Overmod selector Agreed about at least one previous and protracted discussion, perhaps four years ago already. I think I recall a poster who seemed to know steam locomotives well saying that a UP Challenger could produce something like 3700 hp at about 50-60 mph, or something near that. Crandell I'm going to roll several post responses into one. TE is an overrated -- usually very overrated -- index of steam-locomotive performance, and to boot it's fundamentally 'cooked' in some respects (e.g., the effective "TE" changes at different angle of rotation, and the boiler pressure is 'assumed' to be something other than it really is by the time it's doing work in the cylinder. HP for steam locomotives comes in two very, very distinct flavors, and you should avoid confusing them whenever you can. (There is also a boiler HP, but it's about as useful as the old European taxable HP for automobiles... and about as well-grounded in modern technical fact.) Remember for a moment that HP is a measure of work, and with time factored in, speed (at a given "TE") becomes important. That is why the effective "TE" of diesels gets so wretchedly small at higher speed. A reciprocating steam locomotive is not 'constant horsepower' because combustion is not confined to the cylinders to determine maximum heat release (from fuel burn) to produce effective pressure. IHP, indicated horsepower, is a measure of how the steam is used and expanded in the cylinders. It is of course a figure specific to a given cutoff and a given road speed. It is also highly theoretical and dependent on assumptions. Note that Sinclair and others have noted that locomotives with 'beautiful' indicator diagrams may, in fact, show no real-world performance or economy advantages over those with 'small leg of mutton' diagrams. This makes a good number for railfan-forum comparisons of 'who had the most powerful steam locomotive' (usually cherry-picking the speed involved and then not mentioning that too obviously). There are interim figures: wheelrim HP, which tells how much power actually gets from the cylinders to the rail -- this is what is measured on a brake dynamometer -- and test-plant drawbar horsepower, which measures power at the rear of the locomotive frame. But the 'real' measure that makes operational sense is the version of DBHP, which is the HP measured at the (ideally tender) drawbar -- this is a measure of the power the locomotive as a whole actually can exert on a train. When measured via a dynamometer car, the effect of frontal resistance is 'cancelled out' because that portion of developed power that is needed to overcome the locomotive's resistances never 'appears' at the drawbar as instantaneous TE. Some discussion of nominal DBHP for Challengers and Big Boys is here.. Note some of the details that affect a measure of "HP" based on train resistance when that measure is net negative (as on a downgrade of any great percent) -- this appears to apply particularly forcefully to 3985's mythical performance on the container consist. That consist is accelerating (under the resultant of gravitational acceleration) at a determinable rate. In order for a dynamometer car to show any draft (vs. buff) reading at all, the locomotive must accelerate at more than this rate... with the locomotive, too, being accelerated in proportional measure. It is not surprising that very high "drawbar horsepower" estimates based on train weight. If I recall correctly, the peak HP of a Challenger is developed at much the same speed as for a Big Boy (just over 40 mph). The figure of 6290DBHP @41 mph is the highest I've seen listed for the Big Boy, and this was at surprisingly long cutoff.
selector Agreed about at least one previous and protracted discussion, perhaps four years ago already. I think I recall a poster who seemed to know steam locomotives well saying that a UP Challenger could produce something like 3700 hp at about 50-60 mph, or something near that. Crandell
Agreed about at least one previous and protracted discussion, perhaps four years ago already. I think I recall a poster who seemed to know steam locomotives well saying that a UP Challenger could produce something like 3700 hp at about 50-60 mph, or something near that.
Crandell
I'm going to roll several post responses into one.
TE is an overrated -- usually very overrated -- index of steam-locomotive performance, and to boot it's fundamentally 'cooked' in some respects (e.g., the effective "TE" changes at different angle of rotation, and the boiler pressure is 'assumed' to be something other than it really is by the time it's doing work in the cylinder.
HP for steam locomotives comes in two very, very distinct flavors, and you should avoid confusing them whenever you can. (There is also a boiler HP, but it's about as useful as the old European taxable HP for automobiles... and about as well-grounded in modern technical fact.)
Remember for a moment that HP is a measure of work, and with time factored in, speed (at a given "TE") becomes important. That is why the effective "TE" of diesels gets so wretchedly small at higher speed. A reciprocating steam locomotive is not 'constant horsepower' because combustion is not confined to the cylinders to determine maximum heat release (from fuel burn) to produce effective pressure.
IHP, indicated horsepower, is a measure of how the steam is used and expanded in the cylinders. It is of course a figure specific to a given cutoff and a given road speed. It is also highly theoretical and dependent on assumptions. Note that Sinclair and others have noted that locomotives with 'beautiful' indicator diagrams may, in fact, show no real-world performance or economy advantages over those with 'small leg of mutton' diagrams. This makes a good number for railfan-forum comparisons of 'who had the most powerful steam locomotive' (usually cherry-picking the speed involved and then not mentioning that too obviously).
