EMD's Electrics

[Wdobner]

Just out of curiousity did GM's electrics from the 1970s use fairly standard traction motors and such from their diesel designs? I'm fairly certain I heard that the AEM7 used D77 traction motors, and the GF6C used E88 traction motors on an HTC truck. Of course the earlier GM6C and massive 10,000hp GM10B are something of an enigma. I can't imagine a 10,000hp locomotive running it's power through a mere six traction motors, were they a different design from the E88 (F99 perhaps)? Also, does anyone know the tractive effort of the GM6C and GM10B? From the April 1995 Model Railroader the GF6C's starting tractive effort is given as 112,000lbs with a continuous rating of 82,000lbs at 22mph (they give 47,000lbs for the SD40-2, but don't state if this is starting or continuous). Could the GM10B have approached a tractive effort rating of 200,000lbs?

Finally, did the AEM7 and GM10B share some truck design elements? I realize the GM10B used a much larger wheel and such, but they both look like they use a chevron rubber support which appears to suggest an early radial truck design. Were they radial trucks and were they related?

[trainiac]

The GM10B had AC traction motors, which would explain how it could handle so much horsepower. Check out this discussion: http://www.trainorders.com/discussion/r ... nodelay=1I

I also found this: http://www.andrew.cmu.edu/user/tmatteo/ ... val-11.pdf

Scroll down to the railway section. Here are some tractive effort figures that were given by this source (starting ratings assume 25% adhesion; continuous ratings are actual):

SD40-2: 105,000 lbs starting, 82,100 lbs continuous
GM6C: 91,000 lbs starting, 88,000 lbs continuous
GM10B: 97,000 lbs starting, 100,000 lbs continuous

By itself, the extremely high horsepower of the GM10B gives little advantage in terms of maximum starting and continuous tractive effort. Where the horsepower of the GM10B would play a role is in tractive effort at speed. The mere 47,000 lbs of tractive effort mentioned for the SD40-2 would probably be its rating at 22 mph, and would be due to its lower horsepower. It's at 10-11 mph that the SD40-2 will attain a continuous rating in excess of 80,000 lbs.

A more sophisticated wheelslip control system would explain why the theoretical starting tractive effort of the GM10B is less than the actual continuous tractive effort, because a modern AC locomotive with a good wheelslip control system can attain adhesion ratings of more than 25%--and 25% adhesion was used to create the starting tractive effort figures. This would mean that the GM10B's starting tractive effort is probably a good deal higher than 97,000 lbs. However, to approach 200,000 lbs, the GM10B would have to be a lot heavier--it is 15 tons lighter than a "heavyweight" SD40-2.

[timz]

In case nobody else mentioned it: The GM10C motors weren't AC motors like we think of them now-- i.e. they weren't induction motors. They ran on the 25-cycle AC transformed from the catenary, rather than variable-freq AC like AC engines now.

[Nasadowsk]

The AEm-7 used ASEA motors. It was a badge engineered RC-4 in a different body. EMD has little to do with it beyond inserting tab a into slot A and sticking the pan on top.

[USRailFan]

The AEm-7 used ASEA motors. It was a badge engineered RC-4 in a different body. EMD has little to do with it beyond inserting tab a into slot A and sticking the pan on top.

Actually they were built in Sweden with US pantographs I think

[byte]

Actually they were built in Sweden with US pantographs I think

Nope, assembly was done at EMD's LaGrange plant. It was essentially one of those deals where one manufacturer contracts out to the other. EMD has done this a lot in Australia.

[*istDS]

While the GM6C and motors were similar to contemporary (SD40-2) practice, the motors were not identical to those used in the same locomotive.

The DC produced by these locomotives is not as smooth as produced by an alternator/rectifier combo. Thus the design of the motors had to be tweaked to assure proper commutation.

[msernak]

Anyone know what happened to these two test motors? Were they scrapped? How about the E-44 that came back to life after CR pulled the plug on electric freight operations?

[byte]

They were scrapped when EMD realized there was no market for them, sometime around when Conrail pulled the plug on its electric operations.