The "can steam make a comeback" thread has included the inevitable confusion about the supposed advantage the conventional steam locomotive has over a diesel locomotive at, say, 50-60 mph and up. "...ton for ton a steam locomotive can and does pull more tons at higher speeds than a diesel locomotive can." "The H.P. of a diesel is less effective at faster speeds because more electricity is needed to keep the traction motors spinning at the higher speeds." "hp per hp, the steam engine still passes the d/e in tractive effort quite early in speed." "The tractive effort of a steam locomotive increases as the speed increases..." "This is exactly the opposite of what is clearly shown by the published and generally accepted TE/HP curves for the respective motive power types." [The "this" that he was responding to was "the Diesel should always pull at least as much tonnage as a steam engine over the entire practical speed range for a given maximum dbhp."]"At 19 mph, a reciprocating Steam engine that is putting out 5600 hp will generate 50% more TE than a Diesel-electric locomotive(s) generating 5600 hp at that speed." In the last one he probably didn't say what he intended to say, and in the next-to-last he must have misread the other guy's claim, but it all adds to the confusion. This spinoff thread is an attempt to straighten out this one aspect of the argument-- no discussion here about fuel costs or capital costs or air pollution or mining practices. Start with the diesel locomotive. The diesel itself (the prime mover) is happy to produce full horsepower at any locomotive speed, and clearly our aim in designing the locomotive is to arrange a transmission that can transmit that full power to the wheels over a range of speeds, the wider the better. As with any other locomotive, the rail-horsepower-vs-speed curve for a diesel starts at zero at zero mph, and it can only climb so fast as speed increases. But eventually it levels off and, hopefully, remains about constant up to the locomotive's top speed. As it happens I have EMD's graph for the 57:20-geared SDP40F, which (they say) reaches 2500 rail horsepower at 17 mph and 2600 at 25 mph; it's supposed to maintain that to 100 mph. Peak is 2700 rail horsepower from 50 to 95 mph. No reason to think a 62:15 SD40-2 wouldn't do the same, with all the speeds multiplied by 0.69. Some fraction of the road diesels out there couldn't do as well-- it seems high-hp-per-axle diesels like the GP50 (and GP60?) and DDA40X only maintain full rail power up to maybe 90% of their maximum speeds, due to voltage limits, and some? many? all? early C-Cs never got out of series-parallel, so for all we know they did likewise. But plain-vanilla road B-Bs could probably maintain full power pretty well; I doubt anyone can find a power-vs-speed curve for an F3/F7 or RS3 that shows otherwise. The diesel's drawbar horsepower (that is, whatever remains of the rail horsepower after subtracting enough power to move the locomotive itself) will presumably peak somewhere around 20-30 mph, so it isn't 100% true that "for a given maximum dbhp" steam and diesel pull the same-- a 5000-maximum-dbhp diesel will be slightly below 5000 at 45 mph (or whatever speed the steamer reaches its 5000 dbhp peak). As speed increases further the steam advantage may increase slightly for a few mph -- its rail horsepower may still be increasing, while the diesel's is about constant. Eventually the steamer's rail hp will start decreasing, but no way to find out how soon and how much except by trying it-- and in this country that kind of data has always been hard to find. Which brings us to the N&W 2-6+6-4. The claim first appeared in 1936: N&W said an A had pulled 7500 tons (car count not given) at 64 mph on "comparatively level track". Nobody knows how much diesel horsepower we would need to match that, but hard to imagine it would be less than 15000 (on the level)-- probably 12000+ at the drawbar.
N&W originally claimed 6300 dbhp from the A at 45 mph; their graph stopped at 60 mph, but it suggested maybe 5600 dbhp at 64 mph. (Reportedly they later revised those downward a bit.) So people are naturally mystified: if the A can do 64 mph with less than 6000 dbhp, why can't the diesels?
Say the A really did make 64 mph on the level exerting 5600 dbhp-- i.e. 33000 lb of drawbar pull at that speed. That's 4.4 pounds per trailing ton, the same force we'd get by placing the train (without the engine) on a 0.22% downgrade and releasing the brakes. Like I said, nobody knows for sure, but-- anybody think such a train would accelerate to 64 mph?
