SD/GP40 and DDA40X Prime Movers

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SD/GP40 and DDA40X Prime Movers
Posted by VGN Jess on Tuesday, December 17, 2019 3:03 PM

Can anyone speculate (or perhaps know) why the DDA40X "645" 3,300 HP prime mover was not used in the SD/GP40's (we all know that a "645" 3,000 prime mover was and has always been used for those locomotives)? Also, was the 3,300 HP engine ever used in anything other than the DDA40X?

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Posted by caldreamer on Tuesday, December 17, 2019 3:27 PM

Just researched your question.  The only other locomotive to use the 16-645E3A prime mover was the RENFE class 333 locomotives.

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Posted by Erik_Mag on Tuesday, December 17, 2019 6:27 PM

The SD/GP50's used the final tweak to the 645 with 3,500HP to the traction alternator. Reliability wasn't that great as the extra power required 950rpm from the 645 in run 8.

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Posted by VGN Jess on Friday, December 20, 2019 4:39 AM

Thanx for the info.  Any idea (if the 3,300HP engine ran well in the DDA40x) why EMD might have tweaked it to 3,500 (ie..not just left it at 3,300HP)?

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Posted by VGN Jess on Friday, December 20, 2019 4:40 AM

Thanx. So EMD never used it in anything but the DDA40X?

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Posted by VGN Jess on Friday, December 20, 2019 4:44 AM

So, no one knows or can guess why the 3,300 HP "645" was not used in the SD/GP40's?  Why put a 3,000HP engine in when you have a 3,300 HP engine? That's my real question, just phrased another way. I thought someone out there might have read something somewhere or heard something abot why.

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Posted by CSSHEGEWISCH on Friday, December 20, 2019 7:06 AM

As implied in other posts, the extra horsepower comes at a cost in the strain on various engine components.  Earlier, EMD hit a similar maximum at 2500 HP in the 567 engine, and the 645 was developed to address that issue.

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Posted by Leo_Ames on Friday, December 20, 2019 12:58 PM

Since I'm unaware of significant engine issues with the Centennial's higher rating, one possibility is they thought it would be too slippery on a Geep. There's significantly more weight on each axle than your average GP40/GP40-2.

Doesn't explain though why it wasn't tried as a lower cost alternative to the SD45 and SD45-2. 

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Posted by Overmod on Friday, December 20, 2019 3:57 PM

I think the 645E3A as put in the SD45X had very similar 'horsepower density' to the 3300hp version on a per-cylinder basis.  If there were an engine-related problem other than one associated with longer crank, greater torsional stress, etc. the history of those locomotives might serve as a guide.

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Posted by VGN Jess on Friday, December 20, 2019 11:44 PM

Thanx to all who replied.

LEO: "Doesn't explain though why it wasn't tried as a lower cost alternative to the SD45 and SD45-2.:--exactly my point. Unless I hear further I'm going to presume no one has any idea. It just didn't make sense to me.

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Posted by oltmannd on Saturday, December 21, 2019 8:47 AM

VGN Jess

So, no one knows or can guess why the 3,300 HP "645" was not used in the SD/GP40's?  Why put a 3,000HP engine in when you have a 3,300 HP engine? That's my real question, just phrased another way. I thought someone out there might have read something somewhere or heard something abot why.

 

I think the real question is why UP and/or EMD wanted 6600 HP from the DD40AX and not 6000.  

The "X" in the model usually indicated "experimental" and these were generally used to "try out" new things.  I'd hazard a guess EMD want to see if they could push another 10% from a 16-645E3 engine and UP agreed to go along for the ride.

Why didn't other roads want the extra 10% HP?  Most likely because it didn't come with another 10% of tractive effort at minimum continuous speed.

The 3500/3600 HP SD50s had a large dose of extra tractive effort available at MCS due do upgraded traction motor windings and Super Series wheelslip control.

 

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Posted by Backshop on Saturday, December 21, 2019 8:55 AM

It would also put the SD40 too close in the catalog to the SD45.  Why have two products competing against each other.  Also, that would have put a huge gap between the 38 and 40 series.  Notice that neither the U33C or U36C sold that well.  If they had dropped one of the models, the production would have been better.

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Posted by oltmannd on Saturday, December 21, 2019 10:01 AM

Backshop

It would also put the SD40 too close in the catalog to the SD45.  Why have two products competing against each other.  Also, that would have put a huge gap between the 38 and 40 series.  Notice that neither the U33C or U36C sold that well.  If they had dropped one of the models, the production would have been better.

 

The U33C and U36C weren't really different locomotives.  GE just evolved their 6 axle product.  The U36C replaced the U33C in the catalog.  If you wanted lower HP from your U36C, it was pretty simple to arrange.  GE used a constant HP excitation scheme - it was just a blue-faced card change.

