Could steam make a comeback?

[MichaelSol]

I love steam but let's be realistic, it's never coming back.

Well, I don't love steam, but the idea of being realistic recognizes that oil-based energy sources are becoming an order of magnitude more expensive than the cost of mineral coal. At the conclusion of the Dieselization transition, oil had a price advantage over coal of nearly 40% -- that was clearly the main economic driver for dieselization; Coal now enjoys an advantage over oil approaching 800%. And we are at a point with oil that to ensure adequate future supply even at high prices requires massive new infrastructure investment as well.

[TomDiehl]

The focus on the fact that the diesel locomotive reaches its maximum horsepower at 19 MPH is puzzling. The maximum horsepower (or torque, or tractive effort, which ever measure you prefer) is needed to get the train moving. This is one of the advantages of the diesel switcher, which made it the prefered type, even in areas with no smoke abatement ordinances. What advantage the steam locomotive has in developing more horsepower above this point would be lost in the fact that you can't add more cars at speed. It may accelerate a bit faster than the diesel above this point, but is it enough to make it a worthwhile statistic?

It may develop more horsepower above this point, but is that useful in day-to-day operations?

[MichaelSol]

It may develop more horsepower above this point, but is that useful in day-to-day operations?

The horsepower and Tractive Effort needs of a train are at its lowest at 0.01 mph. The amount of horsepower and Tractive Effort needed to move the train thereafter continue to increase indefinitely, up to the limit of the ability of the locomotives to move the train. The train "develops" a need for more horsepower at the same time that a Steam engine "develops" more horsepower, and if the company has purchased the same amount of weight of locomotive on the drivers, it has purchased more horsepower above 19 mph where the horsepower needs are greater.

[YoHo1975]

Yoho,

Read this thread from the beginning and you will find what you are looking for. Michael Sol has posted numbers showing cost per btu. With that comparison you do not have to burn the same fuel to make a valid point. He shows that a coal burning steam locomotive produces btus MUCH more economically than a diesel can burn diesel fuel. And therein lies the origin of this whole thread: Given the price of diesel vs. coal, does it make economic sense to bring steam back? The answer seems to be a resounding YES!

Some have asked if steam is so preferable, then why are we not seeing the transition? They forget that the rise in oil prices has been very rapid. Many economists predict a collapse in oil prices from $120 per barrel to around $80. Given the volatility in the current oil market and the uncertainty about worldwide reasponse to it, it is not surprising that railroads are not ready to ditch the diesel. Give it some time. When prices settle to a more permanent level you will likely see railroads beginning to experiment with alternative fuel sources. 

 

And if you read my post, you'll see that I said same fuel source. 100,000 BTUs of coal is 100,000 BTUs of coal.

I made it clear that I don't care if it's internal combustion, external combustion or mutant hamster in a wheel. I want to know what the consumption rates would be given the transmission and external versus internal for the same fluidized coal fuel. 

this conversation is about two things. Fuel source and most efficent transmission. The fuel source issue is a non-starter, because the fact is that neither coal nor Oil is politically viable even if one or the other is the only immediate practical solution. which is why pages ago we were talking about more legitimate bio-fuels than corn ethanol. The fuel source is a seperate debate.

 

[fredswain]

Working in the oil industry I can easily say that we are nowhere near the end of our supply nor have we passed peak oil. The fact of the matter is that we will never run out. It's not saying we can't. We just won't. Other technologies will come along that we will slowly adapt to long before it ever gets to that. Oil prices aren't high due to low supply. They are high because of speculation, market manipulation, and because of the very people who don't like oil and that is environmentalists. It's because of them that we don't have enough refining capacity. The oil companies would love to spend the money to build it. Oil companies aren't to blame. They are at record profits solely due to quantity being sold. They are not at record profit margins. No I was not paid to say this. I am just really against all the bs that the media circulates. Nothing could be further from the truth. Remember this, gas prices WILL go back down. Will they go back to $1 a gallon again? I seriously doubt it. It'll hit at least $2.50 again at some point though which is still too high in my opinion.

Now saying all of that, coal prices are going to rise at some point specifically if it's use goes up more and more. There is also increasing pressure to not use it for environmental reasons. No decision is made in this country based on efficiency reasons even though it'll be portrayed as such. The addition of ethanol and the associated fuel efficiency decrease is a prime example. It's all about making the environmentalists happy and being portrayed as "green". A steam engine does not portray that. It doesn't matter if it could be clean or not. People have the mental images of thick black smoke billowing from purposefully misfired steam engines all for the sake of a spectacular picture. I'm surprised that they aren't pushing for catalytic converters or particulate filters to be installed on excursion steam engines. It's only a matter of time. You're about to see them be mandated on your lawnmowers and weedeaters with motorcycles in the immediate future. From an emissions standpoint, coal isn't going to be a fuel that is burned directly in locomotives. You need to jazz it up a bit, and extole the virtues of turning it into a "clean" fuel first even though it goes through a dirty and efficiency wasting conversion process. Emissions standards are going to keep going up and up in the process.

