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Union Pacific’s Ex-Missouri Pacific GP50 Locomotives

By Don Strack

(This article is an updated and expanded version of text used in a letter to the editor published in Diesel Era, Volume 5, Number 2, March-April 1994)

To The Editor, Diesel Era magazine

I enjoyed the article about EMD GP50s in the January/February 1994 (Volume 5, Number 1) issue of Diesel Era. Peter Limas and the DE staff presented a very informative article about an interesting locomotive model. I have been preparing an article about Union Pacific's GP50 fleet, but your article was much better and more complete in its coverage. While doing research for my article, I have come across several bits of information concerning UP's ex-MP GP50s that may be of interest to your readers.

While the instructions to renumber the units to the two-digit numbers were indeed issued during November 1985, none were actually renumbered until MP 3507 was renumbered to UP 57 in January 1988, a little over two years later. As was stated in the article, only twelve units were renumbered to the two-digit numbers by the time that the instructions were issued to renumber the entire GP50 fleet to the 960 series, with the first, MP 3503, becoming UP 963 in January 1989. The first and last two-digit numbered units to be renumbered to the 960 series were UP 60, which became UP 970 in August 1989, and UP 71, which became UP 981 in May 1992. UP 71 was also the last unit in the 30-unit GP50 fleet to be renumbered to the 960 series. The last ex-MP 3500 series unit was MP 3525 when it was renumbered to UP 985 in December 1991.

On the subject of dynamic braking for the ex-MP GP50s, I've been fortunate enough to gather information from knowledgeable and helpful individuals at Union Pacific and VMV Enterprises. Ken Ardinger also helped with the date information. As I understand it, the story goes as follows.

During mid-1992 Union Pacific initiated a contract with EMD to add dynamic braking to ten ex-MP GP50s, UP road numbers 960-969, with plans to have dynamic braking added to the remaining 20 units as funding becomes available. Missouri Pacific had originally purchased the GP50s, without dynamic braking, to operate at the head of their fast freights over the mostly flat-terrain route between Chicago and Texas, thereby negating the need for dynamic braking.

Like many railroads which operate across America's flatlands, Missouri Pacific was slow to grasp the advantages of dynamic braking as they relate to fuel efficiency and modern train handling methods. Many operations people on these railroads believed the myth that dynamic braking was useful only in the mountains. By the early 1980's, research and testing by the more progressive railroads had proved that dynamic braking was useful and cost-effective in almost any terrain, as opposed to power braking (sometimes called stretch braking), which uses train brakes exclusively. These tests showed remarkable savings in fuel usage and in wheel and brake shoe wear on the cars. The tests also resulted in further refinement of the use of dynamic braking on the locomotives themselves, to wring out even more fuel efficiency by developing two- and three-speed systems which kept engine rpm's at the lowest possible levels during the use of dynamic braking. By the mid-1980's, Union Pacific was teaching engineers to use dynamic braking whenever possible, and issuing discipline when these instructions were ignored. As these new train handling practices became more of a standard, the railroad noticed a reduction in derailments caused by overheated, cracked or broken wheels, which was yet another benefit derived from the expanded use of dynamic braking.

One Union Pacific operations officer has said that "MP bought locomotives as plain and as cheap as they could be had", adding jokingly that "...if they could've bought 'em without wheels and saved $5, they would have." This same official states that the lack of dynamic braking on virtually the entire MP fleet (along with small fuel tanks and other limiting features) has been a problem in locomotive utilization since the 1982 UP/MP/WP merger, and will continue to be so until the last ex-MP locomotive has left the roster. Union Pacific seriously looked at adding dynamic braking, Coded Cab Signals (CCS) and large fuel tanks to the entire ex-MP fleet of SD40-2s, GP50s, and B30-7s, but these studies showed the cost to be prohibitive, especially on the B30-7s.