There are interim figures: wheelrim HP, which tells how much power actually gets from the cylinders to the rail -- this is what is measured on a brake dynamometer -- and test-plant drawbar horsepower, which measures power at the rear of the locomotive frame.
But the 'real' measure that makes operational sense is the version of DBHP, which is the HP measured at the (ideally tender) drawbar -- this is a measure of the power the locomotive as a whole actually can exert on a train. When measured via a dynamometer car, the effect of frontal resistance is 'cancelled out' because that portion of developed power that is needed to overcome the locomotive's resistances never 'appears' at the drawbar as instantaneous TE.
Some discussion of nominal DBHP for Challengers and Big Boys is here.. Note some of the details that affect a measure of "HP" based on train resistance when that measure is net negative (as on a downgrade of any great percent) -- this appears to apply particularly forcefully to 3985's mythical performance on the container consist. That consist is accelerating (under the resultant of gravitational acceleration) at a determinable rate. In order for a dynamometer car to show any draft (vs. buff) reading at all, the locomotive must accelerate at more than this rate... with the locomotive, too, being accelerated in proportional measure. It is not surprising that very high "drawbar horsepower" estimates based on train weight.
If I recall correctly, the peak HP of a Challenger is developed at much the same speed as for a Big Boy (just over 40 mph). The figure of 6290DBHP @41 mph is the highest I've seen listed for the Big Boy, and this was at surprisingly long cutoff.
According to Lois, the Friend of 611 in the N&W Steam Development thread, who I believe is in a VERY good position to know, 611 should be back and "chuggable" sometime in the spring of 2014.
Say, what happened to DoctorD? I used to enjoy his posts.
I know this thread is months old, but with the announcements of late re UP4014 and NW611, I thought it might be interesting to reactivate the discussion.
I certainly wish I had kept an eye on the topic after I first posted!
===========================
J.D. Gallaway -- http://me.fccorp.us
I don't have that drawing, only loco diagrams which are "D" size. Any way to get a copy to me? Scan and PM off line maybe? I think Neil Burnell will also be interested in this information. There were several adjustments that were made to the back-to-back driver dimensions when trouble was encountered with the 13 deg curved turnouts at the west end of Pittsburgh station. This may be part of that event. Charlie Meyer and I had a lengthy discussion on the geometry differences of 131-lb vs 132-lb turnouts of the same nominal size and how revisions to the T1's driver "gauge" would be involved.
The devil is always in the details, and this stuff can be really detailed!!! Oh well, the T1's were like that...
Just a quick one here, I'll be back later.
I suspect that maybe, just maybe, UP steam guys would think it'd be cool to get a 4-12-2 running again, but who'd want to tackle a restoration with that third cylinder in the picture. They were a pain in the neck to service 60 years ago and would'nt be any less of a pain now.
I'd love to see a 9000 running, that mile-long wheelbase and attendant main rod are just fantastic, but as I see it it just ain't gonna happen.
It WOULD be cool though. Hope time proves me wrong.
Thanks, Dave; I appreciate your contributing here.
Is there a detail record of what was done during the 'eight days'?
feltonhillThe T1's had lateral motion devices on axles 1 and 3, not all four, IIRC.
Aha! But I have the 1947 revision of the 1-1-45 side elevation drawing (A-433857a) that shows the "lateral motion" for each driver axle... perhaps I am misreading it, but it shows a precise figure for each one, and a history of modification (numbers are hatched out so that you can still read what they were, but not use them mistakenly).
Some evidence of the sensitivity involved here is that the amended spec on #4 is 23/32". Not 3/4". Think about it...
Interestingly enough, even the original version of this drawing, and the spring rigging detail drawing referenced in it, show that the prominent 'beam' equalizer between #2 and #3, prominent in early drawings, is completely gone. In fact there is no equalization between them, although carefully tuned coil snubbers are present at the "inner" ends of the respective driver spring rigging and truck equalization connections. LOTS of fine tuning for suspension characteristics, I think almost certainly because of a sense that the high-speed slipping was associated with suspension characteristics.
RME
The valve gear failure on December 10, 1944 was the only negative incident during the month-long test period, which ran to Jan 3, 1945. There are different descriptions of what happened, some of which are considerably exaggerated. Several PRR memos corroborate the actual damage: (1) bent valve gear connecting rod (2) bent eccentric rod (3) loosened eccentric crank, i.e., the crank arm moved on the main pin and (4) damaged reverse gear quadrant, more specifically, the teeth were torn out of the front portion of the quadrant.The blame was assigned to lack of lubrication in the left valve chamber. The story is that N&W's lubrication did not agree with PRR's water treatment chemicals, and this caused the oil to break down. PRR also commented that “excessive speed” was a contributing factor. A further perspective of the damage can be gained by looking at the timekeeping on this run. When 610 was cut off at Ft. Wayne, it had only used eight additional minutes of running time compared to the schedule. This indicates that the failure did not immobilize the locomotive and that it may have happened near Ft. Wayne, perhaps on the 5-mile downgrade approaching MP 321. Eight days later, 610 was back on the job, and there were no more in-service failures.