I'm not saying steam CAN'T make a comeback. I'm saying it WON'T and for a number of reasons. There's a difference. A logical fact based argument has nothing to do with it. What we will end up seeing is a greater push in transportation in general to electric, not steam. Batteries will be pushed to greater and greater extents as technology increases with the desire to use smaller and smaller engines as generators. Now whether or not batteries biodegrade is an argument that will never end but batteries are highly recycled so that may or may not be an issue.

I hate to say it, but as much as I'd love to see a steam engine roaring down the tracks again, it's only going to happen in excursions, special trains, or in videos and pictures. Their day is done. It has nothing to do with if they COULD be made to work. Besides, it's cheaper to just keep buying fuel for what you already have than it is to spend the money on new steam engine development, and then reinstalling the servicing and refueling infrastructure that we once had. The payback would be over a VERY long time.

I'd like to see it. I just know I won't.

[Anonymous]

 

What are the limitations on Diesel electrics that they can't develop HP at higher speeds per hp?

I assume your question is based on the flattening off of a diesel locomotive's horsepower curve as it accelerates, whereas a steam locomotive's horsepower curve continues to rise as it accelerates.  There are two ways to look at this flattening off characteristic of the diesel. One way concludes the characteristic to be a disadvantage, and the other way concludes it to not be a disadvantage. 

It appears to be a disadvantage because a train needs increasing horsepower in order to increase its speed, and the diesel reaches its maximum horsepower early and cannot continue increasing it as the train accelerates.  However, it is not a disadvantage when you consider that the diesel is simply able to deliver all of its horsepower early in its acceleration.  Some might call this a peak in horsepower and say that the diesel's HP peaks early where it is not needed.  In this context, the term peak suggests a high point with an immediate fall-off.  Yet that is not the case with the diesel.  It continues to develop its maximum horsepower all the way to top speed.    

Not only is this ability to reach maximum horsepower early not a disadvantage, in some cases it is actually an advantage; for instance, when pulling a drag freight that requires the locomotive's maximum horsepower, but is so heavy that its balance speed will be say 30 mph. A diesel can deliver all of its potential horsepower at that speed whereas a steam locomotive cannot. 

In MichaelSol's horsepower and tractive effort comparison tables posted in the other thread, besides the obvious flattening off of the diesel's HP and TE curves, there is the continuing increase of the HP/TE curves of the steamer, which seems to further reinforce the idea of a disadvantage with the diesel.  However, in order for the steamer to continuing to develop increasing horsepower to levels greater than the diesel's maxed out horsepower, the steamer must simply be a higher horsepower machine. 

What would the comparison look like if you compared a 5,600 HP diesel to a 5,600 HP steamer, assuming that they both were capable of delivering their full HP to the rail?  The diesel will develop and deliver its full horsepower once it reaches 15 MPH while the steamer will not be able to deliver the same HP until it reaches perhaps 55 MPH.  I make this assumption extrapolating from MichaelSol's table (shown below) comparing the horsepower developed by a steam locomotive to that of a diesel, where the steamer delivers its maximum HP at 55 MPH.

I believe the correct way of looking at this is that it is not a failure of the diesel to keep up with the steamer in developing more and more horsepower, but rather a failure of the steamer to develop its full horsepower until it reaches a relatively high speed.

 

MPH	Diesel-electric	Steam	HP  needed
5	4,278	1,806	307
10	5,133	3,613	743
15	5,600	4,516	1,239
20	5,600	5,600	1,839
25	5,600	6,323	2,562
30	5,600	7,226	3,426
35	5,600	7,677	4,446
40	5,600	7,948	5,641
45	5,600	8,129	7,028
50	5,600	8,310	8,624
55	5,600	8,400	10,447
60	5,600	8,310	12,513
65	5,600	8,219	14,840
70	5,600	8,129	17,445

 

[AnthonyV]

Bucyrus:

Well said.

Anthony V.

[MichaelSol]

What would the comparison look like if you compared a 5,600 HP diesel to a 5,600 HP steamer, assuming that they both were capable of delivering their full HP to the rail? 

I'm going to change this to a 3,000 hp Diesel and a 3,000 hp Steam engine to come a little closer to the reality of the era since a 5600 hp Diesel-electric didn't exist then and statistically isn't much of a presence now.

A relatively big diesel is being compared to a relatively small steam engine. As the steam engine gets larger, its ability to continue to develop horsepower continues to extend to higher and higher speeds.

The physics of the whole thing changes when you take a relatively small steam engine and compare it to a large diesel-electric. In this example, equal horsepower means that the steam engine has about one-third the weight on the drivers as the Diesel-electric and yet -- above about 18 mph, their Tractive Effort is identical. And the maximum horsepower output of the Steam locomotive is reached at about 28 mph -- not all that different than the Diesel-electric. So in your 30 mph train example, it's wrong with locomotives of equal horsepower because they are, at that point, generating the same tractive effort and the same horsepower. The Diesel-electric has zero advantage.