There are 2 things that need to be known to determine which can pull what amount. Those 2 things are TE (tractive effort) and Limit of Adhesion. Neither on their own tells us anything useful as you can have all the tractive effort in the world but no adhesion and you will go nowhere. You can also have all the adhesion in the world but without tractive effort you don't have the necessary force required to pull the train. Therefore you need to know both. This is easy.
Weight on drive wheels / Tractive effort = Limit of Adhesion
To figure out TE, we need to look at steam and diesel/electric separately. To figure out TE of a steam engine we need to know:
Boiler working pressure, piston bore, piston stroke, drive wheel diameter, and then we need a constant that allows for losses incurred in the real world.
To figure out TE of a diesel/electric engine, we need to know:
The torque of the traction motors, the gearing, and the diameter of the wheels. The power of the generator is not a factor.
Notice that I haven't listed weight on driver's as being important in figuring TE. That's because it isn't. TE is Tractive EFFORT. Effort doesn't mean traction. It just means available force. We need to use weight on drivers in conjunction with TE to determine traction or limit of adhesion. Even then we are trying to determine a theoretical maximum limit of adhesion. Real world can be very different and hence the reason for technology to control adhesion more effectively.
You quoted me as saying "hp per hp, the steam engine still passes the d/e in tractive effort quite early in speed." This statement is in fact true. However if you don't think this is so it is because you are forgetting limit of adhesion. Remember adhesion is traction. Effort isn't. Just because tractive effort on one is higher doesn't mean it can necessarily pull more. You need to also know adhesion. Keep in mind my above statement could in fact also be made false. You need to change all of the parameters, most importantly wheel diameter. Play with some numbers, you'll see it. Generally speaking though, with the way in which each engine is typically designed with their typical wheel size differences with steam engines getting larger wheels, that statement does generally hold true but it can be made to go the other way. We just haven't designed an engine that way yet.
Most of the argument that went back and forth only concentrated on TE and there was nothing pertaining to adhesion. You need to know both for there to be any comparison. Without adhesion, the argument didn't tell us anything useful from either side.
I wasn't going to get into the steam being more efficient overall argument because I do have an opinion on it but don't want to get into it. Needless to say, it's not coming back so whether or not we feel it could or not, it won't. Can and will are also 2 totally different things.
The ultimate engine would in fact be steam. It would be a closed loop nuclear heated steam engine much like submarines and aircraft carriers. The steam generated would spin a steam turbine which would turn a generator which would then power the traction motors in the wheels so really it would be a nuclear hybrid of current engine and steam engine technology with a twist.
fredswain wrote: Most of the argument that went back and forth only concentrated on TE and there was nothing pertaining to adhesion. You need to know both for there to be any comparison. Without adhesion, the argument didn't tell us anything useful from either side.
Actually, the chart I produced for the thread was specifically based on the accepted limits of adhesion utilized at that time (1957) for road motive power of the two motive power types, and was specifically keyed to the weight of the respective machines on the driving wheels because it was the weight on the driving wheels that provided a consistent common denominator to compare across the very different motive power types and reflected the practical results of literally thousands of dynamometer tests on American railroads on both Diesel-electric and Steam power.
And although I utilized some fairly generic TE's as measured, and compared each against the resistance force of a hypothetical train, the relationship of the TE curve for the Diesel-electric to the Steam TE curve is in fact the measured relationship taken from generally accepted, published, power curves.
timz wrote: As speed increases further the steam advantage may increase slightly for a few mph -- its rail horsepower may still be increasing, while the diesel's is about constant. Eventually the steamer's rail hp will start decreasing, but no way to find out how soon and how much except by trying it-- and in this country that kind of data has always been hard to find.
As speed increases further the steam advantage may increase slightly for a few mph -- its rail horsepower may still be increasing, while the diesel's is about constant. Eventually the steamer's rail hp will start decreasing, but no way to find out how soon and how much except by trying it-- and in this country that kind of data has always been hard to find.
