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What do you think is more powerful?

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Posted by chefjavier on Friday, December 21, 2007 2:46 PM
 JayPotter wrote:

The for-whatever-it's-worth approach that I take to the SD70ACe 191K "starting" figure and the 157K "continuous" figure is that (a) 191K is the maximum TE that the unit's adhesion-management software will allow it to produce; (b) it will only be able to reach that maximum level if rail conditions are very favorable (i.e. will allow a 46.8% adhesion factor); and (c) under normally expected rail conditions, the unit will have a 38.4% adhesion factor.  Those adhesion figures are based on a unit weight of 408K.

Do you have a math formula or a equation that you use to get this answer.  

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Posted by chefjavier on Friday, December 21, 2007 2:43 PM
 JayPotter wrote:

The for-whatever-it's-worth approach that I take to the SD70ACe 191K "starting" figure and the 157K "continuous" figure is that (a) 191K is the maximum TE that the unit's adhesion-management software will allow it to produce; (b) it will only be able to reach that maximum level if rail conditions are very favorable (i.e. will allow a 46.8% adhesion factor); and (c) under normally expected rail conditions, the unit will have a 38.4% adhesion factor.  Those adhesion figures are based on a unit weight of 408K.

Do you have a math formula or a equation that you use to get this answer ?

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Posted by JayPotter on Friday, December 21, 2007 2:29 PM

The for-whatever-it's-worth approach that I take to the SD70ACe 191K "starting" figure and the 157K "continuous" figure is that (a) 191K is the maximum TE that the unit's adhesion-management software will allow it to produce; (b) it will only be able to reach that maximum level if rail conditions are very favorable (i.e. will allow a 46.8% adhesion factor); and (c) under normally expected rail conditions, the unit will have a 38.4% adhesion factor.  Those adhesion figures are based on a unit weight of 408K.

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Posted by timz on Friday, December 21, 2007 12:11 PM

 ValorStorm wrote:
EMD says the continuous tractive effort of their SD70ACe is 157,000 lbs.... please provide the definition of "continuous tractive effort."
Ah-- so that's the problem. EMD didn't bother including the clarification "157,000 lb continuous TE at 7 mph [or whatever it is]". They certainly never intended to suggest that the SD70 could produce 157,000 lb at 50 mph, or at 30 mph, or even at 10 mph. They just meant, if you want to pull a train up a hundred-mile hill, and the combination of grade and tonnage requires a TE of 157,000 lb, then the SD70 will fill the bill. They're not saying anything about how long it will take to get to the top.

(And they probably mean "adhesion permitting", too. If you send an SD70 up Cranberry with 3000 tons it won't always make it.)

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Posted by ValorStorm on Friday, December 21, 2007 11:37 AM

 GP40-2 wrote:
 ValorStorm wrote:

the GG1 has 303,000 lbs of adhesive weight on its drivers. Let's say the GG1 can convert only 22%-23% of the weight into pulling force.

So you DO know how to calculate tractive effort! What could possibly be the justification for the erroneous results?



 GP40-2 wrote:
Wow! All I can say is you have no idea what you are talking about. Please take a basic physics class!!!

Please calm down. I wasn't making fun of you. And thanx for calling me a "kid." I'm 51. Now the calculation was yours. Converting 22%-23% of the weight into pulling force results in the STARTING TRACTIVE EFFORT. Your answer was correct. EMD says the continuous tractive effort of their SD70ACe is 157,000 lbs. I have taken physics. But I wasn't a physics student. You've proven yourself the most knowledgeable in this thread. So I'm not daring you, I'm asking you, please provide the definition of "continuous tractive effort."

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Posted by JayPotter on Wednesday, December 19, 2007 7:13 AM

 erikem wrote:
my calculation shows that the CTE of the SD70ACE will be horsepower limited above 9.2MPH (assuming 90% transmission efficiency).

To what calculations were you referring?  I understand the concept of calculating the (maximum) continuous tractive effort of a DC-traction unit; but I'm confused by the concept of calculating the (nominal) continuous tractive effort of an AC-traction unit. 

