In the run-up to the GE U50 and Alco C855 is that in 1962, UP had laid out its own idea for a 5000 hp, twin-engined locomotive. A drawing of this is shown at Don Strack’s “Utah Rails” site, at: https://donstrack.smugmug.com/UtahRails ... -T95bPCR/A.
This proposal was shown as using trucks and span bolsters from the GTEL4500 fleet, for which the 5000 hp diesel-electric was to be a replacement. Span bolster centres were the same as for the GTEL4500, and as subsequently used for the U50.
One could infer that the UP found the span bolster running gear to be quite satisfactory, and was happy to perpetuate it. As well, it did have some prior experience with span bolsters. This was on the power cars – locomotives really – for its Streamliners M-10002 (1200 + 900 hp) and M-10003 to M-10006 (2 x 1200 hp). Although not articulated to their respective trains, these power cars were themselves of the articulated body type. But instead of a conventional truck under the body articulation, they had a span bolster that in turn was mounted on a pair of trucks. Thus each power car had four trucks, rather than the three that might be expected for an articulated-body vehicle. Evidently these power cars were satisfactory at very high speeds from the tracking and riding perspectives.
In the case of the GE U50 and Alco C855, UP had to order three prototypes from each builder in order to persuade them to build the desired locomotives, so presumably was able to “dictate terms” as to the running gear. Also presumably GE had no objection to this. Probably neither did Alco, as it had been co-owner, as it were , of the GTEL4500 prototype. On the other hand, EMD elected to build a 15 000 hp prototype combination (GP35+DD35+DD35+GP35) on its own account, so got its own choice of running gear, namely D-D.
There was something of a minor postscript to the UP span bolster story. The trade journal “Railway Locomotives and Cars”, 1968 December issue carried a brief item about UP’s initial order (25 units) for the EMD 6600 hp “Centennial” units. A comment made therein was: “The new locomotives could be carried on Electro-Motive's four-axle trucks which were used on the 5000-hp models or might be mounted on a span-bolster running gear which was utilized by Alco and GE on their 1963 models.”
Mention of the span bolster option could well have been wishful thinking on UP’s part, as it I doubt that it would have been countenanced by EMD at the time.
Cheers,
This proposal was shown as using trucks and span bolsters from the GTEL4500 fleet, for which the 5000 hp diesel-electric was to be a replacement. Span bolster centres were the same as for the GTEL4500, and as subsequently used for the U50.
One could infer that the UP found the span bolster running gear to be quite satisfactory, and was happy to perpetuate it. As well, it did have some prior experience with span bolsters. This was on the power cars – locomotives really – for its Streamliners M-10002 (1200 + 900 hp) and M-10003 to M-10006 (2 x 1200 hp). Although not articulated to their respective trains, these power cars were themselves of the articulated body type. But instead of a conventional truck under the body articulation, they had a span bolster that in turn was mounted on a pair of trucks. Thus each power car had four trucks, rather than the three that might be expected for an articulated-body vehicle. Evidently these power cars were satisfactory at very high speeds from the tracking and riding perspectives.
In the case of the GE U50 and Alco C855, UP had to order three prototypes from each builder in order to persuade them to build the desired locomotives, so presumably was able to “dictate terms” as to the running gear. Also presumably GE had no objection to this. Probably neither did Alco, as it had been co-owner, as it were , of the GTEL4500 prototype. On the other hand, EMD elected to build a 15 000 hp prototype combination (GP35+DD35+DD35+GP35) on its own account, so got its own choice of running gear, namely D-D.
There was something of a minor postscript to the UP span bolster story. The trade journal “Railway Locomotives and Cars”, 1968 December issue carried a brief item about UP’s initial order (25 units) for the EMD 6600 hp “Centennial” units. A comment made therein was: “The new locomotives could be carried on Electro-Motive's four-axle trucks which were used on the 5000-hp models or might be mounted on a span-bolster running gear which was utilized by Alco and GE on their 1963 models.”
Mention of the span bolster option could well have been wishful thinking on UP’s part, as it I doubt that it would have been countenanced by EMD at the time.
Cheers,
