Old 08-02-2006, 10:47 PM   #1
tomcatchamp
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Question Union Pacific SD90MAC-H II

I'm just curious, does anyone have an idea why the Union Pacific gave up on the SD90MAC-H II locomotives ? I've seen several of them in the photo section that are being used by the KCS with the UP markings lined through or removed.

The same can be said for the GE AC6000's. Did the whole idea of attaining 6000 hp in a locomotive and maintaining it prove to be too much of an undertaking ?

I know that the Canadian Pacific has a large number of these SD90MAC-H II in service, just wondering why no American ClassI railroads are using them.

Thanks in advance for the responses.

Joe
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Old 08-02-2006, 11:04 PM   #2
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I'm just curious, does anyone have an idea why the Union Pacific gave up on the SD90MAC-H II locomotives ? I've seen several of them in the photo section that are being used by the KCS with the UP markings lined through or removed.

The same can be said for the GE AC6000's. Did the whole idea of attaining 6000 hp in a locomotive and maintaining it prove to be too much of an undertaking ?

I know that the Canadian Pacific has a large number of these SD90MAC-H II in service, just wondering why no American ClassI railroads are using them.
One word: Reliability. The 265H block had a lot problems. I'm sure someone else can go into detail. You'll still see the 9043MACs out because those have the 710G block, which is standard on the SD70M.

I believe another problem they faced with 6000 HP locomotives was poor adhesion. The last thing you need when pulling a heavy train is wheelslip. I'm not sure if this was caused by a primitive wheelslip control system or the locomotive weight.
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Old 08-03-2006, 05:05 AM   #3
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CP has 4 of those big lemons in service now. There original order was for 20 but reduced to 4. Caleb nailed it on the head with the 265H prime mover, reliablity is a key issue why these big beasts aren't trusted alone on a train.

Quote:
Originally Posted by cmherndon
I believe another problem they faced with 6000 HP locomotives was poor adhesion. The last thing you need when pulling a heavy train is wheelslip. I'm not sure if this was caused by a primitive wheelslip control system or the locomotive weight.
The adhesion, wheelslip control system nor locomotive weight have nothing to do with the way a 6,000 HP locomotive is operated as those things still grip the rails just like the GEVO and ACe do.
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Old 08-04-2006, 07:42 AM   #4
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Quote:
Originally Posted by tomcatchamp
I'm just curious, does anyone have an idea why the Union Pacific gave up on the SD90MAC-H II locomotives ? I've seen several of them in the photo section that are being used by the KCS with the UP markings lined through or removed.

The same can be said for the GE AC6000's. Did the whole idea of attaining 6000 hp in a locomotive and maintaining it prove to be too much of an undertaking ?

I know that the Canadian Pacific has a large number of these SD90MAC-H II in service, just wondering why no American ClassI railroads are using them.

Thanks in advance for the responses.

Joe
there were reliability issues with the SD90MAC-H and due to the fact that they were on a 5 year lease to the UP (lease terms were changed due to the long delay in delivery of the units) they chose to purge the units once the lease expired. Most if not all of the problems with the 265H prime mover itself have been solved, but electrical gremlins have plagued these units. The SD90MAC-H (along with the AC6000CW) was rushed into production far too early as it hadn't been fully developed yet and the units suffered many problems as a result.
Besides reliability issues, the 6000hp units have turned out to be less versatile than lower HP units. In most cases 2 6000hp units are too much power for a train, but one unit is not enough. Then there is the situation where you have a train with a pair of 6000hp units and one of them dies, resulting in the train being underpowered and possibly tying up the whole railroad depending on the particular railroad line and tonnage.
As for adhesion, the 6000hp units tend to be slippery too due to the 1000hp per axle rating of the units. Originally the railroads have pictured these units as being great luggers hauling heavy trains and thats just not the case. These units are best suited to high speed service. In heavy haul service the extra horsepower just increases the train speed, not the amount of tonnage that can be hauled.

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Old 08-05-2006, 02:35 AM   #5
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Quote:
Originally Posted by trainmaster_1
The adhesion, wheelslip control system nor locomotive weight have nothing to do with the way a 6,000 HP locomotive is operated as those things still grip the rails just like the GEVO and ACe do.
Then why does my rear wheel drive truck slide around on snow and ice when the bed is empty, but has better grip (adhesion) when the bed is weighted down under similar conditions?
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Old 08-09-2006, 12:18 AM   #6
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Quote:
Originally Posted by Ru1056
Then why does my rear wheel drive truck slide around on snow and ice when the bed is empty, but has better grip (adhesion) when the bed is weighted down under similar conditions?
I suspect your truck and your right foot are no match for the wheel slip controls used by modern locomotives.
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