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Current and Proposed New-Builds

Discussion in 'Steam Traction' started by aron33, Aug 15, 2017.

  1. 242A1

    242A1 Member

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    Might I suggest that you get hold of a copy of a book by John van Riemsdijk ISBN 0-906899-61-3 Compound Locomotives An International Survey. It isn't perfect but it covers quite a bit of ground, I hope that the printed sources section might prove of use to you and you will find not only a list of English language publications but French, German, Dutch and Italian too. Let me know how you get on. Wet steam is only a part of the story, why should you think about the compound story purely within this narrow widow? Porta, Chapelon, De Casso and many others worked with superheated steam. Read the book and you will learn about Wilhelm Schmidt and his unthinking disciple Robert Garbe. There are reasons why the BR 01 is rated at close on 1,500 hp less than the 231E.
     
    Last edited: Oct 1, 2020
  2. Allegheny

    Allegheny New Member

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    I think your explanations have hit the nail on the head. The smaller heat drop across each cylinder did give some advantage, in terms of heat taken from incoming steam required to reheat the cylinder on each piston stroke, following heat removed by the cooler exhaust steam. Regarding saturated steam, there is some evidence that heat transfer between steam and the metal parts is greater if the temperature of the metal is below the saturation temperature of the steam (at whatever pressure is happens to be at the time). I'm not sure what you mean by steam being over expanded. In this case the pressure would drop below atmospheric pressure for a non-condensing engine or condenser pressure for the condensing type.

    The SS Titanic had three screws, the two outer screws were driven by triple expansion steam engines. The exhaust from these combined to pass through a turbine which drove the middle screw. The arrangement was found to be more successful than other contemporary propulsion systems of the time.

    In my humble opinion the disadvantages of the compound locomotive were additional complexity in terms of building and operating the locomotive, and packaging the additional cylinders within the limited loading gauge and weight limitations of the railway.
     
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  3. LMS2968

    LMS2968 Part of the furniture

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    Of course, as with all marine and fixed land-based systems, the exhaust steam from the turbine passed to a condenser. This allowed to the turbine to produce useful work at BELOW ATMOSPHERIC PRESSURE as the act of condensing the steam caused a vacuum at the turbine's outlet. This isn't an advantage the average locomotive was able to access.
     
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  4. MellishR

    MellishR Part of the furniture Friend

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    What superficially seems good or bad in engineering may be more complicated, depending on the details. Clearly Chapelon and his successors were especially good at the details, getting both better efficiency and better power-to-weight ratios than other designers of steam locos. But surely, at least with Chapelon, compounding was an essential part of the package. Would hypothetical versions of his designs, with simple expansion but otherwise as near as possible the same, have been anywhere near as powerful?
     
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  5. Allegheny

    Allegheny New Member

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    Agreed, I mentioned this in post 3544, above.

    Although condensing, the SAR 25C condensers operated at about 70 degrees C, so only gave a small reduction in back pressure. Their main purpose was to recover and reuse the water. I understand that the hot boiler feed water was of benefit though. They must have had some other means of feeding it into the boiler, rather than injectors.
     
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  6. Allegheny

    Allegheny New Member

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    My understanding of this is that the French relied on more expensive imported coal, often from Wales, and this swung the economic balance towards a more efficient, but more expensive locomotive.
     
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  7. johnofwessex

    johnofwessex Part of the furniture

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    Reading Wardale they used (turbine driven?) pumps although hot water injectors are available
     
  8. johnofwessex

    johnofwessex Part of the furniture

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    Generally most of Europe was not as coal rich as the UK- and much colder in Winter in Northern Europe which made energy efficiency a much higher priority than in the UK
     
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  9. burmister

    burmister Member

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    Not sure about Holland Switzerland Austria Italy but most other countries had/have big coal zones. However a lot is low CV so higher efficiency would have indeed been advantageous. Northern France and Belgium mined the same coal deposits as Kent however.
    The Russians in the 20s especially were far more advanced than Western Europe in Steam Diesel Gas Turbine engine prototypes and experiments although reading about those turbulent murky days it is difficult to separate developments from Russian and Western locomotive engineers. Some of the Gas Turbine ideas pre and post WW1 were thermodynamically amazing in concept and people think Bullied had some odd ideas in his Locos.

