viperman said:
I've seen a few of those BNSF's while at work, and have a (very bad) picture of one. Anyone have any info on these units?
The BN 70 Macs, you mean?
Well, they are historically significant because of several things...
- BN was the first railroad to receive the 70 Mac in 1992.
- The SD70MAC was the first production locomotive to use AC traction motor technology. EMD beat out GE by about a year in introducing AC traction-- GE came out with the AC4400CW a year later in 1993 if I remember right. AC traction has quite a few advantages such as higher tractive effort and easier maintenance since the motors don't have commutator brushes.
- The SD70MAC was the first production locomotive to use a truck with self-steering axles (the HTCR Phase I). The trucks no longer swivel at the bolster, but are fixed in place. Instead, the axles are actuated so they can turn a few degrees in place to keep the wheel flanges parallel to the rail on curves. This cuts down on rail and wheel wear significantly.
Personally, I think that original "executive" green-and-cream paint scheme looked real nice... Then the Bunsuf merger loomed and they started making green-and-cream warbonnets (bleh) and then pumpkins (bleh bleh).. At one point you got SD70MACs in consists with all three paint schemes, plus an odd one or two in straight classic BN black and cascade green (like the one Oldtanker caught on his railfanning trip). It was ridiculous!
