Introduction

Atlas N SD-24 & 26 Locomotive was re-released with new road numbers & paint schemes! It is one of their Master Line. We will examine an SD-24, Southern Pacific 7240, item 40 002 851.

Atlas offers this model as DCC and analog.

SD-24

Electro-Motive Division first introduced a turbocharger for their 16-cylinder 567 engine in the SD24 (Special Duty, 2,400Hp). (That protruding housing behind the cab on the left side of the long hood provides room for the turbocharger.) EMD released the SD24 in 1958 and today turbocharged prime movers whine their way across North America's rail network. A spotting feature of the SD24 are the air reservoirs on top of the body (nicknamed "torpedo tubes"), placed there because the SD24 slung a 3,000-gallon fuel tank between the C-C trucks, leaving no room for the air tanks.

According to Atlas;

With over 220 units produced by EMD between July 1958 and March 1963, the SD-24 locomotive generated a total of 2,400 hp with its turbocharged 567D-3 prime mover and C-C wheel arrangement.

The majority of SD-24s produced were purchased by four roads: Chicago Burlington & Quincy, Santa Fe, Southern, and Union Pacific. Atlas’ N scale model features details unique to each road name:

Burlington (CB&Q): High nose, single-chime air horn on short hood, Gyra-light on short hood (non-operating), winterization hatch

Santa Fe: Low nose, 3-chime horn mounted on left side of hood behind cab

Southern: High nose, 5-chime horn mounted on cab, bell detail on short hood

Union Pacific: Low nose, 3-chime horn mounted between 2nd and 3rd radiator fans, winterization hatch

What about the model?

Master Line Sd24

Atlas securely packs this model in a form-fitted foam cradle set in a jewel box. The foam holds the loco firmly. A sheet of bubblewrap protects the lid side of the loco. A arts diagram and warranty information is provided with my sample.

This 1/160 SD24 is hefty due to the two-piece metal frame that fills most of the body shell. The Five-pole skewed armature motor with dual flywheels, and worm & drive shafts are sandwiched between the halves. It has a indention to accept a decoder. Atlas' plastic body is crisply molded and full of detail. None of the fans, stacks, louvers, intakes nor grilles are molded open. Fine raised and recessed details define doors and other components. Atlas advertises these features:

* Golden-white LEDs
* Separately-applied roof detail
* Directional lighting
* Painted safety rails
* Blackened metal wheels
* Scale Speed™ motor
* Factory-installed AccuMate® magnetic knuckle couplers

The model features all-wheel pick-up. The couplers are mounted on the body.

Detail

Atlas' RP-25 blackened metal 40" wheels are held within plastic Flexicoil C trucks. All 6 of the axles are powered. While the sides appear to be one-piece moldings they are packed with detail. I did not notice the rumps of the brake cylinders are molded softly until I saw them under magnification.

Southern Pacific did not buy any SD24s so this is a fictional locomotive. Otherwise, riding on the trucks is a low nose Santa Fe-style body with a 3-chime horn mounted on left side of hood behind cab. It is crisply molded with high detail. If you would like to view the EMD diagram of the SD24, see Click here for additional images for this review, below. Raised tread details the catwalks. Small handrails and stanchions have good detail and thickness, although the step rails are thicker. Chains protecting the pilot crossovers are molded open! Each of the boarding steps have open backings. Train line and signal hoses are molded onto the pilots, as is a cut lever. In spite of the good detail elsewhere on this loco, those details lack, well, detail.

Plenty of hinges and handles and latches are molded along the body access doors. As previously mentioned, the intakes, louvers, grilles and exhausts for the engine and appliances are not molded open, although they are deeply recessed. The radiator intakes have diamond "chicken wire" screens. All of the ladders and hand grabs are molded on, as are lift rings atop the hood.

Most of the detail is molded on although Atlas attached separate parts worthy of their Master Line. Each side has breather piping with a filter for the fuel tank. Atop the long hood are the "torpedo tube" air tanks. These have a fine air line running along the roof back to the rear of the hood. The 3-chime horn is also attached at the factory.

One other detail that Atlas has improved upon are the headlights. They are golden-white LEDs. These are more authentic than the bright white or bluish lights what were used in the past.

Atlas tooled a lot of detail into this N engine. No doubt individual grabs could have been used instead of molding them on and yet that would add to the cost and potential delicacy of the model.

Paint and Markings

As this model is decorated for "Espee" (S.P. Southern Pacific) it is naturally painted in Southern Pacific (Dark) Lark Gray and Southern Pacific Scarlet, with Lettering Gray stenciling. That is known as the "Blood (or Bloody) Nose" scheme. As noted earlier, SP did not buy any SD24s so this model is an "alternate history paint scheme." Still, the livery is faithfully reproduced. The nose has the "wings" design.

The paint is opaque and yet thin enough that it does not obscure detail. Boundaries between colors are sharp. Lettering is crisp. The EMD plate below the steps behind the cab is almost legible.

