Erie-built traction motor question

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Erie-built traction motor question

Postby Allen Hazen » Thu Mar 10, 2005 7:15 pm

(I will shortly post a related question, "PA-1 traction motors," to the Alco forum.)
The first Eries, at least, had the GE 746 model traction motors. (Railfan literature on the topic seems to agree on this; a trade-press article when the Eries were introduced that I have seen also specifies this model of t.m.) My question is: Did ALL Eries have these motors, or was a change (to 752?) made in the course of production.
Reason for asking: the contemporary Alco equivalent, the PA-1, seems to have been built with at least two, possibly three, different models of GE traction motors: 726, 746, 752. So...
Background: By the late 1940s, GE seems to have standardized on the 752 as its basic motor for large locomotives: Alco's, Baldwins and FMs after Westinghouse quit, GE's own U-series. Before that... Pre-war Alco Dl-109 had either 730 (for exclusively passenger service) or 726 (for dual service, as on the New Haven). According to a post to some Railroad.net forum a while back, the 752 was an upgraded and improved version of the 726 (fairly major upgrade, given the tractive efforts cited for 726 and 752 equipped Alco FA-1, though the upgrades made between 1950 and the 752AH used on GE's Dash-9 freighters without changing the model number are surely greater!). According to a "Trains" magazine article on FM locomotives from a few years back, one of the things that made it difficult for FM to compete was that they had chosen the 746 motor, which was more expensive (I think it had moreelaborate ventilation features). At a GUESS: in 1945, when the Erie was introduced as a dual-service use, suitable for heavy freight, FM decided they wanted something more robust than the 726, and the 746 was what GE could offer them, only later achieving comparable performance from a cheaper, 726-derived, model, the 752. BUT THAT'S JUST SPECULATION. Erie-built production lasted until 1949, after GE had started using the 752 on Alco-GE freight and passenger units. Hence my question: did some late Eries have the 752, or did they all get 746?
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Postby Typewriters » Sat Mar 12, 2005 7:24 pm

Hi there; I followed your posting backwards from the ALCO-GE forum.

I recall Robert Aldag writing that the other GE motors than the 746 did not have enough capacity for the requirements, and so the 746, even though it was more expensive, was selected for the Erie-Builts, and to my knowledge all of them had this motor, regardless of gear ratio or service. Rating in the Erie-Built was 1050 amps continuous on the ammeter; the early 752 was good for 900 amps, and the later version 1085.

I recall also that the 746 was a good bit heavier than the 752. Ol' Loco Guy's posting in the ALCO-GE forum makes me wonder if the 752 didn't use less copper and better, newer insulation with better ventilation. But that's pure speculation.

-Will Davis
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Postby Ol' Loco Guy » Sun Mar 13, 2005 3:26 pm

The FM 2000 hp dual-service units and the Alco passenger units used the same equipment for traction motor ventilation-one GY26 blower per truck.
These were driven off a seperate circuit with its own auxiliary generator.
4000 cfm per blower is a figure that seems to stick in my head.
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Postby Allen Hazen » Wed Mar 16, 2005 4:02 pm

Typewriters & Ol' Loco Guy--
(i) Probably right that AT THE TIME when the Erie-built's specifications were being finalized (1945 or late 1944?) the 746 was the only motor GE had that was suitable for a four-motor 2000 hp FREIGHT unit: the introduction of the 752 was still something like 18mos/2yrs away.
(ii) Kirkland gives continuous tractive effort catings for the FA-1 with 726 and the FA-1 with 752 motors, at the same gear ratio. Would the proportionality here (I have the book where I am staying and can check it) and your figure for 752 amperage limit allow a simple calculation of the amperage limit for the 726?
(iii) (This is to something in a post to the Alco-forum sister string.) The New York Central's diagram book, partially on-line at George Elwood's "Fallen Flags" site, gives generator voltages: the voltages for the postwar 244-engined types (PA-1 with 566 generator and FA-1 with 564), maximum and full load, are somewhat higher than those given for the S-2 switcher (whose powerplant duplicated those on the Dl-109).
(iv) I suggested in my initial posts that the 746 motor might have had more elaborate ventilation than the 726/752, but this was just a guess on my part. Since Ol' Loco Guy (located in Varanasi! does that mean you are involved with New Locos too?) says the Erie-built and the PA-1 had the same traction motor blowers, I assume I guessed wrong.
...And thanks, both of you!
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Postby Typewriters » Wed Mar 16, 2005 9:11 pm

As to your question about the continuous ratings, and amperages, the answer is very vaguely yes, assuming that between the two variants of 564 generator to be used, that the voltages were the same. Please go ahead and post (perhaps the ALCO string is a better place) those figures for the 726 motor FA-1, and let's see what happens.

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