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Old 11-09-2009, 01:13 PM   #6
espeekiwi
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Join Date: Nov 2009
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i was of the understanding that sd45m's were all rebuilds of wrecked/damaged/rebuilt/ sd40's 42's -2's 45's.

the T designation was specificaly southern pacific's own idea taken to GM EMD
and were rolled off the assembly line as such with the modifications to the cooling systems , lower geared truck motors and what we would usually call here in NZ traction Control and multi unit control system..

all for the purpose of mountain railroading.

this is where the long nose and short nose was differentiated as the long nose T's was where all the electronics for the remote slave controls were installed so a swing in helper could be operated from the lead locomotive on the front of the train. aslong as there was one long nose sd40-2t or 45-2t in the lead of the swingin helper consist all others would do what the -2t did and the -2t did what the lead locomotive did.

the later sd40's were built on sd45 frames so were the SDP's as the larger fuel tank was then split in two for carrying water.

also built on sd45 frames were the tunnel motor's

the reason for this was a fopar on GM's part and also a cost saving and face saving operation.

the sd45 proved to have a weak/poorly designed engine so the SP for example opted to purchase the sd40-2's on 45 frames which meant two things.

GM could still sell out the 45' just with out the new prime mover and it also meant that the railroad companies now had a locomotive with a longer range as the sd45 frame could support a larger fuel tank. and B: the option was there to upgrade to the 45 prime mover once the gremlins in the motor were fixed.

this is why all the -2's that were rebuilt were called SD45M's because the were originally meant to be 45's.

Last edited by espeekiwi; 11-09-2009 at 01:21 PM.
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