So, you don't really gain the clever comparison that you expect, because the smaller the steam engine relative to the diesel-electric, the more it actually does start to look like the diesel-electric. So, for locomotives of "equal maximum horsepower", when the Diesel-electric reaches its peak, the Steam engine has already developed 83% or more of its total capacity -- at about half the purchase cost per horsepower, by the way -- and that's really what this is all about; if you want to spend equal dollars, you are buying a much larger capacity with the Steam engine all the way round. 

Another way of looking at it is by trying so hard, as you have been doing, to limit the Steam engine to what the Diesel-elecric can produce, you lower the power scale of the Steam engine so that it gets to full power much earlier than a large Steam engine.

And so the comparison between a Diesel-electric and a Steam engine of equal horsepower becomes pretty much of a big "so-what" because the maximum power of the smaller steam engine is developed much earlier and is within a few mph of the top output of the Diesel-electric. And the Tractive Effort of the Diesel-electric still drops like rock so that those are equal as well after about 18 mph but if the train is still moving at 18 mph, then both motive power types had the tractive effort to get it there.

The problem for your argument is that the Steam engine scales up differently than you apparently expected -- and I didn't look at it as close as I should have either, or I could have put this tangent out of its misery much earlier.

And it is pointless to say that somehow the Diesel-electric develops its power "earlier." The Steam engine can develop the same power at the same speed -- and that is what railroads look at for "comparability." It's "earlier" only if you intentionally underpower the Steam engine and then set an artificial rule that it cannot exceed the Diesel-electric. And that rule comes strictly from baseball cards -- nobody plays this game in the real world. The real rule is that, for the cost, you buy the Steam engine with equal weight on the drivers.

It is useful when a heavy train is being moved to have the capability to move it efficiently at 15 mph. Both types can do that and that is really what the real world is looking for.

The problem comes at 30 mph, when that Steam engine can continue to develop additional power as the train requires more power. The key is that these genuinely comparable engines -- same weight on the drivers, pulling the same load -- is that this large Steam engine has a much longer scale distance over which it continues to develop horsepower compared to the little same-horsepower steam engine -- and which provides an additional advantage over both the Diesel-electric and the "same-horsepower" Steam engine used in what still remains to me an artificial metric standard desperately in search of a purpose or point.

However, we can now maybe put this to rest:

Not only is this ability to reach maximum horsepower early not a disadvantage, in some cases it is actually an advantage; for instance, when pulling a drag freight that requires the locomotive's maximum horsepower, but is so heavy that its balance speed will be say 30 mph. A diesel can deliver all of its potential horsepower at that speed whereas a steam locomotive cannot.

And this is wrong. By imposing a maximum hp limit, at 30 mph, both motive power types develop the same hp and same TE.   Case closed.

 

 

[Anonymous]

What would the comparison look like if you compared a 5,600 HP diesel to a 5,600 HP steamer, assuming that they both were capable of delivering their full HP to the rail? 

I'm going to change this to a 3,000 hp Diesel and a 3,000 hp Steam engine to come a little closer to the reality of the era since a 5600 hp Diesel-electric didn't exist then and statistically isn't much of a presence now.

A relatively big diesel is being compared to a relatively small steam engine. As the steam engine gets larger, its ability to continue to develop horsepower continues to extend to higher and higher speeds.

The physics of the whole thing changes when you take a relatively small steam engine and compare it to a large diesel-electric. In this example, equal horsepower means that the steam engine has about one-third the weight on the drivers as the Diesel-electric and yet -- above about 18 mph, their Tractive Effort is identical. And the maximum horsepower output of the Steam locomotive is reached at about 28 mph -- not all that different than the Diesel-electric. So in your 30 mph train example, it's wrong with locomotives of equal horsepower because they are, at that point, generating the same tractive effort and the same horsepower. The Diesel-electric has zero advantage.

So, you don't really gain the clever comparison that you expect, because the smaller the steam engine relative to the diesel-electric, the more it actually does start to look like the diesel-electric. So, for locomotives of "equal maximum horsepower", when the Diesel-electric reaches its peak, the Steam engine has already developed 83% or more of its total capacity -- at about half the purchase cost per horsepower, by the way -- and that's really what this is all about; if you want to spend equal dollars, you are buying a much larger capacity with the Steam engine all the way round. 

Another way of looking at it is by trying so hard, as you have been doing, to limit the Steam engine to what the Diesel-elecric can produce, you lower the power scale of the Steam engine so that it gets to full power much earlier than a large Steam engine.

And so the comparison between a Diesel-electric and a Steam engine of equal horsepower becomes pretty much of a big "so-what" because the maximum power of the smaller steam engine is developed much earlier and is within a few mph of the top output of the Diesel-electric. And the Tractive Effort of the Diesel-electric still drops like rock so that those are equal as well after about 18 mph but if the train is still moving at 18 mph, then both motive power types had the tractive effort to get it there.

The problem for your argument is that the Steam engine scales up differently than you apparently expected -- and I didn't look at it as close as I should have either, or I could have put this tangent out of its misery much earlier.

And it is pointless to say that somehow the Diesel-electric develops its power "earlier." The Steam engine can develop the same power at the same speed -- and that is what railroads look at for "comparability." It's "earlier" only if you intentionally underpower the Steam engine and then set an artificial rule that it cannot exceed the Diesel-electric. And that rule comes strictly from baseball cards -- nobody plays this game in the real world. The real rule is that, for the cost, you buy the Steam engine with equal weight on the drivers.

