Spotting features for modern locomotives?

[n2mopac]

I posted this question on the Trains forum yesterday, but haven't gotten any response yet. I need some clarification on distinguishing betewen cerain modern locomotives. I know how to tell the difference between AC and DC units, and of course how to tell EMD and GE units apart. But what physical difference distinguishes an SD70MAC from an SD90MAC. I know some of these EMD AC units have flared radiators and some do not. Which ones do and which ones do not? Also, is there a distinguishing difference between GE's AC4400CW and AC6000CW? Finally, when did these units first appear in revenue service (SD70, SD70MAC, SD90MAC, AC4400CW, AC6000CW)? Finally, is there a DC version of the SD90? Thanks for your help.

Ron

[Anonymous]

QUOTE: Originally posted by n2mopac
But what physical difference distinguishes an SD70MAC from an SD90MAC.

SD70MAC's are smaller.

QUOTE: I know some of these EMD AC units have flared radiators and some do not. Which ones do and which ones do not?

SD70ACe's, SD70M-2's, SD80MAC's, SD90MAC's, SD90MAC-H's, and later model (2002-2004) SD70M's and SD70MAC's.

QUOTE: Also, is there a distinguishing difference between GE's AC4400CW and AC6000CW?

The radiators on the AC6000 are larger

QUOTE: Finally, when did these units first appear in revenue service (SD70, SD70MAC, SD90MAC, AC4400CW, AC6000CW)?

I'm not 100% sure, but I'd say 1994, 1994, 1996, 1994, and 1997.

QUOTE: Finally, is there a DC version of the SD90?

Nope.

QUOTE: Thanks for your help.

No problem! [:)]

[n2mopac]

Thanks for the good info. Two quick follow up questions. How much smaller is the SD70MAC than the SD90MAC? How can I tell the difference on a moving train? Second question for clarification, so some SD70MAC's and others listed have flared radiators and some do not? Is this correct? I thought this was the case, but I was uncertain. Thanks again.

Ron

[Anonymous]

Well, SD80MACs and SD90MACs (both the same length and essentialy the same externally) are 82 and 1/2 feet long, making them the largest operating diesels in America (UP's DDA40X doesn't count). So, I'd say the SD70/SD75/SD70MAC would be around 70 feet long.