The Alco C855 was an experimental design built only for the Union Pacific. At the time the model was manufactured it was the most powerful single-unit diesel locomotive ever constructed. Designed during the 1960s, the C855 was quite similar to locomotives constructed by General Electric and Electro-Motive at around the same time; Union Pacific was looking for a powerful single-unit that could decrease its motive power fleet and ordered experimental behemoths from all three builders. What seemed to so often be the case with Alco's locomotives the C855 proved troublesome and problematic mostly due to the fact it had not been given enough research and development. The model's prominent feature was the company's trademark, incredible tractive effort and the ability to pull almost anything. However, this did little to sway Union Pacific's feelings towards the C855 and the three units were scrapped after less than 10 years of service.
Interestingly, the Alco C855 (designated by the builder as the DL-855) was constructed in June of 1964 during the Century line's early years of production. The model was essentially two power plants housed on one frame. The locomotive employed two of Alco's 251C prime movers that together could produce a stunning (for the time) 5,500 horsepower. The unit rode on four B-B trucks and weighed a grueling 551,000 pounds (275.5 tons). Obviously, this extreme weight meant that it would be a liability on the track although it also provided for incredible tractive effort that topped out at 109,000 pounds starting and 88,000 pounds continuous (these numbers put the C855 on par with some of the largest and most steam locomotives ever built, an area Alco was also quite familiar with).
Alco had also developed a model similar to the C855, Southern Pacific's C643H. However, there was a key difference with Espee's locomotive, which used a Voith diesel hydraulic transmission whereas the C855 did not. UP's version used equipment standard in practically all other Century line locomotives; traction motors (model 752) and main/secondary generators (model GT598 and GY27-5) from General Electric along with air components from Westinghouse. Of course, anyone who studies Union Pacific's history knows the railroad is famous for going big during the 1950s and 1960s. In the late 1940s UP had GE and Alco build a gas turbine-electric locomotive that itself could produce nearly 5,000 horsepower.
Additionally, during the C855's construction UP contracted GE and EMD to build similar models (EMD unveiled the DD35 and GE the U50, both of which could produce 5,000 horsepower). The C855 was designed to operate as single units or in A-B/A-B-A lashups. In sequence the locomotives were numbered 60, 60B, and 61 (the cabless "B" unit was designated as the DL-856). In general the carbody had the appearance of the Century line with a short nose and long trailing hood only scaled up to far greater proportions. From an exterior standpoint it didn't exactly carry a clean look with many bulges and protrusions here and there.
The C855 was an incredible 86 feet in length and when all three units were coupled together the set nearly spanned a football field at 258 feet! The whole point of UP going big with diesel technology was an attempt to reduce its locomotive fleet by using fewer units per train (thus reducing maintenance and general locomotive expenses). While both GE's and EMD's models lasted longer in revenue service than did the C855 all three designs had their problems (the C855s were off the roster by 1972). EMD's version, the DD35A lasted the longest and proved the most reliable of the three, remaining in service until the early 1980s. Interestingly, the later DDA40X Centennials turned out to be the most successful of all with the fleet of 47 recording more than two million miles of revenue service, some of which were later rebuilt and operated through the mid-1980s. For technical information related to the C855 please click here.
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.