PRR was concerned about machinery speed for sustained high speed running and made comparisons of the piston speeds of the two demonstrator T1's (6110 and 6111) and N&W's 610. They thought that 80" drivers would be better, and a locomotive similar to ATSF's 3776 class would be satisfactory.
The T1's had lateral motion devices on axles 1 and 3, not all four, IIRC. N&W's J's didn't use them at all, but relied on a very short wheelbase and some gauging adjustments to keep the J's happy on home rails. If you've ever seen photos of N&W's track during the 40s and 50s, you'd swear it was welded rail, in spite of the fact that it was conventional stick rail. Good alignment and surfacing, coupled with high maintenance standards of the locos made the relatively low calculated Fof A for the Js, As and Ys largely irrelevant.
Dr D I particularly have enjoyed Lamb as a new author with his development of the science of engineering through the Industrial Revolution. Most steam was created in the era of "Industrial Arts" rather than the more modern era of "Scientific Engineering."
I particularly have enjoyed Lamb as a new author with his development of the science of engineering through the Industrial Revolution. Most steam was created in the era of "Industrial Arts" rather than the more modern era of "Scientific Engineering."
Cole, Goss, Woodard and a host of others would disagree with you, and truth to tell, so would I. Putting the design of locomotives on a scientifically-grounded basis, and adapting various aspects of scientific theory, methodology, and practice to steam-power problems, were significant even in the early years of the American Locomotive Company -- far more so at Lima with Woodard.
Most steam construction before the 1930"s was the product and the design work of "practical engineers" with a forgone predeliction to the engineering traditions of the past - of those who preceded them.
If anything, the difficulty with the twenty years 'before' the 1930s involved too much, rather than too little, adaptation of modern scientific concepts to railroad engineering. Early approaches to using higher-pressure, high-temperature steam, taken after around 1921 from the evolution of stationary-plant practice, generally didn't come to much. Neither did water-tube fireboxes or poppet valve drive to any significant extent, even though theoretically superior.
I think the issue is far more related to the 'predilections' [note sp., and that 'foregone' actually means something nearly the opposite of what you intended] of the CUSTOMERS -- railroads and shops that considered only their own measures of what constituted 'cost-effectiveness.' Take as a case in point what happened when scientific development was used in manifestly the wrong model: the D&H high-pressure locomotives.
(There are also places where 'science' produced whoppers that experience wouldn't -- see the saga of balancing the ACL R1 4-8-4s, at a time when locomotive engineers really Did Know Better.)
The superheater systems and the feedwater system design sciences being one of the leading factors in moving steam designers beyond "Industrial Arts" and onto modern "Scientific Engineering" age.
What these really reflect is a better overall thermodynamic design, rather than 'science' being applied where it had never gone before. Neither superheating nor feedwater heating was 'new' when Schmidt developed his approach, or the early practical forms of Coffin and Elesco heaters were developed.
Even today, not many steam people understand exactly what the 'scientific' reason for one of the principal gains in superheating is: the reduction of nucleate condensation on long expansion.
Lamb suggested the guiding ability of both two and later four wheel leading truck design...
I'd put this the other way around: four-wheel engine trucks reached a high point of stability long before high-speed two-wheel trucks were developed. Admittedly there were great design improvements in the Thirties (e.g. the Batz truck on ATSF) but these are really refinements on the basic pin-guided truck design.
... as one of the breakthrough technologies needed in the design the American steam locomotive.
The high-speed two-wheel truck, yes. Four-wheel trucks were revolutionary ... in the 1840s. That's a while before scientific design...
The real take-home big 'breakthrough' was the recognition -- seemingly very late in the case of Henderson in particular -- that boiler steam generation was the true limiting factor on power and speed. This was combined with the knowledge that a larger effective grate area led to more effective firing even for the same expected mass per hour of fuel.
Most of the other stuff came as ancillaries for that recognition. Feedwater heaters to improve the Rankine cycle, but also preclude thermal-cycling and distortion effects when higher pressures are used with 'older' matallurgy. Superheating to improve the characteristics of the steam with otherwise-not-fully-used combustion-gas flow. Stokers to reach areas of the larger grates not easily accessed with a shovel, and then to provide reasonable accuracy at higher fuel mass flow than even two firemen could accomplish with strong backs and weak minds.
Likewise the articulation of the rear truck was a similar breakthrough.
"Articulation" of the trailing truck a la Woodard was a bonehead move, and commonly recognized as such, even though it ought to show technical advantages. The chief problem with it is that it provides very little practical restoring force to the yaw induced in the chassis by thrust and longitudinal imbalance inertial forces. That is why the initial Berks, while thermodynamically far advanced even over the 8000 Mike that Woodard kicked off Super-Power with, were emphatically not high-speed engines in regular service, but were emphatically track punishers. As a case history of what to do about this, consider the 1938 rebuild of T&P 610 (it's available in a 'free' collection of articles from Trains Magazine online)
There is that great story about the NYC "mike" leading a freight and the "berkshire" starting after it with a similar train then having entirely passed the "mike" within such short distance.
