The SP and the DRGW had problems with their engines overheating as they were pulling trains thru the tunnels. So EMD developed the tunnel motor, which instead of pulling air in at the top of the radiator and down thru the radiator, (this air that the engines pulled in was heated by engine exhaust and traped by the top of the tunnel, which led to the overheating problems). The tunnel motors instead pulled air for the radiator from down by the walkways which was a lot cooler. These engines are easy to spot because they have large see thru screens at the rear of the engine down near the walkway to draw air in for the radiators.

To add, they made SD40T-2's and SD45T-2's. DRGW, SP and SSW had the 40's. SP and SSW had the 45's.



DRGW SD40T-2



Jim Harrawood

Utah Rails

Thanks guys. Now I am one step further up on the learning curve.

PowerEngineer

id=quote>id=quote>
Not quite, standard EMD GP/SD pull air throught the grills one the sides, near the top, at the rear of the unit, and exhaust out the top. The fans are on top of the unit, pulling air through the radiator. Even EMD is not going to try to make hot air flow down in an open system. The tunnel motors have the inlet grills at the bottom - like GE U-boats - with fans pushing the air up through the radiators.

Nigel F. Misso

Incidentally, tho I'm NOT a GE afficiando or guru, but rather quite the opposite, I do know that GE's U and Dash series of loco's pull in the fresh air from the walkway level by standard design. EMD's pull it in near the roof, so they had to be redesigned and modified for the tunnel motor series. Basically ALL GE units are tunnel motors already! Interestingly, the EMD GP15 small road switcher is a tunnel motor too. I first saw one of these in Texas when I lived there back in 1985 and thought to myself HEY! there is a mini tunnel motor! Since this was a somewhat expensive option when it was first introduced, I always wondered why the GP15 was built this way. Perhaps one explanation is that EMD ran out of tunnel motor orders but still had parts laying around in the inventory, and so adapted them to fit the GP15 series when they were being built (or rebuilt). Anyone know for sure?

I'd also like to add that prior to the introduction of the tunnel motor, the Rio Grande had found a way to adapt some of their current EMD products, namely the GP30's (in the mid-1960's) to operate better in the "many tunnel" environment. They built a radiator spray system that would spray cold water in the radiators to help "cool" them during the operation in the tunnels when the loco was most likely to overheat due to pulling in hot roof tunnel air from the leading diesels exhaust. Apparently this modification made a significant improvement. The Rio Grande pooled power with the CB&Q between Chicago and Salt Lake City during 1965 and 1966. The pool did not last longer because the CB&Q GP30s and GP35s used as pool power were not modified to operate in the tunnel environment, thus they derated themselves when they got hot and lost power.

Not just the GP30's receieved the radiator spray system. The GP35's, GP40/-2's, SD45's all recieved them. Here's a photo of the water storage tank on GP40-2 3109. They were located in front of the rear sand box.


Attachment: drgw3109watertank.jpg 76.8 KB

Mike

http://trainweb.org/railblazer/

Mike,

Thanks for that info... I left out the GP35's so that is my mistake. The only mention specifically of the GP30's and GP35's was in my Rio Grande Color books and Rio Grande Trackside with Jim Ozment. The context was with respect to the D&RGW/CB&Q pool trains over the Front Range. I wondered if any other units received that modification, especially in light of the fact that I never observed the SD45s or GP40s give a preferred arrangement in the consists! You are the first person who has first hand experience with this as a Rio Grande employee who mentioned other models. thanks!

BTW, you didn't mention the GP40's, but I'll assume that they, as well as the GP40-2s received this. What about GP9s and SD9s?

Edited by - jimfitch on 09/11/2002 10:30:17

Jim,

Yes the GP40's did too. I don't know about GP/SD9's, but I really doubt it.

Mike

http://trainweb.org/railblazer/