Covers on EMD radiator fans?

Question

What are the covers over the front raditator fans on EMD's for? Also, what are the roof extensions on some old ATSF emd' and CN diesels

Answer 1

The forward fans are not part of the cooling system.  They are cooling fans located above the dynamic brake grids, which create the bulge, just as Alco pointed out.  But these were not restricted to the SD30s.  They were present on the venerable old SD45's (and 45Xs) as well.

When in dynamic brake, the traction motors are essentially turned into generators.  This produces retarding effort.  The electricity they produce is dissipated as heat, through the DB grids, much like a giant toaster.  The cooling fans are run by the same electricity produced, keeping the grids from melting.  That is why, when an engineer changes the level of retarding effort, the pitch of the characteristic DB "whine" changes, as current rises and falls.

The extensions at the rear of the 45s over the catwalk are housing for the cooling shutters, and an oversize, heavy duty radiator.  These shutters open and close as cooling demands change, automatically.  They are present even on models where they are flush with the body.  But, there is a little trick to use.  When working in grade territory, or extremely hot days, you could open them manually with the shutter test valve, and make sure they stay open, thus helping to avoid a hot engine shut down.  Of course they are completely absent on the T-2s, as the cooling system is much different, designed for tunnel operations.

All covers are for maintenance access.

Good question.  Thanks for asking.

Answer 2

Peter,

The roof extension you're speaking of I am guessing refers to a GP30, which housed the unit's dynamic brakes.  This bulge uniquely identifies GP30s from any other model.  Without seeing a picture I'm not sure what covers you are referring to although a general guess would be that they are in place to keep out dust, dirt, and anything else that might inhibit the radiator fans.