• What **WAS** the 5GT-590?

  • Discussion of General Electric locomotive technology. Current official information can be found here: www.getransportation.com.
Discussion of General Electric locomotive technology. Current official information can be found here: www.getransportation.com.

Moderators: AMTK84, MEC407

  by Allen Hazen
This is an OLD topic: I asked about it several years ago, but I've been thinking about it again.
Short answer is: the GT-590 was the main generator GE produced for Baldwin locomotives when Westinghouse dropped out of the heavy traction (= locomotive (W'house continued to make electrical gear for transit and commuter cars, and even for about half of the original "Metroliner" cars)) business. Many sources agree (but how many ORIGINAL sources I don't know) that GE built 20 sets of locomotive electrical gear for Baldwin, two of which were used in AS-416 for the Norfolk Southern. The rest were "sold".
QUESTION #1: Sold to who? "Acme Copper Recyclers"? or, more interestingly, back to GE?

What particularly bugs me about this is that the U25C was theoretically equipped (like some 6-axle Alco models: RSD-12, RSD-15, C-628) with the GT-586 generator.
((QUESTION #2: I've long **assumed** that the GT-586 was a modified version of the GT-566 used on the first Alco PA locomotives, much as the GT-581 was a modification ("productionized version") of the GT-564 used on the FA-1. Does anyone here know the details of what the various GE locomotive main generators were like? (Bit of evidence suggesting that the GT-586 was similar to the GT-566: Kirkland's Alco book says the RSD-5 had a GT-566 generator, replaced with the GT-586 in its 251-engined analogue the RSD-12.) ))
***BUT*** there is a Pennsylvania Railroad mechanical department diagram of the U25C available on the WWWeb at
http://prr.railfan.net/diagrams/PRRdiag ... &sz=sm&fr=
which lists the main generator as ... a GT-590!
QUESTION #3: How similar were the GT-586 and GT-590? Were they similar enough that-- assuming GE repurchased the unused GT-590 from Baldwin and still had them lying around a warehouse in Erie ten years later-- they could have been altered fairly cheaply to be functional equivalents of a GT-586? (PRR seems to have had 20 U25C, built in two batches of ten each. Even if 18 of them had recycled ex-Baldwin generators, did two of them get new GT-586?)

((Question #4: How does the GT-567 -- introduced on the Erie-built and applied to other Fairbanks-Morse locomotives after Westinghouse abandoned the locomotive market-- compare to any of the above? Given the similarities between an Erie-built and a PA in specs, I would assume that it was a generator whose output was similar to that of the GT-566 but which was optimized to accept input from a diesel engine of lower rpm.))
  by Allen Hazen
According to the lengthy photo caption here:
http://www.railroadforums.com/photos/sh ... hoto/52582
(which seems to derive much of its information from "Diesels from Eddystone" by Dolzall and Dolzall), GE built 22 sets of locomotive electrical gear for Baldwin: which means there were 20 left over, which means... exactly as many as PRR's U25C.
I'm not an electrical engineer. If the speed of the diesel engine has a major impact on the design of the traction generator, it would be surprising for a generator-- the GT-590 -- designed for use with a 625rpm prime mover to be mated with a 1000rpm 7FDL-16 engine. (The Fairbanks-Morse engine was halfway between the Baldwin and Alco prime movers, but that seems to have ben enough of a difference for GE to design a special generator-- the GT-567 -- for use on F-M locomotives.) ... But, not being an electrical engineer, I don't know how much modification a generator designed for use with one engine would need before being used with the other. GE, wanting to stay in the locomotive business, wouldn't have sold the Pennsylvania locomotives with a generator they knew was inappropriate, but if the modification was comparatively minor... And PRR's finances were dubious enough by 1964 that I can imagine them going to GE and saying "Can you think of any way of reducing the price?"
  by Typewriters
I recall having been through this before, Allen; a number of the PRR's U25C units (6500-6503) were actually pre-production U28 units, rated 2800 HP and containing advancements developed for that model (steel heads, single-pipe exhaust manifold). Those units would necessarily have had GT-598 main generators, and I recall coming to the conclusion that the PRR spec card mentioned was for the uprated units and was misprinted.

