Hi All,
Probably the best erector of Steam Locomotives was PRR itself. They could and did build many, many steamers, for themselves. They had their own laboratories, test facilities, design engineering group, test tracks, etc. etc. In short, compared to some steam locomotive manufacturers, they were way ahead of the game, and had more and better facilities than they did. They built to specification requirements, not for sale but for their own use, based on THEIR requirements. The best of both worlds.
Railroad Forums
C&O Allengenhy #1601
- Discussion of steam locomotives from all manufacturers and railroads
Moderators: Typewriters, slide rules
by Donko142
I think the big 5 all built a good locomotive, But one steam man's opinion is your kidding yourself if you think the PRR built the BEST steam, They did mass produce many good locomotive's but Lima was a close second. The N&W Clearly built the BEST steam locomitives in the USA. As was stated 4 models all with a direct purpose. There own shops were always looking for ways to make there own locomotives better. Right till the end.
Be Safe
Be Safe
Main intrestest steam and short line railroads in the East.
Qualified engineer and firemen.
Qualified engineer and firemen.
by Juniatha
Engineer James
Ok, I try to express myself more clearly:
There was an erecting price frame mentioned - about 2 Mio $. For this price you could have an engine made new in Germany. That means: an engine to your specifications - not necesasarily a replica of a DR standard type. It can be a new design of an engine or also a replica of a 1940s US engine class. To be sure, the external looks of an engine can be much designed the way you want to have it. That does little affect technical aspects. For instance the design of a cab does have absolutely no influence on technics of boiler or frames. A design of the tender coal compartment with set-in sides or full width sides or curved sides can be made in Europe as well as in the USA, same with a running board that does not go straight through but is staggered because the power reverser is mounted right in its way. And for sure: smoke wings can be left off in Germany if you like (*g*).
Such a project would be just the reversal of an example historically exercised when building the Mikados series 141-R for the SNCF in the USA.
You must not think that a locomotive built in Germany invariable would be of a standard DR type. There are enough historic examples of non-DR locomotives having been built in Germany during steam days and as we are talking here of a totally special order for a one-off engine, this has absolutely nothing to do with existing DR type engines.
What I mean is: the capabilities are there, the works and shops are there and I can get you in touch with people if you are seriously considering a project of having any steam loco manufactured new.
Just to get you on the right track of thinking:
You could for example have a Niagara made new, as well have a T-1 Duplex made new (and without the slipping characteristics that plagued the original US-made engines, mind it).
But you could instead also have a new type made according to your / your enterprises specifications as of speed / power / axle load / curvature and of course external design.
I will not go into my own philosophy of design and external appearance here or else it will be a very long posting.
I hope you get the idea though.
Juniatha
Add. August 8th:
Engineer James:
Ok, an engine, say a T1 or a Niagara, built todays for sake of rectifying an - also historical - mistake of not preserving one is a replica - by definition of replica, inevitably so, whether the team building it would gather on grounds that happen to be part of the USA or on grounds that belong to any other state. I do not see of what importance it is to you exactly where the erecting process would take place as long as it could at all be realized and so I am not going into that. To me it would be the result that counts.
And for sure: I would prefer an engine amended of her 'historical' shortcomings over one that has these included once again just because of excessive clinging to historic reproduction.
In sail ship building of todays no-one would think of using for instance historic material if they want a ship for sailing proper and not for but exhibition in a museum. Todays ship builders even design new sailing ships that are the best ever. This way one enjoys sailing in an up-to-date way and at the same time continues the engineering spirit that was put into the ships at times of commercial sailing up to the 1920s. As succeessors of the classic ships, of which a few are still sailing, these modern sail ships are thus more true to the development line than would be strict replicas that deny technical progress.
Likewise in the field of automobile restoration and replica building such excessive clinging to history would cause shaking heads. No one who likes 1960s type US muscle cars also likes the fading drum brakes feature of many of these cars and would rebuild such fading unreliable brakes again if they were to reproduce such a car. Likewise, no one who is into old Jaguar cars would love to have his engine freeze pistons on an extended high speed travel just because the original Jags tended to do that.
Same way, I would not see much reason why a reproduced PRR T1 should be 'equipped' with the original 'easy slippage / low adhesion' feature that was their main coffin-nail. Or, I would see no reason why a New Niagara should not be set free of the restricted, choking exhaust that caused so much counter pressure to pistons that it effectively hampered their high speed performance (see their ihp curve beginning to fall at speeds above some 75 - 80 mph while according to cylinder / boiler proportions it should have kept raising well above 100 mph; I should maybe explain that latter - but not in here or else we'd have to go into valve gear, cylinder tribology and exhaust design and the consequences it has on the power output development at various speeds; if that would be of interest you might let me know).
So, if such an engine could be realized, I'd really not care where it was done as long as the engine would prove a good one.
=J=
Ok, I try to express myself more clearly:
There was an erecting price frame mentioned - about 2 Mio $. For this price you could have an engine made new in Germany. That means: an engine to your specifications - not necesasarily a replica of a DR standard type. It can be a new design of an engine or also a replica of a 1940s US engine class. To be sure, the external looks of an engine can be much designed the way you want to have it. That does little affect technical aspects. For instance the design of a cab does have absolutely no influence on technics of boiler or frames. A design of the tender coal compartment with set-in sides or full width sides or curved sides can be made in Europe as well as in the USA, same with a running board that does not go straight through but is staggered because the power reverser is mounted right in its way. And for sure: smoke wings can be left off in Germany if you like (*g*).
Such a project would be just the reversal of an example historically exercised when building the Mikados series 141-R for the SNCF in the USA.
You must not think that a locomotive built in Germany invariable would be of a standard DR type. There are enough historic examples of non-DR locomotives having been built in Germany during steam days and as we are talking here of a totally special order for a one-off engine, this has absolutely nothing to do with existing DR type engines.
What I mean is: the capabilities are there, the works and shops are there and I can get you in touch with people if you are seriously considering a project of having any steam loco manufactured new.
Just to get you on the right track of thinking:
You could for example have a Niagara made new, as well have a T-1 Duplex made new (and without the slipping characteristics that plagued the original US-made engines, mind it).
But you could instead also have a new type made according to your / your enterprises specifications as of speed / power / axle load / curvature and of course external design.
I will not go into my own philosophy of design and external appearance here or else it will be a very long posting.
I hope you get the idea though.
Juniatha
Add. August 8th:
Engineer James:
Ok, an engine, say a T1 or a Niagara, built todays for sake of rectifying an - also historical - mistake of not preserving one is a replica - by definition of replica, inevitably so, whether the team building it would gather on grounds that happen to be part of the USA or on grounds that belong to any other state. I do not see of what importance it is to you exactly where the erecting process would take place as long as it could at all be realized and so I am not going into that. To me it would be the result that counts.
And for sure: I would prefer an engine amended of her 'historical' shortcomings over one that has these included once again just because of excessive clinging to historic reproduction.
In sail ship building of todays no-one would think of using for instance historic material if they want a ship for sailing proper and not for but exhibition in a museum. Todays ship builders even design new sailing ships that are the best ever. This way one enjoys sailing in an up-to-date way and at the same time continues the engineering spirit that was put into the ships at times of commercial sailing up to the 1920s. As succeessors of the classic ships, of which a few are still sailing, these modern sail ships are thus more true to the development line than would be strict replicas that deny technical progress.
Likewise in the field of automobile restoration and replica building such excessive clinging to history would cause shaking heads. No one who likes 1960s type US muscle cars also likes the fading drum brakes feature of many of these cars and would rebuild such fading unreliable brakes again if they were to reproduce such a car. Likewise, no one who is into old Jaguar cars would love to have his engine freeze pistons on an extended high speed travel just because the original Jags tended to do that.