My understanding was that the Berk had a *heavier* train and still achieved the lower running time. No question that it was superior. But it still wasn't the 'best choice' for a high-speed engine: that was the 4-8-4. And later, the AMC versions of Berkshires that were optimized to run faster.
Looking to Bruce for some of these engineering breakthroughs I found the feedwater heating discussion quite lacking...
Stop there for a moment. Let me say this again: Bruce's book is NOT intended as a 'technical' book. He doesn't even go into the thermodynamic reasons for feedwater heating, in case you needed more proof. That is not to say that Bruce and the Alco engineers did not understand feedwater heating very well -- just that it's outside the scope of a historical book to describe the precise detail by which the feedwater became heated and introduced...
... historically they started out as almost "add on" appliances.
Probably because they WERE add-on appliances, made and sold as such. There were a number of companies that were 'sole manufacturers' of various components, and (this is little known, apparently) a number of combines of these suppliers, for example Elesco and the various Coffin interests) were prominent. Locomotive builders bought these, just as they usually bought superheater elements rather than fabricating from scratch, because of the specific distinctive competence of the 'aftermarket' suppliers. That is true for far more systems than just feedwater heating -- consider Pilliod with the Baker valve gear, or any of the injectors that predate feedwater heaters.
Look at any USRA "mike" or "pacific" feedwater systems they are externally hung all over those locomotives like some kind of trimming or decoration! Then look at photos of later locomotives and these "add on" systems became the accepted designs of "an applied technology" such as evident on the more modern "northern" or "texas" type locomotives.
Naturally, once locomotives were being designed with feedwater heaters in mind, it made better sense to put as much of the piping as possible under lagging or elsewhere that heat loss or freezing were less of an issue. The messy pieces are still there; they are just better integrated.
I think your point is more directed at changing esthetics. In the drag freight era, all that external stuff was easy to 'get at' for maintenance, and no one particularly cared that the 'hogs' were remarkably... well, not beautiful. About the lowest point, for me, was the sort of boiler front Alco put on the NYC K6 Pacifics initially, with the headlight offset and an air pump stuck up there. (Fun enough when C&O did this symmetrically, but the asymmetric version is just plain awful -- which is a shame as the rest of the K6 is basically an esthetic treat)
Bruce's lack of discussion of superheating and feedwater heat, and the similar engineering development of the leading and trailing trucks are his most glaring omissions from The Steam Locomotive in America. With everything Bruce has left us in his book I can't find him developing these truly essential subjects. Feedwater clearly developed from the Coffin to the Elesco to the Worthington in concise developmental steps with the earlier designs being almost painfully obsolete before the paint was dry.
Think how much space Bruce would have to use to address this evolution, and then how many people would read it in 1950. Or, for that matter, today. Interestingly enough, even Johnson does not go into great technical detail on how different versions actually work, or what their specific evolutions or improvements were designed to address. Fortunately, we have people like Parker Lamb who get us part of the way... and then historical documents and people like the 'experts' at RyPN who can fill in some of the remaining detail.
UP844, N&W611, C&O611 [sic; you mean 614] all use well designed in Worthington systems and seem glad to have them.
I call BS on this. 614 was built with a wacky design of feedwater heater which was fairly promptly removed, and all this time she has run happily -- if a bit less economically -- without it. (It sat on that funny platform that now has the hose reel). I won't go into the painful details here (they are covered adequately elsewhere, including the C&O historical society's technical magazine) but it ain't a Worthington, it wasn't well-designed, and far from being 'glad to have it' 614 is fine without it.
Note also that many UP steam locomotives, notably the Big Boys, used an exhaust-steam injector rather than a conventional open-type FWH. At one time there was a splendid colored view drawing showing all the piping and what it did -- I wish I still had that link, or those fies.
UP is still developing the superheater as a functional concept for FEF 844 here in 2013. "How to support the superheater within the flue" - developing special clips to hold it centered and keep the flue from being blocked if the superheater becomes calcified or fire damaged. - you don't get to this place without thousands of hours playing with an FEF - Wow!
Or a few weeks looking at modern materials, and what they can do better than the stuff available cost-effectively for railroad use in the '30s and '40s... ;-}
I am not disparaging anything UP does, by the way, and will further note that the modifications they are doing are intended to improve service reliability and not 'better performance'. But in a very real sense, what the steam crew does is usually much more in line with 'implementing practical wisdom' than trying new scientific approaches -- see, for example, the Australian history with things like double Lempors, or Porta's call for Generation 2 steam -- that might not accomplish what was intended.
UP has historically been known for two steam-designs - Big Boy and the 4-12-2 "Union Pacific" type - how long before they wake up and realize they are going to have to get #9000 and re steam it to live out their destiny!?