 

 

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Posted by erikem on Wednesday, December 19, 2007 12:43 AM
 ValorStorm wrote:

The (hp x 375)/speed formula for TE served a purpose. It's not used so much anymore, likely because in physics terms, horsepower is "power" and tractive effort is "force." These are very different animals. It was confusing before, but now it's not. Bed time.

Lessee, POWER=FORCExDISTANCE/TIME, and SPEED=DISTANCE/TIME, so POWER=FORCExSPEED and therefor POWER/SPEED=FORCExSPEED/SPEED=FORCE or FORCE=POWER/SPEED.

So the formula, TE(lbf)=(hp x 375)/speed(mph) is valid as long as the tractive effort is horsepower limited and not adhesion limited.

As for the GG-1 vs the SD70ACe, no one is arguing that the GG-1 has a low speed CTE anywhere near the SD70ACe - my calculation shows that the CTE of the SD70ACE will be horsepower limited above 9.2MPH (assuming 90% transmission efficiency).

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Posted by GP40-2 on Wednesday, December 19, 2007 12:01 AM
 erikem wrote:
... I would imagine that the efficiency of the SD70ACe's transmission varies as a function of both tractive effort and speed. May be as low as 50% at low speeds and high TE, possibly 90% at somewhere around 30 MPH.



On GE AC's efficiency varies from a low of 85% while producing max. TE at low speed, to over 94% at 70+MPH. All the "experts" on this forum yap at CSX for using ACs on fast double stacks, but that's exactly the speed where they are the most efficient.
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Posted by GP40-2 on Tuesday, December 18, 2007 11:45 PM
 ValorStorm wrote:

 GP40-2 wrote:
 ValorStorm wrote:
...There is no circumstance where the tractive effort of a GG-1 can ever approach the tractive effort of an SD70ACe...


Really? Let's say both the ACe and GG1 are traveling at 50 MPH. For the sake of discussion, let's assume the locomotive's respective HP ratings are at the drawbar (e.g. assume machinery and aerodynamic losses are zero) So, we have an ACe producing 4300HP and the GG1 producing 4680HP @ 50MPH.

The ACe is producing 32,250 lbs. TE
The GG1 is producing 35,100 lbs. TE

The GG1 can pull more train than the ACe at 50MPH. Period. With the same weight train, the GG1 is pulling away from the ACe.

Tractive effort is the force that a locomotive can apply to its coupler to pull a train. It's true that the greater the speed of the engine, the more power is needed to produce a given tractive effort. But here is where I think some of us have been miscalculating.
Most locomotive builders calculate tractive effort based on a percentage of the weight placed on the driving wheels. This results in STARTING tractive effort, which is always the absolute maximum possible. Horsepower plays a roll, but in the case of North American motive power IT IS NOT THE PRIMARY CONSIDERATION WHEN DETERMINING TRACTIVE EFFORT. 25% for clean dry rail is the old standard right up until the advent of AC traction. In the case of AC traction, dynamometer tests have shown that the factor can often exceed 35%! This is not the case with DC traction. (Yes, this presupposes high horsepower).
In most cases, tractive effort limits the pulling power of locomotives only at very slow speeds. Above a few miles per hour, horsepower limits prevail. So please understand that "pulling power" & "tractive effort" aren't exactly synonymous. When we say that an SD70ACe exerts 157,000 pounds of CTE that means "at speed," including 50 mph! A GG-1 has a starting TE approaching 80,000 lbs. That's the maximum. It goes down from there.

 GP40-2 wrote:
the GG1 has 303,000 lbs of adhesive weight on its drivers. Let's say the GG1 can convert only 22%-23% of the weight into pulling force. (probably a low estimate--more like 25% w/o sand and 30% with sand) That amounts to 70,000 lbs pull before you start to lose adhesion.

So you DO know how to calculate tractive effort! What could possibly be the justification for the erroneous results?



Wow! All I can say is you have no idea what you are talking about. Please take a basic physics class!!!