 

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Posted by oltmannd on Saturday, December 21, 2019 10:06 AM

VGN Jess

Thanx to all who replied.

LEO: "Doesn't explain though why it wasn't tried as a lower cost alternative to the SD45 and SD45-2.:--exactly my point. Unless I hear further I'm going to presume no one has any idea. It just didn't make sense to me.

 

The SD45 was pretty much a dead model when the DD40AXs came around.  ATSF, EL and Clinchfield took a few SD45-2s - and they were pretty decent - but the SD40 pretty much ruled the roost.  It had the right mix of HP and TE.  It could handle the same tonnage as an SD45, just a bit slower over the road (with less fuel), did not need field shunting, and the early problems with the 20-645E3 engine left a bad taste in CMOs mouthes.

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Posted by Backshop on Saturday, December 21, 2019 12:09 PM

oltmannd

 

 
Backshop

It would also put the SD40 too close in the catalog to the SD45.  Why have two products competing against each other.  Also, that would have put a huge gap between the 38 and 40 series.  Notice that neither the U33C or U36C sold that well.  If they had dropped one of the models, the production would have been better.

 

 

 

The U33C and U36C weren't really different locomotives.  GE just evolved their 6 axle product.  The U36C replaced the U33C in the catalog.  If you wanted lower HP from your U36C, it was pretty simple to arrange.  GE used a constant HP excitation scheme - it was just a blue-faced card change.

 

U33C- 1968-75

U36C- 1971-75

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Posted by Overmod on Saturday, December 21, 2019 2:14 PM

I humbly suggest that the answer to most of these questions could be found reasonably directly in UP's own motive-power preference in this period, more specifically with respect to the inherently  high-speed operation the Centennials had updated horsepower for.

UP did not buy or update 20-cylinder locomotives to run with the Centennials.  What they did use was SD40s, regeared for higher speed but NOT upgraded to 3300hp with E3A mods although all the usual parts and maintenance arguments for engine commonalty would point toward doing that, and the additional horsepower would seem as fully usable at high speed with 12 TMs per 6600hp as with the 8 of a Centennial.

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Posted by VGN Jess on Tuesday, December 24, 2019 2:11 PM

OK, I understand the strain issue. But if it ran in the DDA40X why not run it in the SD40-2?

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Posted by VGN Jess on Tuesday, December 24, 2019 2:15 PM

"I think the real question is why UP and/or EMD wanted 6600 HP from the DD40AX and not 6000."---Great question and "...guessing EMD wanted to see if they could push another 10% from a 16-645E3 engine and UP agreed to go along for the ride.".... is an extremely valid supposition. Thanks. That's changed the whole perspective of my original question.

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Posted by VGN Jess on Tuesday, December 24, 2019 2:17 PM

"Why have two products competing against each other."---One answer would be: If given a choice of 3,600 HP w/20 cylinders vs. 3,300 HP w/16 cylinders I would choose the latter just based on economics.

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Posted by Overmod on Tuesday, December 24, 2019 3:48 PM

.

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Posted by Overmod on Tuesday, December 24, 2019 3:52 PM

VGN Jess
One answer would be: If given a choice of 3,600 HP w/20 cylinders vs. 3,300 HP w/16 cylinders I would choose the latter just based on economics.

Which of course is today's answer, too with 7FDL or GEVO 16 vs. 12 (with only slightly different relative numbers)

The problem, however, is a bit more detailed: would you choose the latter if it involved more frequent periodic inspection, or if there were accelerated failures both of components and in service associated with the 300 extra horsepower?  It seems very clear that UP, which had every reason to install similar or common engines in the Fast Forties to match what it was already using in the Centennials, did not.  And a big point of interest is that I have never seen evidence they even tried, although a test would be almost trivial to arrange.

Arguably the choice is between "3600hp from 20 cylinders, 3300hp from 16 cylinders, or reliable 3000hp from 16 cylinders" and, even today, the resounding 'correct' answer is still an obvious one...

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Posted by Backshop on Tuesday, December 24, 2019 4:19 PM

VGN Jess

"Why have two products competing against each other."---One answer would be: If given a choice of 3,600 HP w/20 cylinders vs. 3,300 HP w/16 cylinders I would choose the latter just based on economics.

 

Which, like ovemod alluded to, would cut down on orders for the '45 and add warranty costs for both the '45 and higher HP 3300.

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Posted by Overmod on Tuesday, December 24, 2019 4:40 PM

To put it another way:  the SD45 was an EMD 'play' to get into the 3600hp club with the power assemblies common to the 645 series -- hence the 'utility' of the extra four fuel-burning cylinders that would, presumably, spend much of their time making full incremental horsepower.  EMD was so proud of the QC that went into making and proofing those special longer crankshafts, too.