Atlas offers this run of SD24s in five road names:

Southern Pacific (Gray/Scarlet)
Santa Fe (Billboard Lettering) (Black/Silver "Zebra Stripes")
Union Pacific (Yellow/Gray/Red)
Burlington Northern (Green/Black/White)
Southern (Black/Imitation Aluminum/Gold)

Each road name is offered with three road numbers. Atlas also offers the Sd26 with other livery.

So was there an SP 7240? Yes indeed. You can access photos of it via Real SP 7240 in the summary box, below.

Performance

My SD24 weights 3 ounces. Atlas states it can negotiate a minimum radius of 9.75". It ran well over Atlas code 55 track including No. 5 turnouts.

Conclusion

Atlas' SD24 is a little beauty of an SD24 in a fictional road name. It features crisp molding and fine details, excellent paint, and golden-white headlight LEDs. The separately applied detail parts enhance the model. Even the molded detail is superior, except for the air hoses, MU cables, and cut lever.

While Espee had no SD24s, fans SD24s and Southern Pacific should be happy to put one or more on their layout. It works and looks great! Recommended.

Please remember to mention to Atlas and retailers that you saw this model here - on RailRoad Modeling.

The EMD SD24*

The Electro-Motive Division's SD24 began the company's entry into the manufacturing of second-generation diesel locomotives. Interestingly, while the model offered new features it kept many of the standard features of the early first-generation Special Duty locomotives like the SD7, SD9, and SD18. It had yet to feature the new Spartan Cab design and stuck with the tapered nose of the SD18. All of this would, change, however, when EMD released the SD28 in 1965. In any even, the locomotive saw modest sales although just a handful of railroads would buy it with most orders taken by the Atchison, Topeka & Santa Fe Railway (the Santa Fe). The SD24 was also the only six-axle model to have cabless B units built. Today, none are known to still be in use for freight service although regional Pan Am Railways keeps two rebuilt as SD26s stored. Also, two others are known to be preserved, Chicago, Burlington & Quincy #504 is completely restored at the Illinois Railway Museum while the National Railroad Museum has CB&Q #510 partially restored.

The SD24, which debuted in July, 1958 and remained in EMD's catalog through March, 1963 was one of the company's rarer designs that did not sell particularly well in comparison to the early Fs as as the GP7 and GP9. However, it is featured here primarily because of its significance as EMD’s leap into second-generation power for six-axle locomotives. The unit was virtually identical to her GP30 (B-B trucks) sister in most aspects except that she carried 2,400 hp instead of the GP30’s 2,250 hp. For instance, the SD24 featured the very same 16-cylinder 567D3 and featured an airtight hood that kept out dust, dirt, and other particles from reaching internal components (to cool these critical components the SD24 featured a single air intake for electrical cooling, with a pressurized cooling system). It was these latter features that, in particular, classed the locomotive as a second-generation design.

The SD24's primary purpose was that the extra two axles produced more traction (which allowed the locomotive to handle stiffer grades), allowed for better weight distribution (which was a big plus on light rail and bridges unable to support heavy loads, found on many branch lines) and its Flexicoil trucks allowed for ease of maintenance on its center traction motor. Another significant difference with the SD24's internal components was its use of General Motors model D47 traction motors, as opposed to the GP30's model D57. Up to that time the SD24 offered the most tractive effort of any of EMD's six-axle models; 97,500 pounds starting and 72,300 pounds continuous.

The SD24 was officially EMD's first to feature turbocharging, a concept that actually dated back to 1955 and 1956 in tests by the Union Pacific to equip its own GP9s with the feature to boost their horsepower. These units became known as Omaha GP20s. At the time, the railroad was wanting and needing higher horsepower locomotives to help move heavier freight trains along its main lines west of Wyoming. EMD was hesitant to turbocharge its own 567 prime mover but after the successful test by Union Pacific went forward with the concept. The SD24 was the first to be cataloged with the feature and more than a year later in November, 1959 the four-axle GP20 went on sale with a turbocharged 567.

Of course, turbocharging was nothing new and certainly not pioneered by EMD. The American Locomotive Company had been turbocharging its road switchers since the 1940s and was so good at it that typically Alco models were very fuel efficient while offering comparable, if not better, horsepower ratings than the competition. While the SD24 was not as successful as its early sisters it did pave the way for future second-generation six-axle models that would become legendary for their durability and reliability like the SD40, SD40-2, SD45, and others.

While the SD24 was offered with an optional steam boiler no railroads ever purchased such for use in passenger service. Additionally, only Kennecott Copper's one unit, #904, did not feature multiple-unit capability (MU). In total, the railroads which went on to purchase the locomotive included the Santa Fe (80, numbered 900–979), Burlington (16, numbered 500–515), Southern/Cincinnati, New Orleans & Texas Pacific/New Orleans Northeastern (48, numbered 2502–2524, 6305–6325, and 6950–6953), and Union Pacific who purchased the only B units (30 As numbered, 400–429 and 45 Bs, 400B–448B). Additionally, EMD's four demonstrators went to UP.

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SOURCES

* Adam Burns. The EMD SD24. American-Rails.com. n.d.