I need some help with a SD70MAC

[TheDerailedtrain]

In the SD70MAC model locomotive, What does the whole thing mean... like what does" SD" stad for aswell as "MAC"

                                                                 -Adam

[Railway Man]

SD indicates six-axle, all powered (the letters now refer to nothing, but originally, in 1949, it stood for "Special Duty" type as opposed to the GP type, where GP stood for "General Purpose."  SD stuck as the EMD designation for six-motor but few people at railroads today recall where it originated).

70 is the design series.  EMD began using this series nomenclature with the 20 series in 1959, and subsequently has used 30, 35, 40, 50, and 60 series for major design changes, as well as 80 and 90, both of which were more powerful than the 70 series but were not successful in the market and were essentially withdrawn except by special order.

M indicates the cab type.  It means "modified."  The standard cab, which has walkways on either side of the nose, was modified circa 1980, initially in Canada, to provide greater safety and comfort, with a full width nose and the front entrance through the nose.  Today the M cab is the defacto standard and the old type is nearly extinct, but the M lives on.

AC indicates Alternating Current transmission, as opposed to Direct Current.  An SD70M would be the D.C. version of the same locomotive. 

RWM 

[sfrailfan]

SD means Special Duty, 70 because theres been other SDs before (SD 7, 9, 20, 35, 40 ect.) M- mean? ok I forget what M stands for -someone will hit that.... and AC means AC power vs. DC power, which was new with this diesel.

 

Dan