It is useful when a heavy train is being moved to have the capability to move it efficiently at 15 mph. Both types can do that and that is really what the real world is looking for.

The problem comes at 30 mph, when that Steam engine can continue to develop additional power as the train requires more power. The key is that these genuinely comparable engines -- same weight on the drivers, pulling the same load -- is that this large Steam engine has a much longer scale distance over which it continues to develop horsepower compared to the little same-horsepower steam engine -- and which provides an additional advantage over both the Diesel-electric and the "same-horsepower" Steam engine used in what still remains to me an artificial metric standard desperately in search of a purpose or point.

However, we can now maybe put this to rest:

Not only is this ability to reach maximum horsepower early not a disadvantage, in some cases it is actually an advantage; for instance, when pulling a drag freight that requires the locomotive's maximum horsepower, but is so heavy that its balance speed will be say 30 mph. A diesel can deliver all of its potential horsepower at that speed whereas a steam locomotive cannot.

And this wrong. By imposing a maximum hp limit, at 30 mph, both motive power types develop the same hp and same TE.   Case closed.

I am still trying to digest this topic of HP/TE curves.  I am not wedded to any particular position, but I am only developing and posing my positions and questions largely upon the information you have provided.  You have made the point several times that a fair comparison requires the locomotives to have equal weight on the drivers.  When you said the following about two locomotives of equal horsepower, are you referring to a size disparity stemming from differing weight on the drivers?

"A relatively big diesel is being compared to a relatively small steam engine. As the steam engine gets larger, its ability to continue to develop horsepower continues to extend to higher and higher speeds."

You said:

"In this example, equal horsepower means that the steam engine has about one-third the weight on the drivers as the Diesel-electric and yet -- above about 18 mph, their Tractive Effort is identical. And the maximum horsepower output of the Steam locomotive drops down to about 28 mph -- not all that far above the Diesel-electric."

You have indicated that there must be equal weight on the drivers in order for the test to be fair, and yet in citing the weight-on-driver disparity (one-third the weight), you go on to say that above 18 mph the TE is identical.  So with equal horsepower producing mostly equal TE in the compared locomotives, how is the unequal weight on drivers making the comparison unfair? 

You said:

"...the smaller the steam engine relative to the diesel-electric, the more it actually does start to look like the diesel-electric. So, at equal horsepower, when the Diesel-electric reaches its peak, the Steam engine has already developed 83% of its total capacity"

"The problem for your argument is that the Steam engine scales up differently than you apparently expected -- and I didn't look at it as close as I should have either, or I could have put this tangent out of its misery much earlier."

Well that is certainly a surprise and it does indeed reverse the point of my previous post.  But it also reverses your counterpoint about steam locomotives fundamentally continuing to increase horsepower during acceleration while, as we agree, diesels reach their maximum HP very early during acceleration.

Or to be completely accurate, it reverses both of our points once a steam locomotive drops below a certain size.  What is the reason for this performance reversal that you say occurs when steam locomotives change in size?  I cannot imagine an explanation.  And what is the rate of this reversal as the locomotive size changes?

[blue streak 1]

I've seen nothing here about pure electrification. The same type traction motors (granted AC and higher gear ratios) on AEM-7,ALPs, HHP-8s sure had good acceleration when I rode them and maintained speed with a long train. This has confused the issue for me. 

[TomDiehl]

The focus on the fact that the diesel locomotive reaches its maximum horsepower at 19 MPH is puzzling. The maximum horsepower (or torque, or tractive effort, which ever measure you prefer) is needed to get the train moving. This is one of the advantages of the diesel switcher, which made it the prefered type, even in areas with no smoke abatement ordinances. What advantage the steam locomotive has in developing more horsepower above this point would be lost in the fact that you can't add more cars at speed. It may accelerate a bit faster than the diesel above this point, but is it enough to make it a worthwhile statistic?

It may develop more horsepower above this point, but is that useful in day-to-day operations?

The horsepower and Tractive Effort needs of a train are at its lowest at 0.01 mph. The amount of horsepower and Tractive Effort needed to move the train thereafter continue to increase indefinitely, up to the limit of the ability of the locomotives to move the train. The train "develops" a need for more horsepower at the same time that a Steam engine "develops" more horsepower, and if the company has purchased the same amount of weight of locomotive on the drivers, it has purchased more horsepower above 19 mph where the horsepower needs are greater.

I restored the rest of my original post. As I said there, the maximum horsepower is needed to get the train moving, which you have agreed with by suddenly having the train moving at .01 MPH (or any speed beyond a dead stop). The horsepower needed to keep the train in motion drops significantly after it is moving, which is where steam loses. The old statement "what a steam locomotive can start, it can pull" is based on this fact. The diesel-electric shines in having more horsepower available to start a train.

[TomDiehl]

I've seen nothing here about pure electrification. The same type traction motors (granted AC and higher gear ratios) on AEM-7,ALPs, HHP-8s sure had good acceleration when I rode them and maintained speed with a long train. This has confused the issue for me. 

