The C643DH, classed by Alco as ithe DL-643, was produced in the
early fall of 1964 as the builder manufactured a set of three for
Southern Pacific who, like rival Union Pacific, often tested big
horsepower in an attempt to see if they could reduce the number of locomotives needed
per train. The SP took this a step a bit further by testing diesel hydraulic
designs during the 1960s, which included Alco's design (the railroad also acquired or purchased new 21 German-built, Krauss-Maffei ML-4000s). The C643DH could produce 4,300 horsepower using two 251C model prime movers rated at 2,100 horsepower each. Unlike the C855 which used four B-B trucks, the C64H carried two, standard C-C trucks and
weighed much less at only 378,000 pounds (interestingly, at 189 tons the
model even weighed less than its six-axle Century line which topped out at over 200 tons).
As you might expect, the C643DH was not a standard model in Alco's catalog although the company would certainly build and test any type of experimental locomotive a railroad requested. Internally, the C643DH was basically two C628s merged together. The model used traction motors (model 752) from General Electric although its main generator was produced by Voith Hydraulic, its notable characteristic. Additionally, air components came from Westinghouse (brakes and compressor). The locomotive was one of the longest the company ever produced (the C855 ranked first in this category) at nearly 75 feet, 10 inches and was capable of producing an incredible 95,000 pounds of tractive effort, on par with some of the largest and most powerful steam locomotives ever built.
Only three C643DHs were ultimately constructed for Southern Pacific, originally
numbered #9018-#9020 (the railroad later classed them as #9150–#9152 and
finally #9800-#9802). Unfortunately, the locomotive was not particularly
successful. First, the diesel hydraulic transmission performed poorly
and due to the fact that it was foreign-made meant parts were
expensive and took time to arrive. Other issues evolved around a lack of proper research and development, similar to the C855. As a result, the '643s experienced numerous problems and trouble-shooting issues while in service,
particularly in regards with the two prime movers functioning as one (timing issues). Because of the locomotives' problems, crews came to loathe operating them, which provided for an incredibly jarring ride. Dissatisfied with their performance Espee pulled the group from service after less than ten years and all were retired
by 1973. Interestingly, UP had scrapped their fleet of C855s a year earlier
in 1972. For more information about the C643DH please click here.
The Century Line
|C-643DH||3 (Built For SP)||1964||4,300|
|C-855||3 (Built For UP)||1964||5,500|
For a comprehensive look at the American Locomotive Company and all of
the motive power types it built from steam, diesel, to electrics
consider the book Alco Locomotives by Brian Solomon. Covering
more than 175 pages Mr. Solomon's book details the history of Alco from
its esteemed 4-6-4 Hudsons and 4-6-6-4 Challengers to vaunted RS and PA
series diesel locomotives. If you have any interest in Alco this book
is a must have! Also consider Mike Schafer's Vintage Diesel Locomotives which looks at virtually all of the classic builders and models
from Alco PAs to early EMD Geeps. To read more about other Century models please visit the Diesel Locomotives section of the site, which can be reached from the top of this page.