    In general however you will not go far wrong in keeping to the simple is best ideal. Turbines and condensers are very efficient but difficult to keep at the necessary parameters, even more so in railway scenarios. I remember delivering the noon log to the Chief Engineers office as a cadet and being bellowed at as I went as I thought for my lunch down the corridor to get my a....e back down to the engine room control plates to find out from the 12 to 4 watch as to why the main condenser vac was down as steam consumption and thus bunker consumption had increased as also shown in the logged boiler fuel oil pressures, fd fan pressures Etc. To be fair he did then explain to me the effect the Vac had on pressures and temperatures throughout the boilers and engine room systems as well as his bunker consumption which was closely by the HO Superintendants when the ship Sent it’s weekly performance data In by Radio.

    Brian
     
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  10. Dunfanaghy Road

    Dunfanaghy Road Member

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    I thought that the task of an engineer was to: 'Simplicate and add lightness.'
    Pat
     
  11. 242A1

    242A1 Member

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    Those who had the good fortune to travel on the footplate of French steam locomotives observed the nature of the coal being used and referred to it as " dusty fines" the firemen had little trouble dealing with it and the locomotives performed well. Metallurgical coke is needed for the iron and steel industry, the only coal available in France that was suitable for this purpose came from seams in the North East that also ran away into Belgium. This source provided only a limited supply and millions of tons of suitable coal had to be imported. Some superior grades of coal were used by the railways but the iron industry was the major user, the railways could manage with the indigenous product, engines could be designed to burn more of this lower grade fuel in order to maintain power outputs, this was done in other parts of the world. The railways got the political blame when it came to the question of French coal imports and this fed into the modernisation arguments. The real issue was that the French iron and steel industry could not survive without suitable fuel and the French wanted to protect this industry.

    The railways needed powerful locomotives. The speed of mechanical land based transport was limited by decree to 75 mph ( yes, I know I just posted this elsewhere). The only way to run fast schedules when faced with these limits is to accelerate quickly and then maintain speed on the gradients and the French railways had some very long and tortuous climbs. With loads of 700 tons speeds of 73.7 mph could be recorded on a 1:125. A Chapelon 4-8-0 could work 635 tons between Paris and Calais averaging 73 mph, it could do this in both directions, with one intermediate stop. There are many other examples and some peculiarities. The PO railway built 70 superheated compound 2-10-0 locomotives between 1909 and 1910 and were used to work the heavier passenger trains on the steeper routes of the Massif Central. After the war the SNCF had a large number of German 3 cylinder 2-10-o locomotives to make use of, reparations and all that, and it was decided to use these engines to replace the PO machines on the grounds that they had a higher tractive effort figure and were significantly heavier at 110 tons against 86 tons. The German machines could start a heavier train but they could not sustain the horsepower of the old French engines and so performance deteriorated steadily over the course of a climb. The boiler pressures were the same but the German engine had a grate area that was larger by some 20%. The German locomotive might have been able to sustain a higher horsepower if it had been fitted with a mechanical stoker but that would simply be a case of throwing more fuel at the problem. The PO engines were hand fired and didn't need a mechanical stoker, with a trapezoidal grate of 41.65 sq ft they were easily managed by the fireman. Some French engineers knew how to produce powerful engines and transitory efforts were not what they were after.

    People did try to engineer simple expansion equivalents of compounds but the results were not successful. Matching cylinder volume was one example, usually just that of the LP cylinders, but the slipping was a huge problem. It is hard to design fair equivalents, railways tried and they carried out testing and trials. If you were a railway with what might be termed a water level route that was one matter and these companies tried to justify simple expansion. However if you had heavy loads, long gradients to climb, then the compounds came to the fore. If you needed high acceleration compounds were better because the cylinders could maintain a higher tractive effort. If you have any doubts there are performance and testing records.
     
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  12. pete2hogs

    pete2hogs Member

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    Again, though, just like articulated locomotives, the complication is only justified if there is not a simple (as in less complicated, not talking about use of steam) alternative. That is if you are faced with designing from scratch, of course.
     
  13. Dag Bonnedal

    Dag Bonnedal Member

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    Sorry,
    you got it all wrong, articulated locos gives you more brute power at the cost of efficiency and maintenance cost. Worth taking if you can't do without it.
    Well built compounds gives you more power per wheight ratio and better fuel economy. Just as the French and Norwegians have proved.
    If you don't care, do without it.
    Just as 242A1 said...
     
