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HiJust two quick questions.1) I know, what a SD45 is. Okay, I don't really know, but I know, how it looks like. But what is an SD45X?Could somebody please point out, what the difference between these two locos is and perhaps also compare it to an SD40-2?2)What exactly is the purpose of the DD - type engines? I thought, UP prefered smaller units because of scalability of power (just enough power for each train). Thank you very much for your info. I just can't learn enough about US railways! Cheers!SebastianFeel free to IM me on: sstyrnol@hotmail.com My email is: sebastian.styrnol@gmx.de
xxxxxxxxxxxxxxxxxxxxxxxxxxx I eat trolls for breakfast! xxxxxxxxxxxxxxxxxxxxxxxxxxx
1) The SD45X was a 20 cylinder locomotive like the SD45 but had 4,200 HP but the same traction motors as an SD45. The SD45X had a few of the electrical goodies of the Dash 2 series, and served as a test bed for these components. Since the SD45X had the same traction motors as a SD45 (or a 16 cylinder SD40), it's continuous tractive effort (pull above about 12mph) was limited by that and no better than an SD40 until speeds of 35+ mph. These would have been interesting on SP intermodals, but not very cost effective elsewhere, as they used more fuel, had slightly hgher costs to maintain, and thus were not built in quantity. The SD45-2 replaced the SD45X and had the reduced 3,600 HP prime mover, along with better still electronic components. 2) The DDA40X was built to combine two slightly hotrod GP40 on one frame. On high speed freight, TOFC and reefers, the DDA40X could replace two GP40s. It could not however replace two GP40s on a heavy train like a mostly grain freight (grain trains rarely ran as pure consists in those days), as its weight was less than two GP40s and therefore it had less ability to start a heavy train. UP liked the double diesels, because they could get the high horsepower needed for fast trains (UP had a lot of high speed track), and provided a weight saving over two units, which meant that the total consist weight was less to lift over the mountains, therefore more efficient, if the weight was not needed to start the train. Hope this helps, Bob
An external difference between the SD45 and SD45X is that the SD45X had 4 radiator fans instead of the SD45 (and all other SD40, 50 and 60 series) 3 fans.
Also, most cooling radiators are symetrical or the same size on the same side. The SD45X had 2 different size radiators on the engineers side and 2 of the same size on the firemans. There were only 6 or 7 made, all of them but #5740 went to Southern Pacfic and it is rummored that 5740 was rebuilt into a sd40-2.
