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WalthersMainline HO scale Plymouth ML-8

Read this review from the June 2017 Model Railroader
Walthers HO Plymouth ML-8
WalthersMainline HO Plymouth ML-8 switcher

Small switchers, such as this Plymouth ML-8 modeled by Walthers, toiled away for decades at various trackside industries and railroad shops. The WalthersMainline model captures the look of its prototype “critter” and features impressive power for such a diminutive locomotive. The model is available in direct-current (DC) or Digital Command Control (DCC) versions. We tested the DCC version that features a SoundTraxx motor decoder (non-sound) with CurrentKeeper technology.

Prototype. Under the name J.D. Fate Co., the first locomotive rolled out of the plant at Plymouth, Ohio, in 1910. The company that eventually became the Plymouth Locomotive Works built more than 7,500 industrial locomotives for customers worldwide until the company was sold in 1997. Although Plymouth designed some heavier locomotives, most of those sold weighed 25 tons or less.

Like many industrial locomotive builders, Plymouth offered several models that could be further customized to meet a customer’s specifications. The locomotives could be powered by gasoline or diesel engines connected to the axles via either a hydraulic or mechanical transmission.

Depending upon the engine used, a 25-ton ML-8 like that modeled by Walthers could produce 220 to 300 hp. On straight-and-level track the switcher could pull 500 tons per 100 hp produced.

Walthers HO Plymouth ML-8
The ML-8 features a die-cast metal hood and plastic cab with clear window glazing. The front and rear headlights are light-emitting diodes (LEDs).

Model. The basic dimensions of the Walthers model match those of a prototype diagram for an M-series standard gauge locomotive in a Plymouth Locomotive Works catalog.

While the model’s cab is plastic, the hood and underframe are die-cast metal. Those components, as well as the mechanism, contribute to the locomotive’s weight of 3.6 ounces.

The engine-access doors and vents are crisply cast in the metal hood. The raised Plymouth lettering on the end of the hood above the radiator is especially well done.

Separately applied plastic detail parts on the model include the footboards and handrails as well as the stack, bell, and sand dome along the top of the hood. The etched-metal radiator grill captures the depth and texture of the prototype part. All the cab windows feature clear plastic glazing.

Our review sample is smoothly painted in a medium blue with a white roof. The blue paint on the die-cast metal hood perfectly matches the shade on the plastic cab. The handrails and Plymouth lettering above the radiator are neatly painted white.

For our unlettered sample, Walthers thoughtfully included a sheet of decals with white and black numbers in both serif and sans-serif fonts. The decal sheet also features heralds for a variety of freelanced trackside industries that Walthers has offered as structure kits over the years. This makes it easy to add a dedicated industry switcher to Medusa Cement, Washington Salvage, Glacier Gravel, and several other popular Walthers kits.

Walthers HO Plymouth ML-8 die-cast metal frame
The switcher’s heavy die-cast metal frame provides solid pulling power for such a small locomotive. The decoder and CurrentKeeper capacitors fill the cab.
A gearbox provides the switcher with all-wheel drive. All the wheels also pick up track power and a three-point suspension provides positive wheel contact with the rails.

Mechanism. As per the instructions, I removed the cab and hood as a single unit. A screw behind the coupler box holds the hood to the chassis, while locking tabs hold the front and rear of the cab to the chassis. I squeezed the cab and gently rocked it back and force until I could get my hobby knife between the plastic shell and the chassis to disengage the tabs.

The cab interior is filled with the DCC decoder and CurrentKeeper capacitors. There’s no additional room for an onboard speaker for those wondering if an onboard sound system could be added.

A worm connects the flywheel-equipped motor to a gearbox that drives both axles.

Performance. The switcher has impressive pulling power for such a diminutive locomotive. On our layout, I easily shifted cuts of four to five scale 40-foot cars, some carrying 3-ounce loads that weighed more than the cars themselves.

As stated on the Walthers product listing and confirmed on our test track, the decoder-equipped model will operate only on DCC layouts. During speed tests the model accelerated smoothly from 4 scale mph in speed step 1 to 64 scale mph in speed step 28. The top speed of the prototype was about 25 mph.

After I set the decoder for 128 speed steps, the ML-8 crept along at less than 1 scale mph. The speed can be further fine tuned, including lowering the top speed, with preset or custom speed tables. Acceleration and deceleration momentum can also be added. A diesel user manual and list of programmable configuration variables (CVs) is available at

The factory-installed SoundTraxx CurrentKeeper capacitor pack is a smart addition on a locomotive with a wheelbase of less than an inch. The capacitors store enough power for the HO switcher to easily roll over an unpowered turnout frog or dirty stretch of track without so much as a headlight flicker.

To test the CurrentKeeper, I covered a 2-foot long stretch of track with tape. I then ran the Plymouth from a powered section of track onto the tape-covered track. The locomotive kept rolling at a steady speed over the unpowered rails.

Although it doesn’t have sound, the SoundTraxx motor decoder has many of the programmable features of the firm’s Tsunami and Econami decoders. I was happy that I could easily set up one of my favorite SoundTraxx features, the train brake, on the Plymouth. With this feature I could use a function button (I used function 9) to independently stop and start the locomotive without touching the throttle setting.

The headlights are bright white light-emitting diodes (LEDs) that turn on according to the locomotive’s direction. To be more prototypical I remapped the lighting functions for independent non-directional control. This also allowed me to have both headlights on and set to dim. Function 7 is factory-programmed to dim the headlights.

The WalthersMainline Plymouth ML-8 not only captures the look of a classic critter, but also features excellent performance that would make this locomotive a worthy centerpiece of an HO scale industrial layout.


Price: $149.98 (DCC-only), $99.98 (DC)

Wm. K. Walthers Inc.
5601 W. Florist Ave.
Milwaukee, WI 53218

Era: 1920s to present

Paint schemes and road names: Painted blue but unlettered; painted yellow but unlettered; Atchison, Topeka & Santa Fe; Union Pacific; United States Army Transportation Corps. Unpainted version also available.

▪▪All-wheel drive and electrical pickup
▪▪Brass flywheel-equipped motor
▪▪Die-cast metal chassis and hood
▪▪Light-emitting diode (LED) headlights
▪▪Proto-Max metal knuckle couplers mounted at the correct height
▪▪RP-25 contour metal wheels
▪▪SoundTraxx DCC motor and lighting decoder with CurrentKeeper capacitors (DCC version only)
▪▪Three-point suspension for positive track contact
▪▪Weight: 3.6 ounces

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