The data has long been available, and I reproduced it on the last thread as follows, upgraded for the very high hp diesel-electric example used by another, and a very large steam engine of the kind planned before the transition ended. A person can use any hp they like, but the relative relationship for each motive power type at the respective speeds is well established:
It seems to me that for as difficult as it is to understand this subject, the greater difficulty is communicating it with words in a discussion forum. I have some understanding of this subject, but I am also learning things as these threads progress. So I would like to lay out some thoughts for review and to check my understanding.
I have heard the term "tractive effort" many times over the years, but apparently have not correctly understood it. I always interpreted it to mean drawbar pull. As I think about it now, I don't recall if drawbar pull is a standard term of measure, or not. In any case, my interpretation of drawbar pull is the actual pulling force of the locomotive exerted at the pulling coupler. It would not only depend upon the pulling force that locomotive could apply to the wheels, but also to the traction of the wheels on the rails. That traction is what I would call adhesion. It is affected by the weight on the drivers and by the slipperiness of the rail/wheel contact.
As I understand it now, according to Fred, tractive effort does not include the affect of adhesion, so it is not drawbar pull. Instead, tractive effort is pounds of force developed at the running tread of the drive wheels. It is not affected by slipperiness of the rail or the weight on the drivers. In fact locomotive tractive effort could be measured without even having a track. I guess the expression of tractive effort would be the total of the drive wheel force of all drivers. So a B-B diesel producing 100,000 pounds of TE would be exerting 12,500 pounds per wheel, at the running tread of each wheel.
In order to compare the fundamental abilities of steam and diesel locomotives, we need to compare locomotives of equal stature for a fair comparison. To determine if two locomotives are of equal stature, we could consider their attributes of horsepower rating, the actual production of horsepower at different speeds, tractive effort at various speeds, adhesion according to weight on drivers, number of drivers, and total locomotive weight. But here is the problem: With so many variables in performance, no two locomotives will be identical unless they are the same model. In fact, in our comparison of fundamental abilities, we expect to find a difference. Yet if a difference is found, it implies that the two locomotives are not of equal stature, and therefore the comparison is unfair. It strikes me that this is the reason that the question, which was the most powerful steam locomotive? has never been answered.
So to at least simplify the task of comparing apples-to-apples in this discussion, I suggest we set aside the issue of adhesion. I realize that the adhesion must be included to determine the ability of a locomotive, but it seems to me that neither locomotive type has any fundamental advantage in weight-on-driver determined adhesion if the other locomotive could be ballasted for the same result. So why not just compare tractive effort at different speeds?
If we do that to find the fundamental difference in tractive effort, what criteria do we use to match locomotives of equal stature, so the comparison is fair?
MichaelSol wrote:The data has long been available
We've using different definitions of "data" here. Your table isn't "data" in the sense of the results of some sort of measurement-- or is it? I'm guessing you (or someone) calculated the horsepower for a hypothetical steam locomotive, based on certain necessarily simplified assumptions. We wouldn't mind knowing the assumptions, but in any case you're not claiming these are measured horsepower for any actual locomotive, are you?
If we are going to discuss the table further, you might as well give us the details of your assumptions and calculations.
To kill two birds with one stone (yet again) here are the actual drawbar horsepower measurements of a Class A:
I can not copy and paste the graph here because it is in an expensive book which will remain intact.
At 10 MPH-3,000 Drawbar Horsepower
At 15 MPH-4,000 Drawbar Horsepower
At 20 MPH-4,800 Drawbar Horsepower
At 24 MPH-5,000 Drawbar Horsepower
At 30 MPH-5,400 Drawbar Horsepower
At 40 MPH-5,600 Drawbar Horsepower
At 50 MPH-5,500 Drawbar Horsepower
At 60 MPH-5,200 Drawbar Horsepower
As can be seen the A reaches 5,000 Drawbar Horsepower at 24 MPH and continually remains above this number until the final measurement point at 60 MPH is reached. The power curve at 24 MPH and above is relatively flat through out this wide speed range.
So then the ability of a standard steam locomotive to produce a high rate of almost continuous horsepower over a wide speed range is clearly evident.
Bucyrus wrote:I have heard the term "tractive effort" many times over the years, but apparently have not correctly understood it. I always interpreted it to mean drawbar pull.
