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Bachmann HO scale DDA40X diesel locomotive

Read this review from Model Railroader magazine
Bachmann HO scale DDA40X diesel locomotive
The roar of two 3,300 hp diesel engines, an airhorn, and more sound effects highlight Bachmann Trains’ upgraded HO scale EMD DDA40X locomotive. The model uses most of the same tooling as earlier releases, but now features the Sound Value system that was developed in conjunction with SoundTraxx. The dual-mode sound decoder works on both direct-current (DC) and Digital Command Control (DCC) layouts.
General Motors Electro-Motive Division built 47 of the 6,600-hp monsters in 1969. All were purchased by the Union Pacific, which named them “Centennials” in honor of the 100th anniversary of the driving of the Golden Spike that marked the completion of the transcontinental railroad. Just one of them, no. 6936, is running today, as part of the UP’s Heritage Fleet. Centennial no. 6900, the number of our sample model, was retired in June 1984. I reviewed an earlier DCC on board version of this engine in our February 2010 issue. That version included a DCC motor and lighting decoder but no sound.
Dual can motors and dual speakers make Bachmann’s HO scale DDA40X powerful both in sound and drawbar pull. The SoundTraxx Sound Value decoder takes the place of the original model’s printed-circuit board.
Inside and out. The body’s major dimensions match diagrams published in the Model Railroader Cyclopedia: Vol. 2, Diesel Locomotives (Kalmbach Books, 1980, out of print). The wheelsets on our sample were all in gauge, and the couplers were mounted at the correct height. The paint job is smooth and even, though the colors don’t quite match UP paint swatches. To my eye, the Armour Yellow is too bright and orangey, and the Harbor Mist Gray has a blue-green cast.

The tooling is the same as the version I reviewed in 2010. Everything I pointed out about the body back then is true of this model as well – 10 short doors on each side under the dynamic brake enclosure instead of 12, a motor flywheel visible through the gap in the middle of the body, and an upper frame that intrudes into the cab. Separate detail parts include acetal plastic handrails and the rear sandboxes along the walkways.

After removing the two countersunk screws that hold on the fuel tank cover (which also serves as the speaker enclosure), I was able to access the four screws that hold the 1-piece plastic body shell to the split cast-metal frame. I also had to remove both of the truck-mounted E-Z Mate Mark II knuckle couplers before
I could lift the shell off the frame.

There are two independent can motors under the hood, one for each truck. Each has a pair of flywheels and a gear tower that drives all eight wheels in its truck. The wheelsets have considerable sideways play to help them better negotiate tight curves and turnouts. Bachmann recommends a minimum ­radius of 24" for this model, though its performance and appearance would be improved on even broader curves.

The DCC sound decoder is incorporated into the printed-circuit (PC) board and is attached to the top of the frame with two screws. Wires connect the decoder to light-emitting diode head and taillights as well as the number boards and the flashing beacon on the cab roof.
Performance. I tested the dual-mode decoder-equipped locomotive both on DC and DCC layouts.

Under DCC, the locomotive started smoothly in speed step 1. Its low speed of 3.9 scale mph was further improved when I switched my throttle to 128 speed steps; then, the engine rolled smoothly at just 1.8 scale mph. At the other end of the dial, the model topped out at 75 scale mph – less than the prototype’s top rated speed of 90 mph, but fast enough for most model railroads.

The sounds from a pair of speakers in the locomotive’s fuel tank were impressive, both in volume and fidelity. The Sound Value system does a credible job replicating the sound of two separate 645E3A diesel engines at startup. When I placed the engine on the track I heard the front engine and then the rear engine start. Under way, the engine didn’t have the slight out-of-phase character of a ­dual-engined locomotive.

The horn, triggered by F2 (long blast) or F3 (short toot), also sounded deep and realistic. Other function keys triggered the bell (F1), dynamic brake fan (F4), warning beacon (F5), number box lighting (F6), and headlight dimmer (F7). Function key F8 mutes all sounds.

When running under DC, a dual-mode sound decoder, regardless of brand, requires a lot of voltage. The sounds and lights came on at 6.5V, and the model moved smoothly at 8V. The engine sounds ran automatically on DC, increasing with the locomotive’s speed.

Like its prototype, this model is a powerful puller. The HO model’s drawbar pull is enough to pull 73 standard HO scale freight cars.

A major upgrade.
The addition of realistic sounds greatly enhanced the experience of running the Bachmann Centennial. I was also impressed with the model’s slow-speed performance and pulling power. If you were considering buying Bachmann’s­ DDA40X before but hesitated, good things come to those who wait.
Price: $275

Bachmann Trains
1400 E. Erie Ave.
Philadelphia, PA 19124

Road numbers: (all Union Pacific) 6900, 6929, 6940

Era: 1969 to mid-1980s

  • All-wheel drive and electrical pickup
  • Chemically blackened RP-25 wheelsets, in gauge
  • Directional light-emitting-diode head and taillights
  • Dual speakers
  • Flashing beacon on cab
  • Illuminated number boards
  • Minimum radius: 24"
  • SoundTraxx Sound Value dual-mode Digital Command Control sound decoder
  • Truck-mounted E-Z Mate Mark II knuckle couplers, at correct height
  • Two skew-wound, 5-pole can motors with dual flywheels
  • Weight: 1 pounds 7.75 ounces

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