EMD SD70ACe series official thread (covers all variations)

[amtrakhogger]

You bring up a good question. The answer is, who knows? EMD is known for really arcane nomenclature. The biggest examples:

-What is the diff between "General Purpose" and "Special Duty"? Especially now that no "general purpose" units are built and everything is "special duty", which means it's the definition of "general purpose".

-What does the "70" mean in SD70? It's not the horsepower. Back in the 60's, GM's marketing machine decided to let the model number grow faster than the horsepower, but nobody was fooled. Railroads don't buy locomotives like suburbanites buy cars.

The list goes on and on, but I quit trying to make much sense of it long ago.

Supposedly, it started with the GP30. It was kind of a pr stunt against GE since the GP30 was only 2250hp and hence the "GP22" did not sound right when GE already had the U25B at 2500hp.

[amtrakhogger]

Article about SD70ACe-T4 including video.

http://www.railwayage.com/index.php/tra ... Itemid=502" onclick="window.open(this.href);return false;

BTW,does the prototype run? I am curious to hear what a 4 cycle EMD sounds like.

[JayBee]

http://www.railwayage.com/index.php/tra ... Itemid=502" onclick="window.open(this.href);return false;

BTW,does the prototype run? I am curious to hear what a 4 cycle EMD sounds like.[/quote]

It probably sounds a lot like these SD90MAC-H except it only has a 12-cyl engine;

https://youtu.be/NaFVippsy2g" onclick="window.open(this.href);return false;

[MEC407]

Sort of Alco-y. Not quite as throaty/barky as a GE.

[mp15ac]

You bring up a good question. The answer is, who knows? EMD is known for really arcane nomenclature. The biggest examples:

-What is the diff between "General Purpose" and "Special Duty"? Especially now that no "general purpose" units are built and everything is "special duty", which means it's the definition of "general purpose".

-What does the "70" mean in SD70? It's not the horsepower. Back in the 60's, GM's marketing machine decided to let the model number grow faster than the horsepower, but nobody was fooled. Railroads don't buy locomotives like suburbanites buy cars.

The list goes on and on, but I quit trying to make much sense of it long ago.

Supposedly, it started with the GP30. It was kind of a pr stunt against GE since the GP30 was only 2250hp and hence the "GP22" did not sound right when GE already had the U25B at 2500hp.

Actually, EMD's use of horsepower based number designations was very short lived. It started in the late 1950's with the SW600, SW800, SW1200, GP18, GP20, RS1325, and SD24. After that the GP's and SD's went to a non-horsepower number system. Only the SW's (SW1000, SW1001, SW1500, and SW1504), MP's (MP15DC, MP15AC,and MP15T), and the GP15 (GP15-1, GP15AC, and GP15T) families kept using horsepower based numbers.

Stuart

[es80ac]

I read other than the completely new engine and reduced emission there are several external changes on the SD70Ace-T4 vs the older SD70ACe

1. SD70Ace-T4 is 3 inches shorter height wise
2. The trucks are now a fabricated design.
3. Cab window went back to the tear drop shape of SD70MAC
4. The frame looks to me like less prominent than the SD70ACe frame, where the bottom frame plate does not seem as bulky as it used to be.

Other than the cab window for improved visibility, anyone know the reasons behind the other 3 changes? Why did Cat intentionally lower the height, did SD70ACe has had any clearance problems?

thanks

[Pj]

No height issue. My guess (only a guess) is that the height with the new engine did not nessesaite the extra sheet metal.

Control stand and layout appears to be the same as the rest of the ACe's, but the conductors desk got a little rework. I personally like the tear drop windows on the older cabs as you just are able to "See" a little more. Does it really make a difference? Not where I work, but I like big windows in general.

If anything, at crew change locations if multiple trains are being swapped out (all three of mine are on four track locations) its nice to see that everyone made it across and you are not going to run anyone over.

The cabs are now frame mounted again which is nice. The last run of isolated cabs were pretty quiet but all had the "bounce" issue. I didn't mind it, but many do. But, you can actually talk in a normal voice across the cab's as they are/were really quiet. The isolated cab was under a little microscope where the cab detached in certain collisions (notably the BNSF rearender a couple of years ago)

They also got rid of the dumb latches for the access panels that never stayed closed as the round ones vibrated loose and caused many miles of duct tape to be used.