Electrics and diesel-electrics have a lot in common as their power is applied to the rails through traction motors. Another way to view it, the modern diesel-electric locomotive is an electric locomotive with a built in, diesel powered generator, removing the need for the overhead wire and central generating stations.

[MichaelSol]

  What is the reason for this performance reversal that you say occurs when steam locomotives change in size?  I cannot imagine an explanation.  And what is the rate of this reversal as the locomotive size changes?

This conversation was highly artificial to begin with. Bigger and smaller isn't really useful; as is the reference to "MAXIMUM" horsepower. By fastening on the Diesel-electric's maximum hp output as THE metric, you have a metric that just doesn't translate well into Steam terms, and snapping back and forth between MAXIMUM hp and weight on drivers snaps between two metrics where steam power "scales" and it scales differently with each criteria. For that matter, train resistance scales as well.

Maximum hp is not even a reasonable criteria, because no one goes down the locomotive store and asks to see a 3,000 hp diesel, and then asks to see a Steam engine that only reaches 3,000 hp at 30, 50, or 70 mph and we absolutely don't want one that reaches 3,000 hp at 19 mph because that would be "wrong" and not comparable. It isn't that this isn't a practical question, it simply doesn't have anything to do with the key elements of railroad decision-making: cost and function. It is the single most irrelevant hypothetical I think I've seen, designed only to make a meaningless, a completely meaningless point that, again, goes neither to cost or function, nor anything else really except an argument for argument's sake, to the point where it becomes a revival meeting for the true believers with hosanahhs, amens and "well saids" with each punctuated flourish of the scripture. The true believers have to find another tent, another cause, another meaningless argument, and I am sure they will ... because as another has pointed out, this is really Anything But Steam and this latest stumble in that mythology will not change one expressed opinion on the matter because this discussion long ago left the useful atmosphere of useful facts applied to meaningful situations.

And because I think its simply not a useful metric, I didn't go to the trouble of actually looking at that metric scale -- compared to the real world, this really has been a colossal waste of time -- but looking at it does indeed change the relationship between steam and diesel-electric because it is indeed a different scale measurement, because it does, in fact, change the relative weights on drivers and therefore changes the relative size differences.

And, it's not a "performance reversal", it is simply the irony that after arguing somewhat shrilly and stubbornly -- a "mind made up" -- about something you plainly didn't care to look at closely -- the argument was more important than the facts -- and a more careful examination showed that the truth really did lay somewhere else and the vast importance originally attached to the proposition dissolved upon examination into a minor distinction instead.

But I don't think facts were important in the first place, or any discussion that actually goes to the facts, either way, because it goes to the underlying importance -- the religious conviction -- that Steam must be dramatically inferior, and that some take it upon themselves to prove it, no matter what it takes.

I am sure this will evolve into some new dramatic difference, because belief systems are designed that way and it will go on and so forth from phony revelation to phony revelation.

 

[Anonymous]

Michael, I did not think I was being shrill and arguing with a mind made up.  It's still not made up.  And I don't have a religious conviction that steam must be inferior.

[MichaelSol]

Michael, I did not think I was being shrill and arguing with a mind made up.  It's still not made up.  And I don't have a religious conviction that steam must be inferior.

Don't take it personally. My students would gladly tell you I have two rules in class: 1) there IS such a thing as a stupid question, and 2) what's it cost? The idea is -- do your homework (read the book), don't make assumptions, think about it, and calculate everything through to the ultimate financial impact. I am not well designed for Trains forums where these useful rules are inverted ...

[YoHo1975]

My question still hasn't been answered.

I've gt a pair of...i don't know GP49/59/whatevers 12-710s in run 8 pulling....some train of known size at track speed 55mph. They're gulping down fuel at a rate of 147.3 GPH per engine or close to 300 gallons of fuel.

Assuming equal fuel quality, how many gallons will an appropriately sized steamer use in the same time frame?

 

 

And on a different note, I'm totally confused by the fact that Last time I was back in Chicago, I saw a number of long trains whip by at track speed on the C&NW 60+ miles per hour 2 SD40-2s don't know trailing tons, but it was mixed manifest average train length and according to the presented curves, that doesn't even seem possible for the D-E. And on top of it all, they weren't even in run 8. So they weren't developing max Horsepower. 

 

I'm missing something obvious I know. 

 

[AnthonyV]

This is the result I would expect to see:

1)      Both locomotives would be producing their maximum horsepower at their maximum speed. 

2)      The maximum speed for both locomotives would be the same. 

3)      The diesel would accelerate the train to its maximum speed in less time than the steamer.

And that's the problem. You've defined a set of conclusions you want to reach, and designed a test ensured to reach them. But, the DE reaches its maximum hp at about 19 mph; Steam at around 40-50. The DE generates its greatest power where it can't use it (slip, etc) and where the train doesn't need it. The Steam engine power parallels the resistance increases of the train more "usefully." Nobody would buy a car based on its maximum hp rating; but rather at a standard that represents a useful measure, i.e., where is the train at in terms of speed and weight.