Re-steaming a 9000 is 'destiny' in the sense that Luke embracing the dark side would have been. Nobody needs a rigid 12-coupled engine in excursion service when just about anything else UP ran is a more appropriate candidate, specifically including the Big Boys. Those things could be pushed up to moderate speed, but what they did to track at that speed doesn't bear much consideration. And to the modern UP, track geometry is money.
This also brings up the question of who would provide the rebuiid money for that turkey, or what operator would subcontract the running and excursions. How many people would ride -- and pay their fair share of -- a 9000 trip, as opposed to freeloading railfans and foamers?
Oddly enough, this question emerged -- briefly -- in a steam_tech discussion this morning. The more or less unanimous consensus there was NO.
I particularly have enjoyed Lamb as a new author with his development of the science of engineering through the Industrial Revolution. Most steam was created in the era of "Industrial Arts" rather than the more modern era of "Scientific Engineering." Most steam construction before the 1930"s was the product and the design work of "practical engineers" with a forgone predeliction to the engineering traditions of the past - of those who preceded them. The superheater systems and the feedwater system design sciences being one of the leading factors in moving steam designers beyond "Industrial Arts" and onto modern "Scientific Engineering" age. This was championed of course by Keifer, Woodward and others who gave us the Super Power Era of steam starting in the 1920s.
Lamb suggested the guiding ability of both two and later four wheel leading truck design as one of the breakthrough technologies needed in the design the American steam locomotive. Likewise the articulation of the rear truck was a similar breakthrough. I believe Woodward was discovering this developing the 600 series 2-10-4 for Texas & Pacific although the early 2-8-4 super power berkshires. There is that great story about the NYC "mike" leading a freight and the "berkshire" starting after it with a similar train then having entirely passed the "mike" within such short distance. NYC was sold on the "berkshire" demonstrator from that moment on.
Looking to Bruce for some of these engineering breakthroughs I found the feedwater heating discussion quite lacking - historically they started out as almost "add on" appliances. Look at any USRA "mike" or "pacific" feedwater systems they are externally hung all over those locomotives like some kind of trimming or decoration! Then look at photos of later locmotives and these "add on" systems became the accepted designs of "an applied technology" such as evident on the more modern "northern" or "texas" type locomotives. It was this technology of the 20s along with the "superheater" that brought the modern steam locomotive to its present state. Bruce lack of discussion of superheating and feedwater heat, and the similar engineering development of the leading and trailing trucks are his most glaring omissions from The Steam Locomotive in America. With everything Bruce has left us in his book I can't find him developing these truly essential subjects. Feedwater clearly developed from the Coffin to the Elesco to the Worthington in consise developmental steps with the earlier designs being almost painfully obsolite before the paint was dry. UP844, N&W611, C&O611 all use well designed in Worthington systems and seem glad to have them.
Watching U-tube the Union Pacific Backshop tour - UP is still developing the superheater as a functional concept for FEF 844 here in 2013. "How to support the superheater within the flue" - developing special clips to hold it centered and keep the flue from being blocked if the superheater becomes calcified or fire damaged. - you don't get to this place without thousands of hours playing with an FEF - Wow!
UP has historically been known for two steam -designs - Big Boy and the 4-12-2 "Union Pacific" type - how long before they wake up and realize they are going to have to get #9000 and re steam it to live out their destiny!? Yah Big Boy! make my day!
Dr. D
GP40-2 Firelock76 There was a bit of discussion on the "Classic Trains" Forum a while back concerning the Pennsy and the T-1, and why didn't the PRR adopt the Class J as used by the N&W after they'd tested one and found it performed magnificently. The PRR's biggest concern with the J, as designed, was its high machinery speeds, and low factor of adhesion. The J had a combination of small drivers and long piston stroke that would result in a lot of maintenance costs at the speed of operation the PRR was looking for. The J also had a very rigid wheelbase, and wasn't forgiving of less than perfect track.
Firelock76 There was a bit of discussion on the "Classic Trains" Forum a while back concerning the Pennsy and the T-1, and why didn't the PRR adopt the Class J as used by the N&W after they'd tested one and found it performed magnificently.
There was a bit of discussion on the "Classic Trains" Forum a while back concerning the Pennsy and the T-1, and why didn't the PRR adopt the Class J as used by the N&W after they'd tested one and found it performed magnificently.
The PRR's biggest concern with the J, as designed, was its high machinery speeds, and low factor of adhesion. The J had a combination of small drivers and long piston stroke that would result in a lot of maintenance costs at the speed of operation the PRR was looking for. The J also had a very rigid wheelbase, and wasn't forgiving of less than perfect track.
If I recall correctly -- and Dave 'feltonhill' Stephenson will correct me if otherwise -- PRR's principal issue was not with the reciprocating machinery, but with characteristics of the valves and valve drive at those high speeds. This was rather conclusively demonstrated when one of the (big) valves seized up (to terminate the high-speed testing) -- when they got in to see why, the cage was blued with heat.
Not to be heretical... but poppet valves would have addressed that problem, even if doubled valves or even better bearing surfaces or tribology didn't get the job done with less tinker.