Of course anything's possible but considering that there's really no way that a generator designed for a Baldwin 600 series engine would bolt up to a GE FDL I'd doubt that these were originally BLW-intended generators. GE changed model numbers frequently for identification purposes; in fact we recall the GT-567 similar to the GT-566 but for the Fairbanks-Morse engine instead of the ALCO 244. That's why I find the "GT-590" on that card most likely a mistake.

I just bought a U25C specification book (ie bid offer for a railroad) and when it arrives I'll look for any details along these lines, but in the extensive data we have here about GE locomotives there's no reference anywhere to the use of anything but the GT-586 on conventional U25C locomotives and the GT-598 on uprated, preproduction U28 and all production U28 locomotives.

-Will Davis
  by Allen Hazen
Will Davis--
I ***THOUGHT*** you'd remember the earlier discussion! (Your son's page(*) is the only detailed source I know on the internet for the GE equipped AS-416, b.t.w.)

Re-use of an obsolete model number and slip of the pen by whoever lettered the PRR diagram are the two obvious explanations, but...

There is nothing on the diagram to suggest it applies only to the up-rated (U28 prototype) units, and it does note that the power of the units it applies to is "2500hp at 1000 rpm." Pity I'm not in Strasburg PA right now: I suspect the Railroad Museum of Pennsylvania would have old PRR paperwork in its archive that would settle the issue once and for all!
(*) For those not acquainted with it:
The Davis family has put a lot of very interesting locomotive material on the WWWeb: I've learned a lot from them.
  by Allen Hazen
As to the "scribal error" hypothesis (viz., that the PRR diagram was intended to refer to GT-598 equipped U25C and the "scribe" miscopied the "8" as a "0"), I asked the question on the "LocoNotes" Yahoo group and got a response from Jeff Morfit, who said:

>I checked the U25C Specifications table on page 894 of Volume 11
>Pennyslvania Railroad Diesel Locomotive Pictorial. It shows that PRR's U25C's
>were indeed built with GE Model GT-590 main generators.

Now, if we knew that the book's information wasn't copied from the diagram in question (Grin!), that would be good evidence that PRR's U25C got a generator that GE at least called a GT-590.

(There are moments when I think it is frustrating not to have access to original source material.)
  by Allen Hazen
I posted (versions of) my silly question on a number of discussion sites: in the interest of having all the information in one place, I'll report back to this string what I find out. Most recently, Jeff Morfit (on the "LocoNotes" site) has consulted a different book... and got a different answer:
>I checked [...] Pennsy Diesels, 194-1968 by Douglas and
> the Locomotive Characteristics table on page 106 of the Douglas and
>Weiglin book shows that the U25C's were built with GE GT-598C4 main
>generators. Is it possible that one order was built with the 590 main
>generator, and the other with the 598 model generator since Pennsy
>placed two seperate orders with GE for these locomotives?

Comment: I don't know how many orders (as in: separate legal contracts) PRR made for U25C. The units were delivered in two blocks of ten each (6500-6509 and 6510-6519), and also can be divided into two "subclasses," the "U28C prototypes" with the higher engine rating, 6500-6503, and the rest, which (I assume) were delivered at an ordinary 2500hp rating. ... Either split COULD have different generators on the two sides, but one of the things that originally made me wonder about the possibility of re-using the left-over GT-590 was that the numbers were equal: 20 GT-590 generators that didn't go into Baldwin locomotives, 20 PRR U25C.
  by Super Seis
A couple of thoughts:
  • GE main generators as applied to Alco and GE locomotives are cantelievered off the diesel engine, with the weight of the magnet frame supported by the engine or generator adapter and the weight of the armature supported by the crankshaft and a large roller bearing on the commutator end.
  • On Baldwin (and FM) units, the weight of the magnet frame is supported by two mounting 'ears', which are affixed to the engine bedplate. The armature is supported by roller bearings on both the engine and commutator ends.
In a DC machine, the voltage output is directly proportional to the speed of the machine. For example, a GT-581 machine could be (and was) used on both the C-420 or a U-23B...with notch 8 engine speed being 1000 rpm. As I recall, rated voltage is approx. 900 VDC.