Do you really think an ACe can produce 157,000 lbs at "speed"? So you are saying that at 50MPH it is producing 157,000 lbs TE? Wow, that means it is producing 21,000 HP. I must of missed the memo that EMD has really uprated the 710!!!

You see kid, Horsepower and Tractive Effort are DIRECTLY related. There is no way to separate them when a locomotive is moving at any speed. I gave you the basic formula--obviously you can't even understand 9th grade math.

I'll repeat, at 50MPH the GG1 produces more TE than the ACe. If you don't understand that, you don't understand anything about tractive effort.

BTW, before you start lecturing me on what makes locomotives tick, I've worked in this industry for 3 decades and have a MSME (Master Science Mechanical Engineering). While at CSX, I worked directly with GE on developing the "heavy" AC4400, so I know a tad bit more than you about TE, HP and AC locomotive efficiency.

Please tell us your academic credentials and industry experience.



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Posted by Railway Man on Tuesday, December 18, 2007 10:36 PM
 ValorStorm wrote:

The (hp x 375)/speed formula for TE served a purpose. It's not used so much anymore, likely because in physics terms, horsepower is "power" and tractive effort is "force." These are very different animals.

Who doesn't use it any more!?!  Maybe I'm just an old-timer (I like to think of myself as chipper as a spring chicken but my knees say otherwise) but I've used this formula in my railroad job at least a dozen times this year, and it's the basis of the calculations in the train-performance  and locomotive-performance software we paid $$$$ dollars for and use for train schedule design and analysis.  It's in the AREMA "Practical Guide to Railroading" Manual too, Chapter 2, page 33.  Am I supposed to be using something else?

www.arema.org/eseries/scriptcontent/custom/e_arema/Practical_Guide/PGChapter2.pdf

RWM 

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Posted by ValorStorm on Tuesday, December 18, 2007 10:07 PM
 Railway Man wrote:

Assuming that 25% adhesion was about as good as it would get, maximum TE on the (GG-1) at any speed would be 75,750 lbs.

And maximum TE is starting TE. And you calculated tractive effort correctly.

Now this is from the EMD website:

SD70ACe Performance Specifications
4,300 THP and locomotive equipped with EMD's
16-710G3C-T2 engine
EPA Tier-2 emissions certified

Tractive and braking effort capability
157,000 lbs continuous TE
191,000 lbs starting TE
106,000 lbs braking effort

Repeat: There is no possible way a GG-1 can have a continuous tractive effort rating anywhere near the 157,000 lbs of an SD70ACe, because a GG-1 can't have a starting tractive effort rating higher than 80,000 lbs.

The (hp x 375)/speed formula for TE served a purpose. It's not used so much anymore, likely because in physics terms, horsepower is "power" and tractive effort is "force." These are very different animals. It was confusing before, but now it's not. Bed time.

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Posted by erikem on Tuesday, December 18, 2007 9:13 PM
 Railway Man wrote:

1.  I've seen statements that the GG1 could exert 9,500 hp at 49 mph.  I'm seeking an explanation how that number could be on a continuous basis.  Short-time, maybe, which might have been useful accelerating a light, short train -- and how short a time is short, anyway?  1-2 minutes at that kind of overload doesn't fill me with enthusiasm that this capability had practical operational value.

The 9,500 hp is short term - don't know how short, depends one what is limiting the power output (motor heating, transformer primary winding?). 1-2 minutes overload wouldn't be much use for freight, but more than adequate for passenger service. 

 

2.  The GG1 didn't have a wheel slip system that would enable it to get that kind of tractive effort at 10 mph.  The data says weight on drivers is 303,000 lbs.  Assuming that 25% adhesion was about as good as it would get, maximum TE on the locomotive at any speed would be 75,750 lbs.

 

Even worse is that it had AC series motors with pulsating torque - though the springs on the quill drives probably filtered out much of that.

 

3.  The SD70ACe probably is a little more efficient than 82%.  The data sheet for the similar SD9043MAC says it produces 185,000 lbs TE up to 11 mph (but also says CTE is 147,000 lbs., so perhaps there are heating limits on the A.C. transmission?).