I guess there's no official definition, but when I say "tractive effort" I mean the force exerted at the rim of the drivers (averaged thru 360 degrees of driver rotation, if necessary). Drawbar pull ... not much mystery about that.
Bucyrus wrote:In order to compare the fundamental abilities of steam and diesel locomotives, we need to compare locomotives of equal stature for a fair comparison....In fact, in our comparison of fundamental abilities, we expect to find a difference. Yet if a difference is found, it implies that the two locomotives are not of equal stature, and therefore the comparison is unfair.
Sounds like you're at a dead end. Far as I'm concerned you're worrying too much about making your comparisons "fair". Go ahead and make the comparison, doing your best to make it fair; if somebody says it's unfair, leave it up to the reader to decide.
Adhesion is mostly or entirely irrelevant to this discussion-- we're discussing TE/drawbar pull at speed, when either locomotive, steam or diesel, is producing TE far below its maybe-adhesion-limited maximum.
wsherrick wrote:here are the actual drawbar horsepower measurements of a Class A
timz wrote: MichaelSol wrote:The data has long been availableWe've using different definitions of "data" here. Your table isn't "data" in the sense of the results of some sort of measurement-- or is it? I'm guessing you (or someone) calculated the horsepower for a hypothetical steam locomotive, based on certain necessarily simplified assumptions. We wouldn't mind knowing the assumptions, but in any case you're not claiming these are measured horsepower for any actual locomotive, are you?If we are going to discuss the table further, you might as well give us the details of your assumptions and calculations.
It is probably pointless to discuss the issue further. I get the impression it isn't for enlightenment. A gentleman asserted on the other thread that a Diesel-ellectric locomotive he once knew generated 5,600 hp. He refused to provide a power curve for the machine when asked.
Given the published horsepower curves for the respective motive power types with the same weight on the drivers, there is an equivalent steam engine for that size and rating. At the time the data was obtained, the models of each at those particular selected horsepower outputs did not exist, however, the gentleman wanted to talk abolut his 5600 hp DE, and experience already had shown that scale changes did not and do not appreciably change the statistical relationships. The "data" is contained in the numbers as those represent the specific proportionate changes with speed for each motive power type according to the published data and, in an Excel spreadsheet, the numbers recalculate according to the predetermined relationships taken from dynamometer tests for any given hp at a specific given speed. If you wished to take each succeeding hp at each succeeding speed, and subtract the preceeding and then determine the percentage change, you will see the power curves for the respective motive power types emerge from the raw numbers. But, the relationships are already taken from existing published curves so why bother? My table simply shows what they would be for the gentleman's specific proposed hp output.
As Fred points out, the idea is to point to trends and relationships. Unfortunately, these threads do tend to degenerate into "oh yeah, what about a five year old engine on a Tuesday on a 1% grade with a headwind?"
The point is to illuminate, not drown, the principles involved. And I think the principles are clearly demonstrated by the existing published power curves. This is a wheel that we don't have to reinvent here nor is there a need to speculate about what they "might" be. They are what they are.
MichaelSol wrote:Given the published horsepower curves
Your figures are based on published curves? Published where, and when?
The (H.F. Brown?) diagram you showed in the last thread is misdrawn, and doesn't purport to represent actual locomotives, does it? I don't recall any other curves being mentioned there, except the figures for the N&W A-- but I didn't go over that thread carefully.
And you really ought to make some slight effort to explain just how you transformed the published curves into the figures in the table above. We agree that they are what they are, but so far none of the rest of us knows what that is.
timz wrote: wsherrick wrote:here are the actual drawbar horsepower measurements of a Class AAFAIK nobody's disputing the A's dbhp figures. The only question is whether that dbhp was enough to pull 7500 tons at 64 mph on the level-- and, if it was, why isn't it now. (I'm going out on a limb and guessing it isn't.)
The N&W officially reported that it did so in testing, in daily service their time freight tonnage rating was 6000 tons which were pulled everyday at 50 to 60 MPH, so there you are. Either the N&W simply lied about the test results or it didn't.
The point about posting the actual horsepower ratings was to give real world data to support the argument about Steam's ability to produce high horsepower over a wide range of speeds and to give credence to the trends supported in the other comparisons above.
wsherrick wrote:Either the N&W simply lied about the test results or it didn't.