After the 1982 merger, and as motive power needs changed, the ex-MP GP50s were assigned to UP's four-axle general freight pool, being used almost exclusively in local and branch line service because of the above mentioned operational limitations. UP soon found that the GP50s were a bit over powered for local service, and with the new train operating practices of expanded use of dynamic braking, the GP50s were also limited as to the actual freight service which they could be used in due to the lack of this now important braking feature. Reflecting this limitation, the units were reassigned to intermodal trains in the old MP and along the lower-grade lines of UP's former Eastern District in Nebraska and Kansas. The advantages of intermodal service (i.e., dedicated train blocks or entire trains made up of long flat cars with trailers and articulated double-stack container cars) actually worked against the usefulness of the GP50s in that service. The lack of dynamic braking could not overcome the diminished air braking capability of the fewer number of axles that make up intermodal trains -- fewer axles for braking due to longer cars and articulated double-stack cars. Intermodal operations did not suffer, however, because there were, and still are, numerous C&NW GP50s assigned to UP to equalize the imbalance in horsepower hours owed to UP by C&NW. (This imbalance in horsepower hours may also be a leading factor in C&NW's sudden increase in its most recent order of GE C44-9Ws, increasing their initial 35-unit order to an unexpected 115 units.)

In 1992 EMD was asked to design an add-on dynamic brake feature for these 3500 horsepower four-axle racehorses. The units selected to receive the braking feature were UP 960-969, chosen to keep dynamic brake-equipped GP50s consecutively numbered after the six GP40Xs (UP 954-959), which were originally built with the dynamic braking feature. Initially, funding was available to have the feature added to only nine units, but a tenth unit was added after additional funding was located. As designed, the new braking for the ten ex-MP GP50s would be extended range dynamic braking, and would require the addition of braking resistor grids and a cooling fan to the roof of the locomotives, along with additional cabling and modifications to the units' electrical cabinets. The high capacity dynamic braking currently being used on today's GP60s is not applicable to the GP50 because the design is dependent on control by the GP60's microprocessor and other expensive-to-retrofit components. Other, successful attempts at adding dynamic braking by other locomotive rebuilders, specifically Morrison-Knudsen (M-K), solved the problem of where to get the grids and actual sheet metal dynamic braking hatch components by using the actual components from retired locomotives that were equipped with the feature. M-K's solution when they added dynamic braking to several ex-MP SD40s as part of a 50-unit rebuild order for CSX during 1990 included using the dynamic braking hatch from retired ex-BN SD45s. EMD chose to fabricate the new dynamic braking hatches for the ex-MP GP50s. EMD selected VMV Enterprises at Paducah, Kentucky to perform the actual installation and modification work. The EMD-fabricated dynamic braking hatches, and other needed components were then shipped to VMV for installation. The units were modified in one and two unit batches as VMV was able to complete the electrical modifications. Two factors affected the delivery of the completed units. First, EMD was having difficulty acquiring the needed components from its vendors, and second, VMV was being challenged by a sudden increase in its overall workload. As VMV was able to accumulate the components and allocate shop floor space, UP would send candidate locomotives to Paducah. The first to be completed was UP 961 in October 1992, with UP 962, 960, and 965 following soon after in November and December 1992. Four more units (UP 963, 964, 967, and 966) followed in February through May 1993, with the last two units (UP 967 and 969) being outshopped in July and August respectively.

The addition of dynamic braking to the remaining 20 ex-MP GP50s is still on the motive power department's wish list. A specific request for 1994 funding was unsuccessful, but hopefully the project will be completed in the near future.

I have seen photos of the post-modification units taken by both Mr. Lon Coone and Mr. George Cockle. Perhaps you could locate photos of a modified unit and share it with your readers. It might be doubly interesting to show the same actual locomotive in all of its various stages of ownership and physical configuration: as an MP blue 3500; as a yellow MP 3500; as a UP 50 series unit; as a UP 960 series unit; and finally as a UP 960 series with dynamic braking.

I look forward to every issue of Diesel Era because your articles are always informative and interesting, and I learn something new regularly. I'll admit that I am strongly interested in Union Pacific, as my own two previous articles and this letter show, but I always make a point of reading every article in every issue, including car and caboose articles. Every issue of your magazine firmly cements my interest in railroading to that of America's railroads during the "Diesel Era".