Introduced: 1983 (Kato/Japan RS-3), 1987 (Kato/Japan RSD-4/5), 1999 (Atlas "Classic" RS-3 & RSD-4/5), 2001 (Slow-Speed Motor RS-3) and 2004 (Slow-Speed Motor RSD-4/5)
Atlas's RS-3 and RSD-4/5 models share a similar evolution and history. In fact, apart from the trucks (four axles on the RS-3 and six axles on the RSD-4/5), the models are identical (both internally and externally). So, to save myself a bit of time I'm going to cover them both here.
The Atlas/Kato RS-3 represents a watershed moment in N scale history and a huge leap forward in N-scale locomotive design (at least as far as North American prototypes are concerned). In late 1981-early 1982, Atlas discontinued their entire line of N-scale locomotives, which at the time included F9, GP9, GP30, E7A, FA-1 and Davenport Switcher models (all manufactured by Roco/Austria). Meanwhile, Stephen Schaffan (Atlas' founder) worked arduously (despite illness) to develop the company's Alco RS-3. The first production run of this model arrived in the latter months of 1983. Sadly, Mr. Schaffan did not live to see the fruits of his labors, as he passed away on March 22 of that same year. The RS-3, a widely lauded locomotive, represented the first in what was to be a new generation of Atlas locomotives. A memorium to Mr. Schaffan appeared in the June, 1983 issue of Model Railroader.
Although the first truly "modern" North American diesel model design, I'd say the Atlas/Kato RS-3 was more evolutionary than it was revolutionary. The pick-up design (split-frame metal truck assemblies transferring current to a split-frame metal chassis) is pretty much the same as the one Kato used in their 1967 Alco PA model. And many of the other noteworthy "new" features had already been seen in Kato's 1978 DD-13 centercab switcher (as imported by Con-Cor). EG, the vertically split-frame chassis (which sandwiched the 5-pole motor, driveshafts and worm gears), the directional lighting scheme (small PC boards mounted on either end of the chassis), the skinny/flexible handrails, and the separate walkway/handrail assembly.
One innovation that the RS-3 had (and that the DD-13 didn't) is the use of bearing blocks to hold the worm gears firmly in place - a now-standard convention for diesel models. On the down side, the RS-3 has open pilots and truck-mounted Rapido-style couplers. Similarly, it doesn't have flywheels either (those wouldn't appear on an Atlas/Kato loco until the 1988 RS-1 model). All wheels are geared (with all the gearing being plastic). The first-run of RS-3's came with one traction tire per truck. Later runs featured all-wheel pickup (IE, no traction tires). The wheels are low-profile, so no problems on Code-55 track. After the first RS-3 run, the wheels came "blackened". All of the RSD-4/5's came with blackened wheels and without traction tires.
Performance on these models is most excellent. They run smoothly and quietly at all throttle levels. Pickup is flawless, slow-speed creep is superb, and pulling power is impressive. The top-end speed is a bit high, but that's a minor nitpick. And running characteristics aside, these things just flat-out look great (especially as compared to the other diesel models available during the early 1980s).
The Kato-made RSD-4/5 came out a few years later, and as mentioned above, apart from the trucks is identical to the RS-3 model.
Atlas eventually severed their ties with Kato in the mid-90s, and in 1999 released completely redesigned (Chinese-manufactured) RS-3 and RSD-4/5 models under their "Atlas Classic" line -
These models have a new shell and a new chassis (now with flywheels). The old metal truck assemblies are replaced by plastic ones (with current collected via metal axle-cups and transferred to the chassis via flexible brass contact strips). The truck-mounted couplers are upgraded to shell-mounts (still Rapidos, though). And as nice as the earlier Kato-made units ran, these run even better (just a little smoother and quieter).
In 2001, a new Atlas Classic version of the RS-3 was issued (with the RSD-4/5 being similarly upgraded in 2004). New features include -
- Separately-applied painted handrails (where appropriate)
- Slower scale speed motor
- Factory-installed AccuMateŽ magnetic knuckle couplers
One thing about the Atlas Classic RSD-4/5 - only four out of the six axles are geared, thus resulting in somewhat diminished pulling power. Why the change? Ask Atlas.
