I don’t recall there being any A - D Units, but they came up with F Units and E Units as some of their earliest production units.
F for “freight” seems logical, but the FP units would then be a natural oxymoron. E for “express” also seem logical, but I doubt that either answer is as easy as that.
Can anyone tell me where the intials came from?
Thx,
The original nomenclature was to indicate horsepower. The F-Series were rated at Fifteen hundred HP while the E-Series were rated at Eighten hundred HP (actually 1750HP but EMD rounded up).
Wow, I knew about the F series, but I didn’t know about the E’s!
The same references will tell you that the “S” in models SC, SW, and SW1 stood for Six hundred horsepower, and the “N” in NC, NW, and NW1 originally was Nine hundred horsepower. The “C” and “W” originally stood for cast or welded frames. There was a cab unit built for the Rock Island, model TA, in which the “T” supposedly stood for Twelve hundred horsepower.
I always thought the “S” in “SW” stood for Switcher.
SW1500, Switcher 1500 horses.
I believe that the “F” stood for “Fourteen Hundred”, and the “T” (in this case) is for “Twin” most FT units being bar coupled pairs which could not operate separately because of shared equipment, batteries being one example. Santa Fe locomotives always had couplers and were referred to as model “FS” in some early documentation for “Fourteen Hundred, Single Unit”. “T” had already been used for “Twelve Hundred” in the TA passenger units built for Rock Island, and wasn’t available for a “rounded down” “Thirteen”. I believe the “FS” went away as other FT sets were broken up into coupled pairs, and minor changes were made to allow them to run separately. The addition of the “T” may have come when Santa Fe first asked for single coupled units. After the first few sets, Santa Fe got their locomotives as A+B+B+B sets while the company and the Brotherhood sorted out how many cabs a single locomotive was allowed, and how many men were needed to crew it. So presumably some of those B units were built with batteries, if only in alternate units. A lot of things were changing quite quickly as 103 was built, and photos show an A unit numbered 1031, which had changed before it went into service.
I think that the correspondences of code letters to original horsepower is so great that it can be taken as read that “S” stood for “Six Hundred” and so on up. The “F” was the only unit in which the power of a 567, rather than a 201A was the basis of the letter. Of course, later codes like GP, SD and BL did not relate to power at all. However, if World War II is taken as the split, the “pre-war” codes appear to be based on horsepower. Some codes, AA and possibly AB, for miscellaneous passenger units may have been part of a post WWII retrospective “tidying up”.
Anyway, that’s my view after years of trying to work it out!
Peter
Strange as it may seem, EMD’s export designations actually make more sense than the domestic models. A=carbody, G=hood, J=double-ended, T=turbocharged, etc. A more thorough explanation can be found at:
Paul
On the switchers, my understanding is the SC was the 600 HP with a cast frame and SW was the 600 HP with welded frame.
Thanks much for the feedback guys - - Stack