Same way, I would not see much reason why a reproduced PRR T1 should be 'equipped' with the original 'easy slippage / low adhesion' feature that was their main coffin-nail. Or, I would see no reason why a New Niagara should not be set free of the restricted, choking exhaust that caused so much counter pressure to pistons that it effectively hampered their high speed performance (see their ihp curve beginning to fall at speeds above some 75 - 80 mph while according to cylinder / boiler proportions it should have kept raising well above 100 mph; I should maybe explain that latter - but not in here or else we'd have to go into valve gear, cylinder tribology and exhaust design and the consequences it has on the power output development at various speeds; if that would be of interest you might let me know).
So, if such an engine could be realized, I'd really not care where it was done as long as the engine would prove a good one.
=J=
Last edited by Juniatha on Tue Mar 13, 2007 5:13 pm, edited 2 times in total.
by Robert Gift
I am intrigued.
Niagara restricted, choking exhaust that caused so much counter pressure to pistons that it effectively hampered their high speed performance (see their ihp curve beginning to fall at speeds above some 75 - 80 mph
#1) How did exhaust problems slow thengine?
Ability of used steam to escape the cylinder and diminish back pressure?
#2) Since the piston rod took up space, was there greater power realized in pushing piston back (towards rear) than pushing forward?
#3) Are today's tracks NOT capable of the loads of these locomotives,
whereas tracks of the 40s/50s WERE?!! Why?
#4) What was the cause of adhesion problems?
Too much weight on pilot and fire box wheels?
Thank you,
Wondering novice -
Niagara restricted, choking exhaust that caused so much counter pressure to pistons that it effectively hampered their high speed performance (see their ihp curve beginning to fall at speeds above some 75 - 80 mph
#1) How did exhaust problems slow thengine?
Ability of used steam to escape the cylinder and diminish back pressure?
#2) Since the piston rod took up space, was there greater power realized in pushing piston back (towards rear) than pushing forward?
#3) Are today's tracks NOT capable of the loads of these locomotives,
whereas tracks of the 40s/50s WERE?!! Why?
#4) What was the cause of adhesion problems?
Too much weight on pilot and fire box wheels?
Thank you,
Wondering novice -
by Juniatha
Hi, Robert
Well, I planned to see ‚Pirates of the Caribean II’ this evening and then go hang around in the NewsCafe, which is a lounge that’s open well into the small hours. I might have a bit of something to eat and then feel nice an comfortable there with a Southern Comfort to go with a cup of hot chocolate and read the news in stern magazine, focus or times magazine, read about general and special madness of Homo Sapiens, so called by themselves because they know a lot, although not how to treat each other in socially agreeable ways and live together on this spaceship earth. My fire is burning low and I calm down in the general buzzing and humming of people coming and going, talking, walking, ordering things. They play very good music there that takes you away on an endless journey through the night - like on board of a luxury liner that continues dividing the waters of a calm, dark sea at constant speed, traveling under the dome of starlight standing high before eternity - on a course to the unknown ...
But since your question touches Niagara performance ...
While you might want to specify your questions more precisely I’ll try to answer, though without any papers and documents at hands as I’m here in an InternetCafe.
As I am necessarily writing about some less than perfect aspects of the engines, one should never forget that they were built more than half a century ago. Critical words thus are not intending to impair their engineering success at their time. And besides, as I quite like the Niagaras myself: real affection means to accept, flaws included. I was born in the USA (Schenectady, NY) and I join Bruce Springsteen in that, but I have also lived in Europe for quite some time now and so I guess I see both sides.
On your -
point 1 – restricted exhaust
The Niagaras had the usual plain round blast nozzle / round chimney draughting that was common on US railroads, with a few exceptions.
This device is characterized generally by a mediocre factor of efficiency, i.e. it takes a relatively high amount of exhaust steam energy to get the necessary draught of combustion gas through boiler.
Basically, all energy used in draughting is taken away from its conversion in the engine into propulsion output. Further, as engines grew in size and evaporation increased, the height of draughting arrangement should have been likewise increased – instead it had to be shortened due to loading gauge restriction. This caused inevitable ‘compression’ of the proportions of the arrangement, injuring its function, lowering its efficiency. This and other factors combine to bent the curve of efficiency of the plain round nozzle draughting so that amount of gas pumped does not remain proportional to steam passed through the nozzle. That means while all may be well up to a medium range of steaming rate, say 1/2 to 2/3 of maximum, there is an increasing deficit of combustion air as steaming rate is further increased. This was a major reason for the well known dark smoke trails of the engines as they charged along at full cry. Of course this impairs combustion efficiency, i.e. more coal is consumed than proportionate to the amount of steam produced - not regarding boiler efficiency for now.
In order to fight this draughting deficit and enable maximum steaming capacity, US design equipped engines with comparatively very small blast nozzles as a method to increase force of exhaust steam column and thus increase draughting. Since nothing is gained for free in the land of technical engineering this went to the expense of cylinder mean effective pressure because, as intended, the small nozzles created a higher exhaust pressure, i.e. increased backpressure in cylinders.
In other words, the exhaust pressure line was not as low as for example in British Railways standard or DB / DR standard simple expansion two cylinder engines: some 0.3 – 0.5 bar ( ~ 4.4 to 7.3 psi) but substantially higher at 1.5 – 2.5 bar (~ 22 to 36 psi), for typical values at nominal output working. As the mean effective pressure is determined by the upper (fill and expansion) work line minus the lower (exhaust and compression) return line in the steam diagram, any increase of back pressure directly decreases mean effective pressure. Since that pressure inevitably is but a fraction (denoted alpha = degree of cylinder fill) of the 19 bar (275 psi) boiler pressure, an increase of back pressure from 0.3 – 0.5 to 1.5 – 2.5 bar causes a noticeable decrease of output.
This combines with inherent imperfections of the Baker valve gear which is an ingenious set up as concerns avoiding radius rod sliding surfaces but makes it difficult to design a long enough lap for cylinders of tolerably large piston displacement volume in sense of absolute value (not in relation to even larger steaming volume of the very powerful boiler).
As far as I recall the Niagara cylinders were 25.5” x 32” or 648 x 813 mm (new). That means a piston swept volume of 263 ltr or 69.5 gal (US). Cylinders of such volume would call for extremely careful streamlining and wide cross sections in steam circuit to be filled and emptied without undue throttling, especially since the long stroke meant that at normal traveling speed (70 – 90 mph) piston speeds were high. The existing Baker valve gear was just about able to handle the steam volume – but no more. There were no reserves.
This shows up by the fact that at speeds around 70 to 80 mph maximum output was attained at 56 % cut off. Further lengthening of c/o brought a decline of output rather than an increase because it caused back pressure to rise over-proportionally while already filling pressure line melted into expansion line with no defined point of cut off, i.e. pressure drop at intake was substantial along stroke. As steam consumption with this c/o was still backed up by boiler output, there was no reserve of cylinder output over boiler output, or: maximum output became identical with continuous output. Normally, maximum cylinder output is well above maximum boiler output, thus enabling short term super-elevated engine outputs for acceleration and for running over ramps as well as running on good expansion ratio at nominal continuous output.
Since cylinder efficiency at c/o in the vicinity of 50 % is clearly impaired because of truncated expansion, maximum engine output at given maximum boiler output was not as high as it could have been if it had been met with shorter c/o in larger cylinders. This was a consequence of cautious cylinder dimensioning in the light of already high absolute values of piston force in view of high speed running.
With such a configuration of boiler to cylinder capacity ihp curve should have been expected to continue to rise over speed well into 100 to 120 mph range, or generally speaking: near or beyond 500 rpm, because steam supply was fully sufficient for even the highest speeds, any reduction of c/o should only have improved expansion and wall effects are being reduced as rpm speed increases. In fact this was not so but ihp curve over speed began to fall at speeds above some 80 mph or above 340 rpm already. This indicates throttling effects in steam circuit / valve gear and negative influence of before mentioned excessive back pressure which makes itself the more felt the shorter c/o and thus the smaller filling factor alpha.
