UNION PACIFIC EMD SD70MDC.

[Overmod]

I have it direct from David Goode that the reason NS hasn't bought AC power is because of the investment in DC motors, infrastructure, etc. (it also helps that they have their own, very good, motor shop).

He also mentioned they were keeping an open mind toward future purchase of AC, particularly if the economics (primarily price) improved.

Very little question in my mind that NS shop forces could work effectively on all AC drive components, even after GE's service/maintenance guarantees expired...

[Anonymous]

Mabe because the NS doesn't know how to them the right way.
BNSFrailfan.

[Anonymous]

NS uses SD40-2's on the Strawberry Ridge coal trains and mostly C40-9W's on the other trains, I've heard that NS tested AC verses DC and found that, of all things, the AC's were in the shop more than DC's!!!

[Mookie]

QUOTE: Originally posted by BNSF SD70MAC

Oh boy this is starting to sound better and better day by day! If the power shortage is that bad why don't they start using EMD GP38-2's on coal trains?
BNSFrailfan.[:D]

They have all ours tied up running freight around. But I will start keeping a list of the comings and goings. Will report back in a few weeks if I start to see a pattern....or even if I don't.

Mook

[Anonymous]

Oh boy this is starting to sound better and better day by day! If the power shortage is that bad why don't they start using EMD GP38-2's on coal trains?
BNSFrailfan.[:D]

[Mookie]

QUOTE: Originally posted by BNSF SD70MAC

I have noticed that more lately mookie,It's realy kind of strange that the BNSF is using C44-9W's on coal trains. What has happend to all the SD70MAC's?
BNSFrailfan.

They all seem to be in Joe's backyard. He sees a lot of them. There is a big change in the power line-up even from just a year ago. Then it was mostly 70's. Now it is a mixture. And while I still see some SD40's and 45's on freight - they are now putting some 9's on the head end. Will have to start keeping track!

Mook

[Anonymous]

I have noticed that more lately mookie,It's realy kind of strange that the BNSF is using C44-9W's on coal trains. What has happend to all the SD70MAC's?
BNSFrailfan.

[Mookie]

QUOTE: Originally posted by CoBo

Interesting conversation.

But what about digital power it seams to combine AC & DC in the model train world. Has this being tried in the real world to?
So if AC is stronger and DC is.... lets say faster? or something like that, couldn't be a digital loco have both characters?
Or do I just talk noses!? (Always was good on that though, lol)

Krgds
Cor

BNSF runs a lot of coal trains thru here - with SD70MAC's, the newer GE AC and just plain old Dash 9's, in any combination. Doesn't seem to make a big difference.

Mookie

[Anonymous]

Interesting conversation.

But what about digital power it seams to combine AC & DC in the model train world. Has this being tried in the real world to?
So if AC is stronger and DC is.... lets say faster? or something like that, couldn't be a digital loco have both characters?
Or do I just talk noses!? (Always was good on that though, lol)

Krgds
Cor

[broncoman]

So does anyone in the operation departments know if a SD70mac spends less time in the shop for other than normal service work than does a SD70m(dc). Isn't this also something that would help in the price difference, if a loco is not out of service? Less miles/day=less revenue.

[Big_Boy_4005]

So what everyone seems to be saying is that the AC motored engines are more of a specialty locomotive, purchased for a particular hauling task. DC power is still the norm for general use. Right????

[Anonymous]

QUOTE: Originally posted by BNSF SD70MAC

If AC is not as good as DC then why did the BNSF buy so many SD70Mac's?
Why couldn't thay have just got the SD70M's instead?
I mean the locomotive is the still the same thing but only the big differnce is the traction motors right?
BNSFrailfan.

BNSF runs many coal trains, so there is a need for AC's. And many of those 70MAC's came from BN, which also ran a lot of coal trains. SD70MAC's can replace SD40-2's on almost a 1-1.5 basis, meaning 3 70MAC's can replace 5 SD40-2's.

SD70MAC's produce more tractive effort than SD70M's, about 28,000 lbs. more, making them much more sutable for low-speed heavy hual service. Also AC traction motors can't burn out like DC can. If a DC powered unit stalls on a grade or goes below the minimum speed (usually about 8 Mph) for too long, chances are the traction motors are going to get fried. AC, on the other hand, can go down to as low as 1 Mph and still pull without risking traction motor damage.

