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Atlas O’s new Trainman diesel: the Alco RSD-4/5

Review and Photos by David Otte

O-scale Alco RSD4/5
0430-1 St. Louis Southwestern #270, 3-Rail TMCC, MSRP: $369.95
0405-1 St. Louis Southwestern #270, 3-Rail, MSRP: $229.95
0455-1 St. Louis Southwestern #270, 2-Rail DC, MSRP: $229.95
0432-1 Santa Fe #2131, 3-Rail TMCC, MSRP: $369.95
0407-1 Santa Fe #2131, 3-Rail, MSRP: $229.95
0447-1 Santa Fe #2131, 2-Rail DC, MSRP: $229.95

Atlas O, LLC
378 Florence Av • Hillside, NJ 07205
908-687-9590 • Fax: 908-687-6282

In the May 2006 issue of Model Railroad News, I reported on Atlas O’s new, affordable 1/48-scale Trainman freight cars. Having found the rolling stock models to be great bargains, we now turn our attention to the first locomotive release in the Trainman lineup: the Alco RSD-4/5 road switcher. For its initial offering, Atlas O is
decorating the six-axle diesel-electric for the Chesapeake & Ohio, Chicago & Northwestern, Cotton Belt, and Santa Fe with two roadnumbers available per roadname. The 3-rail Alco model can be purchased equipped with either horn and bell sound only or with Lionel’s TrainMaster Command Control and RailSounds. A 2-rail DC powered version is also available and includes a DCCready circuit board. The locomotive is being manufactured in China and includes Atlas O’s standard one-year limited warranty.

The Prototype

Alco’s entry into the six-axle road switcher market was not really by its own choosing but rather can be credited to the federal government. In 1942 the U.S. Army took control of the 685-mile Trans-Iranian Railway in order to supply Russia with war materiel. Although military steam locomotives were available, they were not well suited for the mountainous terrain and lack of adequate water
supplies. Diesel-electric locomotives, such as Alco’s new 1,000 horsepower RS-1, were capable of handling this military mission, however, their axle loadings were too high for the railway’s light 70-pound rail and its 20-ton-per-axle weight limitation.

The U.S. government approached Alco for a solution to this problem. Alco’s  chief engineer, James G. Blunt, came up with the answer: a newly fabricated six-axle truck that could be used on the
company’s RS-1. This new truck provided reduced axle loading as well as a third traction motor for added adhesion. The Army accepted the new C-C (six-axles, six traction motors)-truck equipped RS-1s and ordered a total of 157 units by the end of World War Two. While Alco never really cataloged their new design, they subsequently constructed six C-C-truck RS-1s for National Railway of Mexico and four A1A-A1A (six axles, four traction motors)-truck RS-1s for export to Brazil after the war.

Actually, Alco didn’t realize the potential of the six-axle locomotive until its competitor, Baldwin Locomotive Works, began promoting its A1A truck models in the late 1940s. With a renewed interest, Alco began cataloging a six-axle version of its new 1,500 horsepower RS-2 model in 1946. Known as the RSC-2, the diesel featured a redesigned A1A truck with a shorter wheelbase than the truck on the military C-C RS-1, allowing operation on tighter radius curves. The manufacturer would end up building a total of seventy units for four different railroads before the model was superseded by a 1,600 horsepower model in 1950.

Produced concurrently with Alco’s RS-3, the RSC-3 continued the company’s A1A truck diesel offering but found little interest among railroads; only 11 RSC-3s were sold. The six-axle market was not
completely dead, however, for in 1951 the C&NW placed an order with Alco for three RS-3s with C-C trucks which Alco designated as the RSD-4. These units came with a new drop equalizer, swiveltype, three-axle truck the company referred to as the Trimount truck, which was easily differentiated from other A1A
or C trucks by its unequal axle spacing. With its three-point body support system, long equalizers, and deep deflection springs, the new trucks offered crews a smooth ride at speeds as high as sixty miles per hour and they provided the locomotive a higher level of adhesion. Other railroads began to pay attention to the new RSD design as it was well suited not only for service on lightweight rail but, with the additional traction motors, it could perform slow, heavy freight drag service, handle rough topography, and be used in hump yards.

The RSD-4 was equipped with Alco’s 12-cylinder 244-series engine, a General Electric Model GT581 generator (the same used in the RS-3), and six GE Model 752 traction motors. For the most
part it utilized the same carbody and frame length found on the RS-3. Optional equipment included a steam generator and dynamic brakes, both located in the short hood, as well as multiple-unit controls and two different sizes of fuel tanks. RSD-4 production lasted until August 1953 with a total of thirty-six units built for five different customers: Santa Fe, Central Railroad of New Jersey, Chicago & Northwestern, the Kennecott Copper Corporation, and
the Utah Railway.

