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Edward Thompson: Wartime C.M.E. Discussion

Discussion in 'Steam Traction' started by S.A.C. Martin, May 2, 2012.

  1. MellishR

    MellishR Resident of Nat Pres Friend

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    Isn't it rather that you compensate by having the middle crank not at 120 degrees to the outside ones? The conjugated gear necessarily gives 120 degree phasing between the middle valve and the outside valves and you can't change that.
    Having the movement of the piston, and hence the crosshead, not parallel to the movement of the valve would certainly make Walschaerts very tricky to design, whereas that is not an issue for Stephenson. So it would make sense for someone to say "How about Stephenson?" and then rapidly dismiss it because of the different behaviour with changing cut-offs.
     
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  2. Jamessquared

    Jamessquared Nat Pres stalwart

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    I wouldn't beat yourself up about that. One way to look at engineering would be to see it as a means to find technical solutions to practical problems of concern to those paying the bills, so assessing engineering merit in terms of whether it improved or made worse those problems seems like a sound approach.

    Of course, the Chief Officers are the servants of the board, so the board's view of which problems need to be solved will inevitably shift over time. It's entirely consistent to imagine that in the 1930s, the board may have worried about the impact of air transport and asked their chief officers what they could do about it (outcome: the A4s and high speed, lightweight Coronation train, with the traffic people looking at how to create clear paths etc); while in the 1940s, availability and reliability became big concerns, tasking Thompson with coming up with engineering solutions to an entirely different set of problems. In other words, both Gresley and Thompson can be seen to have provided robust engineering solutions to problems of the time, but the problems seen in the 1940s were different from those seen in the 1920s and 1930s.

    Tom
     
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  3. Eightpot

    Eightpot Resident of Nat Pres Friend

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    I've read somewhere that the reason for replacing the Lentz cylinders was that they suffered from cracking. Bear in mind also that when this batch of Lentz-fitted B12s were built there was a dispute between the LNER and Beyer Peacock of the increased cost of these cylinders to BP over piston valve ones which were a later addition and not in the original contract. IIRC the dispute of the extra cost was resolved on a 50/50 basis. Thus it could be that Thompson decided to fit this batch with piston valves more on cost grounds.

    He also did this modernising with redesigned valve gear and piston valves on some of the D16 4-4-0s (the Claude Hamiltons), unfortunately this new wine (cylinders) was a bit too much for the old bottles (frames) with the latter cracking under the extra power, and these locos so fitted were amongst the first to be withdrawn.

    Edit. Without looking up, but wasn't one (or more) J20 0-6-0s also fitted with Lentz gear and also suffered the cylinder cracking problem?
     
    Last edited: Nov 16, 2018
  4. M Palmer

    M Palmer Guest

    I defer to others technical knowledge but I always took the comment to be a not even thinly veiled dig at Pickersgill's 956 class which had Walschaerts on the outside and Stephenson on the inside on a couple of examples and nothing more serious than that.
     
    Last edited by a moderator: Nov 17, 2018
  5. pete2hogs

    pete2hogs Member

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    It's a diversion but I do wonder on what basis those locos were regarded as total disasters? I've never seen any actual discussion on them.

    In hindsight the idea of having two outside gears on a three cylinder engine (one driving the centre cylinder through a rocking shaft) seems a good one, but would it even be possible in the UK loading gauge?
     
  6. Forestpines

    Forestpines Well-Known Member

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    Well that's essentially what Holcroft / Gresley conjugated gear is!

    You can't, I presume, derive the valve events for the middle cylinder off just one of the outside valves, because then the two linked cylinders will have their events synchronised, so you'll have very uneven forces during each wheel rotation.
     
  7. Hirn

    Hirn Member

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    Nock deserves some research. He is tantalising: there are good and useful things in what he wrote but he simply wrote too much - and trying to find what is valuable
    among it.........

