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Geeps and covered wagons MU’d together

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  • Member since
    September, 2017
  • 28 posts
Geeps and covered wagons MU’d together
Posted by Union Pacific 428 on Tuesday, July 10, 2018 8:02 AM

Hi all, 

I have noticed that a lot of railroad pictures from the 60’s and 70’s show locomotive consists made up of both hood units (usually GP7s/9s) and F units, but photos from the 50’s almost always show trains being pulled by one type or the other, not a mixed batch of both. So exactly when and why did this practice of conglomerating locomotive consists start? Thanks. 

  • Member since
    February, 2002
  • From: Mpls/St.Paul
  • 10,567 posts
Posted by wjstix on Tuesday, July 10, 2018 8:16 AM

Initially railroads tended to buy diesels the way they bought steam engines - tailored to meet a specific need. The GP-7 and F-7 both used the same GM diesel engine, developing 1500 horsepower. So a railroad might buy a GP-7 to replace a 2-8-0 steam engine on a branchline, but an A-B-A set of F-7s to replace a 2-8-4 steam engine to haul long mainline freights.

Often the A-B-A sets would all be given the same number (sometimes with subletters like "444A / 444B / 444C") and be treated like one large engine. In part, this was to a response to railroad union's argument that each unit was a separate engine, and required an engineer and fireman, even though the units were connected together as multiple units all run from one engine.

In time, railroads realized that a "building block" idea worked better - combining engines to get the necessary horsepower to haul the tonnage of today's train. If you needed about 4000 HP, you could use three GPs, or three F-units, or a GP and two F-units, or two GPs and an F-unit. Tomorrow if you have a train needing 5500 HP, you would use four engines. Of course, every few years, EMD and Alco and others came up with more powerful engines, so three 1960's engines might pull a train that would have required four 1940's engines.

A few railroads did keep F-units together - Northern Pacific ran A-B-B-A sets of F-units up to the BN merger, and I've seen some of these engines running together in the 1970's in BN colors. Soo Line's A-units only had m.u. (multiple unit) connections on the rear, so A-units had to run at the head or end of the locomotive consist.

Stix

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