[Anonymous]

If AC is not as good as DC then why did the BNSF buy so many SD70Mac's?
Why couldn't thay have just got the SD70M's instead?
I mean the locomotive is the still the same thing but only the big differnce is the traction motors right?
BNSFrailfan.

[Anonymous]

QUOTE: Originally posted by Paul Milenkovic

AC vs DC Diesels:

....
The interesting thing about the SD70M(DC) is that UP wanted to replace their large fleet of SD40s in kind instead committing to the novel AC technology. While the SD70M has all of the limitations and maintenance requirements of the DC traction motor, it is a known quantity while the AC locomotive might have some not-yet-known problems.

The main problem against a AC locomotive: Costs !!!!
A new AC locomotive will cost something between 500.000 and 1 Million $ more than the same engine in DC. (AC4400CW against Dash9-44 CW). An d this is real money!!!

When a RR need engines for fast intermodalservice a "simple" DC is a very good option against an AC!

So the RR´s buy not longer universal engines like the SD40-2, they order exact that engine what they need.

UP for example buyed a large fleet of SD70M for intermodals, manifests and such trains.
For the heavy coal trains they ordered a large fleet of AC4400CW and some SD90MAC and AC6000CW.

BNSF does the same with Dash9-44CW and SD70MAC (since 2003 also AC4400)

[Paul Milenkovic]

AC vs DC Diesels:

Almost all Diesel locomotives in the U.S. have electric drive, where the prime mover drives a generator, which in turn supplies electric current to traction motors, which turn the wheels. Many Diesels in Europe use hydro-kinetic transmissions, similar in operation to the automatic transmission in an automobile. There have been attempts to use hydro-kinetic drive by importing locomotives from Europe (the K-M locos on the Rio Grande and SP), but these applications don't seem to have been successful. My guess is the electric drive is more rugged, especially for the heavier trains in the U.S., and U.S. maintenance crews are unfamiliar with the requirements of the European locomotives.

One feature of many "hydraulic" (hydro-kinetic drive) locomotives is that the wheels powered by a particular Diesel engine through a set of Cardan shafts (similar to the CV joints in a front-drive auto) that all turn at the same speed. This gave the hydraulic loco a pulling power advantage over a Diesel electric which is only as good as its slipperiest wheel. On the other hand, U.S. railroad shops complained that the wheel diameters must match to better than a mm or you are going to tear up those Cardan shafts. How these same shops dealt with steam locos with coupled drivers is now a mystery.

Now the "traditional" Diesel (think F-7) had a DC generator and DC traction motors. DC machines require carbon commutator brushes, which are a maintenance item and a road breakdown item. Also, DC traction motors are limited in the current they can draw (i.e. lugging power) before they burn up. You have minimum speeds and short time ratings and all kinds of games to play to see if you can make a hill.

Second generation Diesels (think SD-40: OK, some people consider them "third" generation, but you know what I mean) had an AC "alternator" in place of a generator, and used silicon rectifiers to turn the AC into DC for the traction motors. The alternator is very much how alternators replaced generators in cars, although your car starter motor is very much a DC machine with brushes and a short-term rating and thermal limits and all of that.

What is currently called an AC loco is quite revolutionary in that it uses AC traction motors -- actually 3-phase "squirrel cage" induction motors. Further advances in high current semiconductors allow building electronic circuits that can feed these induction motors with 3-phase AC of a frequency that is matched electronically to the rotation speed of the motors. Besides getting rid of those pesky carbon brushes, the induction motor is only fed current into the stator (non-rotating winding) while the rotor is simply a solid piece of iron with copper shorting bars (the squirrel cage).

Because of this rugged design, the AC motor cannot easily "bird's nest" (if you run a DC traction motor too fast, all of the rotor wires fly apart and create a ruined motor that looks like a bird's nest). DC passenger locomotives have to be geared for a higher running speed, which means they give up low-lugging power and have higher minimum speeds.

What U.S. railroads seem to be using AC locos for is not running fast but running very slow. With the removal of short-time ratings and minimum speeds, trains can be even more underpowered and creep up hills at even slower speed backing up traffic even more and turning the railroad network into knots.

The other interesting thing about AC locos is that GEs have an inverter circuit for each wheel while EMD seems to economize on one inverter circuit per truck. Having one inverter per truck means all of the wheels have to be the same size once again, and we are back to the days of the steam locomotive. How EMD sold the railroads on that one when the railroads didn't like the Diesel hydraulics for the same reason is another mystery.