Throttling in exhaust is especially detrimental to engine thermodynamic efficiency since the steam is passed through cylinders, but is not made best use of. In contrast, throttling at intake, while reducing output also reduces the amount of steam passed through cylinders. Additionally, intake throttling while reducing filling line steam pressure increases superheating of steam in cylinder, thus lifting mean cylinder steam temperature and exhaust steam temperature and this is helpful against wall effects. So, intake throttling is directly harmful to power output, yet within a certain reasonable extent and as long as full steam chest pressure is reached at dead centre it has a limited detrimental effect on thermodynamic cylinder efficiency. However, exhaust throttling is always directly harmful to both.
This is why Churchward, when CME of the GWR, in his typical British sarcasm had said ‘it is more important to get steam out of cylinders than it is to get it in’. By saying so he also pointed out that it was more difficult to avoid throttling at the exhaust side because of the large volume of low pressure steam.
Although André Chapelon had made his Kylchap exhaust known to P.W. Kiefer on his 1938 visit to US railroads, the latter did not want to investigate into sophisticated draughting systems on grounds of costs and rapid wear of the existing nozzles and chimneys with the fierce blast at full output running. However the logic in this argument falls somewhat short because the Kylchap exhaust would have enabled to do away with just that fierce blast and its eroding effects while its higher and more even efficiency over a wide working range would have enabled an improved combustion efficiency at boiler outputs that were maximum with plain nozzle (i.e. lower consumption, cleaner exhaust) as well as an improved cylinder efficiency (i.e. increased output at same steaming rate).
I recall a calculation I did years ago when studying in Vienna following a discussion of Niagara performance characteristics with student colleagues. This suggested that by improved exhaust alone, trimming back pressure down from 2 bar (29 psi) to 0.7 bar (10 psi) an additional output in the vicinity of 680 ihp could have been gained around 90 mph – on given coal consumption, i.e. for free, mind it!
With improvements to the valve gear and steam circuit plus an increased superheating temperature by rearrangement of tubes and flues to bring steam temp to 440 °C (824 °F) at nominal boiler output, necessary to take best advantage of 19 bar steam at shorter c/o, development of the indicated output curve could have been substantially changed with output continuing to rise from an already increased value of ~ 7300 ihp at 80 mph to ~ 7800 ihp at 100 mph to level off at ~ 8090 ihp at a speed range around 120 mph. (- All ihp are metric! -) All this while retaining the original cylinder volume since that determines mechanical stress on drive and thus cannot be enlarged without substantial redesign of drive which would have been off limits in a thermodynamic improvement of the existing engine.
The mentioned improvements would have meant an indicated steam heat consumption of 18.69 MJ/ihp or an indicated thermic cylinder efficiency of 14.2 % and a thermodynamic cylinder efficiency of 80 %, both very good values for a simple expansion engine. Since combustion efficiency at full boiler output was also somewhat improved with the proposed triple Kylchap draughting, indicated thermic engine efficiency from coal heat content to cylinder output was to be 8 % or slightly better at full power working, ~ 9 % with an essentially cleaner combustion at outputs close to the former maximum of the un-modified engine and ~ 10 % around 4400 – 5000 ihp output. With improvements of stoker to reduce abrasion of coal which produces unburnt losses, further improvements of boiler efficiency could have been attained, advancing engine efficiency into the vicinity of 11 % at outputs around 5000 ihp.
Be it mentioned: if the Niagara's efficiency in the lower to medium speed range was to be increased by working the engine on shorter expansion, cylinder volume would have needed to be enlarged. In view of the already large piston force and the existing design of drive and in view of better balancing of reciprocating masses an enlargement of cylinder would not have been adviseable but the engine could have been rebuilt into a three cylinder simple. Intriguingly, existing cylinder proportion to adhesion weight was such that the existing cylinders should have been used, allowing for an increase of 50 % of piston displacement volume in the three cylinder rebuilt. That would have resulted in a cylinder tractive effort / adhesion weight relation close to that of the N&W J class. Inevitably a little more sensitive handling of throttle would have been necessary at starting but with an early bringing c/o in to some 50 % starting would have still been sure footed - and more vivid. The 8000 ihp mark could then have been surpassed at the same speeds that gave 6690 ihp in the existing engine - but to go further into that would lead to far within such a posting.
point 2 – piston tail rod
Omission of piston tail rod was mainly done for maintenance considerations: no front glands. It also saved a little bit of reciprocating weight, but that was not significant as the tail rod was usually hollow bored. It did have consequences of piston lubrication and cylinder wear, though. The slight difference in front and rear piston displacement volume is of no practical effect. Tail rod suspended piston with just piston rings touching cylinder wall could be preferable with high superheating.
point 3 – axleloads
I’m not sure what you mean. I have not mentioned present day’s tracks and loads. Principally it is of advantage for track upkeep and maintenance if maximum axle loads can be reduced. The drive axle loads of some of the 1940s Super Power, especially that of the C&O H-8 were extreme and were a borderline case as concerns track maintenance costs, considering that it were just the drive axles that carried such loads yet track had to be made supporting them while all the cars axles in the train had lower loads.
point 4 – Duplexii
Hhmmmmm – oh-yeeaah! Just what was it that made them so temperamental!? Weight: well there was an axle load limit and it was pretty much reached, so nothing could be done on that side. As it was, adhesion weight was comparable with that of 4-8-4s of the same engine weight, so that was ok. Any engine naturally has a limit of tractive effort which is governed by adhesion weight.
The problem of notably the T-1 was that the engine did not reliably pull according to her adhesion weight and to an inherent typical value of adhesion to be expected on dry rails. In other words, on opening up a driver could not predict engine behavior as well as in a conventional one-drive-unit type. The T-1 had a varying engine adhesion value. That meant a loco driver could not do much more than open up cautiously and feel how she would react and if she did take up, then open up a bit further. But overdoing it could cause a slip and that in turn could have spoiled the set up so upon re-opening she would slip again, this time more easily than before. It could also happen vice versa: an easy slipping at start and then more solid marching thereafter. It was also possible that a nice and stable performance at continuous speed was suddenly turning into a violent run-away slipping.
This sort of behavior put stress on loco drivers because they had to keep alert for possible slip while with a more regular engine once traveling speed was attained they could sit back, let the engine run and concentrate on line side signals. An erratic, varying performance was of course abortive to reliable traffic handling and schedule keeping if full exploit of the engines was asked for, as usually it was on PRR and on US railroads generally.
An immediate cure would have been to reduce train weights which could have been done with introduction of the then new light weight stock of coaches and establish a service of through running high speed express trains to connect major cities, ranking above the classic LTD. Much of the trouble could have been contained by creating a special corps of T-1 crews to be given special up-grade training for better handling of these engines. The system of double or triple manning of engines widely used in Europe before WWII for valued engine classes could have helped if adapted to PRR long hauls or with braking long hauls by engine change instead of re-coaling at head of train.
This system encouraged crews to take best care of each ‘their’ engine, which was usually kept at very good, sometimes mint condition and incident free running was brought to all-time high. It evoked a competition as to best running, regularity, on time record, coal consumption and what have you. It was considered vital for best running of the delicate French four cylinder compound Pacifics and was successfully maintained on East German DR right to the end of express steam traction. It also produced a couple of fancies and spleens about individualization of engines such as white tires, extra edging lines, in some cases even a chrome ring around chimney or a smoke box door vignette – but what the heck, that’s how people are. It could have improved T- 1 reliability and performance and could also have helped to keep a nicer, cleaner look of the engines.
By the way, to help the latter, though principally for better combustion, the T-1s also were candidates for an improved draughting by double Kylchap – one for each drive set, or Giesl ejector and, preferably, oil-firing to avoid trouble with smoke box char and ash pan cleaning on these streamlined engines and reduce external soot up, to reduce servicing time, make quicker turn-around, increase daily mileage and keep boiler performance more uniform over long trips and quicker adapting to output demands.