The importance of the weight on the drivers, and using that as the standard is well established.  Older annual reports reported fleet data exclusively in terms of tractive effort, and purchasing decisions were based on that. HP offers a surrogate that most -- most -- people understand more intuitively, but it is an imperfect surrogate. There is "a" correlation between weight on drivers and TE, but because these motive power types produce power so differently, it is likewise imperfect and, because the power curves themselves are not linear, but in fact, curves -- and since the hp curves are different for Steam and Diesel-electric, your approach simply chooses two end points and assumes therefore a straight line between them. That generates misinformation, not useful information, aside from the fact that the endpoints you choose -- maxiumum hp -- are located at very different points on the scale even as you "define" them to be identical for the purpose of reaching a specific conclusion.

From a tractive effort standpoint, a view similar to the hp chart earlier, shows key differences for these types throughout their operating range. The column on the right is the resistance of the train at different speeds. The TE ratings of the motive power types must exceed the resistance of the train and where the TE rating does not exceed the train resistance, that represents the speed limit of the train.

MPH	Diesel	Steam	Resistance
0	100,000	60,000
5	60,000	59,000	14,825
10	42,000	58,000	17,939
15	32,000	56,000	19,924
20	28,000	52,000	22,194
25	22,000	48,000	24,749
30	19,000	40,000	27,588
35	16,000	33,000	30,713
40	14,000	29,000	34,123
45	11,000	24,000	37,818
50	9,000	22,000	41,798
55	8,000	20,000	46,062
60	7,000	19,500	50,612
65	6,500	18,750	55,447
70	6,000	18,000	60,567

At 50 mph, the train would need the equivalent of five Diesel-electric units to move at the speed, but only two reciprocating Steam engines. And this is where the capitalization of the Diesel-electric weighs heavily on railroads seeking operating efficiencies by operating at higher speeds. To operate at 50 mph, the train needs five equivalent Diesel-electric units with a combined TE of 300,000 lbs. But at 5 mph, the train has therefore 300,000 lbs of TE to move 15,000 lbs of resistance! That is extremely expensive tractive effort.  Maybe it looks good to you on paper, but to me it says that this is a power type that generates its power on the wrong parts of the power curve and that represents an expensive misapplication, waste, of power and capital.

A Diesel-electric that can substantially outpull a Steam engine at 1 mph loses its TE advantage pretty quickly, and by 30 mph can pull only half the train that the Steam engine is pulling. And yet the Steam engine had plenty of TE to start that train; it simply has substantially greater capacity to run that train at the higher speeds. Practically speaking, if the Railroad wants to run that train at 30 mph, it can only assign half the tonnage to the Diesel-electric that it can assign to the Steam engine. The higher TE of the Diesel-electric available at very low speeds is useless, meaningless, from that standpoint because that's not where it needs the TE. It's an utter waste of a perfectly useless statistic. And at that 30 mph speed, the Steam engine will still have slightly greater TE available per pound of train resistance, notwithstanding that it is hauling twice the tonnage.

And so what is it that the Steam engine missing there? They can both start their trains just fine. The train is at its lowest overall resistance at the low speeds. High available Tractive Effort at those speeds is a meaningless statistic because that's not the range in which the train is going to develop its need for high Tractive Effort. It's the Diesel-electric that fails to carry its burden at the higher speeds, not the reciprocating Steam engine. And that is a fundamentally different characteristic of the motive power types.

In this instance, even if these TE curves are adjusted in the fashion you desire -- maximum hp reached by each motive power type -- the adjustment still presumes, even by the standards of steam locomotives extant 60 years ago, a relatively small steam locomotive even by comparison with the average hp Diesel-electric road locomotive today.

Is there a point in comparing a relatively large Diesel-electric locomotive with a relatively small reciprocating Steam engine? Yes, it is the only way to get the results you want because, ironically, the Steam engine at the identical "maximum" hp as the Diesel-electric has a substantially lighter footprint than the Diesel-electric at that horsepower, which limits its tractive effort to that of the Diesel-electric. But, that offers the "unfair" advantage to the Diesel-electric by limiting the Steam engine to the Diesel-electric's inherent limitations, by carefully setting the "maximum" hp at completely different points: 19 mph for the Diesel, 50 for the Steam, and calling them "equal" which yield's Steam's advantages of substantially higher hp, single units with greater TE per pound of locomotive on the driving wheels.

In other words, your test is carefully calibrated to produce exactly the results you want, by eliminating all of the advantages of Steam power, and testing only on the advantages of the Diesel-electric. While that may be satisfying, it will not translate accurately nor usefully into meaningful economic data, and will in fact give false and misleading results. Testing both motive power types against genuinely common metrics yields completely different results.

What that illuminates is that the reciprocating Steam engine, pound for pound on the driving wheels, delivers more power than the equivalent hp Diesel-electric. That is why, when the weight on the driving wheels is comparable, the Steam engine can generate a substantially greater hp and TE -- it is more efficient at producing power at the speeds where the power is needed and through the means that the power is applied: through the driving wheels at the rail.