  14. JJG Koopmans

    JJG Koopmans Member

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    I am really highly amazed the way this discussion is going. Most of you seem not to be aware of the fact that compounds run with about double cut-off figures, if a simple runs at 25% a compound runs at 55-60%. Steam locomotive improvement is about curbing losses just as superheating, larger steam passages or long travel-longlap valves and a method that gives larger port openings is such an improvement. Chapelon discusses this in his 1938 book, page number 701. As a consequence compounds were used in countries that lacked coal supplies, Austria, Switserland, Bavaria, France. The more expensive locomotive costs were less than the cost of additional coal transport and consumption for simples. This situation did not exist in the U.K.
    As for saturated and superheated compounds, both enjoy the larger cut-off, so any argument about "superheat is replacing compounding" is a fake argument.
    Kind regards
    Jos
     
    Last edited: Oct 2, 2020
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  15. bluetrain

    bluetrain Member

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    Thank-you to you and your friend for this useful summary. German "nassdampf" and "heissdampf" literally translate to "wet steam" and "hot steam", becoming "saturated" and "superheated" in technical English. I just wish I knew a few more German words! But having looked through this 12-page paper, I think that even if it was written in English, some sections will be too technical for me to understand. So I have to leave others to discuss the complicated stuff, but can offer a few general comments.

    In his conclusions, Prof Nordmann advocates the building in Germany of some new compound express locomotives, which of course never happened. Krupp had built two experimental "medium pressure" (25 atm/355 psi) Class 04 compound Pacifics in 1932, but they were deemed failures and scrapped in 1940.

    I was struck by the comment in the paper's final paragraph that compounding would never again achieve the dominance that it had gained in the saturated steam era. Because in Britain, it had never gained such dominance in the first place. British use of compounding had been transient and mainly confined to the LNW, North Eastern, Midland and Belfast & Northern Counties.

    In Germany, as in many other countries, compounding was almost universal around 1900 for new building of main-line passenger and freight types. But a factor often overlooked in discussions of compounding is that the vast majority were two-cylinder compounds, costing little more than two-cylinder simples in construction and maintenance. So if we look at what the Prussian State (Germany's largest railway) was bulk-building around 1900, we find the S3 express 4-4-0, the P4 small-wheeled (5ft 9in) 4-4-0 and G7 0-8-0 - all of which were 2-cylinder compounds, although there were also 2-cylinder simple variants of the P4 and G7. There are drawbacks to the two-cylinder compound model and it became less popular after 1900, but British builders supplied some large examples of the type (Broad-gauge 2-8-2s and 4-8-4Ts) to Argentina until the late 1920s.

    After 1900, the 4-cylinder compound model, already common in France, also became more popular elsewhere for the largest engines. But as superheating arrived on the scene, there was a parallel move away from compounding altogether. Compounding continued to be favoured by the South German railways, and the Reichsbahn continued building the Bavarian S3/6 4-6-2 until 1930.

    The Norwegian Type 49 or "Dovre Gubben" 4-cylinder compound 2-8-4 was introduced in 1937, so was a a post-Chapelon design, unlike Germany's own compounds. That appears to the reason for the Germans' close interest in its abilities. It is an interesting design, intended for Norway's mountainous main lines and more specifically for the Oslo to Trondheim route via Lillehammer and Dovre. This was an express engine with 5ft driving wheels, weighing 97 tons but with an axle-load of only 15½ tons. So it could be seen as a "niche" design, quite unlike anything in the locomotive ranges of Britain, France and Germany. Norway had continued to favour compound propulsion, no doubt partly the result of having to import all its coal supplies.

    EDIT: https://en.wikipedia.org/wiki/File:NSB_type_49a_Dovregubben_Oppdal.jpg
     
    Last edited: Oct 3, 2020
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  16. 242A1

    242A1 Member

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    Thank you for this. I would say that the "Dovre Gubben" 2-8-4 made use of the ideas that Chapelon had originally tested on the rebuilt 3566, the subsequent 3500 class Pacific rebuilds and the rebuilding of some of the 1907 built Pacifics as 4-8-0s, they did not incorporate oscillating cam poppet valve gear but included much else. They were credited with being capable of hauling 350 tons on a 1:55 gradient at 37 mph which demanded a substantial horsepower output. If Chapelon's later developments could have been incorporated in the design as part of a development or improvement package it would have been interesting to see what else they might have achieved but they were impressive enough on their own account. It was such a pity that they were rushed into service, a big mistake as it so frequently is. The 2-8-4 tested in Germany did well and should have given the Germans some food for thought, perhaps say 231E or maybe a 240P should have been included in the trials then the German Pacific could not only have been totally out accelerated it would also have lost when it came to maximum speed. The outcome in terms of locomotive development might just have been a little more interesting as a result.