As things were, in contrast, putting the engines off to commuter trains meant fighting fire with gasoline because of the frequent starts and low speeds of these trains and the inherently slow starting of these engines with but four driven axles against a total of sixteen on engine and tender, let alone the inefficiency of a 400 tons engine on a local train.
You may pardon me for not going into details on the topic of how to resolve the slipping problem because I want to leave that to a friend of mine who has really put a lot of thought and energy into it to come up with perfectly feasible design solutions. He has actually put up a number of detail and overall layouts for Duplex types and has made side elevations of complete engine types. Just so much: inner coupling would inevitably remain but a ‘chaining’ of units and a 'tongue in cheek' method to solve the problem, all in all less than desirable. While it would of course end individual slipping of one unit it could not prevent slippage of both units which would then happen since the inherent characteristics would still remain untouched. Also, if you were prepared to have two crank axles with inner connecting rods, you could as well replace the 4-4-4-4 with a four cylinder 4-8-4.
At this point, suffice it to say, if there ever was a project of building such an engine – or if you ask me: preferably the 6-4-4-6 as that surely was the most uncanny, unbelievable engine of them all and the unofficial steam speed queen of all times - design solutions would be there to be contributed and as concerns performance at speed to make it an engine that with a technical potential of over 10000 ihp around 120 mph could leave any 4-8-4 way behind ...
Juniatha
Well, I planned to see ‚Pirates of the Caribean II’ this evening and then go hang around in the NewsCafe, which is a lounge that’s open well into the small hours. I might have a bit of something to eat and then feel nice an comfortable there with a Southern Comfort to go with a cup of hot chocolate and read the news in stern magazine, focus or times magazine, read about general and special madness of Homo Sapiens, so called by themselves because they know a lot, although not how to treat each other in socially agreeable ways and live together on this spaceship earth. My fire is burning low and I calm down in the general buzzing and humming of people coming and going, talking, walking, ordering things. They play very good music there that takes you away on an endless journey through the night - like on board of a luxury liner that continues dividing the waters of a calm, dark sea at constant speed, traveling under the dome of starlight standing high before eternity - on a course to the unknown ...
But since your question touches Niagara performance ...
While you might want to specify your questions more precisely I’ll try to answer, though without any papers and documents at hands as I’m here in an InternetCafe.
As I am necessarily writing about some less than perfect aspects of the engines, one should never forget that they were built more than half a century ago. Critical words thus are not intending to impair their engineering success at their time. And besides, as I quite like the Niagaras myself: real affection means to accept, flaws included. I was born in the USA (Schenectady, NY) and I join Bruce Springsteen in that, but I have also lived in Europe for quite some time now and so I guess I see both sides.
On your -
point 1 – restricted exhaust
The Niagaras had the usual plain round blast nozzle / round chimney draughting that was common on US railroads, with a few exceptions.
This device is characterized generally by a mediocre factor of efficiency, i.e. it takes a relatively high amount of exhaust steam energy to get the necessary draught of combustion gas through boiler.
Basically, all energy used in draughting is taken away from its conversion in the engine into propulsion output. Further, as engines grew in size and evaporation increased, the height of draughting arrangement should have been likewise increased – instead it had to be shortened due to loading gauge restriction. This caused inevitable ‘compression’ of the proportions of the arrangement, injuring its function, lowering its efficiency. This and other factors combine to bent the curve of efficiency of the plain round nozzle draughting so that amount of gas pumped does not remain proportional to steam passed through the nozzle. That means while all may be well up to a medium range of steaming rate, say 1/2 to 2/3 of maximum, there is an increasing deficit of combustion air as steaming rate is further increased. This was a major reason for the well known dark smoke trails of the engines as they charged along at full cry. Of course this impairs combustion efficiency, i.e. more coal is consumed than proportionate to the amount of steam produced - not regarding boiler efficiency for now.
In order to fight this draughting deficit and enable maximum steaming capacity, US design equipped engines with comparatively very small blast nozzles as a method to increase force of exhaust steam column and thus increase draughting. Since nothing is gained for free in the land of technical engineering this went to the expense of cylinder mean effective pressure because, as intended, the small nozzles created a higher exhaust pressure, i.e. increased backpressure in cylinders.
In other words, the exhaust pressure line was not as low as for example in British Railways standard or DB / DR standard simple expansion two cylinder engines: some 0.3 – 0.5 bar ( ~ 4.4 to 7.3 psi) but substantially higher at 1.5 – 2.5 bar (~ 22 to 36 psi), for typical values at nominal output working. As the mean effective pressure is determined by the upper (fill and expansion) work line minus the lower (exhaust and compression) return line in the steam diagram, any increase of back pressure directly decreases mean effective pressure. Since that pressure inevitably is but a fraction (denoted alpha = degree of cylinder fill) of the 19 bar (275 psi) boiler pressure, an increase of back pressure from 0.3 – 0.5 to 1.5 – 2.5 bar causes a noticeable decrease of output.
This combines with inherent imperfections of the Baker valve gear which is an ingenious set up as concerns avoiding radius rod sliding surfaces but makes it difficult to design a long enough lap for cylinders of tolerably large piston displacement volume in sense of absolute value (not in relation to even larger steaming volume of the very powerful boiler).
As far as I recall the Niagara cylinders were 25.5” x 32” or 648 x 813 mm (new). That means a piston swept volume of 263 ltr or 69.5 gal (US). Cylinders of such volume would call for extremely careful streamlining and wide cross sections in steam circuit to be filled and emptied without undue throttling, especially since the long stroke meant that at normal traveling speed (70 – 90 mph) piston speeds were high. The existing Baker valve gear was just about able to handle the steam volume – but no more. There were no reserves.
This shows up by the fact that at speeds around 70 to 80 mph maximum output was attained at 56 % cut off. Further lengthening of c/o brought a decline of output rather than an increase because it caused back pressure to rise over-proportionally while already filling pressure line melted into expansion line with no defined point of cut off, i.e. pressure drop at intake was substantial along stroke. As steam consumption with this c/o was still backed up by boiler output, there was no reserve of cylinder output over boiler output, or: maximum output became identical with continuous output. Normally, maximum cylinder output is well above maximum boiler output, thus enabling short term super-elevated engine outputs for acceleration and for running over ramps as well as running on good expansion ratio at nominal continuous output.
Since cylinder efficiency at c/o in the vicinity of 50 % is clearly impaired because of truncated expansion, maximum engine output at given maximum boiler output was not as high as it could have been if it had been met with shorter c/o in larger cylinders. This was a consequence of cautious cylinder dimensioning in the light of already high absolute values of piston force in view of high speed running.
With such a configuration of boiler to cylinder capacity ihp curve should have been expected to continue to rise over speed well into 100 to 120 mph range, or generally speaking: near or beyond 500 rpm, because steam supply was fully sufficient for even the highest speeds, any reduction of c/o should only have improved expansion and wall effects are being reduced as rpm speed increases. In fact this was not so but ihp curve over speed began to fall at speeds above some 80 mph or above 340 rpm already. This indicates throttling effects in steam circuit / valve gear and negative influence of before mentioned excessive back pressure which makes itself the more felt the shorter c/o and thus the smaller filling factor alpha.
Throttling in exhaust is especially detrimental to engine thermodynamic efficiency since the steam is passed through cylinders, but is not made best use of. In contrast, throttling at intake, while reducing output also reduces the amount of steam passed through cylinders. Additionally, intake throttling while reducing filling line steam pressure increases superheating of steam in cylinder, thus lifting mean cylinder steam temperature and exhaust steam temperature and this is helpful against wall effects. So, intake throttling is directly harmful to power output, yet within a certain reasonable extent and as long as full steam chest pressure is reached at dead centre it has a limited detrimental effect on thermodynamic cylinder efficiency. However, exhaust throttling is always directly harmful to both.
This is why Churchward, when CME of the GWR, in his typical British sarcasm had said ‘it is more important to get steam out of cylinders than it is to get it in’. By saying so he also pointed out that it was more difficult to avoid throttling at the exhaust side because of the large volume of low pressure steam.
