Ever Again

[Kris94]

Will there ever be another DC Traction locomotive built? No ES44DC or SD70M-2 locomotives haven't been ordered or built since 2009. Anyone know or have any insight? ES44DC and the SD70M-2 are still in production.

 

[SlackAction]

On the class 1s, it's about moving as much freight with as little power as possible. DC units are easier to burn up, so it may be beneficial for many roads to exclusively order AC power.

 

[opus722]

There is also a lot of rebuilding going on for older DC units to extend their longevity rather than buying a new one.

 

[JohnnyC1]

Trains magazine has several articles concerning AC vs DC traction motors. AC traction is more expensive than DC, and they are used in the higher horsepower locos. Lower HP locos, Gensets, and rebuilds are almost exclusively DC. Also DC traction is still being used, exported outside the US.

John

 

[pdkoester]

My guess would be since AC power can handle more power, that is where the demand is, so that's why you probably wouldn't see new DC units. Like it was mentioned, DC units are rebuilt, too. But those aren't new orders, so there you have it.

 

[Kris94]

So then how did railroads manage to move trains that demanded a lot of horsepower before the emergence of the AC Traction Motor Unit? I.E. coal trains, iron ore trains, etc. NS and CSX are the only railroads that use DC traction motor units on their coal trains. NS has 17 SD80MACs after the June 1, 1999 split, 166 ES44AC units, and 65 SD70ACe locos. Canadian National is still a pure DC Traction motor railroad, and someone on here said they saw four SD40-2 diesels on a CSX coal train.

 

[cascaderailroad]

They hooked on more locomotives ... or cut a train into sections ... perhaps the added the asset "AI Brake" which adds braking power, and horsepower ... IDK ... Maybe they got out and pushed ?

They were hauling long trains way before the diesel locomotive came into being ... how do you "think" they manage it before high tech AC units came into being ?

 

[SlackAction]

So then how did railroads manage to move trains that demanded a lot of horsepower before the emergence of the AC Traction Motor Unit? I.E. coal trains, iron ore trains, etc. NS and CSX are the only railroads that use DC traction motor units on their coal trains. NS has 17 SD80MACs after the June 1, 1999 split, 166 ES44AC units, and 65 SD70ACe locos. Canadian National is still a pure DC Traction motor railroad, and someone on here said they saw four SD40-2 diesels on a CSX coal train.

DC units can still do the job, but AC is more efficient. Simply put, DC motors aren't really designed to be under extremely heavy load at low speeds for extended periods of time.

Also, CN has 30 or so AC EVO units, with more on the way.

 

[opus722]

So then how did railroads manage to move trains that demanded a lot of horsepower before the emergence of the AC Traction Motor Unit? I.E. coal trains, iron ore trains, etc. NS and CSX are the only railroads that use DC traction motor units on their coal trains. NS has 17 SD80MACs after the June 1, 1999 split, 166 ES44AC units, and 65 SD70ACe locos. Canadian National is still a pure DC Traction motor railroad, and someone on here said they saw four SD40-2 diesels on a CSX coal train.

The engineer usually called his buddy and told him to bring his truck and tow bar to pull the train the rest of the way up.

Really though, as others said, it's not that DC units can't pull heavy loads it's just that AC is better at doing it. 2 or 3 ES44ACs instead of a string of SD40s on the front and another group pushing up the back doesn't look as nice from a railfan view, but they get the job done with less fuel and less of a chance for a mechanical error.

 

[JohnnyC1]

I got this from another source:

Maintenance, the additional DC-AC turn would be more parts with more things that could go wrong, shutting down a locomotive. I know you wish to ignore cost, but upfront cost is a good heck of a lot more for AC than DC. Considering some railroads cheaped out on buying isolated cabs for crews, the much bigger cost of AC when it is unneeded would definitely be avoided.

Also, on CSX there is a powered axle rule. No train, except for the Pope Creek coal trains in Maryland and the Q090-Q091 produce express train I believe, may have more than 24 powered axles. A DC unit is counted straight up (i.e a six-axle ES44DC is six axles), but an AC locomotive is counted at 1.5 axles per physical axle (a six-axle SD70ACe counts as 9 axles). This limits CSX to having at most two AC locomotives running on power on one train (9+9=18, which is good, but 9+9+9=27, not good). A DC locomotive may be added with the two AC locomotives (i.e. an ES44DC-AC4400CW-AC4400CW [6+9+9=24, good], which I mention because I have physically seen it). However this wastes the advantage of the AC motors, as the DC motor cannot operate at the low speed of the AC motors without burning up, so this would be used mostly on faster trains such as intermodals and auto racks, which wastes the slow speed capability of the AC motors. The best thing for the railroad is to buy AC for slower coal trains and things like that, and use the cheaper DC where the AC does not have advantages, such as over-the-road intermodals.

John

 

[opus722]

Also note that hi-adhesion locomotives, like the SD70M-2 and ES44DC, have a 1 1/3 powered axle equivalent when it comes to calculating that stuff. So Dash 9s, that are commonly used on the NS and CN for slow and heavy trains, are better than an SD40-2 without requiring the same capital investment that an AC unit would. Now it seems that railroads are leaning towards making that initial investment to save money in the long run.

 

[pdkoester]

The DD35 and DD40 unit used by UP were DC motors, right? Look at how HUGE the locomotive had to be to utilize that many motors. The modern equipment now a days uses two less axles. Does that equate to having about the same horsepower per axle, on the AC motored units? Going basically 6000 HP divided by 8 axles is 750 HP, 4500 HP divided by 6 axles is 750 HP. Does that sound right?


Paul

 

[Kris94]

Now I get it. I was getting the vibe that DC units were vastly inferior in all aspects compared to the AC Traction Motor.

 

[JCitron]

Here's another forum thread on the same subject over at Train-sim.com

http://www.trainsim.com/vbts/showth...motors-that-much-more-powerful-than-dc-motors

John