While the RSD-4 was still in production, Alco introduced a revised 1,600-horsepower C-C road switcher, designated the RSD-5, in March 1952. Generally, it was mechanically and visually identical to the RSD-4, but it was upgraded with a GE Model 566 generator. The RSD-5 continued to shadow RS-3 production, too, and reflected the various design changes incorporated in that model’s carbody and air-filtration system. When production of the 1,600 horsepower C-C model was discontinued in March 1956 in favor of the 2,400-horsepower RSD-15 model, some 204 RSD-5s had been manufactured. Original owners of this model included: Santa Fe, Birmingham Southern, Central Railroad of New Jersey, Chesapeake & Ohio, Chicago & Northwestern, Ferrocarril del Pacifico, Milwaukee Road, National Railway of Mexico, Pennsylvania, Southern Pacific, and the Utah Railway.

The Model

In my review of the Trainman freight cars, I referred to this new Atlas O series as the great train compromise because it undertakes the production of scale-sized models at a much more affordable price compared to the top of the line O-scale equipment currently available. The Trainman RSD-4/5 continues in this endeavor by offering modelers motive power with scale proportions built to Atlas O’s high standards priced as low as $230.00. That’s about a fifty-percent savings over many of the recently released O-gauge locomotives reviewed by Model Railroad News. Best of all, the Alco model is not being limited in its production. Instead, it will be a regularly stocked item, like all of the Trainman series, which you can order from your Atlas O dealer at any time. Trainman is a great
idea and, as you will see by reading further, offers the O-scale fan another nice model for their motive power roster.

Construction of the RSD-4/5 is basically the same as other Atlas O
models: a one piece plastic long/short hood body shell with separate cab and walkway components, a heavy stamped metal chassis, and diecast metal pilots, trucks, and fuel tank. As with the Trainman freight cars, most of the details on the carbody are molded-in and exhibit good relief. Add-on parts include wire handrails with simple stamped metal stanchions, a brass single-note air horn, window glazing, sand fill hatches, brake wheel, and headlight lenses. Additionally, and unexpected on a model at this price, the Alco model has fourteen metal wire grab irons appropriately placed on the carbody and a see-through etched metal radiator grille with a separately applied 3-bladed fan visible underneath.

The O-gauge six-axle engine compares well overall to most published dimensions of the full-size Alco, but does stray a bit from its length. As mentioned earlier, the RSD-4/5 mimicked most of the design characteristics of the RS-3 including its 55-foot, 11.75-inch (and later on the Phase 2 model 56-foot, 5.75- inch) length, however, by my measurements the Atlas O model is almost a scale three feet or .75 inches too long. My guess is that the extra length was required to allow the model’s six-axle trucks, which have the proper wheelbase, to freely pivot, clearing the pilot and fuel tank, when operating on the tight O31 curved track encountered on many 3-rail layouts. For most O-gauge operators, though, this discrepancy would probably not be noticeable visually.

Keeping this slight deviation in mind, it is a good time to bring up an important characteristic of the Trainman line: low production costs. This means the models in this series are more generic in nature and usually will not display road specific details. The idea here is to keep tooling and assembly expenditures down and pass the savings on to the consumer. Having said that, I would like to point out some of the details Atlas O has incorporated into their model and paint schemes that will provide the hard-core prototype modelers among us with a basis for comparison to their favorite railroad’s RSD-4/5. However, please take note that this analysis is meant to be informational only and not a criticism of this locomotive or the Trainman philosophy.

RSD-4/5 production can be broken down into three phases. RSD-4 and RSD 5 Phase 1b units, the closest prototype for the Atlas O model, had horizontal louvers along the long hood’s access doors and horizontal louvers in the battery boxes. Louvers in the long hood were absent on RSD-5 Phase 2 car body versions. Rather they had single-element filter ducts located horizontally across the upper side of the long hood. Finally, RSD-5 Phase 3 variants, with their centralized filtered air ventilation system are identifiable by their two-element filtered air intakes near the cab and a three-element unit adjacent to the radiator shutter panel.

Furthermore, most railroads ordered their RSD-4/5s with the larger rectangular 1,300 gallon fuel tanks mounted lengthways under the frame while a couple of roads, C&NW and C&O in particular, ordered their Alcos with smaller, 800 gallon tanks mounted across
the underframe (in some cases to make room for steam generator water tanks). The Trainman model is equipped with the smaller tank, but there are no indications of any provision for either the dynamic brake or steam generator options on our sample locomotives. In addition, the Atlas O model has a rectangular-shaped exhaust stack whose length runs parallel with the long axis of the hood signifying an air-cooled turbocharger which was known as the Achilles Heel of the 244-series engine. Stacks mounted crosswise on the hood indicated the presence of the more successful water-cooled turbochargers, which were eventually retrofitted to many Alco units as well as being standard on the later phases.

A detail often missed by railfans when studying the Alco RS and RSD series concerns the cab window arrangement. Alco built their cab with two side windows for the engineer and three side windows for the fireman with forward being the direction the engineer was looking while sitting at the controls. The Atlas O cab also displays this attribute and its orientation on the model indicates that the long hood is to be run forward.

On the other hand, the model has a centered hand brake wheel on the end of the short hood, which happens, oddly, to be devoid of any other structural detail except the twin-beam headlight. Based on the photos I have, this orientation and lack of detail is not typical of RSD-4/5 production. Rather, most Alco units’ short noses appear to have had an off center brake wheel located adjacent to a
crew access door.

