MichaelSol wrote: AnthonyV wrote: 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%.
AnthonyV wrote: 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.
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.
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.
YoHo1975 wrote: 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.
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?
MichaelSol wrote: Bucyrus wrote: 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 Resistance0100,00060,000 560,00059,00014,8251042,00058,00017,9391532,00056,00019,9242028,00052,00022,1942522,00048,00024,7493019,00040,00027,5883516,00033,00030,7134014,00029,00034,1234511,00024,00037,818509,00022,00041,798558,00020,00046,062607,00019,50050,612656,50018,75055,447706,00018,00060,567At 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.
Bucyrus wrote: 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.
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.
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.
Bucyrus wrote: 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.
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 ...
Bucyrus wrote: 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.
blue streak 1 wrote: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 wrote: TomDiehl wrote: 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.
TomDiehl wrote: 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 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.
MichaelSol wrote: Bucyrus wrote: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.
Bucyrus wrote: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?
"...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?
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.
Bucyrus:
Well said.
YoHo1975 wrote: What are the limitations on Diesel electrics that they can't develop HP at higher speeds per hp?
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.
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
1,839
25
6,323
2,562
30
7,226
3,426
35
7,677
4,446
40
7,948
5,641
45
8,129
7,028
50
8,310
8,624
55
8,400
10,447
60
12,513
65
8,219
14,840
70
17,445
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.
tpatrick wrote: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.
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.
TomDiehl wrote: It may develop more horsepower above this point, but is that useful in day-to-day operations?
fredswain wrote: I love steam but let's be realistic, it's never coming back.
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.
I did find this quote very interesting from the AC3000 page:
The ACE 3000 was to be capable of 3000 (nominal) draw bar horsepower (4000 hp peak), an efficient operating speed range of 15 to 70 MPH, have computer-controlled firing, and a typical (not peak) thermal efficiency of 15%. While the ACE team acknowledged that this efficiency was much less than a modern diesel-electric locomotive (which had an efficiency of about 30%), they knew that the immense cost difference in coal and diesel oil would allow a less-efficient coal burning locomotive to be much more economical to fuel than a very efficient oil burning diesel locomotive.
They were designing an advanced steam locomotive but it's efficiency was only half of the comparable diesel of the time. They were relying on the fact that coal was cheaper. Today with environmental and emissions concerns, especially with coal as a fuel source, as well as today's prices, would coal cost half as much as diesel fuel to use? This may be a viable engine to use for coal trains but I can't see it working everywhere as then you have to create the infrastructure to have on site coal which we no longer do not to mention the fact that you'd have to haul it to locations that never see coal.
Here's a 21st century steam engine design proposal:
http://www.5at.co.uk/
tpatrick wrote: Some have asked if steam is so preferable, then why are we not seeing the transition?
Some have asked if steam is so preferable, then why are we not seeing the transition?
Simply put it takes time to develop a concept and a prototype, and then to build it.
The return of steam doesn't mean that we pull all steamers out of tourist operations and museums, overhaul them and set them back on active rails. Any appropriate return of steam powered locomotives would be more in line with the ideas developed for the ill-fated AC3000. In principle the AC3000 had some great advantages but it was never taken from concept to an actual locomotive. More about the AC3000 can be found at this url: http://www.trainweb.org/tusp/ult.html
Additional information can be found at the following websites:
http://www.trainweb.org/tusp/ace.html
http://www.trainweb.org/tusp/ace_det.html
http://www.freepatentsonline.com/4425763.html
The ideas developed with the ACE 3000 are good ones, many of which are key to creating a modern day steam locomotive. The real question is whether or not railroads will consider this as an option and back such an endeavor... but given that diesel fuel and all remains so high they need to be taking a serious look at it.
So then, what are the fuel consumption curves?