PRR worked themselves into something of a corner with the high-speed emphasis, implicitly going for engines with sustained high-speed potential far beyond what most of their railroad -- and ALL of their freight service -- could use, let alone require. Staufer pointed out that the M1 was originally designed with 80" drivers, as a kind of 'next evolutionary step' of the K4, but in the event the 72" drivers were much more practical, and resulted in no particular practical reduction of over-the-road timing...
Meanwhile, there was PRR building All Those K4s, right up to the late Twenties. By the time they were actually in a position to build larger power for high speed, they went to double Atlantics and other duplex things, because that was the flavor of the month in that 'design window'. Fads were not limited to Baldwin -- consider how Alco diverged into three-cylinder design, with almost every road that could afford to rebuild them doing so by the end of the Thirties. The Alco solution for reducing inertial mass effects (the Timken rods, close spacing, sleeved bushings and then roller bearings, etc., as described in Bruce's book, came along later than the siren call of the duplexes...
It was not so much that the J had a 'very rigid wheelbase' -- it was that the EFFECTIVE 'rigid' wheelbase was much longer, because of the stiff lateral necessary to permit zero overbalance (for high speed without vertical unloading and concomitant slip potential). That is also what made the locomotive so '[un]forgiving of less than perfect track'
Meanwhile, the T1 was getting lateral motion on ALL FOUR DRIVER AXLES for its own rigid-wheelbase issues -- which, to me, more than strongly suggests that a very similar degree of stiff lateral in lead and trailing trucks was being applied to get reasonable guiding at high speed.
I don't think there was any dissatisfaction about the J's steam generation capacity! And it might be easily demonstrated that a slight driver-diameter increase (from 70" to 72") would have produced just as satisfactory a result as it did -- admittedly for different detail reasons -- on NYC with the later Mohawks.
I think the PRR was happy with the boiler performance of the J, it was the running gear that they were not satisfied with.
Well, hello Dr. D!
I suspect when Mr. Bruce wrote the book and left out certain technical things such as a discussion of two wheel leading trucks or a detailed explaination of feed water heaters he was probably doing a bit of self-editing to keep the book interesting to the general public and to keep it moving along. I've been reading history all my life and personally I'd rather have a book where the narrative moves along smartly. I've read a number of books that I've termed "over-researched", that is, so many details are packed in they get in the way of the narrative and act like "speed bumps" for the eyes. In my opinion Bruce's book is like Goldilock's porridge, "not too hot, not too cold, just right!" He wasn't writing for engineers in my opinion, but for the reader who wanted to learn something about the steam locomotive without "majoring" in it, if you get my meaning.
There was a bit of discussion on the "Classic Trains" Forum a while back concerning the Pennsy and the T-1, and why didn't the PRR adopt the Class J as used by the N&W after they'd tested one and found it performed magnificently. I suspect that both the Pennsy and Baldwin didn't want to admit those "hillbillys" down in Roanoke were better at steam engine design than they were! Can't prove it of course, but it wouldn't surprise me. Wouldn't be the first time Yankees underestimated Southerners either!
Oh by the way, there's another railroad here in the US still operating under it's original name that's even older than the Union Pacific. Yep, the little old Strasburg Railroad, originally chartered in 1832! And a haven for steam locomotion as well!
Wayne
Firelock 76,
I have been reading Bruce, Steam Locomotive In America for about 40 years and continually enjoy distilling the explanations on steam. I am surprised at your scholarship on the TE vs horsepower discussion by Bruce. He leaves a number of other subjects undeveloped in his text too. There is insufficient explanation on the development of 2 wheel leading truck design, and there is little on the feedwater system complexities. As an overall exploration of steam locomotives in America it is a consumate work though. I continually enjoy going back to learn more about subjects I thought I had fully understood. I also enjoy his archive of photos that include a surprisingly complete collection of most American steam locomotives. His economic engineering discusssion, as well exploration of the late steam electric drive designs and little known nor researched locomotives is fantastic. Pennsys late duplex drive is covered very well. You can't get a better basic text that Bruce.
Regarding 611 - This engine built almost after the steam era by a railroad committed to steam is a landmark engine design. It is no wonder the Claytors were so enamored with it. Not only built by the railroad but engineered and developed by it. It would seem only NYC and Paul Keifer were the equal in this engineering capacity. As with any machine the development process can add significantly to the end product. I would say N&W and NYC and possibly PENNSY got more out of their steam designs than anyone. Keifer tested his first Hudson extensively on the road before ordering the several hundred copies. His redesign of the J3 showed a total upgrade of an already surpurlative engine. I would guess that his Niagra was a last chance to show what steam could produce and was an effort to meet the challenge of the diesel.
N&W obviously wanted to continue in steam production and usage and the engineering designs of A, J, and Y are without equal. The 600s had side rod redesign eliminating the tandem rod configuration very late in life - what railroad would bother with this were it not totally commited to steam engineering. Cylinder size and stroke, wheel diameter, firebox design, superheater design, all the subtle changes that added to produce a small drivered northern the equal of Keifer's NYC "Niagra" design. I would say these two engine designs brought the development of the 4-8-4 Northern to its full potential. Too bad Pennsy didn't do a 4-8-4 instead of that 4-4-4-4.