Although André Chapelon had made his Kylchap exhaust known to P.W. Kiefer on his 1938 visit to US railroads, the latter did not want to investigate into sophisticated draughting systems on grounds of costs and rapid wear of the existing nozzles and chimneys with the fierce blast at full output running. However the logic in this argument falls somewhat short because the Kylchap exhaust would have enabled to do away with just that fierce blast and its eroding effects while its higher and more even efficiency over a wide working range would have enabled an improved combustion efficiency at boiler outputs that were maximum with plain nozzle (i.e. lower consumption, cleaner exhaust) as well as an improved cylinder efficiency (i.e. increased output at same steaming rate).
I recall a calculation I did years ago when studying in Vienna following a discussion of Niagara performance characteristics with student colleagues. This suggested that by improved exhaust alone, trimming back pressure down from 2 bar (29 psi) to 0.7 bar (10 psi) an additional output in the vicinity of 680 ihp could have been gained around 90 mph – on given coal consumption, i.e. for free, mind it!
With improvements to the valve gear and steam circuit plus an increased superheating temperature by rearrangement of tubes and flues to bring steam temp to 440 °C (824 °F) at nominal boiler output, necessary to take best advantage of 19 bar steam at shorter c/o, development of the indicated output curve could have been substantially changed with output continuing to rise from an already increased value of ~ 7300 ihp at 80 mph to ~ 7800 ihp at 100 mph to level off at ~ 8090 ihp at a speed range around 120 mph. (- All ihp are metric! -) All this while retaining the original cylinder volume since that determines mechanical stress on drive and thus cannot be enlarged without substantial redesign of drive which would have been off limits in a thermodynamic improvement of the existing engine.
The mentioned improvements would have meant an indicated steam heat consumption of 18.69 MJ/ihp or an indicated thermic cylinder efficiency of 14.2 % and a thermodynamic cylinder efficiency of 80 %, both very good values for a simple expansion engine. Since combustion efficiency at full boiler output was also somewhat improved with the proposed triple Kylchap draughting, indicated thermic engine efficiency from coal heat content to cylinder output was to be 8 % or slightly better at full power working, ~ 9 % with an essentially cleaner combustion at outputs close to the former maximum of the un-modified engine and ~ 10 % around 4400 – 5000 ihp output. With improvements of stoker to reduce abrasion of coal which produces unburnt losses, further improvements of boiler efficiency could have been attained, advancing engine efficiency into the vicinity of 11 % at outputs around 5000 ihp.
Be it mentioned: if the Niagara's efficiency in the lower to medium speed range was to be increased by working the engine on shorter expansion, cylinder volume would have needed to be enlarged. In view of the already large piston force and the existing design of drive and in view of better balancing of reciprocating masses an enlargement of cylinder would not have been adviseable but the engine could have been rebuilt into a three cylinder simple. Intriguingly, existing cylinder proportion to adhesion weight was such that the existing cylinders should have been used, allowing for an increase of 50 % of piston displacement volume in the three cylinder rebuilt. That would have resulted in a cylinder tractive effort / adhesion weight relation close to that of the N&W J class. Inevitably a little more sensitive handling of throttle would have been necessary at starting but with an early bringing c/o in to some 50 % starting would have still been sure footed - and more vivid. The 8000 ihp mark could then have been surpassed at the same speeds that gave 6690 ihp in the existing engine - but to go further into that would lead to far within such a posting.
point 2 – piston tail rod
Omission of piston tail rod was mainly done for maintenance considerations: no front glands. It also saved a little bit of reciprocating weight, but that was not significant as the tail rod was usually hollow bored. It did have consequences of piston lubrication and cylinder wear, though. The slight difference in front and rear piston displacement volume is of no practical effect. Tail rod suspended piston with just piston rings touching cylinder wall could be preferable with high superheating.
point 3 – axleloads
I’m not sure what you mean. I have not mentioned present day’s tracks and loads. Principally it is of advantage for track upkeep and maintenance if maximum axle loads can be reduced. The drive axle loads of some of the 1940s Super Power, especially that of the C&O H-8 were extreme and were a borderline case as concerns track maintenance costs, considering that it were just the drive axles that carried such loads yet track had to be made supporting them while all the cars axles in the train had lower loads.
point 4 – Duplexii
Hhmmmmm – oh-yeeaah! Just what was it that made them so temperamental!? Weight: well there was an axle load limit and it was pretty much reached, so nothing could be done on that side. As it was, adhesion weight was comparable with that of 4-8-4s of the same engine weight, so that was ok. Any engine naturally has a limit of tractive effort which is governed by adhesion weight.
The problem of notably the T-1 was that the engine did not reliably pull according to her adhesion weight and to an inherent typical value of adhesion to be expected on dry rails. In other words, on opening up a driver could not predict engine behavior as well as in a conventional one-drive-unit type. The T-1 had a varying engine adhesion value. That meant a loco driver could not do much more than open up cautiously and feel how she would react and if she did take up, then open up a bit further. But overdoing it could cause a slip and that in turn could have spoiled the set up so upon re-opening she would slip again, this time more easily than before. It could also happen vice versa: an easy slipping at start and then more solid marching thereafter. It was also possible that a nice and stable performance at continuous speed was suddenly turning into a violent run-away slipping.
This sort of behavior put stress on loco drivers because they had to keep alert for possible slip while with a more regular engine once traveling speed was attained they could sit back, let the engine run and concentrate on line side signals. An erratic, varying performance was of course abortive to reliable traffic handling and schedule keeping if full exploit of the engines was asked for, as usually it was on PRR and on US railroads generally.
An immediate cure would have been to reduce train weights which could have been done with introduction of the then new light weight stock of coaches and establish a service of through running high speed express trains to connect major cities, ranking above the classic LTD. Much of the trouble could have been contained by creating a special corps of T-1 crews to be given special up-grade training for better handling of these engines. The system of double or triple manning of engines widely used in Europe before WWII for valued engine classes could have helped if adapted to PRR long hauls or with braking long hauls by engine change instead of re-coaling at head of train.
This system encouraged crews to take best care of each ‘their’ engine, which was usually kept at very good, sometimes mint condition and incident free running was brought to all-time high. It evoked a competition as to best running, regularity, on time record, coal consumption and what have you. It was considered vital for best running of the delicate French four cylinder compound Pacifics and was successfully maintained on East German DR right to the end of express steam traction. It also produced a couple of fancies and spleens about individualization of engines such as white tires, extra edging lines, in some cases even a chrome ring around chimney or a smoke box door vignette – but what the heck, that’s how people are. It could have improved T- 1 reliability and performance and could also have helped to keep a nicer, cleaner look of the engines.
By the way, to help the latter, though principally for better combustion, the T-1s also were candidates for an improved draughting by double Kylchap – one for each drive set, or Giesl ejector and, preferably, oil-firing to avoid trouble with smoke box char and ash pan cleaning on these streamlined engines and reduce external soot up, to reduce servicing time, make quicker turn-around, increase daily mileage and keep boiler performance more uniform over long trips and quicker adapting to output demands.
As things were, in contrast, putting the engines off to commuter trains meant fighting fire with gasoline because of the frequent starts and low speeds of these trains and the inherently slow starting of these engines with but four driven axles against a total of sixteen on engine and tender, let alone the inefficiency of a 400 tons engine on a local train.
You may pardon me for not going into details on the topic of how to resolve the slipping problem because I want to leave that to a friend of mine who has really put a lot of thought and energy into it to come up with perfectly feasible design solutions. He has actually put up a number of detail and overall layouts for Duplex types and has made side elevations of complete engine types. Just so much: inner coupling would inevitably remain but a ‘chaining’ of units and a 'tongue in cheek' method to solve the problem, all in all less than desirable. While it would of course end individual slipping of one unit it could not prevent slippage of both units which would then happen since the inherent characteristics would still remain untouched. Also, if you were prepared to have two crank axles with inner connecting rods, you could as well replace the 4-4-4-4 with a four cylinder 4-8-4.