    The Prussian State railway system, the KPEV was well served by 237 modest compound saturated Atlantics, some of these were von Borries design the others were de Glehn. Train weights were increasing so the Hanover district of the KPEV required some more engines in order to handle these trains. More Atlantics but with a greater evaporative capacity were desired so 99 locomotives were built at the Hanover Locomotive Works to the class S9 design. The Hanover Works wanted to fit this enlarged design with superheaters following their satisfactory experience with the Bavarian State Railway and other lines. Robert Garbe was one of the senior engineers on the KPEV and he prevented this action. Garbe was a disciple of Schmidt and followed his beliefs without thought or the acid test of experiment. One of Schmidt's beliefs was that superheating made it possible to reduce boiler pressure and use simple expansion. This idea was rather well tested in a number of countries and was disproved in nearly all cases. The S9 had a 44 sq ft grate area and weighed a little less than 75 tons. The Prussian system what might be called level and these engines could run with 500 ton trains however their limited adhesive weight of 33 tons was a weakness, stops and starts were a problem and frequent ones were an unrealistic expectation. These engines were never fully developed and in 1911 the S10/1 four cylinder compound 4-6-0s were introduced designed by Georg Heise of Henschel. In 1918 the S9 class were nearly all off-loaded as war reparations to France and Belgium. Garbe did design one successful locomotive, a 4-4-0 of class S6. He did also design a 4-6-0, the P8 which was another disaster story, not yet the P8 that some might be familiar with. Another KPEV engineer by the name of Lubken had to substantially redesign Garbe's P8 and as a result it gained some 10 tons but did end up being much admired and looking somewhat familiar.

    Wilhelm Schmidt produced a practical device which proved to be of substantial benefit to locomotive engineers throughout the world. However the steam locomotive design theories which were associated with it were in the main flawed.
     
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  17. Monkey Magic

    Monkey Magic Part of the furniture

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    I wonder if exogenous factors played a role? The border revisions of 1918 profoundly impacted on the ability of Germany, Austria and Hungary to access coal. (Silesia to Poland and Czechoslovakia, Bohemia to Czechoslovakia, Saar, Rhineland etc etc). I find it hard to imagine that changes such as that to a core resource would not impact on design choices.
     
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  18. Hermod

    Hermod New Member

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  19. Richard Roper

    Richard Roper Member

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  20. bluetrain

    bluetrain Member

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    I read somewhere that the Reichsbahn continued building the Bavarian S3/6 compound Pacifics until 1930 because they had difficulty in designing the new standard Class 03 light Pacific to achieve the same level of performance. The Norwegian 2-8-4s worked until replacement by diesels in the late 1950s - one of them survives in the Railway Museum at Hamar.

    Looking at the lists of locos constructed for the Prussian Railways in 1900-20, I was struck by the inconsistent designs and overlapping building of different classes for similar jobs. It looks less like the later Reichsbahn, more like 1920s LMS. Obvious uncertainty between the relative merits of compounding, superheating and superheated compounds. Parallel building of both De Glehn and Von Borries variants of S7 small Atlantic alongside superheated simple 4-4-0s, parallel building of G7 compound and G8 simple 0-8-0s, four different cylinder layouts for the S10 express 4-6-0. G12 3-cylinder 2-10-0 with Henschel conjugated valve gear, but the P10 2-8-2 has 3 separate valve gears. This variation may be partly the influence of regional offices and of locomotive building firms having a major say, but clearly forces pulled in different directions, with no single focus to decide design and procurement policy.

    Although compounding found only limited favour on Britain's railways, I notice that most steam road rollers and traction engines have one cylinder bigger than the other, indicative of two-cylinder compound propulsion. So compounding must have been seen as beneficial in that environment. Back on rail, I don't suppose the NRM's preserved NER No 66 "Aerolite" will ever be restored to working order. The last two-cylinder compounds to work in the British Isles were possibly those on the narrow-gauge lines in Northern Ireland. Perhaps a good candidate for the fantasy new-build list for a 3-ft gauge line!

    https://en.wikipedia.org/wiki/BNCR_Class_S
     

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