And of course, this underscores the point of the thread -- no matter how you slice and dice the data, the capital cost of reciprocating Steam likely remains substantially lower than equivalent Diesel-electric hp, and the operating costs of the Diesel-electric are now so high that it represents, by a substantial margin, the most expensive operating alternative for railroad motive power.

 

Michael:

I developed my own analysis of train resistance using the Davis formula.  The effect of grades was also included.  The results are comparable to yours for operation on level track.  However, grades have a dramatic effect on train resistance.

For example, operation of a 6,000 ton train on level track at 15 mph requires 18,827 lb of tractive effort, which equates to only 753 dbhp.   Operation at 15 mph up a 1 percent grade increases the required tractive effort to 138,827 lb, which equates to 5,553 dbhp.

Did you include the effect of grades in your analysis?

 

Anthony V.

 

 

[MichaelSol]

Michael:

I developed my own analysis of train resistance using the Davis formula.  The effect of grades was also included.  The results are comparable to yours for operation on level track.  However, grades have a dramatic effect on train resistance.

For example, operation of a 6,000 ton train on level track at 15 mph requires 18,827 lb of tractive effort, which equates to only 753 dbhp.   Operation at 15 mph up a 1 percent grade increases the required tractive effort to 138,827 lb, which equates to 5,553 dbhp.

Did you include the effect of grades in your analysis?

Anthony V.

Well, I'm glad you did, because its an interesting process to develop the formula into a broader perspective, and I think its an education to do so. My kids think its weird because I actually think its fun to develop such models. The program I am familiar with is General Electric's original Locomotive Fuel Use program, a Fortran model which I developed into the Excel version that shows fuel consumption over mileage resulting from grade, curvature, distance, and the particular fuel consumption characteristics of an individual locomotive type, including dynamic braking on negative grades, and, in those instances applicable -- since that's my background -- the impact of regeneration on overall power cost, all of which can be adjusted for train tonnage and car type (because the cross-sections and air resistance are different for different freight applications). And I will not suggest that developing the model for any mainline, on 1000 foot increments for curvature and gradient, is nothing less than time-consuming.

However, something to remember: the average US train and locomotive combination encounters the following average North American rail system gradient: 0.00000%.

 

[wsherrick]

My question still hasn't been answered.

I've gt a pair of...i don't know GP49/59/whatevers 12-710s in run 8 pulling....some train of known size at track speed 55mph. They're gulping down fuel at a rate of 147.3 GPH per engine or close to 300 gallons of fuel.

Assuming equal fuel quality, how many gallons will an appropriately sized steamer use in the same time frame?

 

 

And on a different note, I'm totally confused by the fact that Last time I was back in Chicago, I saw a number of long trains whip by at track speed on the C&NW 60+ miles per hour 2 SD40-2s don't know trailing tons, but it was mixed manifest average train length and according to the presented curves, that doesn't even seem possible for the D-E. And on top of it all, they weren't even in run 8. So they weren't developing max Horsepower. 

 

I'm missing something obvious I know. 

 

The N&W Class A maxed out at FULL capacity; That is pulling 5,000 to 6,000 tons at 60 MPH or 15,000 tons at 25-30 MPH burned 7 tons of coal per hour and evaporated 116,000 gallons of water per hour.

The trains of the size you saw in the Chicago region, a region which is almost totally flat, once were pulled by much lighter engines than the A, most likely a light mikado type which on average, off the top of my head burned about 3 to 4 pounds of coal per horsepower per hour.

On the 4501 a 1911 light mikado locomotive with no modern appliances would get 20 miles to the ton with 2,800 tons on the drawbar and constant running at the then track speed of 55 MPH.  I know the consumption of this locomotive because I was busy putting it in the firebox at the time.

BTW, how can you be sure of the throttle setting while on the ground?

[YoHo1975]

I know it wasn't in run 8, because I know what a 16-645 sounds like in run 8 at speed.

[daveklepper]

Will someone please elucidate me as to how anyone can maintain that any locomotive develops its maximum horsepower when starting a train?   As an MIT trained engineer who spent a summer a student entineer at EMD and then worked for the B&M part time the following winter before going into first electronic transformer design and then architectural acoustics, I know that horsepower, power in general, watts, killowatts, is related to tractive effort times speed (force times velocity).   In a diesel, the starting tractive effort is limited by the current the motors can handle and their particular gear ratio and the diameter of the wheels, with of course the adhesion factor and all the weight on drivers, but NOT HORSEPOWER (above a lower limit, in most cases less than 600HP).   How fast the train accelerates is related to horsepower, but not the ability to start the train.

It may appear that when starting from a stop and an engineer has to yank the trottle out to RUN 8, that this is because he needs maximum horsepower to start the train.   In truth he is really getting maximum tractive effort, and a lot of the diesel generated horsepower at the moment of starting is really going up in heat in the armature and field coils of the motors and generator.  Also in accelerating the diesel itself from idle RPM to full horsepower RPM.

Some of you engineers may wish to test a little theory, and see if the train won't start, perhaps a bit smoother by starting a train in a situation where you have always used Run *, and try a lower throttle position.   The train should start, just takes a bit longer, since the diesel takes longer to increase RPM, but the start will be smoother.

