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Compounds ex time machine thread

Discussion in 'Steam Traction' started by Copper-capped, Jan 1, 2018.

  1. pete2hogs

    pete2hogs Member

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    And no CO2 is emitted in the process of converting the coal to oil ? You have to take the whole cycle in to account (as people consistently fail to do with electric cars)
     
  2. Hermod

    Hermod Member

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    The Fischer Tropps/Sasol proces conserves ca half the heating value of used coal and a post WW2 diesel converted 25%plus to traction. where a typical steam locomotive was 5% on a good day.
     
  3. johnofwessex

    johnofwessex Part of the furniture

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    Um so the two major users of the technology were Nazi Germany & Apartheid Era South Africa, which may well cause you to draw the conclusion that it at best wasnt very 'cost effective'
     
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  4. Hermod

    Hermod Member

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    A Baldwin proposal for a powerfull GCR engine

    https://imgur.com/a/WJCOB

    Two round cylinders
     
  5. andrewshimmin

    andrewshimmin Active Member

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    One of the problems with assessing compounding is that in the UK at least there weren't (or almost weren't) any simple and compound locos similar enough to compare properly.
    The exception, as far as I know, is the Lanky Dreadnaught rebuilt as a compound (10456). This was rebuilt in 1925, but only actually tested against an (otherwise identical) simple in a single test in 1930. There was a 8-10% saving in coal. This probably underestimated the savings possible, as in this test the simple was pretty fresh from overhaul while the compound had run over 40000 miles. On this class (both types) fuel consumption increased markedly with time after shopping due to air leakage into the smokebox and leaking of the piston valves (the latter was fixed in the early 1930s, too late to do any good). As a result the engines probably weren't comparable baselines... See Cox' 1946 paper for details.
    I believe the Nord built some simple versions of their SuperPacifics, which they found less satisfactory than the compounds.
    But I believe often in these matters one finds the results one wants to find...
     
  6. paulhitch

    paulhitch Part of the furniture

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    The Nord tested simple expansion versus compound, Cossart valves versus poppet valves versus piston valves. It would appear they would be the last place who could be accused of finding the results they wanted to.

    Paul H
     
  7. Jamessquared

    Jamessquared Resident of Nat Pres

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    Another comparable example on the LSWR: In 1888, after trials with some LNWR compounds, Adams obtained permission to convert one of his 445 class 4-4-0s to a 2 cylinder Wordsell-Von Borries Compound.

    Leading dimensions were left hand (HP) cylinder 18"*24"; right hand (LP) cylinder 26"*24".

    Bradley gives the following comparative figures, based on running on Waterloo - Salisbury expresses:

    446 (Compound)
    - Coal consumption per train mile: 32.7lb
    - Water evaporated per train mile: 26.8 gallons
    - Oil and Tallow used per 100 miles: 8.1lb

    448 (Simple)
    - Coal consumption per train mile: 34.2lb
    - Water evaporated per train mile: 26.1 gallons
    - Oil and Tallow used per 100 miles: 6.2lb

    The compound's coal consumption was slightly lower, but not enough to compensate higher oil and tallow usage, and accordingly after working 83,272 miles, 446 was converted back to simple form in 1891 (presumably at its next heavy overhaul).

    Tom
     
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  8. 242A1

    242A1 Active Member

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    And the relevance of this with respect to the compounds of the 1930s, 40s and 50s to say nothing of more recent designs is what exactly?
     
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  9. Jamessquared

    Jamessquared Resident of Nat Pres

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    It's a direct comparison between otherwise identical simple and compound engines, as an example / response for @andrewshimmin . I wasn't aware that we were only discussing three specific decades.

    Tom
     
  10. 242A1

    242A1 Active Member

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    I understand that Tom but it gives something of a false impression to those reading who don't know a great deal about the development of these machines. You could take the example of when simple expansion engines were superheated and proved to be superior to compounds that were saturated, you could also dial in the superheated simples having a higher working pressure too. Then the problems involved in making simple engines that were truly equivalent to compounds in order to obtain helpful test results which produced simples that were close to impossible to use because the large cylinders involved made slipping a huge problem. And so it goes on and there just aren't any good books on the subject readily available. Not at the moment.
     
  11. LesterBrown

    LesterBrown Member

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    Weren't Deely's 990 class for comparison with the 1000 class compounds? I don't know about performance but the simple locos didn't last very long whereas the compounds were rebuilt and updated over a long period.
     
  12. andrewshimmin

    andrewshimmin Active Member

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    I believe that was one reason for their construction, but they were different in myriad ways, and not used on comparable duties.
     
