(This is an offshoot of the "PA1 traction motors" string... which was getting long enough I decided to split it. Particularly since THIS part seems less puzzling.)
Story so far: Kirkland's Alco book ("The Diesel Builders, vol. 2") says that the Dl-100 series (the pre-war, "Needle-nose," A1A-A1A passenger cabs with two "53X" engines) had either 730 traction motors or 726: 730 for pure passenger units, with optional gear ratios for 120mph, 100mph and 80mph top speeds, and 726 motors, with a DIFFERENT 80mph gear ratio, for dual service. (With the confusing minor fact that the gear tooth size -- or at least the sum of the numbers of teeth on the gear and pinion -- for the 726 version was the same as for the faster 730 versions, but different from the 80mph 730 version.)
But which units got which?
Well, the 730 motor was apparently in some sense "standard" for these models (or so I interpret the fact that more contemporary references are to the 730), but the New Haven's units -- acquired with the idea of dual service in mind -- seem to have had 726. (So the overwhelming majority of the production run was "non-standard".)
Now, "Railfan scholarship" has a somewhat dubious reputation, and articles in model railroad journals.... But I think this may be trustworthy. "Mainline Modeler" published several articles by Robert L. Hundman on these locomotives that seem to draw on original documents: I have issues with the Dl-103b (prototype, with rear radiators) article (May 1984) and for the "Dl-105" (May 1998). (The article in the latter promised photos of the GM&O's units "next month"; I don't know what other articles in the series appeared.
For the Dl-103b, Hundman is very specific about the electrical gear: GT542E2 main generators, GTB542C2 auxiliary generators and, what interests us here, 730A1 traction motors. The suffixes for subvasriants of these models make me think Hundman had some original documentation to look at.
He ALSO gives tables showing gear ratios for all Dl-100 series locomotives built. The New Haven's and the GM&O's (GM&0 had two 8 units listed as Dl-105 and one as Dl-109) were built with 64:19 gearing for an 80mph top speed. So perhaps 63 units were built with the 726 motor dual service option. (Note that the first two GM&) units were the second and third units of the series built -- shipped in September 1940 -- so any option they incorporated was available early on.)
ALL other Dl-100-series units were built with 58:25 gear ratios for "120mph" top speeds. (Other sources suggest that the recommended maximum speed for 58:25 geared Alco passenger units was only 117 mph.) So they must have been built with 730 motors, if Kirkland's book is accurate. The Rock Island's four units (the Dl-103, a November 1940 Dl-105, and two Dl-107 shipped in December 1940 and November 1941) were later re-geared for 80mph, with -- NOT 64:19, but -- 77:21 gearing. I take this as confirming that they had a different motor from the one used on GM&O and New Haven units (otherwise, why the different gear ratio?).
There's one fly in the ointment. The Santa Fe's A-B set (Dl-107/Dl-108, shipped in May 1941) were delevered with 58:25 gearing. (Maybe this is why the Santa Fe later usually assigned them to mid-West service: they can't have been good for mountain districts!) But a Santa Fe passenger unit roster in "Extra 2200 South," issue 130, says they had ... 726 motors. Possible explanation (this is just one possibility that occurs to me-- another is that some one or another of my sources has it wrong): they were re-motored at some stage (they had long lives, apparently being in service until 1960), and the more common 726 motor was used instead of the original 730.
Story so far: Kirkland's Alco book ("The Diesel Builders, vol. 2") says that the Dl-100 series (the pre-war, "Needle-nose," A1A-A1A passenger cabs with two "53X" engines) had either 730 traction motors or 726: 730 for pure passenger units, with optional gear ratios for 120mph, 100mph and 80mph top speeds, and 726 motors, with a DIFFERENT 80mph gear ratio, for dual service. (With the confusing minor fact that the gear tooth size -- or at least the sum of the numbers of teeth on the gear and pinion -- for the 726 version was the same as for the faster 730 versions, but different from the 80mph 730 version.)
But which units got which?
Well, the 730 motor was apparently in some sense "standard" for these models (or so I interpret the fact that more contemporary references are to the 730), but the New Haven's units -- acquired with the idea of dual service in mind -- seem to have had 726. (So the overwhelming majority of the production run was "non-standard".)
Now, "Railfan scholarship" has a somewhat dubious reputation, and articles in model railroad journals.... But I think this may be trustworthy. "Mainline Modeler" published several articles by Robert L. Hundman on these locomotives that seem to draw on original documents: I have issues with the Dl-103b (prototype, with rear radiators) article (May 1984) and for the "Dl-105" (May 1998). (The article in the latter promised photos of the GM&O's units "next month"; I don't know what other articles in the series appeared.
For the Dl-103b, Hundman is very specific about the electrical gear: GT542E2 main generators, GTB542C2 auxiliary generators and, what interests us here, 730A1 traction motors. The suffixes for subvasriants of these models make me think Hundman had some original documentation to look at.
He ALSO gives tables showing gear ratios for all Dl-100 series locomotives built. The New Haven's and the GM&O's (GM&0 had two 8 units listed as Dl-105 and one as Dl-109) were built with 64:19 gearing for an 80mph top speed. So perhaps 63 units were built with the 726 motor dual service option. (Note that the first two GM&) units were the second and third units of the series built -- shipped in September 1940 -- so any option they incorporated was available early on.)
ALL other Dl-100-series units were built with 58:25 gear ratios for "120mph" top speeds. (Other sources suggest that the recommended maximum speed for 58:25 geared Alco passenger units was only 117 mph.) So they must have been built with 730 motors, if Kirkland's book is accurate. The Rock Island's four units (the Dl-103, a November 1940 Dl-105, and two Dl-107 shipped in December 1940 and November 1941) were later re-geared for 80mph, with -- NOT 64:19, but -- 77:21 gearing. I take this as confirming that they had a different motor from the one used on GM&O and New Haven units (otherwise, why the different gear ratio?).
There's one fly in the ointment. The Santa Fe's A-B set (Dl-107/Dl-108, shipped in May 1941) were delevered with 58:25 gearing. (Maybe this is why the Santa Fe later usually assigned them to mid-West service: they can't have been good for mountain districts!) But a Santa Fe passenger unit roster in "Extra 2200 South," issue 130, says they had ... 726 motors. Possible explanation (this is just one possibility that occurs to me-- another is that some one or another of my sources has it wrong): they were re-motored at some stage (they had long lives, apparently being in service until 1960), and the more common 726 motor was used instead of the original 730.
