Okay, a lot of us have our favorites and manufacturer biases, but let me rephrase this in a more practical manner:
If you were a Class 2 railroad, and had X millions of dollars to spend to purchase a fleet of 50 brand new locomotives of the same model from a manufacturer, and had to choose between the SD70ACe and a GEVO (any of the AC models), which one would you purchase, and why?
If the railroad would operate in a very hot climate, I'd go for the SD70ACe every time.
In the Pilbara area of Western Australia one railroad uses stock standard SD70ACe units while the other uses ES44DCi units which are ES44DC units built on an AC6000 frame with larger AC6000 radiators with twin radiator fans.
Building units on a special frame must cost much more, and they wouldn't do that unless the ES44 wouldn't work properly in the high temperatures.
I've spoken to EMD engineers about this but because it is a specialised market they don't seem to know much about this. A third railroad in the area has gone directly for the SD70ACe.
Interestingly, the Dash9-44CW didn't have as serious a problem with heat and ran with just larger air intakes.
If you plan to keep the units for a long time, EMD locomotives (particularly the engines) tend to last longer (definitely longer than the FDL, nobody knows about the GEVO yet).
M636C
M636C If the railroad would operate in a very hot climate, I'd go for the SD70ACe every time. In the Pilbara area of Western Australia one railroad uses stock standard SD70ACe units while the other uses ES44DCi units which are ES44DC units built on an AC6000 frame with larger AC6000 radiators with twin radiator fans. Building units on a special frame must cost much more, and they wouldn't do that unless the ES44 wouldn't work properly in the high temperatures. I've spoken to EMD engineers about this but because it is a specialised market they don't seem to know much about this. A third railroad in the area has gone directly for the SD70ACe. Interestingly, the Dash9-44CW didn't have as serious a problem with heat and ran with just larger air intakes. If you plan to keep the units for a long time, EMD locomotives (particularly the engines) tend to last longer (definitely longer than the FDL, nobody knows about the GEVO yet). M636C
Price is always a large consideration for any major purchase such as 50 new locomotives. GE leasing has been a factor in the price war and will probably continue to be since they did not pay any Federal income tax this past year. They have a better idea!
CZ
Well, look at the "less than Class 1s" that have bought. It seems pretty split in the Americas between MRL's ACes and Iowa Interstate's GEVOs.
Although EMD has come a long way, they have a longer way to go to catch GE. The SD70ACe is a good machine (especially with the isolated cab), but the newer units have been experiencing problems with 1) software; 2) piston rings; and, 3) electrical components. Meanwhile, the GEVOs keep thumping along with only minor gaffes (some fuel injector issues and problems with some turbochargers attributable to a supplier). It seems their 6% better fuel economy is settling the debate, especially in view of the 40 percent rise in fuel costs over the last year. The 70 ACe's engine had finally caught (and maybe even slightly surpassed) the FDL in fuel consumption, but the GEVO has ended the argument and the SD70 cannot close this wide a gap. At least 2 railroads have thrown in the towel on the 70 ACe based on fuel economy alone. P.S. I am an engineer and prefer EMD products, but reality is reality.
Another difference which I believe CPR found significant is the control system for the AC traction motors. The GEs have an inverter for each traction motor while the GMs had one for each truck. Should a problem occur with a traction motor, and say you have two units, with GEs you have lost about 8% of hauling capacity and the train likely can keep moving. With GMs you have lost 25% of hauling capacity and may have to reduce tonnage or perhaps stall on the next upgrade.
While in CP's case the GMs are the older SD9043 model I believe the system remains the same. CPR uses only GEs west of Calgary through the mountains.
John
If the Class 2 railroad needed new AC units to handle unit bulk commodity trains I would go with the ES44AC and finance them on a 15 year lease. The reason being as an engineer who runs both models on a regular basis I can tell the ES44AC model is one of the most powerful locomotives I have ever run. The dynamic brakes on these units are so strong one would think you were applying the independent brake when you go into dynamic. And unlike Dash 8 and Dash 9 units they load faster in power. The UP C45ACCTE and BNSF ES44AC units are absolutely the best locomotives General Electric has ever produced.
On the other hand, if the Class 2 railroad needed new units for general freight service I would purchase the SD70M-2 or perhaps a fleet of older SD60s and have them rebuilt with new 16 cylinder 710 ECO engines to save money. Here the tables are turned in that I have noticed the SD70M-2 outperforms the ES44DC hands down both in power and dynamic brake. Also, if history remains the same look at any Class 1 roster and notice GE units built prior to 1990 are few and far between, whereas one can still see EMD products going back to the 1960s. That fact alone speaks volumes!
TBG
One of the reasons that old EMD locomotives seem to last longer than any others comes down to parts availability. GE has never been that anxious to manufacture or license parts for their older locomotives, while EMD has done so with only a few exceptions. As an example, the mass retirement of remaining SW1's in the early 1980's came about because EMD announced that it would no longer manufacture replacement parts unique to the 567 V-6 engine.
In recent times there have been two disastrous wrecks that I know of involving SD70ACe's, one even with a pipe breaching the cab and entering the crew area. Are EMD cabs inherently more dangerous now than GE cabs, or are they the same?
----------------------------------------------------------------------------------------------------------------------------------- K.P.’s absolute “theorem” from early, early childhood that he has seen over and over and over again: Those that CAUSE a problem in the first place will act the most violently if questioned or exposed.
They meet the same standards. The BNSF wreck in southern Iowa, the flatcar came in through the windows, not much can be done short of doing away with windows and going to gun slits or cameras.
If I needed 50 Units for Genreal Purpose hauling instead of getting 50 SD70M-2's I would get 50 GE44AC4's instead. Why get the Power of AC tractionb but only have 4 traction motors to maintain. Yet they will out pull any 6 Motor DC loco out there at lugging speed. No Short time rating to worry about less moving parts and they have been proven Big Time on the BNSF. No RR orders close to 300 total unless they are very happy with them. Also they are as cheap as the DC motor version of the GEVO so you get that advantage.
edbenton . No RR orders close to 300 total unless they are very happy with them. Also they are as cheap as the DC motor version of the GEVO so you get that advantage.
. No RR orders close to 300 total unless they are very happy with them. Also they are as cheap as the DC motor version of the GEVO so you get that advantage.
Is it true that the C4s can easily converted to 6 axel AC motored units?. Wonder what the cost would be if so ?
I'd assume that it's simply a matter of swapping out trucks and traction motors (and inverters maybe) and reprogramming the computer.
Not sure on the Follow up orders but the First 25 were setup so that very quickly they could be converted with the addition of 2 Traction motors 2 invertors and removal of the Center axle lifing and some minor Reprogamming of the Computers. The Followups I think have the Extra Invertor Spots removed and no extra TM cables installed unlike the first 25 ordered.
Alternating Current Generators are called Alternators and they do use them. Have since the GP38AC (etc) They generate AC which is rectified to DC then inverted back to AC.
I believe that the two-step method (AC to DC to AC) is required since modern AC control systems use variable-frequency AC to control motor speed. Any corrections would be appreciated.
Variable frequency AC can be converted from fixed frequency AC by cycloconverters, but the device count with that approach would be higher than the AC to DC to AC approach. The one advantage of cycloconverters was that the AC source would provide for commutation of the active devices (thyratrons and thyristors). Modern power devices, e.g. GTO thyristors, IGBT's and SiC FET's can turn off (commutate) by themselves, and thus a rectifier followed by an inverter is the preferred method.
And yes, modern AC traction motors do require a source of polyphase variable frequency variable voltage AC.
- Erik
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