I've always been curious, why did EMD put the Tunnel style radiator on the GP15-1/AC/Ts?
If the SD40T-2/SD45T-2 is any indication, this type of system uses up more space on the frame than the standard setup would have.
What was the reasoning?
YoHo1975 I've always been curious, why did EMD put the Tunnel style radiator on the GP15-1/AC/Ts? If the SD40T-2/SD45T-2 is any indication, this type of system uses up more space on the frame than the standard setup would have. What was the reasoning?
To use standard parts with the MP15AC, especially the radiator. In turn the MP15AC switched from the MP15DC's vertical mounted radiator with belt driven cooling fan, as this was a higher maintenance arrangement. As it is the GP15 series was lengthened from the MP length frame so that a larger fuel tank could be offered.
Well, that makes sense.
So then the next question is why does the MP15AC use the Tunnel style as opposed to electric fans up top?
Was there a perceived need for drawing in cooler air somehow?
YoHo1975 Well, that makes sense. So then the next question is why does the MP15AC use the Tunnel style as opposed to electric fans up top? Was there a perceived need for drawing in cooler air somehow?
Because all EMD switchers had that radiator arrangement from the very beginning... Most of these were cooled by a vertical fan in the hood end, but the MP15AC used an electric fan in the Tunnel Motor arrangement.
But that is just pushing the question further into the past. In the switcher, visibility is important and the radiators just below the hood top improve visibility compared to the fans on the hood top. The radiators under the fans were almost always in a vee which would raise the hood level compared to the flat (or very shallow vee) switcher arrangement. There are a number of switchers rebuilt with geep radiators in fitted in an ugly hump...
EMD use the "tunnel motor" arrangement in many export units where height is critical, so I think there is a gain if a reduced height is desired.
M636C
EMD cooling systems are designed to drain the radiators when the engine is shut down to prevent water remaining in them and freezing in cold climates. To drain, they need to be above the top deck of the engine and the water tank. So M636C is correct that to maintain a low hood height, the radiators need to be at the top of the hood as is typical on EMD exports. A cold side fan arrangement also has the advantage of the fan pumping ambient air rather than hot air off the radiators. As EMD fans are fixed speed in relation to the engine rpm (2X max), a cold side fan pumps a higher mass of air than a hot side fan, everything else being equal. This is why an SD40T-2 gets by with 2 fans while the same radiators in an SD40-2 require 3 fans. For the MP/GP15 it is likely a hot side fan arrangement would have required 2 fans so it was cheaper to use the cold side fan arrangement.
Belt drive fan on a SW1500:
GP15-1
MP15AC
Can see the fan at the top of the screening.
The MP15Acs are a pain to walk around the front end of, though. Too bad there couldn't be more room to allow for a full-width walkway near the step area. Cans are cramped as well. Electrical cabinet right in the middle, maybe a foot on each end to walk around, bar stool seating position. If some GP15ACs became available, those might be nice. The GP15-1 shown had a DC main gen, too much maintenance.
Mike WSOR engineer | HO scale since 1988 | Visit our club www.WCGandyDancers.com
Thanks for the explination guys.
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