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Old 04-09-2012, 06:07 PM   #1 (permalink)
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Default UP "Giant of the West" - EMD DDA40X Centennial, UP 6936

This is the beginning of a very long project....!!!!! :~}

Owner: Matt Abreu, of Granite Bay, CA,... aka "Cab-forward" on these pages!

Builder: Dirk Carmichael, of Dragoon, AZ,... aka "SD90WLMT' to You by now ...

Project: build as close as possible, a 1/29th scale/45 mm, model of UP 6936

One unit (6936) has been retained as a part of UP's "Heritage Fleet" based in Cheyenne. It is currently painted in a "Lightening Stripe with Wings" scheme.

"Castle Gate, Utah, 2011"

Union Pacific's Centennial locomotives were the largest railroad locomotive in the world. These distinctive giants dominated the railroad's western mainlines from 1970 through early 1980, and were seen on all of the railroad's most important trains. Built as a unique-to-UP design, they were constructed by the Electro-Motive Division of General Motors Corporation.

Numbered as UP 6900-6946, they were known as "Centennial" locomotives because the initial deliveries started on the 100th anniversary of the May 10th 1869 driving of the golden spike at Promontory Summit, Utah. UP 6900 was rushed to completion to allow it to be part of the various ceremonies that took place in Utah on May 10th 1969. Delivery of the rest of the units began a month later and continued until September 1971. The 6900s were delivered in two groups: UP 6900-6924 (delivered in June to December 1969), and UP 6925-6946 (delivered in June 1970 to September 1971). The two groups were identical except for some very minor differences.

These 47 locomotives were the longest diesel locomotives ever built, at 98 feet, 5 inches. Their frames were too long for EMD to manufacture and were fabricated by the John Mohr Company of Chicago. Their fuel tanks were also the largest of any diesel locomotive, with a capacity of 8,000 gallons of diesel fuel, making the fuel tank weigh 30 tons fully loaded.

Union Pacific experimented in the 1960's with high horsepower double diesels from all three major builders - EMD, GE & Alco. The ultimate double-diesel was created in an effort between the UP Mechanical Department and EMD. They had the latest state-of-the-art mechanical and electrical components at the time - including two 16 cylinder, 3,300 HP 645-E3A prime movers for a total of a reliable 6,600 HP! These were released to the railroad during UP's Centennial year - 1969. For that reason, they were called "Centennials". These units were, at the time, "The Worlds Most Powerful Diesel Locomotive". UP finally had 47 of these giants which were used throughout the system.

The Union Pacific Railroad earned a reputation for using very large and powerful steam locomotives and in 1941 began using the largest of them all, the Big Boy, to carry freight over the Rocky Mountains.

In the diesel era, the tradition continued with the use of the most powerful locomotives available. In 1969 UP purchased the very largest and most powerful diesel ever built, the DDA40X, with 6600 HP provided by two diesel engines (prime movers) mounted on one frame,

These 270 ton, 98 foot long behemoths were built by the Electro-Motive Division of General Motors Corp. (EMD) and were named "Centennial" in honor of the 100th anniversary of the "Driving of the Golden Spike Ceremony" (May 10, 1869). In all, 47 units were purchased (numbered 6900-6946) beginning in May of 1969 with deliveries continuing through 1971. They were numbered using the "6900" series to mark the '69 dates.

The "Centennials" were designed for high-speed freight and by 1980 had successfully run up an average of 2 million miles a piece. With the decline of freight movement in 1980 the fleet of DDA40Xs were taken out of service and put in desert storage at Yermo, CA. Then in March of 1984 an economic recovery brought a demand for more motive power and 25 were returned to service. However, high maintenance costs caused the retirement of most of them by the close of 1986.

Rob Leachman wrote on August 26, 2004:

The Centennials were all equipped with experimental "advance excitation" of the traction motor fields. They could get a forwarder train up to speed faster than anything on the rails. I remember Jack Bowen, UP General Superintendent of Transportation, stating in a staff meeting that substituting any other power for Centennials on the North Platte - Ogden segment of the Overland Mail train would require adding 45 minutes to the schedule (just because of the time difference accelerating out of terminals, restrictive curves and slow orders). I also recall that in the early 70s, UP would regularly add a unit in Pocatello to the 2 Centennials that brought WB forwarder trains out of North Platte. (Another unit was needed for tractive effort to get over the steep grades on the Northwestern District. A similar policy was adopted for South Central District hot trains west of SLC.) The extra unit was often added on the point. When these trains started up, one could see and hear the Centennials bump the leading unit. The walk-over plates on the extra units (typically GP30s, GP35s, GP40s, or SD40-2s) were always dented in because the Centennials would be pushing them along whenever the power was accelerating. By 1975, UP was powering the forwarder trains with 3 Centennials (one LA RT started getting four) instead of with mixed units, just because any other power could not keep up with the Centennials. In the late 70s, when "Big Mac" lash-ups (2 Centennials bracketing a high-geared "fast forty" SD40-2) became the norm, I bet they still could not quite match the same running times as the previous all-Centennial lash-ups, even at the same HPT.

Rob Leachman wrote on January 24, 2009:

Before the Centennials were stored (early 80s), they were very popular with the engine crews. They were a tremendous source of pride throughout the company. After they came out of storage they weren't the same. Problems with the units, rare in the 70s, became more common as their age was showing and the harmful effects of long-term outside storage were apparent. From a railfan point of view, the show after they came out of storage was much less impressive, with only one or two Centennials on a train, usually mixed with SD40-2s, in lieu of the impressive 3-unit and 4-unit lash-ups of Centennials common back in the 1973-75 era.

Very smooth riding and pretty quiet in the cab compared to its contemporaries. The acceleration beat the pants off of anything else. In Omaha we found that a set of Centennials on average could make the run North Platte to Ogden 45 minutes faster than any other motive power at the same horsepower per ton. On the Hinkle - Kenton run down the Columbia Gorge, a good engineer on a set of Centennials with green signals the whole way could do the run in three hours. Impossible with any other power back then.

The Centennials were normally assigned to hot trains with high horsepower per ton, so when you were called to take a train with a 6900 on the point, it almost always meant you were going to get a good run.

The Centennials were high-speed merchandise engines. They were not mountain luggers. The engineers in the Blue Mountains preferred to have a set of SD40s. But just about everywhere else on the system, they were the favorite of the crews.

This model is being built from a variety of parts; including - parts from 2 - SD45 locos, 2 - GP38 hoods, 1 - SD45 cab/1 - SD 40 cab/1 - SD70Mac cab. And any hand built parts as needed, walk ways from box car roofs. It will run on a custom set of spliced "Siamese motor blocks", using 4 - SD70 power blocks as donors. That is 4 motors in one loco! OR twice the typical pulling power.

Enjoy the thread folks,

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