What is the reasoning behind the different styles of d/b brake blisters on EMD units? For example, early SD/GP40's had a d/b profile that was similar to to that of the older 35 series, but later units, they changed to a profile that was eventually carried over to the dash2 line. And then on the GP40-2, only the left side was lengthened while the right side reverted to earlier (short) blister. By the time the GP50 came around, the blister was the inverse of that of the GP40-2 (which by this time had undergone some changes itself). What is the rhyme or reason for this?
EMD evolved the dynamic brakes . The locomotives with early extended range had a small hatch in the blister for the grid shorting contactors. The contactors in my opinion were junk , they had way too many moving parts and weren't big enough. EMD identified this and in later locomotives used a bigger more robust contactor which of course meant that the box in the hatch had to be bigger.
There were some locomotives that had higher capacity dynamics that needed even bigger grid shorting comtactors so of course the grid hatch changed appearance. In later EMDs they got away from the small individual grids arranged along the side of the locomotive (4 grids for a 4 axle and 6 grids for a 6 axle ) and went with a big round grid bank that took up much less space , and provided more room for extended range equipment.
I remember that on the SD45 there really wasnt a terminal board for the cabling going to the grids , the cables were spliced and insulated with rubber boots. On later engines they actually installed insulated standoffs for the cable connections and extended the grid hatch on one side to make room for the cables (like the GP-40-2), a big improvement in my book.
Randy
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