gp50t

[BaltACD]

SD70Dude

6 axle units not only produce far more tractive effort at lower speeds, they also provide much more dynamic braking effort at all speeds. 

A lot of carriers didn't see any benefits to Dynamic Braking and did not order it to be installed on their locomotive purchases.

Brakes? They only slow you down.[/sarcasm]

[SD70Dude]

BaltACD

SD70Dude

6 axle units not only produce far more tractive effort at lower speeds, they also provide much more dynamic braking effort at all speeds. 

A lot of carriers didn't see any benefits to Dynamic Braking and did not order it to be installed on their locomotive purchases.

Brakes? They only slow you down.[/sarcasm]

But Rio Grande was not one of them.  Didn't they buy PA's instead of E's in large part due to their DB capability?

CN actually disabled the DB on some early units that had been delivered with it, and kept ordering road power without DB until it became a standard feature on new units during the 1980s.  

MoPac, Rock Island, Northwestern and Illinois Central were other notable anti-DB holdouts.  

[Leo_Ames]

My impression is that the Rio Grande didn't run drag freights as often as say the Southern Pacific did. So they seemed willing to forgo the benefits of C-C power like increased low speed tractive effort for much of their traffic, remaining a 4 motor GP advocate right until the end.  

One thing to keep in mind with this time, is the rise of the micoprocessor and other advanced onboard electronics and the many promises the builders made based on the benefits they offered. EMD for instance advertised a 33% increase in "hauling capability" for 50 series locomotives compared to their Dash 2 predecessors.

If you read literature from the time for things like EMD's Super Series wheel slip control and such, it helps shed some light on what the Rio Grande's line of thinking may have been with their interest in an advanced high horsepower B-B with a cooling system tailored for hard running in tunnels.

[YoHo1975]

Rio grande also had (and the route still has) the problem that their route is less desirable than the Transcon to the north. A drag freight is going to prefer going through the Wasatch. Rio Grande wanted to take advantage of their "potentially" faster route. Especially prior to the MP being pulled up.

[CSSHEGEWISCH]

SD70Dude

MoPac, Rock Island, Northwestern and Illinois Central were other notable anti-DB holdouts.  

 

Note that all of these roads were generally level with few to no heavy grades.  The practice of using D/B to control speed on level track had not yet been developed.  As an aside, C&NW was noted for its SD45's without d/b.