A BLH, with maximum engine speed of 625 rpm, would require a generator of different electrical design in order to produce rated voltage at a lower notch 8 engine speed. FM rated engine speed was 800 rpm ?

BTW, I am fairly certain that a number of BLH S-12's (including the last one built) were built with GE transmissions.

Hope this clears the air a bit.

  by Allen Hazen
Super Seis--
Thank you! I had assumed that a fairly minor modification to the wiring, or perhaps even a change of excitation, would be enough to compensate for the change in engine rpm: if this is not so, then it would probably have been uneconomic to adapt the (ex-Baldwin) GT-590 for use on U25C. You also say that there is a difference in MECHANICAL as well as ELECTRICAL design: are you sure this is intrinsic to the engine and not a difference between GE and Westinghouse approaches to generator design? That is, are you sure the description you give of Baldwin and FM units applies to Baldwins and FMs with GE generators?(*)

I think you're right that a number of S-12 switchers were built with GE electrical gear, though I don't have any references at hand for details. I think I remember that the GE generator used on the switchers was a different model, and that the GT-590 was supplied only for use on the 1600 hp locomotives.

Thanks again. (Right now it looks as if the evidence is running in favor of the "scribal error" hypothesis.)


(*) I do have a description of the connection between the FM engine and the GE GT-567 generator on the Erie-builts (from an article in the May 1948 issue of "Railway Mechanical Engineer," reprinted in "The Train Shed Cyclopedia" #64): "A general Electric shunt wound commutating pole type GT-567 generator is directly connected to the engine crankshaft through a flexible coupling of the multiple disk type. The commutator end has a spherical roller type anti-friction bearing which takes end thrusts of the armature. The generator is self-ventilated by a fan at the coupling end. A discharge vent is provided to discharge heated air outside of the cab and a damper is located in the discharge duct to permit the re-circulation of air through the engine room in cold weather." Is this any help?
  by Typewriters
The total number of Baldwin-Lima-Hamilton diesel-electric locomotives built with GE transmission equipment was 13; 11 of these were S-12 switchers with GT-591 main generators while two were AS-416 road switchers with GT-590 main generators. The locomotives used combination auxiliary generator / exciter sets of model GMG166 for the road locomotives and GMG167 for the switchers.

Of further interest is the fact that the standard main generator for the U25C was the GT-586, but that we're considering that the GT-598 was employed. This generator was used in all U28 locomotives and in point of fact the large, comprehensive Conrail-specific GE Diesel Engine Overhaul manual we have here lists all of the former PRR units, in both orders, as model "U28C" which to me indicates that all were equipped with GT-598 main generators. It would stand to reason that all of the units were so equipped in the event that following the experimental period (whatever that was) the units could all have been uprated to 2800 HP (instead of downrating 6500-6503 to 2500 HP.)

I myself am certain that not only would it have been unlikely that the BLW generators would have sat around that long, but also it would have been very expensive to modify the generators and/or engines to mate them. I'm sure that the PRR U25C units were all fitted with GT-598 generators, and that the first four were certainly delivered rated 2800 HP. It seems that the first four were derated after the test period was completed, since they're never listed in Conrail documents elsewhere as 2800 HP units.

-Will Davis

PS Do not confuse the units referred to above with the U28C production units ordered by PRR - these are not in doubt although interestingly several of these units were preproduction prototype U30 units with 3000 HP engines and AC/DC transmissions.
  by Allen Hazen
We know that Conrail official documents sometimes contain errors, but...
Is the Diesel Engine Overhaul manual a Conrail production or a GE publication? Either way, it seems to support your idea, Will, that "590" on the PRR diagram was a miscopying for 598.
  by Typewriters
That manual I'm referring to is a very large and heavy GE publication for Conrail, covering all of the General Electric locomotives Conrail owned as of April, 1979. It's GEK-30130A.

I'm thinkin' GT-598 Allen!