At this point, suffice it to say, if there ever was a project of building such an engine – or if you ask me: preferably the 6-4-4-6 as that surely was the most uncanny, unbelievable engine of them all and the unofficial steam speed queen of all times - design solutions would be there to be contributed and as concerns performance at speed to make it an engine that with a technical potential of over 10000 ihp around 120 mph could leave any 4-8-4 way behind ...
Juniatha
Last edited by Juniatha on Tue Mar 13, 2007 5:14 pm, edited 1 time in total.
by Robert Gift
Wow, Juniatha!
Thank you for your explanations in such depth and detail.
That is kind of you and I appreciate it even though not deserving of it.
Where do you ever gethe time to write all of this?
Would take me forever because I never learned to type.
You must be a marvelous typist.
I was also asking questions of a previous post.
I am a niave novice and do not understand many things
ihp = indicated horsepower?
As a top-hat and tailed chimney sweep, schornsteinfeger sp?, I understand about draught.
But did not realize the draft jet nozzles created so much backpressure as to actually degrade cylinder output.
Couldn'they have placed an electric blower to pull draft, or force air
into the firebox to assist combustion. Even ram air at high speeds?
Why do oil burners (UP's 844 which my wife and I saw in July in Denver) produce so much smoke? Can'they aerosol the oil and make it burn more cleanly?
Still unclear about the adheasion problem.
Is it because not enough %weight was on the drivers, or the potential for a lot more power to go to the cylinders if they began to slip.
(No restriction of power limiting their "run-away"?)
Story:
My great uncle was a locomotivengineer on the PRR.
He loved to go to work every day andidn't especially like vacations
away from "his" engine.
As a too young child, he told me that he happened to be looking behind the engine when the trucks of the first car "fell apart and wheels went down the embankment."
He braked the train while keeping tension on the coupler by engine
pulling and kept the car from dropping and creating a horrible derailment.
"Got an isolator from the railroad."- I heard.
(A nice letter from the railroad)
Again, thank you so much,
Thank you for your explanations in such depth and detail.
That is kind of you and I appreciate it even though not deserving of it.
Where do you ever gethe time to write all of this?
Would take me forever because I never learned to type.
You must be a marvelous typist.
I was also asking questions of a previous post.
I am a niave novice and do not understand many things
ihp = indicated horsepower?
As a top-hat and tailed chimney sweep, schornsteinfeger sp?, I understand about draught.
But did not realize the draft jet nozzles created so much backpressure as to actually degrade cylinder output.
Couldn'they have placed an electric blower to pull draft, or force air
into the firebox to assist combustion. Even ram air at high speeds?
Why do oil burners (UP's 844 which my wife and I saw in July in Denver) produce so much smoke? Can'they aerosol the oil and make it burn more cleanly?
Still unclear about the adheasion problem.
Is it because not enough %weight was on the drivers, or the potential for a lot more power to go to the cylinders if they began to slip.
(No restriction of power limiting their "run-away"?)
Story:
My great uncle was a locomotivengineer on the PRR.
He loved to go to work every day andidn't especially like vacations
away from "his" engine.
As a too young child, he told me that he happened to be looking behind the engine when the trucks of the first car "fell apart and wheels went down the embankment."
He braked the train while keeping tension on the coupler by engine
pulling and kept the car from dropping and creating a horrible derailment.
"Got an isolator from the railroad."- I heard.
(A nice letter from the railroad)
Again, thank you so much,
by Juniatha
Hi Robert
Well, first of all: I have studied engineering (Maschinenbau), besides that I had an early introduction to steam locomotives starting with stories my father told me when I was still quite young; my father had been working at ALCO as an engineer when he was a young man - he later got a completely different job.
Yes there could be less smoke - properly set up there should be practially NO smoke. But -a- these are old machines and the oil firing equipment they have is far from being up to date, -b- many photographers like smoke the blacker the better although it bespeakes bad combustion and internal sooting up of tubes and flues and superheater elements. To me this sort of show is quite deplorable because it only serves to petrify the image of the steam locomotive as an environment polluting machine - which it needs not be. Figuratively speaking this is a bit like listening to a Janis Joplin record just for those moments where she doesn't really sing anymore but just screams, her abused voice gets hoarse and croaky and she starts coughing and drinks on stage. Actually, the principle of external combustion inherent to the steam locomotive could be much cleaner in combustion than the internal combustion engines and that without help of catalysts.
Adhesion: I invite you to re-read my notes under point 4, first paragraph.
It was American practice to dimension cylinders so that the engines would take 'full throttle full gear at start' i.e. the largest piston thrust could still be handled by adhesion - on dry, clean rails, that is! This was so in the PRR K-4s for instance. The T-1 was likewise dimensioned - only this type of locomotive did not / not always prove of the same surefootedness and thus did slip when theoretically there should not have been slippage. So, that was not a question of adhesion weight which was well up to the axle load limit but a deficiency in design. As drivers initially relied on the usual engine behavior at start, they tended to fully open regulator unreflectingly - and got a vicious roar as response! Depending on human mentality, repeated such inefficaciacy could result in either in learning how to do better or just cursing and abusing the machine for responding to human error. So one person could live with what the other rejected.
Maybe I should mention that of course the cylinders were made accordingly smaller than in a 4-8-4 of same adhesion weight so as to compensate for the different number of cylinders, or in other words: each one of the drive sets had in its own the cylinder to adhesion weight relation that was usually designed into a 4-8-4 - no more. Of course a locomotive with but 1/4 of total of sixteen axles driven will always be a slow starter! There is a lot of weight in relation to adhesion and in relation to t.e. as well. I have mentioned in another posting (under Alfred Perlman) that with improved coal handling and improved combustion a twelve wheel tender could have sufficed where a sixteen wheel tender was applied. This would have contributed to improve adhesion to total loco service mass proportion but it could never have made sort of a dragster of such an engine.
By the way: this sort of cylinder volume dimensioning led to engines having to be run on comparatively very long c/o to make full use of boiler output and thus just when asked maximum power they were making but incomplete use of steam because of truncated expansion, which impaired their output of course - as mentioned in the Niagara paragraph before.
In Europe cylinders were generally dimensioned larger in relation to adhesion and to boiler output. This of course demanded a more sensitive regulator handling at start (regulators were designed to ease adjusting steam chest pressure as desired) - no full throttle, full gear starts. With this driving practice well established, engine acceleration in the medium to upper speed ranges was improved over the small cylinder school of design as well as was maximum output for a given amount of steam.
For instance, an 03 class DR standard two cylinder Pacific attained adhesional limit tractive effort (t.e.) at start when using only 60 - 67 % of boiler pressure (b.p.) at some 70 % c/o which usually sufficed (max 83 %). This meant that with c/o brought in during acceleration, throttle could be further opened and below 50 or 40 % c/o full trottle could be applied thus increasing steam chest pressure and (partly) compensating for lowering t.e. by shortening of c/o . This sort of cylinder dimensioning also allowed for full output running at c/o decidedly shorter than the usual c/o in US Super Power and thus at better effieciency. Further, it allowed short term extra efforts substantially above nominal continuous output for running over ramps or for vigurous acceleration in the medium to upper speed ranges.
However to the very large US Supr Power engines of 1940s built this design principle could have been applied but to a limited extent because piston thrusts threatened to become excessive with the two cylinder type of engines. In other words the two cylinder machine had pretty much reached its constructional limits with the materials then available or then used and further increase in engine size was over-proportionally emphasizing boiler, firebox - and consequently tender, as can be seen in the late engine types.
With present day materials the limitations of the two cylinder machine could substantially be pushed up using equally higher b.p. But while this would enable to build an engine in straight-forward extension of the then cut Super Power types development line, and should result in an engine well superior to the most powerful 1940s types, in this way being a marvellous engine in the eyes of those who adore classic steam, it would not be an edifying example as to the scope of perfection that could be designed into steam locomotives today's as a special engine by using multi cylinder machine types.
