EMD GP-15

[Anonymous]

The GP-15 units have that tunnel motor style air intake along the walkway.
Anybody know why EMD did that for these units?

Thx -
- - Stack

[M636C]

EMD do things for pretty logical reasons. I think the GP15 grew out of the MP15AC, which also had the tunnel motor fan arrangement. I think it was used in the MP15AC because it provided a lower profile hood without fans on top to reduce visibility.

The MP15 DC retained the vertical end radiator and mechanical drive fan because it saved money, and you didn't have to fit a "Companion Alternator" (a D14 or similar) that produces the alternating current to run the radiator fans in GP and SD units. The AC fans and alternator increase the purchase price but lower the through life operating cost because they just sit there an run when the thermostat asks them to, wheras the mechanical fan has driveshfts and bearings that need attention and can fail in the rough life a switcher gets. So when they built the MP15AC, initially for SP who probably spent more on the headlights anyway, they went for lower operating costs.

EMD are really keen on using standard parts, and a lot of medium size export units had the tunnel motor arrangement because it allowed the unit to fit in tight, narrow gauge clearances. These standard parts were available for the MP15AC, and later the GP15-1. The export units were often also 1500 HP, model G22 and G22C (the latter with six axles for light track, as in New Zealand). So EMD designers had the standard parts, and just fitted them into the MP15AC and GP15-1 because they were the simplest option.

One other fact is that the tunnel motor arrangement is slightly more efficient. In the tunnel motors, the air is blown through the radiators, while in standard EMD units it is sucked through by fans above two radiators set in a vee arrangement.

If you look at an SD40-T2, you will see that there are two hatch panels to give access to the two fans blowing through the radiators, and three hatches on the SD45-T2 which has three fans. In the standard SD40-2, three fans are used above the radiators. So on an SD40, you save the cost of one fan by using the tunnel motor layout.

In Queensland GL22C units, which have conventional fans above the radiator, you need one 48" fan and one 36" fan to cool a 12-645E. Now it often gets hot in the tropics, but the GP15 can run with one 48" fan under the radiators, so by using the "Tunnel Motor" arrangement, EMD saved one 36" fan on every MP15AC and GP15-1 or even MP15T and GP15T they built.

Sounds pretty smart to me - what I don't know is why they didn't build more SD40-T2s!

Peter

[dwil89]

I thought I read somewhere that GP15-1's used components or frames from trade-in fodder..older Geeps..etc....kinda like the CF-7 program...All I know, is they are a nice sounding engine...that nice growl to it..Dave Williams http://groups.yahoo.com/group/nsaltoonajohnstown

[M636C]

Mark,

I hadn't thought of the additional erosion! That makes more sense now! In the case of export units, there wasn't really much choice in most cases in order to fit the tight clearances. Clyde must have realised that the erosion is a major factor. They have managed to squeeze hood top fans and vee type radiators into everything except the Queensland GT42CU-AC units which are jam packed with equipment, but need a lower height than the Western Australian JT42Cs, which as DC units get conventional radiators and a second cab on the same weight as the Queensland units.

To enter the GE vs EMD argument, you don't have to worry about erosion on the GE units, they won't last long enough to need a replacement radiator. In fact, the big fans on the GE might be able to run more slowly for the same throughput, and this might reduce the erosion significantly.

As an aside, the second hand SD40s bought for BHP Billiton have all been rebuilt from the SP configuration with low profile fans so they can squeeze through the old Oroville Dam dumper. We are anxiously awaiting an indication of what the twelve SD70ACe units will look like - the cab and radiators might look quite different to fit a dumper designed for nothing bigger than the original U25Cs. There are two other dumpers with better clearance, but BHPB believe in Murphy's law. Their AC 6000s have cab sides angled in at window level, and I think they have even bigger radiators than the US versions.

Peter

[M636C]

Mark,

It wasn't just the Dumper! They left us with 150 gondolas as well, most of which are still in service in 2004! That makes them 40 years old I think! One train is mostly made up of Oroville Dam cars, and they haven't been repainted. In the right light you can see the different shade of silver where the "ODCX" and the car number used to be. The black paint itself has long since flaked off, but the slight difference in fading is still visible!

As a person whose grandfather emigrated from Scotland, I hate throwing anything away, and I'm reasonably happy that these cars are still around. They don't cost much to maintain, and the steel bodies have lasted better than some later local cars! A difference between Cor-Ten and our Aus-Ten in formulation, I guess.

Peter

[Anonymous]

Thanks for the data guys - much appreciated
- - Stack