[MEC407]

SD70ACe-T4 demos on UP:

http://www.railpictures.net/viewphoto.php?id=568782" onclick="window.open(this.href);return false;

[Fan Railer]

I'm surprised no one else has found this yet; not ideal, but it's something:
http://www.youtube.com/watch?v=c3cnvK-yfiw" onclick="window.open(this.href);return false;

[MEC407]

Two more SD70ACe-T4 demos; these ones are in UP colors:

http://www.rrpicturearchives.net/showPi ... id=4480160" onclick="window.open(this.href);return false;

http://www.rrpicturearchives.net/showPi ... id=4480159" onclick="window.open(this.href);return false;

[MEC407]

Photos by RailfanTerry:

http://www.railpictures.net/photo/580666/" onclick="window.open(this.href);return false;

http://www.railpictures.net/photo/580665/" onclick="window.open(this.href);return false;


Photo by Charles Buccola:

http://www.railpictures.net/photo/580650/" onclick="window.open(this.href);return false;

[MEC407]

Not sure if this has been covered already but I just came across this photo of a B-B version of the SD70ACe, which also has some pretty substantial modifications to the cab and carbody.

Photo by Rodrigo Matheus:

http://www.railpictures.net/photo/583114/" onclick="window.open(this.href);return false;

[Allen Hazen]

Now that's downright weird! My impression was that AC locomotives were heavier than their predecessors (at least by the weight of extra electrical gear, and the structure needed to accommodate it), so that a BB version of a SD-70assortedsubscripts or ES44 was almost ruled out by weight considerations! And now we see one on 39 3/8 inch gauge!
Thoughts--
---Brazilian railroads aren't limited by U.S. "Tier 4" air pollution requirements. So they can have locomotives with much simpler radiator (etc) arrangements… which probably allow for a shorter and so lighter-weight carbody.
---American locomotives have far heavier frames than are needed for purely structural reasons: essentially they are ballasted. An export EMD model like the (sorry to cite something so old, but I don't have stats for more recent types) like the GT26C were C-C units with the same 'innards" as an SD-40, but could, by use of lighter underframes, smaller fuel tanks, etc, come in at closer to the weight of a GP-40, so just maybe…
---The cab has obviously been redesigned to fit into a smaller loading gauge: this is a modern, heavy-duty, railroad, but it was built to narrow-gauge standards and is probably still limited by it.
---Ain't it a pity we don't have a photo from an angle which shows the trucks better? (Though it certainly does look as if they are two-axle.)
---
We probably won't see a domestic analogue: railroad managements are intensely conservative, and won't like a new idea even if it makes sense! (I think the choice of "SD70something" as the model designation for the new EMDs is a response to this: with an all-new engine, the technical difference between model and earlier SD70whatnots is surely greater than that between earlier models that got distinguished by name, but marketing obviously thought it would reassure the customer to pretend it was a mere tweak to the earlier design!) But surely there are some applications -- maybe short/medium distance intermodal, with frequent short trains to compete with the truckers -- where a "GP70AC" (or an "ET44B") would make sense!

[chrisf]

Now that's downright weird! My impression was that AC locomotives were heavier than their predecessors (at least by the weight of extra electrical gear, and the structure needed to accommodate it), so that a BB version of a SD-70assortedsubscripts or ES44 was almost ruled out by weight considerations! And now we see one on 39 3/8 inch gauge!

These are 8-axle units with two B trucks under each end. http://www.railroadforums.com/photos/sh ... bb/cat/589" onclick="window.open(this.href);return false;
shows it quite clearly.

[MEC407]

Now that's downright weird! My impression was that AC locomotives were heavier than their predecessors (at least by the weight of extra electrical gear, and the structure needed to accommodate it), so that a BB version of a SD-70assortedsubscripts or ES44 was almost ruled out by weight considerations!

Don't forget the GE ES43BBi — that's AC, too.