But that is another story ...
P.S.: check my notes unter 'Famous people in RR history' / 'Al Perlman' :
http://www.railroad.net/forums/viewtopi ... 9&start=15
ihp - indicated hp
dbhp - draw bar hp
t.e. - tractive effort
c/o - cut off;
the percentage of piston stroke by which steam is being admitted to cylinder;
actually 'scale or virtual c/o' since at increasing speed actual admission is being throttled down earlier because of closing valve
factor of adhesion:
US: adhesion weight : t.e. ; typical (US-engine) values: 3.6 - 4.5
European: t.e. : adhesion weight; typical (European engines) values: 0.25 - 0.37
Juniatha
Pennsylvania RR T-1 when brand new in the yard at Baldwin: A view on the central admirable part of the locomotive
the stunning double drive sets with 80" wheels and shiny roller bearing rods - outer simplicity by poppet valve gear
(photo: Baldwin, slightly retouched by Juniatha)
Well, first of all: I have studied engineering (Maschinenbau), besides that I had an early introduction to steam locomotives starting with stories my father told me when I was still quite young; my father had been working at ALCO as an engineer when he was a young man - he later got a completely different job.
Yes there could be less smoke - properly set up there should be practially NO smoke. But -a- these are old machines and the oil firing equipment they have is far from being up to date, -b- many photographers like smoke the blacker the better although it bespeakes bad combustion and internal sooting up of tubes and flues and superheater elements. To me this sort of show is quite deplorable because it only serves to petrify the image of the steam locomotive as an environment polluting machine - which it needs not be. Figuratively speaking this is a bit like listening to a Janis Joplin record just for those moments where she doesn't really sing anymore but just screams, her abused voice gets hoarse and croaky and she starts coughing and drinks on stage. Actually, the principle of external combustion inherent to the steam locomotive could be much cleaner in combustion than the internal combustion engines and that without help of catalysts.
Adhesion: I invite you to re-read my notes under point 4, first paragraph.
It was American practice to dimension cylinders so that the engines would take 'full throttle full gear at start' i.e. the largest piston thrust could still be handled by adhesion - on dry, clean rails, that is! This was so in the PRR K-4s for instance. The T-1 was likewise dimensioned - only this type of locomotive did not / not always prove of the same surefootedness and thus did slip when theoretically there should not have been slippage. So, that was not a question of adhesion weight which was well up to the axle load limit but a deficiency in design. As drivers initially relied on the usual engine behavior at start, they tended to fully open regulator unreflectingly - and got a vicious roar as response! Depending on human mentality, repeated such inefficaciacy could result in either in learning how to do better or just cursing and abusing the machine for responding to human error. So one person could live with what the other rejected.
Maybe I should mention that of course the cylinders were made accordingly smaller than in a 4-8-4 of same adhesion weight so as to compensate for the different number of cylinders, or in other words: each one of the drive sets had in its own the cylinder to adhesion weight relation that was usually designed into a 4-8-4 - no more. Of course a locomotive with but 1/4 of total of sixteen axles driven will always be a slow starter! There is a lot of weight in relation to adhesion and in relation to t.e. as well. I have mentioned in another posting (under Alfred Perlman) that with improved coal handling and improved combustion a twelve wheel tender could have sufficed where a sixteen wheel tender was applied. This would have contributed to improve adhesion to total loco service mass proportion but it could never have made sort of a dragster of such an engine.
By the way: this sort of cylinder volume dimensioning led to engines having to be run on comparatively very long c/o to make full use of boiler output and thus just when asked maximum power they were making but incomplete use of steam because of truncated expansion, which impaired their output of course - as mentioned in the Niagara paragraph before.
In Europe cylinders were generally dimensioned larger in relation to adhesion and to boiler output. This of course demanded a more sensitive regulator handling at start (regulators were designed to ease adjusting steam chest pressure as desired) - no full throttle, full gear starts. With this driving practice well established, engine acceleration in the medium to upper speed ranges was improved over the small cylinder school of design as well as was maximum output for a given amount of steam.
For instance, an 03 class DR standard two cylinder Pacific attained adhesional limit tractive effort (t.e.) at start when using only 60 - 67 % of boiler pressure (b.p.) at some 70 % c/o which usually sufficed (max 83 %). This meant that with c/o brought in during acceleration, throttle could be further opened and below 50 or 40 % c/o full trottle could be applied thus increasing steam chest pressure and (partly) compensating for lowering t.e. by shortening of c/o . This sort of cylinder dimensioning also allowed for full output running at c/o decidedly shorter than the usual c/o in US Super Power and thus at better effieciency. Further, it allowed short term extra efforts substantially above nominal continuous output for running over ramps or for vigurous acceleration in the medium to upper speed ranges.
However to the very large US Supr Power engines of 1940s built this design principle could have been applied but to a limited extent because piston thrusts threatened to become excessive with the two cylinder type of engines. In other words the two cylinder machine had pretty much reached its constructional limits with the materials then available or then used and further increase in engine size was over-proportionally emphasizing boiler, firebox - and consequently tender, as can be seen in the late engine types.
With present day materials the limitations of the two cylinder machine could substantially be pushed up using equally higher b.p. But while this would enable to build an engine in straight-forward extension of the then cut Super Power types development line, and should result in an engine well superior to the most powerful 1940s types, in this way being a marvellous engine in the eyes of those who adore classic steam, it would not be an edifying example as to the scope of perfection that could be designed into steam locomotives today's as a special engine by using multi cylinder machine types.
But that is another story ...
P.S.: check my notes unter 'Famous people in RR history' / 'Al Perlman' :
http://www.railroad.net/forums/viewtopi ... 9&start=15
ihp - indicated hp
dbhp - draw bar hp
t.e. - tractive effort
c/o - cut off;
the percentage of piston stroke by which steam is being admitted to cylinder;
actually 'scale or virtual c/o' since at increasing speed actual admission is being throttled down earlier because of closing valve
factor of adhesion:
US: adhesion weight : t.e. ; typical (US-engine) values: 3.6 - 4.5
European: t.e. : adhesion weight; typical (European engines) values: 0.25 - 0.37
Juniatha
Pennsylvania RR T-1 when brand new in the yard at Baldwin: A view on the central admirable part of the locomotive
the stunning double drive sets with 80" wheels and shiny roller bearing rods - outer simplicity by poppet valve gear
(photo: Baldwin, slightly retouched by Juniatha)
Last edited by Juniatha on Tue Mar 13, 2007 5:16 pm, edited 2 times in total.
by Juniatha
Engineer James wrote:Do they make T1's over there in germany? Because that did not look like an Old Pennsy T1.Engineer James
Well I'm prepared to answer to questions for sure. But I got the impression you are maybe making a little fun of me.
As concerns the T-1 picture in my previous posting I invite you to read the text below it. In general, I do not think that I could be misunderstood either to say that Germany has a regular steam traction still or does produce steam in a commercial, regular way. I have extended on explaining that the technical and industrial means would be there to manufacture a steam locomotive new if one wanted to either reproduce a classic type or want a new one.
There are a lot of steam locomotives running in Germany in the hands of preservation groups or privates - arguably more than in the whole United States. These engines are kept in running order by being overhauled on a regular basis according to legal regulations.
When having passed inspection and run by an accepted group or organization, they are then licened to run on DBAG mainlines to do special trains which range from the classic steam fan tour to occasional freight train handling as called as an replacement engine by one or the other private commercial railway enterprise or even participating in track construction as a work train engine for such private enterprises on a hire basis including steam loco staff by the owner group; owners of steam locomotives are seeking jobs to do for their engines and thus are sometimes making very competitive offers for such odd jobs.
And there are more engines returned into serviceable condition by professional rebuilding that includes manufacturing new components like boilers, cylinders, and what have you. Some historic engines have been rebuilt from most deplorable conditions lacking a lot of parts, even cylinders and whole set of rodding and in cases even axles. All these missing things have been made new and engines have been rebuilt into working order.