-Will Davis
  by Super Seis
The following is a summation of the theory behind DC generator design:

DC Generators Summary DC generator theory is summarized below. DC Generator Theory Summary The three conditions necessary to induce a voltage into a conductor are: - Magnetic field - Conductor - Relative motion between the two The left-hand rule states that if you point the index finger of the left hand in the direction of the magnetic field and point the thumb in the direction of motion of the conductor, the middle finger will point in the direction of current flow. The terminal voltage of a DC generator is adjusted by varying the field strength. The voltage rating of a DC generator is based on the insulation type and design of the machine. The current rating of a DC generator is based on the size of the conductor and the amount of heat that can be dissipated in the generator. The power rating of a DC generator is based on the mechanical limitation of the device that is used to turn the generator. The upper speed rating of a DC generator is determined by the speed at which mechanical damage is done to the machine. The lower speed rating is based on the limit for field current. There are four internal losses that contribute to lower efficiency of a DC generator. - Copper losses - Eddy-current losses - Hysteresis losses - Mechanical losses
My memory of the actual calculations that develops the number of field coils, armature coils, etc is that they of a 'cookbook' nature (the science), where the 'art'
pertains to the nuances. In other words, the devil is in the details-so to speak.

Allan wrote:
((Question #4: How does the GT-567 -- introduced on the Erie-built and applied to other Fairbanks-Morse locomotives after Westinghouse abandoned the locomotive market-- compare to any of the above? Given the similarities between an Erie-built and a PA in specs, I would assume that it was a generator whose output was similar to that of the GT-566 but which was optimized to accept input from a diesel engine of lower rpm.))
I would agree that the 567 is similar in performance characteristics to the 566, save for the lower rated speed. Based on the equipment list, it appears that the
"Erie-Builts" are very close in electrical design to the 2000 hp Alco passenger units, save for the use of electrical jacket water cooling fans on the FM's and the use of 746 motors vs. 726 on the Alco


Based on Wills' comments, it appears that the BLW application of GE equipment used 'split pole', or open loop control a la' the Alco 539 powered switchers.
  by Allen Hazen
Will Davis--
I was just checking: your previous post did seem to imply that it was a GE book. ... I suppose that, in principle, if it was specifically an ENGINE manual, it might not say anything about generator oddnesses, but it certainly is suggestive if GE thought of these units as (preproduction prototype?) U28C rather than U25C. Right now I'm with you: thinking GT-598!

Does the book have notes on any of the other odd GE units on Conrail, like the late NYC U25B delievered at a higher rating, or the two U30B that served as U33B prototypes? (Since-- it has been reported-- the latter two units were derated to 3000hp after a short test period, it may be that there was no need to mention them specially in a manual GE prepared in 1979.) ... A fairly small number of units delivered as U25 were uprated later: would this manual have details of the modifications involved?

Super Seis--
Given the dates, and the over-all similarity in locomotive specification, it would be surprising if there WEREN'T major similarities between the GE equipment on the Erie-builts and on the PA! ... A while back there was a long discussion of the traction motors used on these two locomotive types (strings on this, the Alco forum, and the F-M forum): summarizing in a nutshell:
(i) When the Erie-built was designed-- particularly since it was intended for dual service-- the 746 motor may have been the best option, as the 726 wasn't robust enough, but a year or so later GE developed the 726 design into the 752, and even early 752 were as robust as the 746 used on the Erie-builts
(ii) The 752 motor was standard on later PA, but there is a ... lack of clarity ... in available sources as to applications of 726 and/or 746 motors on some of the earliest ones.
  by Allen Hazen

Just re-checked. There was no string on this (GE) forum about PA traction motors: there is a long string "PA-1 traction motors" on the Alco forum (currently on page 3 of the index) with a short spin-off on the F-M forum ("Erie-built traction motors").