I wouldn't be surprised if there were heating limits on the traction motors - induction motors are rugged but not indestructable. I would imagine that the efficiency of the SD70ACe's transmission varies as a function of both tractive effort and speed. May be as low as 50% at low speeds and high TE, possibly 90% at somewhere around 30 MPH.

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Posted by Railway Man on Tuesday, December 18, 2007 2:44 PM

It's hard to compare two locomotives when we're working from incomplete sets of data.  All I know of the GG1 is what's written on what appears to be the railroad's data sheet, which says 72,800 lbs maximum tractive effort (at what speed that's taken, and what % of adhesion, I know not), and 4,620 continuous horsepower (385 per motor, 12 motors).

These specs are taken from this sheet here, which appears to be a PRR sheet (comments?)

http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=gg1.gif&sel=ele&sz=sm&fr=ge

Tractive effort at any given speed for any locomotive is calculated using the formula TE = (hp x 375)/speed.  For diesel-electric locomotives, the constant 375 is typically replaced by 308 to account for the 82% efficiency of the electric transmission.  For the GG1, for the sake of argument, let's assume the 385 horsepower per motor is taken at the output shaft, so using the formula,

10 mph: 173,250 lbs.

25 mph: 69,300 lbs.

50 mph: 34,650 lbs.

For the 4,300 hp SD70ACe, assuming it's only 82% efficient:

10 mph: 132,440 lbs.

25 mph: 52,976 lbs.

50 mph: 26,488 lbs.

Some caveats:

1.  I've seen statements that the GG1 could exert 9,500 hp at 49 mph.  I'm seeking an explanation how that number could be on a continuous basis.  Short-time, maybe, which might have been useful accelerating a light, short train -- and how short a time is short, anyway?  1-2 minutes at that kind of overload doesn't fill me with enthusiasm that this capability had practical operational value.

2.  The GG1 didn't have a wheel slip system that would enable it to get that kind of tractive effort at 10 mph.  The data says weight on drivers is 303,000 lbs.  Assuming that 25% adhesion was about as good as it would get, maximum TE on the locomotive at any speed would be 75,750 lbs.

3.  The SD70ACe probably is a little more efficient than 82%.  The data sheet for the similar SD9043MAC says it produces 185,000 lbs TE up to 11 mph (but also says CTE is 147,000 lbs., so perhaps there are heating limits on the A.C. transmission?).

I'm comfortable that from 0 to somewhere around 20 mph the SD70ACe can produce more useful tractive effort than the GG1.  At higher speeds the GG1, if the 4,620 hp is something that its traction motors can do continuously, will produce somewhat more tractive effort and pull away from the SD70ACe -- or maybe it will produce a lot more TE if the claims of immense horsepower at high speed are true, and if this hp could have been put to practical effect before exceeding the motor heating limits or exceeding the locomotive's adhesion.

(Not a sales plug, but every time these discussions come up, I reread the explanation of locomotive physics in the back of the Kalmbach "Contemporary Diesel Spotter's Guide," which is as succinct and complete an explanation of tractive effort, horsepower, adhesion, train resistance, and grade resistance as I have found.)

RWM 

 

 

 

 

 

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Posted by ValorStorm on Tuesday, December 18, 2007 1:49 PM

 GP40-2 wrote:
 ValorStorm wrote:
...There is no circumstance where the tractive effort of a GG-1 can ever approach the tractive effort of an SD70ACe...


Really? Let's say both the ACe and GG1 are traveling at 50 MPH. For the sake of discussion, let's assume the locomotive's respective HP ratings are at the drawbar (e.g. assume machinery and aerodynamic losses are zero) So, we have an ACe producing 4300HP and the GG1 producing 4680HP @ 50MPH.

The ACe is producing 32,250 lbs. TE
The GG1 is producing 35,100 lbs. TE

The GG1 can pull more train than the ACe at 50MPH. Period. With the same weight train, the GG1 is pulling away from the ACe.