[AnthonyV]

Michael:

I developed my own analysis of train resistance using the Davis formula.  The effect of grades was also included.  The results are comparable to yours for operation on level track.  However, grades have a dramatic effect on train resistance.

For example, operation of a 6,000 ton train on level track at 15 mph requires 18,827 lb of tractive effort, which equates to only 753 dbhp.   Operation at 15 mph up a 1 percent grade increases the required tractive effort to 138,827 lb, which equates to 5,553 dbhp.

Did you include the effect of grades in your analysis?

Anthony V.

Well, I'm glad you did, because its an interesting process to develop the formula into a broader perspective, and I think its an education to do so. My kids think its weird because I actually think its fun to develop such models. The program I am familiar with is General Electric's original Locomotive Fuel Use program, a Fortran model which I developed into the Excel version that shows fuel consumption over mileage resulting from grade, curvature, distance, and the particular fuel consumption characteristics of an individual locomotive type, including dynamic braking on negative grades, and, in those instances applicable -- since that's my background -- the impact of regeneration on overall power cost, all of which can be adjusted for train tonnage and car type (because the cross-sections and air resistance are different for different freight applications). And I will not suggest that developing the model for any mainline, on 1000 foot increments for curvature and gradient, is nothing less than time-consuming.

However, something to remember: the average US train and locomotive combination encounters the following average North American rail system gradient: 0.00000%.

 

Don't the specifics characteristics of a route (grades, grade length, curvature, etc.) determine the amount of power assigned to pull a certain tonnage?

I suppose that if power was assigned based on the average topography of the county, all trains of a certain tonnage would be pulled by the same power.  I also suppose there would be no need for helpers.

 

Anthony V.

[JayPotter]

Don't the specifics characteristics of a route (grades, grade length, curvature, etc.) determine the amount of power assigned to pull a certain tonnage?

That's correct.  And system-wide characteristics of a railroad can determine the type of power that it acquires.

One of the primary characteristics that CSXT desires in its road locomotives is the ability to minimize stalling on grades.  As a result, its current locomotive-of-choice is an AC-traction unit with a maximum horsepower of about 4400 and a fully serviced weight of about 431,000 pounds.  One of these units produces about 20,000 pounds of TE at 70 mph and about 47,000 pounds of TE at 30 mph.  Rail conditions permitting, it can produce 200,000 pounds of TE in the speed range from less than one mph to around seven mph; and since it's an AC-traction unit, it can continue to operate within this speed range for an essentially indefinite length of time.

Knowing next to nothing about steam-locomotive performance, I have no idea what the steam-technology counterpart to this diesel would be. 

[Anonymous]

Hi Jay,

the only succesful and widely used Steamengine that produces such a high TE at low speeds were the later, refined Y6b ( in the ~'50ties and later)

They could deliver a starting TE of 170.000lbs, to 150.000lbs at 7mph and 125.000 at 10mph.

From here, until 40mph they had more output than a 4400AC, after 40mph the diesel will surpass.

Hope these infos are useful for you.

Kind Regards

Lars

 

[JayPotter]

The only succesful and widely used Steam engine that produces such a high TE at low speeds were the later, refined Y6b ( in the ~'50ties and later).

I have -- but have never thoroughly read -- a two volume set of books by Eric Hirsimaki entitled Black Gold - Black Diamonds.  They deal with the PRR's shift from steam to diesel; and  I have a vague recollection that they mention Y6b performance in comparison to the performance of PRR steam power.  Being from West Virginia, I've heard of Y6bs; but I've never concentrated enough on non-B&O steam to learn much about them.

[Anonymous]

I do not own much Steam-Books, unfortunately, but please have a look at

http://locofonic.alphalink.com.au/te1.htm

There is a nice comparison between Y6b, Class A and Jawn Henry. That's my information source.

Kind Regards

Lars

[Phoebe Vet]

You guys are trying to teach a pig to sing.

Never try to teach a pig to sing; it wastes your time and it annoys the pig.

[JayPotter]

There is a nice comparison between Y6b, Class A and Jawn Henry.

Thank you.  I was especially interested in the steam turbine data.  I couldn't tell if its maximum TE was 180K or if the curve just wasn't plotted any higher.  The CSXT units that I mentioned would be capable of 216K (i.e. 36K per traction motor); however the 200K limit was imposed to prevent two-unit consists from breaking drawbars by exceeding 400K.

[JonathanS]

Michael, I did not think I was being shrill and arguing with a mind made up.  It's still not made up.  And I don't have a religious conviction that steam must be inferior.

Don't take it personally. My students would gladly tell you I have two rules in class: 1) there IS such a thing as a stupid question, and 2) what's it cost? The idea is -- do your homework (read the book), don't make assumptions, think about it, and calculate everything through to the ultimate financial impact. I am not well designed for Trains forums where these useful rules are inverted ...

A college prof!!! Now I see why you answer and argue as you do.

[JonathanS]

[

However, something to remember: the average US train and locomotive combination encounters the following average North American rail system gradient: 0.00000%.

While that statement is an obvious truth for the rolling stock, what is the average gradient in the US for the lading?