There's the truth, and there are lies, and then there's everything else-- my feeling is the last category is maybe 90% of the total, but there's room for dispute on the exact figure.
Silly me for chiming in way out of my element, but......... I agree that adhesion is a necessary, but irrelevant, factor in comparing the engines unless the adhesion is ever overcome in a side-by-side comparison of any two engines of any type. In other words, if one has 10K ponies and the other has a modest 1200 in a switcher's body, but the 10k spins all the time, which engine can actually to the work? So, forget the adhesion for now. Just deal with two "really heavy" engines that have a less than 0.0001 probability of spinning in any one test, and deal with how much resistance they can overcome at the tire tread. Let's say they will always be evenly matched for adhesion. So, let's now concentrate on getting tonnage down the linear axis of the rails.
Is that sensible?
timz wrote: MichaelSol wrote:Given the published horsepower curvesYour figures are based on published curves? Published where, and when?The (H.F. Brown?) diagram you showed in the last thread is misdrawn, and doesn't purport to represent actual locomotives, does it? I don't recall any other curves being mentioned there, except the figures for the N&W A-- but I didn't go over that thread carefully.
We already had this discussion the previous thread. The curve was posted there. It shows the relationships that exist within the motive power types and between the motive power types. These relationships are defined by physics and, unless you can identify a heretofore unspecified change in the physics -- such as adhesion improvements -- the relationships will always hold true.
The chart uses the word "comparative" and that is designed to offer a specific piece of information: because the relationships are tested and true -- from there you can play with individual numbers all you want, but the relationships have to remain.
I've seen similar curves in various publications but that was long ago. The Steam Engine, by Ralph Johnson, published by a regular railroad publishing house, Simmons-Boardman, shows the same chart.
The interesting thing is that if we focus solely on TE and ignore adhesion, the results will be biased towards one type of engine. If we were to focus only on adhesion and ignore tractive effort (which would be hard to do as it's a required variable in adhesion), then we may get a result that favors the other engine. I think the original intent of this little debate/discussion is to know which one can physically pull the most and at what speed in the real world. Everybody can bench race with only certain variables and anyone can win this way with some creativity. The unfortunate part as has already been pointed out is that there are so many different variables between each type of locomotion that a true equal comparison becomes very difficult if not impossible.
I do feel that just because there are those who disagree with anothers perspective, they shouldn't just automatically write them off as completely wrong altogether and then demean them publicly for their views. Debates can be friendly and when done properly everyone involved can hopefully benefit from it in the end. The point of this shouldn't be to try to prove everyone else wrong but rather to get all the facts out in the clear so the fundamental physics behind it are understood. Let's face it, everyone could completely understand it but there would still be opinions as to which one would be beneficial to the world of today. Keep opinions to yourselves for this thread and let's get all the facts out. If anyone's "facts" disagree with others, let's figure out why. Everything I have typed I have learned in the past couple of days and I studied it because of this forum. the debate has had merit for me. Let's make it have merit for everyone.
timz wrote: Bucyrus wrote:In order to compare the fundamental abilities of steam and diesel locomotives, we need to compare locomotives of equal stature for a fair comparison....In fact, in our comparison of fundamental abilities, we expect to find a difference. Yet if a difference is found, it implies that the two locomotives are not of equal stature, and therefore the comparison is unfair.Sounds like you're at a dead end. Far as I'm concerned you're worrying too much about making your comparisons "fair". Go ahead and make the comparison, doing your best to make it fair; if somebody says it's unfair, leave it up to the reader to decide.
Well are we only comparing individual locomotives to see which one does what? Or are we comparing locomotives to discover some fundamental difference between steam and diesel locomotives?
selector wrote: Just deal with two "really heavy" engines that have a less than 0.0001 probability of spinning in any one test, and deal with how much resistance they can overcome at the tire tread. Let's say they will always be evenly matched for adhesion. So, let's now concentrate on getting tonnage down the linear axis of the rails.Is that sensible?
Just deal with two "really heavy" engines that have a less than 0.0001 probability of spinning in any one test, and deal with how much resistance they can overcome at the tire tread. Let's say they will always be evenly matched for adhesion. So, let's now concentrate on getting tonnage down the linear axis of the rails.
