making things interesting. UP’s fleet of SD24s included both high- and low-nose units (such as UP 410 above), ex-EMD demonstrators, and, most notably, 45 cabless boosters (below). Both photographs, Dolzall collection.

Southern Railway acquired 44 SD24s, many of which were earmarked to do battle with the railroad’s famed and tough Rathole Subdivision. At Louisville, Kentucky, in May 1975, Southern SD24 6328 shares the Youngtown Yard engine facilities of the Kentucky & Indiana Terminal with Baltimore & Ohio GP30 6945. Photograph by Gary Dolzall.

Still wearing its Burlington Route Chinese red and gray livery, Burlington Northern SD24 6249 (originally CB&Q 509) stands at Wenatchee, Washington, in July 1970. One of 16 SD24s acquired by the CB&Q in 1959, the locomotive served until 1982. Dolzall collection photograph.

Santa Fe extended the life of its robust fleet of SD24s by running the diesels through a major rebuilding program at its San Bernardino (California) shops. As exemplified by AT&SF 4668 (ex-Santa Fe 968) at Barstow, California, in 1979, the rebuilding program converted the SD24s into 2,600-horsepower units classified by AT&SF as SD26s. Rebuilt in 1973, this SD26 remained in AT&SF service until 1986, then later served Guilford’s Springfield Terminal. Dolzall collection photograph.

Electro-Motive’s GP20 proved to be largely a creature of the West, but the exception was a group of 15 low-nose GP20s acquired by the New York Central in 1961. NYC’s GP20s were the only such units built without dynamic brakes (above). Dolzall collection photograph. NYC’s GP20s – in de-turbocharged form – would live to serve both Penn Central and Conrail. At Avon Yard in Indianapolis, Indiana, Penn Central GP20 2102 is bringing a freight into the yard in 1976 (below). Photograph by Gary Dolzall.

Hustling a freight near Duluth, Minnesota, in 1985, Burlington Northern GP20 2003 began life in 1960 wearing the colors of the Great Northern. Both the GN and Western Pacific opted for GP20s equipped with high noses. Mike Danneman photograph; Dolzall collection.

Looking far different than when it rolled out of EMD’s plant a quarter-century earlier, Santa Fe GP20 3012, wearing the short-lived livery intended for AT&SF’s ill-fated merger with Southern Pacific, waits to depart from Chillicothe, Illinois, in May 1986 (above). Well-maintained and upgraded, many Santa Fe GP20s went on to secondhand buyers, such as ex-AT&SF GP20 3040 serving the regional Toledo, Peoria & Western (below). At Chatsworth, Illinois, in 1990, four ex-Santa Fe GP20s are lugging a unit coal train. Both photographs by Gary Dolzall.

In what can only be described as a train-watcher’s dream lash-up, short-lived regional railroad Fox River Valley calls upon an ex-CB&Q SD24, an ex-Santa Fe Alco DL-600B, and an ex-Southern Railway SD35 to tote tonnage through Eden, Wisconsin, in 1990. Today, SD24 No. 2402 (which was originally CB&Q 510) is preserved at the National Railroad Museum of Green Bay, Wisconsin. Photograph by Gary Dolzall.

Truly unusual was Illinois Central’s rebuilding, beginning in 1979, of 35 aged ex-Southern Railway and Union Pacific SD24s (including boosters), which IC ran through its legendary Paducah (Kentucky) shops to emerge as IC “SD20s.” Remarkably, IC SD20 2005, rolling south along IC’s main line at Chebanse, Illinois, began life as a Union Pacific SD24 cabless booster! Photograph by Gary Dolzall.