PENNSY wow after generations of standard locomotive production to launch into the duplex drive project! Here is a huge unresearched subject. Did any railroad have the equal of the test dyno facility they developed. Not even Baldwin, Alco, or American could do this. Pennsy also did the elaborate prototype development of 6-4-4-6 and 6-8-6 as well as 4-4-6-4 and 4-6-4-4. And the streamlining! I think we are all left speachless looking back at this. What unspeakable tragedy with no really successful engine development! And none saved! Yet almost one or more of every class of standard steam survives. With none running or restored. Alas Pennsy the love for you is unrequited! Yea we weep equally for the glory of the Central. Pearlman I hope you are resting in the appropriate place!
UP - how I love the west! The railroad that brought us 4-12-2 and 4-8-8-4 has not disapointed. Must be something in the Wyoming that grows the hearts of great men. The greatness of America is born out there somewhere. Imagine an American railroad in the 21st century with its original name and shield! And steam program too. I must be dreaming!
Well! Looks like they got pretty close, didn't they?
Firelock76 Just a quickie here. The New York Central assigned 6000 numbers to it's Niagara series of locomotives because 6000 horsepower is what they expected of them.
Just a quickie here. The New York Central assigned 6000 numbers to it's Niagara series of locomotives because 6000 horsepower is what they expected of them.
6000 INDICATED horsepower, not actual drawbar horsepower.
Highest IHP on test was, in fact, higher -- 6680, I believe.
Hey Jay,
One other thing you may find interesting: The 90,000 lbs. TE you reported for the EM-1 @ 19 MPH is 4,600 HP at the drawbar. This is well above what a modern ES44AC can produce at that speed.
The only locomotive CSX has than can out power an EM-1 at that speed is the AC6000CW.
Realize at 19 mph the EM-1 was only starting to get into it's power curve. Impressive stuff for something that was designed in 1944!
Jay, you bring up another example why it is fruitless to compare locomotive performance across different railroads.
When testing steam locomotives, I have never seen a B&O dynamometer report stating maximum horsepower (everyday or absolute) at at what speed it occurred. The B&O was more interested in the economics of a locomotive running a typical tonnage train over a division at a typical speed. From these test reports, they would them use the engineering talent at the Mt. Claire shops to makes changes to increase the efficiency of the locomotives during a rebuilt cycle. Increasing the efficiency may have well increased the maximum HP, but they were more interested on the bottom line - how much money it will save - rather than some maximum figure than was uneconomical to sustain during typical operations.
What you reported is very typical in the first generation diesel-electric vs. steam tests. The DE units would produce high TE at low speeds, and as speed increased, you would see power fall off at a rapid pace. This was due to the relatively poor efficiency on the electrical side of the locomotive for the early DEs.
A late model steamer such as the EM-1 would have an increasing power output, with a max reading somewhere in the 40 to 60 mph range. Again, to my knowledge, the B&O never tested them this way, so we will never have the knowledge of an accurate max HP reading. What is known about the EM-1 is that they were phenomenal performers when moved to general merchandise and express service, again suggesting their maximum power curve was on the high end of their operating speed range.
One final note: The EM-1 was the only B&O locomotive that wasn't changed extensively during shop cycles, showing Baldwin "nailed" the design and engineering of this locomotive right out of the box.
The laws of physics has many variables and is not etched in stone. It is interesting how one equation can have so many answers. I like to see the opinions here . Much food for thought, I would guess that the bottom line is all that matters whether it works or fits.
Respectfully, Cannonball
Y6bs evergreen in my mind
That's the story anyway. Don't know if it's true, I wasn't there!
In May 1944, three months after delivery of B&O's 2-8-8-4 articulateds had begun, the railroad used a dynamometer car to compare the performance of those articulateds against the performance of its four-section 5400-hp FTs between Cumberland, Maryland and Grafton, West Virginia. The railroad cited 4870 as the articulated's horsepower; however I don't know the speed at which that horsepower was produced. Based on graphs of the locomotives' performance, the FT was capable of producing more TE than the articulated was capable of producing at speeds below about 19 miles per hour. Both locomotives were capable of producing about 90,000 pounds of TE at about 19 miles per hours. Above about 19 miles per hour, the articulated was capable of producing more TE than the FT was capable of producing.
erikem Horsepower figures based on measurements taken with dynamometer cars should be trustworthy for evaluating locomotive potential under equivalent conditions...
Horsepower figures based on measurements taken with dynamometer cars should be trustworthy for evaluating locomotive potential under equivalent conditions...
That's the problem, none of these tests were recorded under standard, equivalent conditions. Even with the locomotives that had dynocar records, what were they testing for? Horsepower that was sustainable under every day economical conditions? Horsepower developed just to "see what she will do" and was in no way sustainable for economics or reliability?