I do not see where you did misunderstand my words but maybe you want to send me an e-mail so to tell me what the problem is and I hope I can sort it out for you.
= J =
by Engineer James
Junitha> No, offence. I am not making fun of u at all. All I am saying is that the photo shown does not look like any T1 I have ever seen.
Germans care more about history than us Americans do, so thats why they probably have more of them. Actually if we (Americans) got together and took out all the static displays at museums, the one that sit at parks,and the others who are sitting on industrial spurs no one has ever found, we would probably have more steam than the Germans.
Germans care more about history than us Americans do, so thats why they probably have more of them. Actually if we (Americans) got together and took out all the static displays at museums, the one that sit at parks,and the others who are sitting on industrial spurs no one has ever found, we would probably have more steam than the Germans.
by CASI
Hello,
I just found this wonderful message board at Google.
In according of Juniatha´s post of rebuilding or building up a new steam loco: Yes, it´s true!
The company which is able to do this is the "Dampflokwerk" in Meiningen, former east germany. ( http://www.dampflokwerk.de )
In fact, that in former east germany Steam Locos were in service since the reunification (1989), this company is still preserved until now.
After reunification the company was able to be kept alive by the "enthusiasts" in Germany.
Many enthusiasts associations in west germany have kept some steamers from being scrapped. Some enthusiasts did general overhauls on their own, but after reunification they were able to give the locos to Meiningen works for general overhaul.
Some locos (DR 01 519, 01 066 and others) were taken from the scrapyard (really scrap!!) and are now performing well.
I don´t think, that Meiningen works ist able to rebuild an American Niagara, or a T1 because they won´t fit onto their turntable, but building up a new boiler and many other parts might be possible.
A few months ago for example, a new boiler for the british A1 Pacific was finished. ( http://www.dampflokwerk.de/deutsch/bdm0706.htm )
In 2004, I visited "meiningen works" at the "open day" and I made a picture gallery:
http://www.trabi.dns2go.com/gallery/vie ... me=album01
Meiningen Works starts at Page 4 - before you can see my favourite 012 and other locos hunting to the happenig.
Sorry for my awful english but after 6 years without practice, it get´s a bit rusty.
I just found this wonderful message board at Google.
In according of Juniatha´s post of rebuilding or building up a new steam loco: Yes, it´s true!
The company which is able to do this is the "Dampflokwerk" in Meiningen, former east germany. ( http://www.dampflokwerk.de )
In fact, that in former east germany Steam Locos were in service since the reunification (1989), this company is still preserved until now.
After reunification the company was able to be kept alive by the "enthusiasts" in Germany.
Many enthusiasts associations in west germany have kept some steamers from being scrapped. Some enthusiasts did general overhauls on their own, but after reunification they were able to give the locos to Meiningen works for general overhaul.
Some locos (DR 01 519, 01 066 and others) were taken from the scrapyard (really scrap!!) and are now performing well.
I don´t think, that Meiningen works ist able to rebuild an American Niagara, or a T1 because they won´t fit onto their turntable, but building up a new boiler and many other parts might be possible.
A few months ago for example, a new boiler for the british A1 Pacific was finished. ( http://www.dampflokwerk.de/deutsch/bdm0706.htm )
In 2004, I visited "meiningen works" at the "open day" and I made a picture gallery:
http://www.trabi.dns2go.com/gallery/vie ... me=album01
Meiningen Works starts at Page 4 - before you can see my favourite 012 and other locos hunting to the happenig.
Sorry for my awful english but after 6 years without practice, it get´s a bit rusty.
by Robert Gift
Your English is wonderful, Casi.
Thanks to you and Juniatha for the wealth of information I so enjoy learning and contemplating.
Question: The UP Challenger 3985
Leading 102,300 lbs
Driving 404,000
Trailing 121,600
Why so much weight placed on leading and trailing trucks?
Don't you want more weight on drivers?
Or would that be too much weight in one place?
Also, how do they derive 4.17 adhesion factor and what does it mean?
Thank you,
Thanks to you and Juniatha for the wealth of information I so enjoy learning and contemplating.
Question: The UP Challenger 3985
Leading 102,300 lbs
Driving 404,000
Trailing 121,600
Why so much weight placed on leading and trailing trucks?
Don't you want more weight on drivers?
Or would that be too much weight in one place?
Also, how do they derive 4.17 adhesion factor and what does it mean?
Thank you,
by Juniatha
Robert Gift wrote:Question: The UP Challenger 3985
Leading 102,300 lbs
Driving 404,000
Trailing 121,600
Why so much weight placed on leading and trailing trucks?
Don't you want more weight on drivers?
Or would that be too much weight in one place?
Also, how do they derive 4.17 adhesion factor and what does it mean?
Hi, Robert:
On weight on drivers:
No, we don't want more weight on drivers!
As any members of 'Weight Watchers Anonymous' could tell you, too much weight is a burden. With locomotives, there would be an additional risk of the engine burying itself in the ground and sinking towards the centre of the earth where it is hard to find and be of little use anyways.
Now seriously:
please see my point 4 in my pre-previous comment: there is an axle load limit and usually American engineers left little if any margin unexploited in their designs of domestic US steam locomotives which at any rate were the heaviest in our solar system (as far as we know there were no railways on Mars while at present we cannot tell about Venus because of her dense atmosphere (typically feminine!) - Venus' hot climate should be ideal for steaming capacity of boilers, although water supply could present a slight problem).
In short:
You can only load up drivers so much and that's it then. That was done to the limit permanent way engineers admitted on each the railroads. Because Challengers found their challenge limited by such trivialities, it was for BigBoys to take over. Next step, the BiggerBoys were choked in the wake of dieselization. Now we have diesel-unit trains, i.e. trains of diesel-units piled up to run a freight that was formerly handled by just one Boy.
What would have happened had they ever realized a GreatGirls design
(detectable by her large smoke deflector wings) ...
If you are still with me: now -
On adhesion factor:
This is simply the qoutient of adhesion weight / cylinder tractive effort, whereby:
t.e. is calculated using a factor of boiler pressure of between 0.7 to 0.85 %, whereby the larger value was used in - of course - American design for domestic railroads (because we never stop before having loaded engines to the very limit).
The factor's values as put up could be misleading in that they would at first glance give an impression of an engine being stronger with a larger value - while the opposite is true:
With a given adhesion weight (as noted above: the maximum admitted by permanent way) the higher value indicated a lower t.e.: while the engine is more safe from slipping, cylinders produce a lower torque at wheel rim.
In Europe adhesion factor was calculated the other way around:
t.e. / adhesion weight - which was especially handy with the metric kp-m-s units system, because t.e. was in kp or t (metric) and adhesion weight in kg or t (metric).
This gave factor values of 0.2 to 0.35 depending on engine design and factor of boiler pressure used (between 0.5 - 0.75).
In this rating, the higher value denoted the more powerful engine, although it was also more sensitive to slipping of course.
Present days SI-units are kN (kilo-Newton) for tractive effort and t (ton metric) for adhesion masse. This makes for adhesion factor values of 2.0 - 3.5 respectively, as 9.8065 kN = 1 kp.
Cylinder t.e. was generally designed more generous in relation to adhesion weight in European design.
This for two reasons:
- adhesion weight was generally lower;
- the engines were designed to run on much shorter cut-off.
Vice-versa it was more difficult for engineers to design mechanical drive to stand the already very high piston thrusts put up by US domestic large two cylinder engines. It became piston thrust rather than adhesion weight which governed cylinder dimensioning and this tended to limit cylinder output in the end so that further increase of adhesion weight (above that reached in 2-10-4 design) became meaningless because it could not fully be exploited with a two cylinder engine. (... and that was one reason for simple expansion Mallet design)
(Next question, I guess: why not use three cylinder designs?
- ok, see you later
alligator!)
Juniatha