Well, it is, but that goes to the idea of equivalent weight on the drivers, and if they are different, the lighter engine can't put as much of its theoretical TE to the rail. If you impose a weight difference, you impose a penalty on the lighter engine, regardless of its power.
Look at the general equation posted above a little differently.
Tractive effort = Weight on drivers/Limit of Adhesion
There are some things missing to make it accurate, that show the curve with changes in speed, and that each power type has different coefficients, but it is the basic principle.
What is the fundamental determining factor of tractive effort: weight on the drivers.
Therefore, to obtain the benefits of the fundamental principle in terms of understanding the concept, you can't go off and use a metric that is not, in fact, relevant to the fundamental principle because then you are not comparing "tractive effort" on the comparable basis that defines tractive effort. Because it is the fundamental principle, how could you compare tractive effort of two motive power types with different weights on the drivers?
Lowering the weight on the drivers on one motive power type until it finally matches the output of another motive power type doesn't really tell you anything except that, sure enough, lower weight will reduce tractive effort. That's not a conclusion: that's an assumption already built into the formula!! You lose the benefit of any meaningful comparison by abandoning the metrics upon which the principal of tractive effort is defined and in that case you cannot, therefore, compare tractive effort outputs. You might as well compare paint colors.
If you wish to determine a meaningful difference in power output between two motive power types, that can only be assessed when they have the mathematical equivalence of weight and adhesion. Then, when one motive power type does, in fact, show a significant advantage in TE, it is only because of a qualitative difference in how it produces TE and how it gets it to the rails. And that qualitative difference will be measured by a specific coefficient that acts upon the weight of the drivers and the limit of adhesion.
That coefficient is the specific qualitative measure that mathematically compares motive power types.
And that coefficient will only compare the quality of tractive effort output, if the weight on the drivers is equal because that is how tractive effort is defined.
And you can't fight the math on choices of metrics on that.
Okay, I think I got really close to getting it at the end of your reply, Michael. I'll continue to ponder it and re-read to see if it will click. It's close.
-Crandell
timz wrote:Which brings us to the N&W 2-6+6-4. The claim first appeared in 1936: N&W said an A had pulled 7500 tons (car count not given) at 64 mph on "comparatively level track". Nobody knows how much diesel horsepower we would need to match that, but hard to imagine it would be less than 15000 (on the level)-- probably 12000+ at the drawbar.
Using a 4400-hp AC4400CW as a basis for comparison, it is rated for about 3800 tons at that speed and would have to slow slightly below 50 mph to pull 7500 tons.
MichaelSol wrote:It [the curve he helpfully repeated about 60% of the way down page 1 of this thread] shows the relationships that exist within the motive power types and between the motive power types. These relationships are defined by physics and, unless you can identify a heretofore unspecified change in the physics -- such as adhesion improvements -- the relationships will always hold true.
Not the relationships in that chart-- they'll never hold true. Take another look at his chart, everyone-- can you see why it's worthless?
MichaelSol wrote:The Steam Engine, by Ralph Johnson, published by a regular railroad publishing house, Simmons-Boardman, shows the same chart.
Hopefully you mean The Steam Locomotive? If so, I sure don't remember him including anything that wacky, but I'll check.
Bucyrus wrote:Well are we only comparing individual locomotives to see which one does what? Or are we comparing locomotives to discover some fundamental difference between steam and diesel locomotives?
Any way to do the latter without first doing the former?
timz wrote: Hopefully you mean The Steam Locomotive? If so, I sure don't remember him including anything that wacky, but I'll check.
"Worthless," ..."Wacky", eh?
OK, we're up to name-calling .... I had a feeling you were looking for that opportunity with this thread. Yes, the book is The Steam Locomotive: Its Theory, Operation and Economics Including Comparisons With Diesel-Electric Locomotives, Ralph P. Johnson, Simmons-Boardman Publishing Co, 1944. It was first published in 1942; reprinted in 1944, and again in 1981. Apparently it was the definitive classic.