Circa 2013, Atlas revised the internals on these models slightly. As pictured below, the hex nuts on the flywheel end of the worm shafts were removed and replaced instead with U-joint connectors -
As of this writing, Atlas has yet to release DCC-Ready versions of these models (although I'm sure it's only a matter of time before they do).
Collector note- it is possible to find one of these models in a box that looks exactly like a contemporary Kato box (including the inserts) and makes no mention of Atlas. What I've been told is that Hobby Center Kato sold all of the Sekisui Kinzoku (IE, Kato) production in their shops in Tokyo and Osaka in Kato boxes (regardless of the US label). Hence, one might have found Con-Cor, Atlas, and Stewart US profile locomotives in Kato boxes with no mention of those brands. The most notable example of this "gray market" is the batch of Atlas GP7s and GP9s that made it into the USA via a distributor which were in standard Kato packaging.
Trivia - the same Kato RS-3 chassis was used for the Atlas/Kato RS-11, RSD-12, GP7, and GP9 models (all released in 1986/1987). Unfortunately, this cost-saving measure resulted in a whole lot of models that weren't particularly accurate.
More trivia - Bill Denton (Skytop Models) makes a "Phase III" replacement shell that is a direct swap for the most recent RS-3 shell (the stock Atlas model represents a "Phase I" RS-3) -
Even more trivia - Brigg's Models makes MLW RS-3 replacement shells in three different BCR/CP styles that are direct swaps for the most recent RS-3 shell -
Still more trivia - the old Atlas/Kato RS-3 shell is reportedly a good fit for the Life-Like/Walthers RS-2 chassis. Similarly, the Atlas Classic RS-3 shell reportedly fits on a Bachmann RS-3 chassis (although not vice versa). Lastly, it is possible to mount an old Atlas/Kato RS-3 shell on the newer Atlas Classic RS-3 chassis (a set of cab clips must be removed and you need to install a Micro-Trains pilot conversion kit).
Removing the shell requires a bit of patience and a gentle hand (IE, leave the elbow grease at home). I use a small screwdriver to pry the shell away from the chassis a little bit at a time (starting at one end and working my way around). Eventually it'll slide up and off.
Grade: A (all versions)
Kato RS-3 reviewed: 2/84 Railroad Model Crafstman, 1/84 Model Railroader: ("This Atlas model, manufactured in Japan by Kato, is a fine N scale representation of the RS-3 diesel. It closely follows the scale dimensions and proportions of the real locomotive. Except for the concessions usually found in (N scale) models (deep wheel flanges, open platform ends, and large couplers), this engine is as well detailed as many larger scale models. The molded handrails on this model are much smaller in diameter than the ones found on most commercial N scale models. They scale a little over 3" (.020") in diameter, which is pretty good for a plastic N scale model...
"The motor frame has two cast zinc alloy pieces - one right-hand and one left-hand - enclosing a five-pole, open-frame motor, worm shafts and gears, and universal joints... The truck gear-frame assemblies also have insulated metal halves. On each side the truck gear frames make electrical contact with one of the motor frame halves. Thus no wires are needed to complete electrical circuits. The directional headlights are each mounted on a small piece of circuit board with a diode. They plug into clips on the ends of the motor frame assembly. The well-engineered mechanism is easy to assemble and disassemble...
"The scale 41"-diameter metal wheels (40" on the real locomotive) are mounted on plastic axles. One wheel on each side has a traction tire, so each side of the locomotive has three wheels for electrical pickup... The (traction tires) on this model are smooth and true... The wheelset check gauge on our sample was .010" under the recommended standard, but it ran over commercial prefab track and sectional track with no difficulties... The wheel flanges may have to be turned down if you operate the model over commercial Codes 40 and 55 track where there are plastic tabs extending over the top of the rail base... The model runs as smooth as any N scale model I've seen. While the top speed is excessive, it will throttle down very nicely and will run smoothly at the slowest speeds... I like this model a lot. It has fine detail, is simply constructed, soundly engineered, and it runs well... Undec, Pennsylvania, Norfolk & Western, Rock Island, Louisville & Nashville. Price: $39.00")