Tractive effort is the force that a locomotive can apply to its coupler to pull a train. It's true that the greater the speed of the engine, the more power is needed to produce a given tractive effort. But here is where I think some of us have been miscalculating.
Most locomotive builders calculate tractive effort based on a percentage of the weight placed on the driving wheels. This results in STARTING tractive effort, which is always the absolute maximum possible. Horsepower plays a roll, but in the case of North American motive power IT IS NOT THE PRIMARY CONSIDERATION WHEN DETERMINING TRACTIVE EFFORT. 25% for clean dry rail is the old standard right up until the advent of AC traction. In the case of AC traction, dynamometer tests have shown that the factor can often exceed 35%! This is not the case with DC traction. (Yes, this presupposes high horsepower).
In most cases, tractive effort limits the pulling power of locomotives only at very slow speeds. Above a few miles per hour, horsepower limits prevail. So please understand that "pulling power" & "tractive effort" aren't exactly synonymous. When we say that an SD70ACe exerts 157,000 pounds of CTE that means "at speed," including 50 mph! A GG-1 has a starting TE approaching 80,000 lbs. That's the maximum. It goes down from there.

 GP40-2 wrote:
the GG1 has 303,000 lbs of adhesive weight on its drivers. Let's say the GG1 can convert only 22%-23% of the weight into pulling force. (probably a low estimate--more like 25% w/o sand and 30% with sand) That amounts to 70,000 lbs pull before you start to lose adhesion.

So you DO know how to calculate tractive effort! What could possibly be the justification for the erroneous results?

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Posted by GP40-2 on Sunday, December 16, 2007 5:11 PM
 ValorStorm wrote:
...There is no circumstance where the tractive effort of a GG-1 can ever approach the tractive effort of an SD70ACe...


Really? Let's say both the ACe and GG1 are traveling at 50 MPH. For the sake of discussion, let's assume the locomotive's respective HP ratings are at the drawbar (e.g. assume machinery and aerodynamic losses are zero) So, we have an ACe producing 4300HP and the GG1 producing 4680HP @ 50MPH.

The ACe is producing 32,250 lbs. TE
The GG1 is producing 35,100 lbs. TE

The GG1 can pull more train than the ACe at 50MPH. Period. With the same weight train, the GG1 is pulling away from the ACe.

So some of you are saying "What about the ACe's fancy-smancy traction system?" Totally ineffective at those speeds. The AC'e traction system only comes into play at very low speed to allow the ACe to develop the high adhesion needed for the increased low speed tractive effort.

Besides, the GG1 has 303,000 lbs of adhesive weight on its drivers. Let's say the GG1 can convert only 22%-23% of the weight into pulling force. (probably a low estimate--more like 25% w/o sand and 30% with sand) That amounts to 70,000 lbs pull before you start to lose adhesion.

If the GG1 was overloading its motors to 8000HP @ 50MPH to accelerate a train, it would be producing 60,000 lbs TE. This is still well within its adhesive capacity, and it would be producing twice the TE of the ACe at this speed.
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Posted by spikejones52002 on Saturday, December 15, 2007 3:15 PM

Thank You Railway Man for the great source of Infomation on the

GG1.

Spike

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Posted by erikem on Saturday, December 15, 2007 2:01 PM
 YoHo1975 wrote:
 

Unless of course the SD70ACe is utilizing it's modern Anti-Slip and Adhesion control to maintain said 30MPH in which case, the GG-1 would be unable to maintain control of the train.

Quite true.

My recollection is that the GG-1 had a continuous rating of ~4500 HP and a short time rating in excess of 8000 HP. The short time rating is about the same as two SD70ACe (rail horsepower).  Keep in mind that these two locomotives are designed for very different services - the GG-1 is emphatically not the locomotive to use for low speed drag service, which is where the SD70ACe excels.

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Posted by YoHo1975 on Saturday, December 15, 2007 2:02 AM
 erikem wrote:
 ValorStorm wrote:
 erikem wrote:

As mentioned earlier, at starting an SD-70 can easily outpull a GG-1 (possibly a couple of GG-1's), but the GG-1 could outpull the SD-70 at speeds over 30MPH. 

But "outpull" needs a definition. Do you mean a GG-1 can outpull, above 30, the same kind of train that an SD70ACe is called for?