Too many questions, not enough information for us to compare locomotives.
If we could gather all these locomotives, and test them under the same parameters, my gut feeling is that we would find most of the later model 4-8-4's producing max "everyday" DBHP in the 4500 to 5000 HP range, and most of the late model big articulated locomotives somewhere around 6000 DBHP, with the Allegheny topping the list at around 6500 DBHP.
GP40-2 Steam locomotive horsepower figures have been discussed ad nauseam here in the past.
Steam locomotive horsepower figures have been discussed ad nauseam here in the past.
At least some of the forum members are still interested in the discussion and the discussion has been quite civil.
Virtually all the figures found in books and on the net are very suspect and inflated, and except for a few, cannot be trusted.
Horsepower figures based on measurements taken with dynamometer cars should be trustworthy for evaluating locomotive potential under equivalent conditions. Doing a direct comparison between steam HP and diesel HP is a bit of a fool's errand - peak continuous steam HP occurs over a limited speed range, while diesel electrics maintain peak HP over a wider speed range (advantage diesel), though steam is capable of short time power ratings significantly higher than continuous due to the latent heat in the boiler water (assuming that continuous power is limited by heat transfer and not steam flow in the piping).
- Erik
Railroads for the most part were more concern with how big a train the locomotive could pull (tractive effort) as opposed to how the train could be pulled (horsepower) until near the end of the steam locomotive era. Competition from trucks made speed an important factor for merchandise traffic, and the improved highways that allowed for long distance trucking started to appear at the end of the 1930's.
I read a very interesting book a few years back called "The Steam Locomotive" by Albert Bruce, written as the steam era was drawing to a close. I found it interesting that Mr. Bruce made almost no mention of horsepower until the very end when steam turbine locomotives with traction motors became part of the discussion. Prior to that power was expressed in tractive effort, and in nothing else. Wonder why? I can only surmise that "horsepower" for "horsepower's" sake was secondary, or they didn't trust the figures, or something.
I just found it odd, that's all.
RME,
It has been a thoughtful exchange! You act as if you have spent some time in steam engineering. The weight of the eccentric rods on PM1225 is not as heavy as you would think. I can lift the entire I beam rod with one arm. In fact PM1225 has the eccentric rod from another PM1200 as the parts were apparently mixed in rebuilding. PM1206 if memory serves me right. I believe NW611 could run with that rod missing and the valve blocked in the fashion described. Speed in this condition would seem unwise.
I did a thumbnail comparrison of some horsepower figures for NW611 compared to others. This is a quick research and I was not careful with DHP and IHP figures so there is room to argue here.
NYC 4-8-4 6,680 horsepower
PRR 4-4-4-4 6,550 horsepower
NW 4-8-4 6,000 horsepower
SP 4-8-4 5.500 hp
C&O 4-8-4 5,000 hp
AT&SF 4-8-4 4,590 hp
UP 4-8-4 4,700 hp
NYC J3 4-6-4 4,700 hp
NYC J1 4-6-4 3,900 hp
PRR K4 4-6-2 3,500 hp
Of course horsepower is not the full measure of any maching, it is also the ability to sustain that power and the wear on the machine that produces it, as well as the speed at which the power is produced. These are all mainline passenger engines designed for speed and endurance. The power produced by Paul Keifer surely shows the work of a master. I wonder if AT&SF really ever developed their design, as it should have had the most potential with its size. Obviously C&O and the N&W were cousumately well designed although C&O track record with the 2-6-6-6 shows it used its steam power as designed and did not develop the potential either. NYC has to be the champion at taking the time to evolve the machine to its height. NW611 should be in this catagory as they built the engine from the ground up as well as developed its design.
Other steam locomotive horsepower rating in passing are the power champion PRR 4-4-6-4 Q2 I believe this design was not considered a success from the maintance standpoint and was clearly out matched by its rival PRR 2-10-4 design in this capacity.
PRR 4-4-6-4 7,987 horsepower
C&O 2-6-6-6 7,500 horsepower
PRR 6-4-4-6 7,200 hp
PRR 6-8-6 6,900 hp - direct drive steam turbine
N&W 2-6-6-4 6,800 hp
UP 4-8-8-4 6,290 hp - Big Boy
DM&R 2-8-8-4 6,250 hp
UP 4-6-6-4 6,200 hp
SP 4-8-8-2 6,000 hp - cab forward design
N&W 2-8-8-2 5,000 hp - compound mallet design
AT&SF 2-10-4 5,000 hp
UP 4-12-2 4,700 hp
Steam engine power was a product of the design of the engine as well as the skill of the engineer at operating the machine. Quality of coal, oil and water all affected the performance daily.
In this chart, these engine statistics form an overall comarrison that spans the "drag era" freight design to the "dual purpose" super power design. When Isaac Watt developed the "horsepower" measurement designation it was to tell us a basic facts about potential for performance.
Our community is FREE to join. To participate you must either login or register for an account.