E6A to E7A nose change

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E6A to E7A nose change

Postby SSW921 » Mon Oct 22, 2018 6:58 am

When did the EMD design team modify the slant nose E6A to the bulldog nose of the E7A? Was it just a matter of fitting the nose to the existing design?
The last E6As were built in September 1942. The first E7As were built in February 1945.

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Re: E6A to E7A nose change

Postby Allen Hazen » Mon Oct 22, 2018 8:18 pm

"Railfan and Railroad" has published a number of articles on the history of E and F units (by P. Cook). I'd have to search the basement to find them right now, but my recollection is that at some point during WW II (so: in the period of construction of the FT) EMD started building the cab-nose section as a separate subassembly. I ***think*** the E7A (and subsequent E-series A units) used the same cab-nose subassembly, so reducing the slope on the E-unit nose reduced production cost. (That said, I think there was also a positive reason: with the more nearly vertical nose, the cab could be a bit further forward, so lengthening the engine compartment, making it easier to fit things into it.)
(Sorry-- that doesn't go anywhere in trying to answer your actual question about WHEN the design change was decided on. There may be hints in the Cook articles.)
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Re: E6A to E7A nose change

Postby Allen Hazen » Mon Oct 22, 2018 8:31 pm

Re: lengthening the engine compartment.
I just eye-balled (finger nail as ruler) the scale drawing in the "Model Railroader Cyclopedia" diesel locomotive volume. The rear edge of the cab side door on an E6 is pretty much over the forward hanger of the leaf-spring assembly between the middle and trailing axles of the front truck. On an E7 it is close to being over the center axle. So the rear of the cab is about roughly maybe approximately two feet further forward on the later design.
So I guess I'd answer the "Was it just a matter of fitting the nose to the existing design?" negatively, though I think the design change was made by fitting the existing (F-unit) design for the whole nose-cab assembly onto an E-unit platform. (Note that the E-unit, like the Baldwin 2000 hp passenger units, as a twin-engine design was ALREADY significantly longer than, say, an FM Erie-built or an Alco PA. So there was good reason to compress the nose-cab region rather than lengthen the whole platform if more space was wanted in the engine room.)
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Re: E6A to E7A nose change

Postby RAS » Wed Oct 24, 2018 8:30 pm

See the discussion of the equipment rearrangement for the E7 locomotive by Preston Cook in Summer 2012 Classic Trains E-units feature, Pages 30 and 31,

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Re: E6A to E7A nose change

Postby Allen Hazen » Thu Oct 25, 2018 12:09 am

Thanks for the reference, RAS! I'm pretty sure some of Preston Cook's articles(*) on E and/or F units were in "Railfan and Railroad," but probably mis-remembered and thought this one was too.
(*)Author of some of the highest quality, best informed and most informative, articles in any railfan magazine!
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Re: E6A to E7A nose change

Postby Allen Hazen » Thu Oct 25, 2018 12:27 am

On the general topic of EMD noses (and at the risk of straying too far away from SSW921's questions, which still haven't been answered!)...
I've always felt that the TA units that EMD built for the Rock Island in the 1930s should, as 4-axle cab units with a V-16 engine, be counted as somehow in the F-unit family. (My favorite just-so story about the model designation FT -- Preston Cook has a different explanation -- is that it meant "in the same model family as the T, but a Freight version thereof".) But the TA had a long sloped nose, like that on pre-war E-units. So why did EMD, when it designed the FT, shorten the nose? I think the obvious answer would be that (since a freight unit didn't need such visually dramatic styling) it was to shorten the over-all unit length. There would have been, it seems to me, good reasons to keep the freight diesel as short as practicable, both
---structural (make the unit unnecessariiy long and you are in effect installing a lever to multiply transverse forces when going around a curve, with attendant increased risks of derailment and structural damage) and
---operational (even as built, a four-unit FT set was significantly longer than a Big Boy with its tender, and locomotive length is part of train length: an EMD salesman wouldn't want to go to a railroad president and have to say "We've got the best ever heavy freight locomotive... but you're going to have to lengthen all your passing sidings to use it).
(But that's tangential to the main point of the string.)
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Re: E6A to E7A nose change

Postby urrengr2003 » Mon Dec 31, 2018 11:40 pm

Unsubstantiated recollections from service in the 1960's as traveling diesel foreman. The ACL had one 500 class psgr unit that had a short nose on an E-6 frame. Don't remember its number, it came back from LaGrange after being the lead unit on #1 that went into the countryside running 90MPH at Dillion, SC account defective point lock at south switch to center pass track that location. Unit went to east side and plowed thru cornfield turned 180 degrees and came to rest facing south on left side killing Fireman Charlie Hunt. It had standard E-7 throttle drum and controls but rear cab wall was located as an E-6 providing enough room in cab for a ball team to practice. The rear cab wall on E-6 & E-7's were identical with a center door to the engine room. The difference was you walked farther forward in an E-7 to gain access to the stairs to the cab crossing a drive shaft guarded with a sheet metal cover. This was not the case with an E-6 as the drive shaft was under the stairs. Both models had the air brake rack on the right hand side of the cab wall and the high voltage cabinet for the #1 engine on the floor up against the back of the cab on the left side of the locomotive. It's my thought EMD had sufficient space in the engine room that it made no design changes relative to long or short nose psgr units until E-8 design placed high voltage cabinet for #1 engine across rear cab wall with access doors both in cab and engine room. Access to engine room now was a door on each side of high voltage cabinet that always seemed to interfere with side cab door. Instead of long distance from cooling belt sheeves on #1 engine as in E-6/7 to rear wall of cab, E-8 was so tight that access to rear of high voltage cabinet was difficult because it was so close to #1 Traction Motor blower.
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