by Tony Cook/photos by the author except as noted
As Atlas Model Railroad Co. celebrates its 100th anniversary this year, there are a number of popular releases from the company’s past which are about to celebrate their 50th. At the end of 1974, Atlas provided the HO market with a bolt from the blue, announcing a model of an Electro-Motive Division (EMD) SD24 diesel locomotive. This SD24 replica was the first in a succession of EMD diesel locomotives to arrive across 1975. As frequently occurs as we dive into hobby history for this column, I usually come away — even from a familiar topic such as this one — with some knowledge I didn’t have when I began, and that’s always fun and satisfying.
Going back half a century to the mid-1970s, the HO-scale diesel locomotive market was firmly in the grasp of Athearn and its “blue box”-era kit releases for many hobbyists. On the entry side of HO, TYCO was at its “brown box”-era zenith with a wide range of train sets and accessories. When Atlas debuted its HO-scale SD24, competitors would include Athearn’s recently delivered General Electric U-boats (see June 2022 Collector Consist) and EMD F45, FP45, and SD9 were new. AHM’s FT A-unit, GP18, and Alco C-424 (see September 2019 Collector Consist) were new for its line in HO. Bachmann’s U36B, Lionel HO’s GP30, Life-Like’s C-628 and GP38-2, TYCO’s C-630, and Cox’ F3A and GP9 were new in HO, as was Model Power’s Alco FA and Shark (see September 2021 Collector Consist). From this list AHM’s Alco Century and Model Power’s cab units all share a common element — they were all produced in Austria by Roco. 
ABOVE: This is Atlas’ “yellow box” design as it’s referred to by many collectors. The run of Roco-made EMDs in 1975 started this package look that ran well into the 1990s.
Atlas’ efforts in HO scale date to the early days of the company. Atlas famously introduced its sectional Snap-Track, pre-assembled turnouts, innovative flex track, and more to its catalog in the 1950s. The company imported HO structure kits beginning in the 1960s. The nearest Atlas came to a locomotive may be its Turbo Racer of the early/mid-1960s. This propeller-equipped race car shell rested on Athearn’s Hustler switcher drive mechanism and was a curious competitor of the slot car craze (in which Atlas also participated) that lands in the hobby beginning in the early 1960s. In 1968, Atlas leapt into N scale in a big way with a line of locomotives and rolling stock produced by several overseas manufacturers; however, HO remained a world made of only track and structures for Atlas as the 1970s got underway.
I noted Roco was the manufacturer in Europe producing AHM’s C-424 and several Model Power releases in the early-to-mid-1970s. Atlas had Roco as a source for its early 1970s 2-rail O scale (see March 2022 Collector Consist) and several offerings in its N-scale locomotive and rolling stock catalog. The collection of EMD diesel locomotives that rolled into HO beginning in late 1974 all came from Roco. The group included the debut SD24, followed by an SD35, then a high-nose GP38, a GP40, an FP7, and a low-nose GP38.
In his March 1975 review in Railroad Model Craftsman, then-editor Tony Koester says of the SD24, “First in a new line of HO motive power from this established firm, the Austrian-made model is an excellently scaled copy of the prototype.”
ABOVE: Roco’s original drive from 1975 is shown on left and the revised drive from 1984 appears on right. The mid-1980s modification included directional control for the headlight bulb.
Design elements and components are shared across various models. For example, the six-axle chassis under the SD24 and SD35 are the same, and the GP38s and GP40 shared a chassis. The plastic four-axle Blomberg truck sideframes are common across the Geeps and the FP7, while the two six-axles share the same Flexicoil sideframes. The innovative, single-piece, flexible engineering plastic handrail sections served across more than one model type in many situations. Under the detailed plastic shell, a large motor was the heart of the powerful and smooth operating drive mechanism.
Let’s take a closer look at the Atlas GP40 diesel produced by Roco. This second-generation EMD 3,000-hp four-axle model has always been a favorite with me. Currently, we are enjoying a big GP40 renaissance with not one, but at least three all-new HO GP40s under development and/or announced and soon to arrive in the hobby.
EMD began building GP40s in late 1965, and they remained in the manufacturer’s catalog through late 1971, when it was succeeded by an updated GP40-2. GP40s could be found on railroads big and small across the United States, Canada, and Mexico. Rosters ranged from a single unit on Toledo, Peoria & Western (an EMD warranty loaner unit that later became Santa Fe’s only GP40 for a short time) to more than 200 serving Baltimore & Ohio and Chesapeake & Ohio. Penn Central was up there, with 170 bought after 1968 and 105 inherited from New York Central (including the first production GP40, NYC 3036)…