  13. andrewshimmin

    andrewshimmin Active Member

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    There is one good book: Compound Locomotives by John van Riemsdijk.
     
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  14. paulhitch

    paulhitch Part of the furniture

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    Probably not in print now. Fortunately I have a copy. Certainly a most illuminating work, ideally to be read in conjunction with a visit to Mulhouse museum.

    Paul H
     
  15. huochemi

    huochemi Well-Known Member Friend

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    It's OK but not great. Even with the resources of the NRM he does not give details of the relationship between the cut-offs for the HP and LP for those locos where they were fixed, such as the Midland Compound, which is fairly fundamental information.

    There was an interesting article in the SLS Journal last year spread over two issues (905/906) on compounds which drew the conclusion (based on such performance info as is out there) that the French locos were not as superior as they should have been over good simples at normal steaming rates.
     
  16. 242A1

    242A1 Active Member

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    Your book shelf and mine must look rather similar. Not a bad book, one or two pages that were not type set properly but no great distraction. A new book expanding on the general overview would be appreciated but only by a few I suspect.
    I agree with you about the Museum, seeing some of the historical development in the metal is so important.
     
  17. andrewshimmin

    andrewshimmin Active Member

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    Thanks Tom. Very interesting.
    I wonder why the lubricant use went up? Both simple and compound locos were 2-cylinder, and the only differences in lubrication requirements were presumably an extra valve (for starting) and larger surfaces in the LP cylinder...?
    Even in cases like this (or the Hughes Dreadnaughts) there are various factors which make the tests not as illuminating as is sometimes claimed.
    The Compound locos were one-offs: were their crews fully familiar with the best ways to drive them? Were fitters familiar with their maintenance requirements? Something which is different from the norm will always be treated differently - which could be for good or ill.
    And on the tests - were the crews aware they were being tested? If so, did the crews drive the simples more expansively than normal, knowing that fuel and water consumption was being measured closely?
    One of the most plausible cases for compounding is that it forces expansive working, when in normal everyday service with two-cylinder simples many drivers didn't drive expansively. Any account from the footplate by Nock, Ahrons, etc., often indicates that two drivers on the same train and duty would drive quite differently - one on the regulator and one on the reverser.
    Of course, it would be impossible to organise valid double-blind trials of compound vs. simple...!
     
  18. Hermod

    Hermod Member

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    Not knowing the numbers ,but if half the heritage buisness is on 2 and a half feet or less,it could be fun to have a two-cylinder compound version of the Darjeling Himaleya B-class.
    There is already a simple/ original in England.
    Comparison and betting will be easy and it will be miles cheaper to build than a mainline 6 coupled or worse..
    The class B was constructed in 1887 and one was working for life in a coal mine in Assam recently.




    Some awfull good engineering.
    How much change shall be allowed ?
    If I pay, inside frames and frame water tank will be allowed ,but no visible welding.
    Two cylinder compound with steam jacked HP cylinder ,reheat and nicely isolated LP cylinder.
    Some of the movies on Youtube shows how dangerous the cylinders are when being within 2 inches of tomatoes and humans.

    https://reflectiveindian.files.wordpress.com/2013/01/dhr.jpg
    A bigger LP cylinder makes it much worse.Inside frames helps.
     
    Last edited: Jan 14, 2018
  19. Hermod

    Hermod Member

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    The Bulleid MNs were rebuilt after the Crewkerne incident.
    If we asume the ratio of starting tractive effort to adhesive weigth on Webbs A 0-8-0 class was OK,we can use that as a model for an alternative three cylinder MN rebuild.
    Strokes were the same 24 inches and the webb piston areas shall go down with pressure ratio ie 175/280 and go up with wheel diameter ratio and up with adhessive mass.Very close to same size.
    The Webblike MN can have two 15 inch Walscharts high pressure cylinders with steam jackets instead of Bulleids18 inch and a 30 inch inside low pressure with stephenson valve gear.Mr Nordman measured a norwegian fourcylinder compound and compared to best german two and threecylinder simples.The Norwegian used between 6 and 18 % less steam for same work.
    The Webb thing will be even more frugal.
     
    Last edited: Jan 14, 2018
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  20. Hermod

    Hermod Member

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    Just to finish this Webb phantasy journey.
    A 9F with two 15 times 28 outside high pressure cylinders will allow fitment of a Krauss Helmholtz truck and an inside 30 times 28 low pressure will allow very good economy and much less footplate vibration at high speed.
    Webb was rigth all the time.
     
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