As it turned out, the market went a different way entirely, and in those days the '40 was a much better general-purpose proposition, and certainly a better part-load proposition, than the higher-displacement '45.  We get further proof that "3300" was a bit of a step too far by the dramatically limited interest in the corresponding 'amping up' of the 20-cylinder engine in the SD45X (4200hp, no takers), but against this, to my knowledge we don't see UP derating the 3300hp in the C3As either, even later in the locomotives' lifetimes.

I was hoping someone like Don Strack would have taken up this precise issue with some detailed technical evidence ... perhaps someone still will.  Has anyone asked Preston Cook his opinion?

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Posted by SD70Dude on Tuesday, December 24, 2019 7:16 PM

Overmod

I was hoping someone like Don Strack would have taken up this precise issue with some detailed technical evidence

Here's a interesting writeup from his site on the last four 40-series units purchased by Union Pacific.  Designated SD40-2S, they were rated at 3300 HP.

https://utahrails.net/articles/up-final-four-sd40-2.php

I have another question relating to the Centennials and their higher horsepower.  As they were essentially two GP40-2's on a common frame, did they automatically derate at lower speeds as well?

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Posted by Paul Milenkovic on Wednesday, December 25, 2019 11:48 PM

Was there not some discussion about the F40PH passenger locomotives, whether they were really rated at 3000 HP at the alternator shaft or maybe a little bit more by tinkering with the "fuel rack" or governor settings?

Is a passenger locomotive, in a way, a less heavy-duty application than some freight locomotives inasmuch as a passenger locomotive is not operate flat-out at Run-8 for hours at a time?  That it uses its HP in acceleration, but the high HP/ton in passenger service means they aren't cruising at full power?

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
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Posted by VGN Jess on Wednesday, December 25, 2019 11:49 PM

Thanks for the info. Why do you use the word reliable when referencing the 3kHP 645 but not for the 3.3kHP 645? I've still read nothing that indicates the 3.3k 645 was unreliable in any way, which is what generated my original question. Two (2) reliable prime movers but when the SD40's came out the lower HP engine was used.

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Posted by VGN Jess on Wednesday, December 25, 2019 11:51 PM

Except for the 300HP difference, I suppose you could say they were 2 GP-40's on one frame (like the DD35X was 2 GP-35's on one frame).

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Posted by Overmod on Thursday, December 26, 2019 5:27 PM

I think (but you'd be better consulting Don Strack and Preston Cook) that all of this was cooling-limited.  Working backward from the issues given for the four SD40-2Ss, one additional panel 'in proportion' to the nominal 300hp gain wasn't enough, and UP was one of the Western roads confronted with very high ambient temperature even with 2-speed fans on high.  Overheat is a quick way to accelerate problems with EMD engines.  

Not to say that running them at accelerated rpm wasn't a problem where a few extra rpm could easily increase certain types of failure, or limit MTTF, dramatically.  This is likely more an issue with inertial force than with, say, the induction of cavitation that killed the reliability of both the 6000hp original 265H and the GE Deutz equivalent in North American practice.  And this is something that the 'heavy' crankcase and block construction wouldn't necessarily have mitigated.

I suspect also that a reason for two uprated engines in the Centennials was that they had no alternative uses to high-speed main-line freight service, where every horsepower counts, a high percentage of the running time.  (That still doesn't, to me, explain the absence of trying the experiment on the Fast Forties, but working it on the SD40-2S after the days of cost-effective or revenue-justified high speed were effectively over.)

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Posted by SSW9389 on Friday, December 27, 2019 12:37 PM

See the J. David Ingles article on pages 16-17 of the April 1972 Trains. The article "A Little Change From La Grange" is about the then new Dash 2 line of EMD locomotives. Ingle's states EMD's humble brag about having 80% of the diesel locomotive market speaks volumes. He also noted that the 47 DDA40Xs and 7 SD45Xs had been testing Dash 2 components since 1969. With such a large slice of the market, EMD had no need to push the horsepower envelope and was content to work toward maintainability and reliability. Within a short time GE mirrored EMD's move with their XR Extra Reliability line of improved diesels.  

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Posted by SSW9389 on Friday, December 27, 2019 2:18 PM

VGN Jess

Can anyone speculate (or perhaps know) why the DDA40X "645" 3,300 HP prime mover was not used in the SD/GP40's (we all know that a "645" 3,000 prime mover was and has always been used for those locomotives)? Also, was the 3,300 HP engine ever used in anything other than the DDA40X?

 

You're looking at an EMD marketing decision that was made sometime in 1971. A decision was made not to offer a 3300 horsepower GP50/SD50 or the 4200 horsepower SD55. EMD had to be getting feedback that their product was not reliable enough. And that's why the Dash 2 line was offered. Much of the electronics that debuted in the DDA40X and the SD45X were offered in the then new Dash 2 line. You could say that the diesel  horsepower race had reached a plateau of sorts. The 1972-buzz words for new diesel locomotives would be reliability and maintainability. 

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