This model (manufactured by Mehano of Yugoslavia) originally appeared as part of MRC's big plunge into N scale in 1969. Yes, MRC dove head first into the N scale market, releasing a line of N scale locomotives and rolling stock and proclaiming that they were "in it to stay". Well, that lasted about four years, after which they dropped their entire N scale line. Since that time, this model has had various importers (Model Power most notably). And like the rest of their line of N scale diesels, the Mehano RSD-15 has undergone numerous changes over the years (although the shells have remained the same throughout).
The original MRC models were available in both "high nose" and "low nose" versions (the mechanisms themselves being identical). And although fairly crude by today's standards, these models earned a fair amount of acclaim back in the day due to their directional lighting and dual-truck eight-wheel drive/pickup (all the rest of the Mehano line of N scale diesels having simple, non-directional headlights and single-truck pickup/propulsion).
The MRC RSD's are easily identified. First off, they're the only versions that came with directional, two-way lighting (all subsequent versions being equipped with a non-directional headlight). Additionally, the driveshafts are white plastic and the words "MRC Yugoslavia" can be found on the bottom of the trucks.
Despite that "back in the day" reputation of awesomeness, I have yet to find one of these old MRC's that wowed me with its performance. They're very loud and the traction tires make for a very wobbly ride. Then you have the whole "wires running everywhere" situation - IE, cross your fingers and pray that all those decades-old solders have held. From what I've experienced, pickup on these ancient locos is a big nightmare (IE, they'll run around in circles at full throttle just fine, but tend to die a miserable death at slow speeds).
Circa 1976, Model Power became the new importer for all of MRC's Yugoslavian-made diesel locos, excepting (for whatever reason) the high-nosed RSD-15. That one resided in limbo until 1981, when a company called Regal Way imported them briefly (and only in two roadnames - ATSF and UP). In 1982 AHM "reintroduced" the old high-nosed MRC/Mehano RSD-15 in several new paint schemes and packaged it with a caboose. But for the most part, the RSD-15 saga continued on as basically a Model Power project (and sans the high-noser).
The first Model Power version represents a slight improvement over the original MRC imports -
Although the directional headlights are gone (still scratching my head over that one), the motor appears to have been slightly improved (still 5 poles, but seemingly a tad more robust). These do seem to run a little stronger and smoother, but the traction tires still introduce way too much wobblitude into the equation.
As pictured above, some of these have white plastic driveshafts (ala the MRC version) whereas others have black plastic. Just guessing here, but my assumption is that the ones with the white plastic are a little older than the black plastic ones (IE, Mehano probably recycled leftover parts from the MRC days for the first Model Power models). Both versions are stamped "Yugoslavia" on the trucks.
Sometime in the 1980s, Mehano/MP unleashed yet another new version -
The major new feature here being "spring" driveshafts (as opposed to plastic). Better still, the traction tires have been relegated to the scrap heap where they belong. These are very respectable runners, especially as compared to the earlier versions (although at this point, that might just be a factor of age). Pickup is great and performance is nice and smooth at all throttle levels. Hell, it even runs relatively quietly. This version is easily identified by its white truck gears (all previous versions having black gears).
Circa 1989, Mehano came out with their "killer" final version. And yes, these are about as good as it gets for Mehano -
The major change here is a gigantic new 3-pole motor. So big, in fact, that they had to get rid of the under-the-motor weight found in all of the previous versions (this also necessitated running a lot of additional wiring over the top of the motor - wiring that was hitherto tucked away beneath the motor). Performance is actually very nice - smooth, relatively quiet, great pickup, nice slow speed creep, etc. In fact, if it weren't for the 1960s era ugly shell, bloated handrails, truck-mounted Rapido couplers and other obscenities, I might be tempted to actually give this one an "A" rating. Still and all, it's definitely worthy of a "B" (at least until somebody comes out with a "real" RSD-15). This version is easily identified by checking out the bottom of the fuel tank - no weight anymore, so no giant screw.
Model Power's RSD-15 was a staple of ads in model railroading magazines for years, but eventually vanished sometime around 1998. This perhaps due to all of the conflict in the former Yugoslavia? Oddly enough, these models remain in high demand (even the older, crappier versions). Since it's basically the only game in town when it comes to this particular prototype, I guess people are just going with what's available. FWIW, I'm told that the shell is a perfect fit for the Atlas U25B mechanism (or if you're more ambitious, an Atlas Dash 8-40B chassis with Atlas C-630 trucks).
Trivia - an Netherlands outfit called ATSF N Scale Models makes shells (via Shapeways) for ATSF, SP and SSW RSD-15's. These make use of a modified Atlas C628/C630 chassis -
Grades: D (for the MRC versions and the first Model Power version), C (for the second Model Power version) and B (for the last version)
Reviewed: 8/70 Model Railroader ("The model, like the prototype, is available in either low- or high-nose versions. It follows the scale dimensions and proportions of the 62-foot prototype closely with only minor exceptions. It is about 12" too high and 9" too wide. The general appearance is good. The well-detailed cast plastic body has all detail cast on. Side and end rails and clear plastic window inserts are to be added to the basic casting. Our samples were neatly painted and lettered. The model is available in SF, PRR, and CB&Q decoration schemes. CB&Q did not actually have this class.
"The frame is cast plastic, as are the gearboxes and truck frames. The frame snaps into the body casting and can easily be removed for servicing the mechanism. A five-pole 12-volt double-shafted motor drives four wheels on each truck... All gears are plastic, as are the ball universal joint drives between the motor and gearboxes. The Rapido-type automatic couplers are truck-mounted... All wheels are metal; two on each truck have rubber friction treads. They scale 42" in diameter - the prototype had 40" wheels - with flanges .039" deep. Check gauge is .312". The model features reversing headlights which are controlled by two small diodes placed atop the motor. Our test sample ran smoothly, but tended to leap into action when starting... With the help of the friction treads our sample pulled a 37-car freight train... The light plastic superstructure is ballasted with soft metal weights over the trucks and in the fuel tank... Our sample had a slightly bowed body. The window castings appeared to be a little too large... A close examination of the truck frames shows a deviation from actual prototype proportions, but the model is generally well proportioned and performs excellently. Price: $13.98")