Another Page of the Lancaster and Atlantic Rail Road

From what I can gather, there are at least 5 distinct classifications.

Ok the last two are refinements of the third…

 1. 193x to 1945: classed about the same as steam engines. EMD SW1 3908 built 1937 original class AA5

            Sort of like a class A5 steamer was a 0-4-0 so an SW1 with two trucks of two driving wheels each (0-4+4-0) became an AA type engine.

 

2. 1945 to 1947 AAR type designation

            So our SW1 now becomes a (B-B)6E – two b trucks 600 horsepower EMD builder.

 

So guess what a (2D+D2+2D+D2)60B was?

You guessed it a Baldwin BP60

And the + (as per then AAR rules) is correct between the units as they where semi-permanently coupled together.

 

3. 1947 to 1952

A letter designation for the builder

A letter designation for the horsepower nearest 100s

A sub letter may be used to denote a different model number from the same builder –

 A Baldwin VO660 is PRR class BS6 while a Baldwin DS-4-4-660 is a class BS6a

Our SW1 is now an ES6 number 5911

 

4. 1952 (the first year an updated 109-J since 1948) to 1962(?) unit identification consolidation and corrections

Basically the same as the 3^rd generation, but now showing sub lettering - includes steam and multi unit capabilities.

A Baldwin DS-4-4-750 that had multi unit controls added is now a BS7m

Our SW1 is still an ES6

 

5. 1962-1967 preparation for PC

Mostly renumbering of units and such

Addition of the RS (Road Switcher) classification;

An Alco RSD15 class AS24m becomes an ARS24

The Baldwin BS12ams becomes a BRS12s

How about an ERS15ax – Madison Hill SD7s

Our intrepid SW1 now approaching 30 years old gets it third and final PRR number 8511