A world-wide audience of professional engineers read the identical graph in H.F. Brown's 1961 paper: the graph you have termed "wacky". Brown had 40 years experience as a motive power specialist at the Pennsylvania Railroad and at Gibbs & Hill; the acknowledged premier motive power consulting firm of the era. A P.E., he also had a PhD in engineering. As a combinaton of education and practical experience, there are few people who have ever had the qualifications to comment on motive power as H.F. Brown. His article was and remains to this day perhaps the most widely and thoroughly vetted article on railroad motive power in the history of the industry. The correspondence regarding the article shows no one challenging that particular presentation, using the words "wacky" or otherwise ... David P. Morgan commented on it, and missed that one; Trains missed it; General Motor's chief of locomotive marketing who commented extensively on the article, missed that one; Railway Age editors assisted in preparing the Brown piece -- they missed it too? British Rail, the veritable inventors of modern railroad locomotion, and for whom the study was ultimately prepared, didn't understand the graph???
I mean, you are the only guy in the rail industry that figured out that this was "worthless" and "wacky"? Really? There is a point in a conversation like this that credibility plays a role. When you are the one challenging the credibility of reputable, published authorities you raise the question: who are you and what is your background and specific experience to challenge these people? And I don't mean to make a personal challenge here, but I'm not the one throwing around the terms "worthless" and "wacky" regarding the observations of experienced, knowledgeable, professional engineers who subjected their conclusions to peer review and publication. If you raise issues of personal credibility, you raise them in both directions. We know who they are. Who are you? Are you suggesting your credentials are better than theirs? Well, if so, what are they?
That graph has enjoyed a very wide usage and circulation in major industry publications written by recognized motive power specialists and heavily reviewed by virtually all the other recognized motive power experts. I mean, you'd think someone might have noticed, if what you say is even remotely plausible, let alone true.
Do you have one that shows differently?
timz wrote: Bucyrus wrote:Well are we only comparing individual locomotives to see which one does what? Or are we comparing locomotives to discover some fundamental difference between steam and diesel locomotives?Any way to do the latter without first doing the former?
No, you have to do the former to do the latter, but you can do the former without doing the latter, which is what I meant. If you are not concerned about a fair test, I think you would have to stop after doing the former.
This is regarding your earlier comment:
"Sounds like you're at a dead end. Far as I'm concerned you're worrying too much about making your comparisons "fair". Go ahead and make the comparison, doing your best to make it fair; if somebody says it's unfair, leave it up to the reader to decide."
I thought the whole point of a comparison was to prove something rather than to just leave the conclusion to the eye of the beholder.
MichaelSol wrote:That graph has enjoyed a very wide usage and circulation. Do you have one that shows differently?
I'd suggest the "Steam and diesel-electric locomotive drawbar characteristics" graph on page 406 of The Steam Locomotive In America Its Development in the Twentieth Century by Alfred W. Bruce, published in 1952. It compares a 6000-hp diesel against a 6600-hp steam locomotive and shows tractive-effort and horsepower figures on the vertical axes. Although I doubt that a 1952 diesel consist is the best subject for a current comparison, I can't cite a graph comparing a more modern diesel against a steam locomotive.
JayPotter wrote: I'd suggest the "Steam and diesel-electric locomotive drawbar characteristics" graph on page 406 of The Steam Locomotive In America Its Development in the Twentieth Century by Alfred W. Bruce, published in 1952.
I'd suggest the "Steam and diesel-electric locomotive drawbar characteristics" graph on page 406 of The Steam Locomotive In America Its Development in the Twentieth Century by Alfred W. Bruce, published in 1952.
Can you post it?
MichaelSol wrote:Can you post it?
I'm afraid not. I'm behind-the-times to the point of not even owning a scanner. For whatever it may be worth, the related narrative (page 405) is as follows: "A typical 484 steam locomotive of 6,000 ihp with an axle loading of 70,000 lb will have a weight of about 280,000 lb on drivers with a tractive effort of perhaps 70,000 lb maximum. A 6,000 bhp diesel-electric three-unit locomotive with an axle loading of 53,000 lb will have a weight of about 630,000 lb on drivers and a tractive effort of perhaps 157,500 lb." The use of exemplar diesels having four axles and 2000 hp seems strange to me.
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