Above 30 MPH, the GG-1 could generate more tractive effort than the SD70ACe. At low speeds, there would be no contest - the SD70ACe would win hands down.  A similar case would be comparing a GP40 with and SD7, at low speeds where the SD7 is adhesion limited and not horspower limited, the SD7 could generate more tractive effort than the GP40. get up to 20MPH or so, then the tractive effort from the SD7 would be horsepower limited and the GP40 (having twice the horsepower) could generate more tractive effort.

To get back to your question of whether a GG-1 could handle the same train as an SD70ACe - if the SD70ACe could maintain 30MPH with the train, then the GG-1 would likely be able to handle it as well. Since the continuous horsepower rating of the GG-1 isn't much higher than the SD70ACe, the GG-1 wouldn't be much faster than the SD70ACe, unless the trip involved frequent acceleration from 30 to 60-70MPH.

 

Unless of course the SD70ACe is utilizing it's modern Anti-Slip and Adhesion control to maintain said 30MPH in which case, the GG-1 would be unable to maintain control of the train.

In short on straight dry track, yes.

Nobody has given a CTE number for the GG-1.

 

Oh, and if the SD70ACe has radial trucks then fugedaboutit. 

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Posted by ValorStorm on Friday, December 14, 2007 10:44 PM
 YoHo1975 wrote:

the GG1 can produce 70,700 lbs TE unspecified via DC (unspecified is always assumed to mean starting TE.)

The SD70ACe can produce

191,000 lbs starting TE 

157,000 continuous TE

So, (an SD70ACe) can ALMOST produce as much as 3 GG1s. 3 gg1s producing 213,000 lbs TE  

I'm trying not to hurt anyone's feelings, but a proper understanding of terms is needed in this thread. YoHo1975 is absolutely correct. There is no circumstance where the tractive effort of a GG-1 can ever approach the tractive effort of an SD70ACe. CTE is never equal to or higher than STE. Not at any speed. I think some of us are making valid points but using the wrong terminology. I know a good primer on HP curves, TE curves, & adhesion. But I'll have to dig thru the mess that is my bedroom to remember the name of the book. I'll get back to you.
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Posted by erikem on Friday, December 14, 2007 1:02 AM
 ValorStorm wrote:
 erikem wrote:

As mentioned earlier, at starting an SD-70 can easily outpull a GG-1 (possibly a couple of GG-1's), but the GG-1 could outpull the SD-70 at speeds over 30MPH. 

But "outpull" needs a definition. Do you mean a GG-1 can outpull, above 30, the same kind of train that an SD70ACe is called for?

Above 30 MPH, the GG-1 could generate more tractive effort than the SD70ACe. At low speeds, there would be no contest - the SD70ACe would win hands down.  A similar case would be comparing a GP40 with and SD7, at low speeds where the SD7 is adhesion limited and not horspower limited, the SD7 could generate more tractive effort than the GP40. get up to 20MPH or so, then the tractive effort from the SD7 would be horsepower limited and the GP40 (having twice the horsepower) could generate more tractive effort.

To get back to your question of whether a GG-1 could handle the same train as an SD70ACe - if the SD70ACe could maintain 30MPH with the train, then the GG-1 would likely be able to handle it as well. Since the continuous horsepower rating of the GG-1 isn't much higher than the SD70ACe, the GG-1 wouldn't be much faster than the SD70ACe, unless the trip involved frequent acceleration from 30 to 60-70MPH.

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Posted by oltmannd on Thursday, December 13, 2007 11:23 AM
 ValorStorm wrote:
 erikem wrote:

As mentioned earlier, at starting an SD-70 can easily outpull a GG-1 (possibly a couple of GG-1's), but the GG-1 could outpull the SD-70 at speeds over 30MPH. 

But "outpull" needs a definition. Do you mean a GG-1 can outpull, above 30, the same kind of train that an SD70ACe is called for? (It is the ACe we're talking about & not the SD70.) Or is it simply that the GG-1 pulls its train better than an ACe pulls its train? Does "outpull" refer to horsepower or tractive effort? They're not synonymous. And as mentioned earlier, continuous tractive effort of a GG-1 is nowhere near that of an SD70ACe.