Will Davis found a lot of the original documentation that got referred to, including amperage limits for the 746, the original (ca. 1947) 752 and the first upgrade of the 752 (about 1950). I'd misremembered when I posted a few minutes ago: the 746 has a higher amp limit than the first iteration of the 752 design (so: might have paid for itself on late Erie-builts intended for freight service), but not as high as the second iteration.
  by Typewriters
As far as the Conrail GE Diesel Engines manual is concerned, by the time it was produced in 1979 all units had their originally ordered horsepower ratings. What I mean by that is this: All of the units nominally produced as U25 models, either four or six axle, were rated 2500 HP; all units nominally produced as U28 models were rated 2800 HP and so on. No delineation of the two NYC units produced in the middle of the U30 order as preproduction prototype/test U33 units is made, and due to this and the clear statement in the Edson book that the units were derated later it's an easy thing to understand.

Now, it's also becoming clear that sometimes, in some cases, whole classes of units may have been upgradable - for example, the two orders of U25C units for PRR now appear all to have had GT-598 main generators which was required for a rating of 2800 HP. The first four were delivered, again, as preproduction prototype/test units rated 2800 HP but after the testing was completed, those four units were derated to 2500 HP and the rest remained 2500 HP.

So we have to make a point - it's necessary to really carefully read what's available, and understand what GE was doing at the time. We have many Conrail documents that list the former PRR units in question as 2500 HP and U25C, but the GE book, made for Conrail by GE (in other words with all relevant bulletins and manuals included based on GE's records of units transferred to, and bought by, Conrail) indicates the PRR units in question as U28C. The fact that some units were delivered as 2800 HP units (heck, we can look at Al Staufer's book written right directly from PRR technical information at the end of the road's life) is known, clearly - and we are aware of GE's ongoing program during the whole U-Series of including specially arranged preproduction prototype / test units. It's then very easy to see, taking ALL of this together that the units of both orders were upgradable to U28 status. This is not known to have happened, specifically, on any other railroad - and by "this" I mean making a whole order upgradable by inclusion of equipment vital to the upgrade. Now, did the rest of the PRR units have the engine upgrades necessary for 2800 HP? We don't know - even with this massive GE manual. It does not delineate unit by unit in that way -- it's just not written that way. It's the book you'd think you'd have to have to tell, but you can't. Moreover, what about ACL's U25C's? We can go on!

It looks as if on some roads GE U-series preproduction prototype/test units were later derated to the standard horsepower at the time they were built, while on other roads units kept their increased ratings for their entire lives. I do not know for certain how many units are in this latter category but some were. As one example, some units were built for MILW (or for you oldtimers CMStP&P, and YES, I prefer to refer to old roads by initials!) nominally in a group of U30C units but were actually U33C test units. We might all recall the shot in Pinkepank's Second Diesel Spotter's Guide that actually notes the MILW horsepower class on the unit pictured (which was one of these) showing "3000 HP" when the unit obviously has the wide radiator. Anyway, I have right now in my hand a MILW Locomotive Load-Speed Rating Chart book, published in 1982. It lists the normal U30C units 5651-5658 but has a special class for units 5701-5703; it calls them "U30C @ 3300 HP." It refers to them this way throughout. Clearly these are really U33C units and are still running at 3300 HP in 1982. So, some test units on some roads were derated and some were not. Some units on some roads were upgradable as well in some respects, but were not upgraded, we now know. This is the reality of ongoing industrial manufacturing during a period of product development.

Isn't searching for the REAL FACTS much more fun than supposition and imagineering? I think so.

I'm not sure what you mean by your description of units delivered as U25B and upgraded later; all U25B units were built with GT-598 generators, and there's nothing to prevent the engine/governor modifications necessary to get such units up to 2800 HP if you wanted to spend the money. I know SP did that with a couple U25B units (and learned later on a Pentrex video that they gave 'em AAR compliant control stands at the same time too with AAR standard eight notch throttles and everything.)

Finally, documentation on ALCO-GE Road Passenger Locomotives here never shows any application of the 726 motor. In fact, we have no indication here of that motor in Road Freight locomotives either. TP-400, page 830 is a large chart showing various relay settings for 244-engine units and it delineates both gear ratio and traction motor type and shows only 752 for the 1500 HP units and either 746 or 752 for the 2000 HP units. So, I can't help further on this point. Our GE documentation is much, much better than ALCO-GE at this point (and in fact our BLW/BLH info is much more complete) so I'll leave this one to the ALCOphiles.

-Will Davis