compare SD70 to SD75

[Anonymous]

What are the major differences between the SD70 and the SD75 ? On the BNSF we have SD70 macs which I know are AC traction. We also have SD75M's and SD75 I's which has an isolated cab, which by the way are virtually silent inside ! I would like to know the differences between the SD60, SD70, and the SD75.

[Anonymous]

HMMMMMMM, You say "WE" like you're a BNSF employee but wouldn't someone who worked for the RR know the answers to these questions? At least an employee in train service would...........

[Anonymous]

Yes I am A conductor for the BNSF and no I don't know every difference between every locomotive made. The fact of the matter is the majority of engineers know very little about the history and differences between models. To most of us it is merely A job and not A hobby. When an engineer gets called for A train he is usually only interested in the HPT, number and type of dynamic brakes, TOB, and length, and not whether it's an EMD or GE.

[Jackflash]

I agree, where I work we have engineers with
20 plus years service and they dont know (and
dont care) the differnce between one model and
another, and dont want to talk about it either.
jackflash

[oltmannd]

In terms of train performance, there are two basic dimensions to be concerned about. They are tractive effort and horsepower. Tractive effort determines the max tonnage a loco can move up the ruling grade and HP determines the speed at which it can move the train.

For the 3 models you're asking about, the SD60 is a 3800 HP model with about 100,000# TE, the SD70MAC is 4000 HP with about 140,000# TE (the AC traction motors allow better adhesion than the DC) and the SD75 is 4300 HP with about 100,000# TE (or maybe a bit more, depending on loco weight).

For the same train on the same route, the SD75 would give the fastest running time, followed by the SD70MAC, then the SD60. The difference would be some what less than proportional to the HP difference, though, and fuel consumption would be highest for SD75 powered train, followed by the others, somewhat greater than proportional to the HP difference.

However, for a given ruling grade, the SD70MAC can take ~40% more tonnage without stalling because of it's AC traction motors. So, for the same route, if you run a train that has the max tonnage the locomotive handle w/o stalling, the SD70MAC will have the lowest HP/trailing ton ratio and will take the longest to get over the road. This is why the AC power rules the day in high tonnage, low schedule requirment service and the high HP DC locos are found on the time frts and intermodal trains.

[Anonymous]

I do not work for the railroad. (I just like watching trains, I couldn't tell which model or make a locomotive is.) From your explaination it sounds like A.C. is the way to go to provide the best all around fit. Are all railroad companies going to A.C. locomotives?
TIM A

[wabash1]

Jonathan as a engineer i can tell you what engines i am getting after looking at the engine numbers if i dont recognize a number i look it up. with that said i couldnt tell you what the differance between a sd 40 sd 45 or a sd 60 sd 60abcdefg and so on. it dont matter a sd 60 is 3800 hp and a sd 70 is a 4000 hp unit and are rated the same tonnage on my terrain. other than that it dont matter to me what the differance is or do i care. and most guys i work with are the same way. all we want is enough power to pull the train and hold track speed with no break downs.

[Jackflash]

No not at this time, they cost more, and some
companys management dont see the benefit.

[Anonymous]

Plus, with greater emphasis on time sensitive intermodal & guaranteed service, the drag freight is not the gorwth segment. So ironically the older tech DC traction is the growth locomotive section. Who would have guessed this, back in the 90s fanfare of "AC 6000 HP future for all!"

[edblysard]

Sound like its the way to go, but..
like Donald said, the hp to trailing ton rating for AC is less, add in the hight cost of AC locos, the fact that you have to have dual shop forces and parts, and the supposed "cost savings" of AC start to dissappear. Yes, AC traction motors have less moving parts, and in theory should require less mantainance, but when they do fail, and they will, they cost more to repair. Ever wonder why Santa Fe had 4 axle EMD GP50 and 60s on their intermodel trains, both DC traction? Remember, Santa Fe did intermodel right, they bet a lot of the farm on it. Turns out the needed less of the DC traction engines to haul the same size trains than AC could handle. Why Buy a engine model that requires three locos to do the work one and a half of another model can, at less cost in fuel, parts? They didnt need any of the benefits AC had to offer,nor any of the really high horsepower engines, because the trains wernt going to stop for anything but crew changes, and once they got going again, the crew were going to run them as fast as the dispatcher would let them. At 70 mph+, it make no real diffrence if you riding on AC, DC,six or four axles, the only diffrence is the number of engines you needed to get the train up to 70 and keep it there. DC was cheaper, did the job at less cost with less locomotives .
Ed