I think you're exactly right!  The definition of terms really determines the answer.

"Pull" means force, and "outpull" might mean peak force or it might mean maximum sustained force.  Then, you would have to specify the conditions.  Dead stop?  Clean rail? 

But, based on the numbers, a coupler to coupler tug of war would be won handily by the SD70ACe.

If you start talking about "pulling" at some speed, then you are talking about HP since force x speed = power.  If you are talking about the max, then you are definitely allowing short time operation and at speed, the GG1's gonna generate more tractive force.

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

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Posted by JT22CW on Thursday, December 13, 2007 7:33 AM

Looks to me like all these comparisons are apples/oranges.  When indeed was the last purpose-built freight electric locomotive built in the USA?  The early 70s, for Black Mesa & Lake Powell RR?  The "big dog" in the diesel arena back then was the SD40-2, and the top speed on those, apart from UP's 90-mph "Fast Forties", was about 65 mph.  Besides that, there was no market for electric freight motors due to Conrail eschewing electricity in the Northeast.

It's certainly not fair to compare a passenger locomotive from the 30s-40s to an AC-traction diesel from the 21st Century.  You've got a technology gap of over seven decades, there.  Now were GE to suddenly create a new E-(something), such a motor would make the AC diesels look quite anemic.  But until then, we've got what we got and there are no real valid comparisons.

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Posted by ValorStorm on Thursday, December 13, 2007 6:25 AM
 erikem wrote:

As mentioned earlier, at starting an SD-70 can easily outpull a GG-1 (possibly a couple of GG-1's), but the GG-1 could outpull the SD-70 at speeds over 30MPH. 

But "outpull" needs a definition. Do you mean a GG-1 can outpull, above 30, the same kind of train that an SD70ACe is called for? (It is the ACe we're talking about & not the SD70.) Or is it simply that the GG-1 pulls its train better than an ACe pulls its train? Does "outpull" refer to horsepower or tractive effort? They're not synonymous. And as mentioned earlier, continuous tractive effort of a GG-1 is nowhere near that of an SD70ACe.

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Posted by erikem on Wednesday, December 12, 2007 12:52 AM

Short term rating is likely more important for passenger operations than freight (one possible exception being fast freight service). For example, the tractive effort of an F40PH is horsepower limited above 15 MPH, where the short term rating for the AEM-7 is adhesion limited to ~45MPH and the short term tractive effort can exceed the low speed continuous tractive effort at speeds less than 80MPH. In short, the electrics will get up to track speed quicker than a diesel.

As mentioned earlier, at starting an SD-70 can easily outpull a GG-1 (possibly a couple of GG-1's), but the GG-1 could outpull the SD-70 at speeds over 30MPH. 

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Posted by GP40-2 on Tuesday, December 11, 2007 6:38 PM
 Railway Man wrote:

 ndbprr wrote:
The other factor being overlooked is that G's could be overloaded for a short time and generate much more HP than rating.  So if they could get it to the rails they should be superior.

I don't think anyone has overlooked short-time ratings; their existence is widely known.  It doesn't matter much anyway, as short-time ratings are not a place where a locomotive can usefully go very often.  Typically a locomotive that is trying to exert that kind of amperage is also up against its adhesion limits; there's no point in trying to design a locomotive with greater adhesion to make use of the short-time because the short-time is VERY short.

And the GGI couldn't get it to the rail; they didn't have enough drivers with enough weight on them as well as a primitive wheel-slip system.

RWM



Not entirely correct when talking about pure electric locomotives. By virtue of the overhead power supply, the GG1 could overload its traction motors at speed--it was not just limited to overloading the traction motors in a high amp/low speed manner such as with a unit with a fixed power level (e.g. the diesel-electric, turbine electric, etc). A DC motored diesel-electric can only go into the short time rating zone at low speeds and high amps--a situation used to develop high tractive effort for a heavy pull where adhesion is a huge factor. The GG1 could go into overload after the train was moving at a steady clip. It could double its standard rating for a short time to provide acceleration. At the higher speeds, any locomotive will need to develop less tractive effort for a given horsepower (Drawbar Horsepower=Tractive Effort x Speed/375 therefor as speed increases, tractive effort must go down). In these situations, rarely is adhesion a factor with dry rail. At speed, the GG1 had enough adhesive weight to fully use the short term 8000HP-9000HP it could develop.

