BNSF SD40-2R ?

[roland1]

Hello ,

what is the reason for repowering  SD45-2's ( 7950 &7951 ) to SD40-2 standards ? My first thought was the fuel consumption or maintenance but then I found a pic of an SD45-2 ( 7952 ), fresh repainted without any signs of the repowering (rear fan position). May be lack of motors or parts ?

regards

Roland Marx

Germany 

[Awesome!]

Interested question!

[carnej1]

 I am not sure about BNSF but I remember reading in DIESEL ERA that Southern Pacific (who had one of the largest fleets of 20 cylinder EMD 6 axles) rebuilt SD45/45T-2's with 16 cylinder engines because of fuel economy issues. Although the resulting SD40M-2's still handled mainline assignments they were also used in secondary service and the extra 600hp was not useful enough to justify the higher expense of "care and feeding" of the bigger prime mover.....

[WCfan]

Actually to my knowledge the SD45 had a better fuel consumption to Horse Power ratio than a SD40-2. Meaning that the SD45 produced more HP per about of fuel compared to a SD40-2. But the SD45 had different problems too such as the very long crank shaft. But that's another thread.

I have no idea about the BNSF and doing that. I know I've seen a picture of a former ATSF SD45-2 in the new swoosh scheme that still had its original radiators.

[M636C]

The big problem with the 20-645E3 was the length of the crankshaft. This suffered from "torsional vibration", it twisted in operation. There was a special torsional damper added to reduce this but operators doubted its effectiveness and EMD were reluctant to provide details of its operation.

In 1977, I was shown over the EMD facility at La Grange and I noticed that about one third of the engines under repair then were 20 cylinder engines, a far greater number than would be justified by the proportion of 20 cylinder engines compared to 16 cylinder engines, for example.

So the big problem with the 20 cylinder was reliability, not fuel consumption. Of course, if the engines spent a long time idling,the four extra cylinders would use more fuel, but at full power the specific fuel consumption was better than a sixteen cylinder.

There is no reason for the radiators to be changed if a 20 cylinder engine is replaced by a 16 cylinder although in some cases this was done in order to fit reconditioned radiators that were available. Some SD45T-2 (or SD40T-2) locomotives were rebuilt with SD40 radiators which left a large space at the rear. The Tunnel Motor radiator arrangement resulted in erosion of the radiator cores and they needed replacement more often. Because of this, the T-2 radiators were often in poorer condition than standard radiators and would have been replaced when locomotives were rebuilt because it was cheaper to do so.

But if an SD45-2 had radiators in good condition when rebuilt with a 16 cylinder engine, there would be no reason to change them. In fact, the larger radiators might help by reducing the chances of overheating under heavy load.

It has been reported that the SD90 units with 4300 HP 16-710G3 engines were very reliable, partly due to the larger radiators fitted for the 6000 HP 265H engine. Larger radiators are often an advantage.

M636C

[oltmannd]

The original 20 cylinder engines weak "A" frames and would flex.  Added to the torsion, this would snap the cranks.  EMD strengthened the A frames a couple of years in and the crankshaft problem disappeared.  I can't recall Conrail losing a single crank on any of it's 13 SD45-2s.

The SD45s were originally built with 8 row soldered radiator cores, which where horrible.  The Dash 2s had 6 row cores, which were better, but by the early 1980s, mechanically bonded cores were available and this fixed the radiator leaking problem completely.  This is why the SD45 16 cyl retrofits didn't bother with reconfiguring the radiators.

The SD45s also had a field shunting in order to get the full 3600 HP to the rails at top speed.  Dropping down to 3000 HP allowed the field shunting to be removed.