Plymouth WDT Diesels    

These little critters kind of popped up out of nowhere in December 1968. In the September and October 1968 issues of Model Railroader, Atlas was advertising the Pacifics and GP40s as "Coming Soon" but there was no mention of the WDTs. The November ad didn't feature N scale and then, all of a sudden, the December ad announced the Pacifics, GP40s, AND these little industrial switchers as new releases. The prototypes were available with different tonnage ratings according to my digging on the 'net. The insert for the Atlas version states it is a model of a 15 ton unit but I have seen references to others of 30 and 40 tons. They were built in the sixties by, what was then, Plymouth Locomotive Works in Plymouth, Ohio. Unlike locomotives built for the large railroads, these are diesel-hydraulic, rather than diesel-electric. Instead of having a diesel engine driving an electric generator providing current to traction motors, diesel-hydraulics are similar to an automobile in that the engine drives a transmission and power is transmitted to the driving wheels through gears or driveshafts. They are used by a variety of industries where a larger locomotive would be impractical. The company still exists under the name of Plymouth Industries. Atlas offered these with the following roadnames although I don't know if any of the roads actually owned any (I doubt it): Santa Fe, Great Northern (Big Sky Blue), Burlington, and Pennsylvania. This was yet another locomotive (like most Atlas A1G locos) later offered by other companies but Atlas was the first! Also, don't confuse this release with the later Roco built model released in 1972.

Manufactured by Mehanotehnika in Yugoslavia, it is a departure from their previous locomotive construction (except, of course, for the lateral locks that hold the body on). Instead of a plastic mainframe, it has one made of zinc alloy. The drive wheel axles, spur gears and worm gear are inserted into holes in this casting. A plastic plate mounted on top of this has plated copper or brass strips along either side of it ,on the underside, and wipers that hang down to make contact with the front and rear drivers. Two large tabs, one on each strip, extend up through the plastic plate and the holes in these tabs "snap" onto the ends of the motor brush holders. This also retains the motor and, in fact, is the only thing holding the motor to the chassis. It seems to work effectively though. The worm, mounted on the motor shaft, turns the worm gear and, through a series of spur gears on the left side of the axles, drives the wheels. This drive was dubbed "side-winder" and is also used in the 0-6-0 Steam Locos (and also in the later small locomotives made by Roco). The motor is a variation of the Mehano motor used in the larger diesels. Instead of the magnet being mounted on one end of the armature, it is mounted above and the pole pieces extend down around the armature. This gives the motor an "L" shape. The headlight bulb is soldered to two smaller tabs that extend up through the plastic plate near where the side strips are riveted to the plastic plate in the front. A single weight rests over the worm/worm gear area. For a side view of this chassis (without the weight), click here for a full sized picture:

 In spite of its small size, these little engines can be made to run very decently, as is true of all the Mehanos, with a little work (OK sometimes a lot of work). This is addressed on the "Model Specific Issues" page.

Another thing of note; the Zamac deterioration of castings wasn't only Rivarossi's problem. I have seen frames from these locos just as bad.

Atlas Identification: Unfortunately, there are absolutely no Atlas logos or part numbers (or any markings at all) on any parts of this locomotive. So, unless a unit is of a roadname (or paint scheme) that nobody else released, its impossible to tell if it is an Atlas A1G if it is Mehano made. I know Bachmann had a version of this engine but it was not made by Mehano. It was made in Hong Kong or China. Taking the body off and examining the Chassis can at least narrow it down. But if it is a Mehano made loco of a roadname and paint that was A1G, it can't really be determined if it is genuine A1G (unless it was bought new from an Atlas dealer, of course).

Variations: The only variation I've seen is in the color of the worm, axles, gears, and axle spacers used. There are white, black, and red.

Please contact me with any additions or corrections: dgosha@aol.com

Links to images of the available liveries. Click on the description or thumbnail to view a full sized picture:

The Burlington image courtesy of Mark Peterson from his Locomotive Encyclopedia site.

The Pennsylvania image courtesy of Edward Borgh.
#2161 Santa Fe Road #332
#2162 Great Northern No road number
#2163 Burlington Road #9280
#2164 Pennsylvania Road #21

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EMD E8s FM C-Liners IHB 0-8-0s
Alco RSC-2s EMD GP40s USRA Pacifics (4-6-2s)
0-6-0 Steam Locos EMD SD45s USRA Mikados (2-8-2s)
0-4-0 Locos and Tenders SW1500 Cows and Calfs Atlas Model Specific Issues
Atlas Locomotive Disassembly The Rivarossi Motor The Mehanotehnika Motor
Zamac Frame Repair Atlas Locomotive Reassembly AIG Locomotives Around the World
The Treble-O-Lectric Main Page Treble-O-Lectric Locomotive Service Treble-O-Lectric Documents
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