To answer to original question, the SD70 can develop more low speed pull than the GG1, but the GG1 will blow the SD70 away with higher speed horsepower.
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Posted by Railway Man on Monday, December 10, 2007 9:43 PM

 ndbprr wrote:
The other factor being overlooked is that G's could be overloaded for a short time and generate much more HP than rating.  So if they could get it to the rails they should be superior.

I don't think anyone has overlooked short-time ratings; their existence is widely known.  It doesn't matter much anyway, as short-time ratings are not a place where a locomotive can usefully go very often.  Typically a locomotive that is trying to exert that kind of amperage is also up against its adhesion limits; there's no point in trying to design a locomotive with greater adhesion to make use of the short-time because the short-time is VERY short.

And the GGI couldn't get it to the rail; they didn't have enough drivers with enough weight on them as well as a primitive wheel-slip system.

RWM

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Posted by ndbprr on Monday, December 10, 2007 1:59 PM
The other factor being overlooked is that G's could be overloaded for a short time and generate much more HP than rating.  So if they could get it to the rails they should be superior.
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Posted by da_kraut on Saturday, December 8, 2007 8:01 PM

Hi there,

here is the web site from Siemens,  they manufacture in whole or part a lot of locomotives for all around the world.  Just browse on the site and you will see the data of the different locomotives that they have produced. Modern technology, sheer weight of the locomotive, gearing as well as HP and torque play a huge roll in the abilities of the locomotives.  With so many variables it seems that it is impossible to determine which locomotive is more powerful.  

Here is the web site:

http://transportation.siemens.com/ts/en/pub/products/lm/refs/electrical.htm

Frank 

"If you need a helping hand, you'll find one at the end of your arm."

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Posted by Virginian on Friday, December 7, 2007 12:33 PM
If you are interested in electrics you need to look at the VGN electrics.  The EL-2Bs were quite unique.
What could have happened.... did.
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Posted by beaulieu on Friday, December 7, 2007 12:21 AM
 carnej1 wrote:
 CSSHEGEWISCH wrote:

 wjstix wrote:
I suspect if we compare apples and apples - 1930's electric engines vs. 1930's diesels, the electrics would come out far ahead. It would be interesting to see what could be built today as far as a straight electric freight engine.

The most recent straight electric freight designs that we have were the GM6C and GM10B demos of the late 1970's and the GF6C's in British Columbia of the 1990's.  The GM10B seemed to be the design that was pushing the limits of the envelope.

 I am no engineer(of either stripe) but my understanding of the difference in design between High Horsepower European and North American locomotives are all about high speed versus tractive effort. There are a number of European electrics with impressive ratings (10,000 HP or greater!) but they do not have the pulling power in heavy freight service of the average North American unit (4400 HP GE or 4300 HP EMD). They are designed to pull passenger and short freigth trains at 100 MPH plus speeds.

 

That is an oversimplification, the current SD70ACe and ES44AC are capable of 75mph, and UP runs them at 70 mph on the Z-trains were track conditions allow. BNSF does similar with their ES44DC locomotives. One of the most powerful European locomotives, the Swiss Re 6/6 (now Re 620) is rated at 10,500hp. and has a top speed of 87mph. But is designed around the requirement of pulling a freight train up the 2.7% grade of the Gotthard Pass at 50mph. The Re 620 paired with a Re 420 (6300hp.) is required to take a 1540 ton (US) freight up the 2.7 % grade at 50mph without helpers. 

 

The best match for US diesels would be the IORE electrics built for MTAB in Sweden. They are double unit, but cutting the figures in half yields 7300hp  134,000lbs Continuous TE. top speed 50 mph.

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