The interesting thing about the SD70M(DC) is that UP wanted to replace their large fleet of SD40s in kind instead committing to the novel AC technology. While the SD70M has all of the limitations and maintenance requirements of the DC traction motor, it is a known quantity while the AC locomotive might have some not-yet-known problems.

[Anonymous]

Thanks I like that.......I got a good laugh from that.
BNSFrailfan.

[Anonymous]

QUOTE: Originally posted by BNSF SD70MAC

I call them SD70MDC's because that's what thay are,Thay have DC traction motors insted of AC. I just don't understand why thay don't them that. Thay call an SD70MAC an SD70MAC, and yet thay don't call an SD70M an SD70MDC same as an SD70MAC. You where im coming from?
BNSFrailfan.

LOL, always thought AC/DC was a pop music group.

Sorry guys, [:D]
I know I have bad humor, [:D][}:)] I am just a simple model railroader from Europe.
But, I’ll just wonder........

In modern model railways, we have Digital power to feed our (model) trains.
In Europe we have Marklin and a few who are AC powered en well.... the rest is DC power.
Due the come of digital power it possible to use components of both systems because we have digital systems which we call Multi-protocol. (E.g. the Intelibox from Ulhenbrock)
Of course not the loc's since DC track hasn’t the power pick-up in the middle of the track.
but more like decoders and ocupation devises and such.

But how is this in real life locomotives?
Is it by the big example still an issue whether a locomotive is AC or DC?
Or would they be able to solve it like we modelrailroaders do it with digital power or something like that?

Just curious, that’s all
Thanks for you’re reply in advance.
Krgds
Cor

[Anonymous]

[(-D]!
BNSFrailfan.

[Mookie]

QUOTE: Originally posted by dougal

All Dash 7, 8, and 9 series loco's are DC, the only AC Locos are the SD60MAC, SD70MAC, SD70ACe, SD80MAC, SD90MAC, SD9043MAC, AC4400CW, AC6000CW, and AC60/44CW.

Well, I got that part right at least!

Mook

[Anonymous]

All Dash 7, 8, and 9 series loco's are DC, the only AC Locos are the SD60MAC, SD70MAC, SD70ACe, SD80MAC, SD90MAC, SD9043MAC, AC4400CW, AC6000CW, and AC60/44CW.

[Mookie]

Can someone clear up a somewhat confused Mookie? Aren't the Dash 8's and 9's DC?

They run those on the front end of the coal trains. Or am I really confused? And are you just talking UP power, of which I am really unfamilar!

Help!

Mookie

[Anonymous]

When I was at kennard yesterday yes thay were EMD SD70M's:Back to Back pulling an empty MAXX coal train...........Yes! They were Not EMD SD90MAC's.Flags,Yes!
BNSFrailfan.

[Anonymous]

QUOTE: Originally posted by BNSF SD70MAC

I have a Question for you railfans.
Their are times on the UP that I have seen a pair of UP EMD SD70MDC's on empty coal trains like the one I saw at Kennerd,ne today.
I didn't jot down the numbers because to me It's just not me, but anyway,I realy love It when I see a set a back to back EMD's leading the point of an empty UP coal train. I just wi***hat I could catch a pair of SD70MDC's on a loaded coal train............NOW THAT WOULD MAKE MY DAY!
Have any of you railfans seen a set of SD70MDC's on coal trains?
Another Question Id like to ask is,do you like the standard or the Flaired radiators on the SD70MDC? Or do you just like both type's?
I love seeing BIG EMD's on coal trains.
BNSFrailfan.

Are you sure you didn't mistake them for SD90MAC's? Did the units have flags on the long hood? DC units are pretty rare on UP coal trains these days.

[Anonymous]

UP doesnt own any AC EMD's except for the big ol SD90MAC. they would be hard to mistake for a SD70M

but, i have never seen a SD70M on a coal train before. i guess their power shortage must be getting bad to make them put DC locos on coal trains.

[jeffhergert]

Originally posted by eolafan

We see SD70M units on UP pulling loaded coal trains all the time through Rochelle, IL and the old CNW western suburbs. Nothing new there.

Are you sure you aren't seeing the UP's AC EMDs on those coal trains? I won't say they never use the SD-70m on loaded coal trains, but it would be rare. I have seen them on empty hopper trains occasionally, usually one of a kind symbols, not the normal every day hopper symbols.

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