30 or so years ago SP and DRW ordered tunnel motor locomotives to deal with locomotives stalling in tunnels due to insufficient air. None of the modern locomotives are tunnel motors..has the problem been solved some other way?..have the offending tunnels been daylighted?... why no more need for tunnel motors?
Basicly the 40 series cooling capacity wasn't sufficient. The Tunnel motors were a "band-aid" fix for that model.
That's a good way of putting it, Chad.
Cooling capacity (heat rejection rate) was increased on subsequent models -- thicker radiator cores with higher surface areas and better heat transmission rates, higher-volume water pumps, higher-capacity cooling fans.
RWM
Which is not to suggest that diesels no longer overheat in tunnels.
I wonder who now has the worst tunnel in that respect-- Cascade is an obvious candidate, as is SP's tunnel at the top of Donner Pass, but in both of them the grade in the tunnel is maybe 25% less than the steepest grade the train encounters on that subdivision, so trains will not ordinarily enter them at a desperately low speed. Does any RR have, say, a mile-long tunnel on a ruling grade? And are freights thru that tunnel often loaded heavily enough that many of them enter the tunnel at, say, 10-12 mph?
(N&W's Elkhorn tunnel is likewise not as steep as its approach grade, and it's double track-- wonder how much difference that makes.)
How about Mt MacDonald? Is it 1% in the tunnel as well as outside? What's a typical coal train speed thru there?
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