Finally, the model is outfitted with Trimount trucks with friction type
journals as used on the C&O, Kennecott Copper, and Milwaukee RSDs; the use of SKF or Timken roller bearing journals was much more prevalent. So, bottom line, the Atlas O locomotive is an example of either an early-production RSD-4 or RSD-5 with a small fuel tank, but, based on my research, it is not really an exact match for any RSD. If I had to pick a specific prototype, I would say it is closest to one of the C&O’s 26 RSD-5 Phase 1b units delivered by Alco between March and July of 1952.

Our 2-rail and 3-rail review samples came decorated for the Santa Fe and Cotton Belt respectively. The Santa Fe owned ten RSD-4s and fifty-three RSD-5s: the largest fleet of RSD-4/5s. Our number 2131 was delivered with a group of eight RSD-5 Phase 2 units (2130 –2137) in June 1953. It was retired on November 6, 1969 and traded in to EMD on an order of GP38s. While all the Santa Fe RSD-4/5s were delivered in the black and silver zebra stripped scheme, the Atlas O model wears the later blue and-yellow colors introduced by the railroad in 1960. Unlike the majority of owners, the Santa Fe designated the short hood as forward, which required Alco to turn the cab around when assembling the Santa Fe’s units. For the purist, the cab on the Atlas O model will need to be turned around as well, so the window orientation is correct, and the air horn repositioned to the short hood.

On the other hand, the Cotton Belt ran their Phase 2 RSD-5s long hood forward so the Atlas O cab position is good-to-go on this model. Number 270, along with 271 and 272, were all delivered to the SP subsidiary in April of 1953. These units were renumbered by the SP to 2888 – 2890 in 1965 with all three units retired by 1969 and traded in to EMD on an SD45 order. The Atlas O model wears the as-delivered paint colors, a version of the SP’s Black Widow scheme, with the railroad initials on the sides of the long hood. By 1956, the RSD-5s received “Cotton Belt” lettering in place of these initials. The SP/Cotton Belt fan will certainly appreciate the beautifully rendered decoration on this Atlas O offering and needs only to apply the high visibility yellow paint to the handrail to finish off an otherwise prototypical paint job.

As usual, Atlas O’s paint and graphic application was top-notch and I have no complaints with the execution of the decoration or the overall quality of assembly regarding our review samples.

Moving over to the test track, I put our tinplate Black Widow unit through the paces first. All versions of the RSD 4/5 are equipped with two vertically mounted can motors with brass flywheels. Three-rail models have operating die cast metal knuckle couplers with their pilots attached to the trucks. This assembly allows the model to easily maneuver through minimum O31 curves and Lionel number O22 turnouts, which was confirmed by my test results. I clocked our sample at a low speed of 16.3 scale miles per hour while the high speed was well beyond the prototype’s sixty-mileper-hour maximum. The Cotton Belt unit was equipped with horn and bell sounds only. Both audio effects sounded realistic, but the air horn is only able to play a single recording of four horn blasts, similar to a grade crossing signal. Directionally controlled lighting rounds out the features of this 4-pound, 2.5- ounce model.

Weighing in slightly less at 3 pounds and 10.9 ounces, the Santa Fe 2-rail RSD unit was a smooth and responsive model under direct current power. I initially began to test this sample with a MRC Tech 4 power pack, but the Santa Fe model did not like the pulsing DC produced by this power source. However, using a straight DC power pack by Kato, the RSD performed as advertised with a slow speed of 3.8 scale miles per hour at 1.97 volts and 0.46 amps and reached 72.7 scale miles per hour at 12 volts and 0.64 amps. The 2-rail locomotive, which had no problem traveling on minimum 36-inch radius curves and through number 5 turnouts, is equipped with fixed pilots, Kadee-compatible magnetic operating knuckle couplers, and directional lighting. Atlas O has designed the RSD-4/5s circuitry to accept a DCC decoder, but it is not plug-n-play. Instead, they have included both a power and a function connector that can be wired to a decoder of the modeler’s choice. The only stipulation Atlas O makes regarding a decoder is that it must be able to handle up to 6 amps of current draw, which is the maximum
stall amp rating of the combined motors with a 15-volt power source. Either a NCE Corporation D408SR or a Digitrax DG583S decoder, both with 10 amp stall ratings, should do the job.


The new Trainman series locomotive is definitely good news for the O-gauge hobby. First, it provides 2-rail and 3-rail operators with affordable motive power that is compatible with scale NMRA DCC or TMCC command control systems. Second, the RSD-4/5’s highquality decoration and crisply molded details allow it to fit in, almost undetected, with other higher priced O-scale models. Finally, it allows new blood to enter our hobby with minimal investment, but with maximum 1/48-scale play value. Yes, folks, the Trainman offerings or, shall I say, the great train compromises, in general appear to be surefire winners to this reviewer and I look forward to bringing our readers continued coverage of this innovative product line as new releases become available.


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