Here are the consumption numbers for a 12-710G3A (07/1988)
which I got from poster Robbman on trainboard.com
TP ___ RPM ___ HP ___ GPH 8 ____ 904 __ 3030 __ 147.3 7 ____ 820 __ 2253 __ 116.7 6 ____ 729 __ 1502 __ 79.6 5 ____ 651 __ 1244 __ 67.1 4 ____ 568 __ 1000 __ 50.7 3 ____ 490 __ 675 ___ 34.8 2 ____ 343 __ 350 ___ 18.9 1 ____ 269 __ 191 ___ 13,1 Idle __ 200 __ 0 _____ 2.4 DB-6 _ 729 __ 0 _____ 18.6 DB-4 _ 568 __ 0 _____ 10.9 DB-1 _ 269 __ 0 _____ 4.4
What are the consumption curves for a steam engine,I'm not sure what steam engine might be comparable based on the arguments back and forth.
The primary limiting factor for how much drawbar horsepower can be be generated by a diesel electric is how much power can be generated by diesel engine itself and the efficiency of the electric transmission. A secondary limiting factor is adhesion, below a speed that depends on the maximum output of the diesel engine, the weight on drivers, the conditions of the rail (e.g. dry or wet), the sophistication of the traction control system, the drawbar horsepower will be limited by adhesion.
The best a diesel electric locomotive can do is produce slightly over 0.9 drawbar horsepower for each horsepower available for traction from the diesel engine. Recent locomotives with AC transmissions are capable of this from under 20 MPH to 60 to 70 MPH.
I assume that size of the wheels plays some part. Obviously, the nature of the reciprocating transmission is what makes the Steam Horsepower curve what it is.
Some of this has been gone over before, but what's the rate of fuel consumption for the diesel and the steam engine across those curves. Lets assume for the sake of argument that both engines are using some form of liquified coal product for fuel.
Obviously after that, the question is one of water consumption versus lubricant consumption etc.
My point about asking these questions is of course to find out what the costs are of developing that horsepower.
I feel like this thread has covered two very broad topics. "Is steam better than diesel "on the dynometer" and, is steam better than diesel environmentally.
The first question is pretty obvious. The second is a little more ambiguous, but also more immediately relevent. There's no reason an internal combustion/electric can't run on the same fuel source, so strip that boondoggle from the equations. What is the fuel consumption curve, what is the power curve, what is my desired speed.
From that you can get a pretty good equivelency. Given enough fuel and engines for either, the two engine types can each pull a train of any size at any speed the track can support. The answer could end up being that both perform certain tasks well. perhaps grainger lines with flat terrain and high speeds will move back to steam and mountain districts stick with AC traction D/E. Or it could be that some new design that is neither D/E nor reciprocating steam takes over.
Phoebe Vet wrote: You seem to be using the 19 MPH horsepower to declare that the engines are similar when, in fact, you should be using MAXIMUM horsepower, to determine whether the engines are similar power.
You seem to be using the 19 MPH horsepower to declare that the engines are similar when, in fact, you should be using MAXIMUM horsepower, to determine whether the engines are similar power.
The Steam engine does the equivalent work as the Diesel-electric right up to 19 mph, when the Diesel-electric loses its capacity to continue to develop additional horsepower.
But, throughout that range, those engines can do comparable work. In the real world, those are comparable engines. Among other similarities, such as work, they have comparable weight on their drivers.
But then it makes zero sense to impose the Diesel-electric's limit at that speed on the Steam engine at all speeds, which is exactly what you are doing by making that specific limit - the ability of BOTH engines to deliver the same performance at 19 mph -- the MAXIMUM that the Steam engine is ALLOWED to develop over the remainder of the power curve.
That is not a physical limitation: the Steam engine can continue to develop power. It's simply an artificial limit that seeks to impose the Diesel-electric's limitation on the Steam engine and argue the completely false implication that the Steam engine couldn't develop additional power -- and that is simply false.
And make that clear: you are saying that a Diesel-electric and a Steam engine that are comparable, aren't really comparable if the diesel-electric reaches a limit that does not limit the Steam engine. Well, that will teach those Steam engines ...
What's the point, except to find a small Steam engine that doesn't deliver anything equivalent to the Diesel-electric. Maybe that is the point ...
The analogy would be that its not really a fair fight between you and another if you are the same age and weight and conditioning. It is a fair fight if you are 19, weigh three times as much, and he is 60.
And you argue that is "comparable."
The only salvation on Trains forums is that there are people here that believe that makes complete sense.
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