    He did study mechanical engineering at Imperial College and one of the Professors was Dalby who was a member of the Royal Society, published a book " Steam Power ",
    chaired the locomotive balancing committee in the mid 1920s and in the late 30s did the valuable wind tunnel work on the A4s streamlining. Nock belonged to and
    attended the Institution of Locomotive Engineers where he recorded Fowler's reaction in person to Diamond's explanation of the cylinder losses in the Midland Compounds.
    He worked in railway engineering in a specialist contractor's - brake cylinders and signalling frames - but not in a locomotive drawing office, maintenance or running shed.

    He came to write - from his autobiography - because he was concerned that his job with Westinghouse was not was not certain. And it is quite clear that he wrote for
    the income and took care not to upset neither his sources of access and information nor his employer.

    I think he was careful not to misrepresent Thompson and to rock no boats. It must have been a memorable occasion for him - he hadn't long got his feet well under the table
    as a journalist -to be given such a briefing by Thompson in person and even if he made no notes I think it would have stuck in his mind pretty well. In technical journalism
    at that time there was simply a considerable emphasis on accuracy - the grilling the young Ian Allan received.

    I think what Nock wrote on this does deserve to be considered seriously : as most likely true.
    The two people we have a contemporary account from with detail who were not LNER men are him and Cox who do not contradict one another.
     
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  8. MellishR

    MellishR Resident of Nat Pres Friend

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    pete2hogs said: (but the post seems to have disappeared)
    In hindsight the idea of having two outside gears on a three cylinder engine (one driving the centre cylinder through a rocking shaft) seems a good one, but would it even be possible in the UK loading gauge?
    I think pete2hogs was referring to a design where the centre valve is driven from a second return crank on one of the driving wheels instead of an eccentric on the axle. If you can fit two return cranks for Stephenson's, as was done on 4767, it ought to be possible to fit two return cranks for two sets of Walschaerts.
     
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  9. sir gilbert claughton

    sir gilbert claughton Well-Known Member

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    I have been off line for a few days so have not been able to participate so a few comments on what has been said .

    I am aware of contradictions in OSN output , and also share the view of others that much of his later work contained little ( if any ) original material .

    It is not true to say that Nock gave no hint of the problems facing ET . he did . Locos of the 20thC vol 2 chapter 8. he does not labour the points but he does give enough info (including WAS involvement )for a student to find out more if he so wished .

    he was honest enough to admit that he could not tell the whole truth of events he heard about or witnessed . he needed access to the railway to make his writings possible so could not always be candid

    just because fault can be found with some of OSNs output is not reason enough to rubbish all he has said . I have read OSNs output over nearly 65 years . I think I can see the wood behind the trees


    he was very far removed from being as objective as he should have been in matters relating to ET . clearly he was a fan of HNG . he did say that ET had imparted info that he probably should not have . little ( if any) of that info was ever made public . at least he had a degree of discretion -which may well have robbed us of valuable insight.

    Holcroft was entitled to be unpleased about HNG use of the conjugated gear . Holcroft designed it , and HNG pinched it with a few minor changes and never gave Holcroft any credit . that may tell you summat about HNG --or it may not ………
     
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  10. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    I am afraid I would take a different view. He dismisses the Stanier/Cox report quite often in his body of work with a simple "Stanier merely said he would not use it [conjugated valve gear]".

    Which is neither accurate, nor fair, on Thompson and his staff.

    I am not rubbishing everything he says.

    I am saying - take with a pinch of salt his writings on Thompson. His views vary wildly the older he gets and much of what has been written on Thompson and his locomotives is not a balanced, objective viewpoint that you would expect.

    I think Tom made the point earlier that Nock concentrated on the exceptional runs rather than the everyday - whereas Thompson's focus was on the economics and practicality of the everyday.

    You could cogently argue that Nock did not understand Thompson's remit and certainly did not pay it any heed, based purely on his writing.

    The level of discretion, I fear, is not with Nock - but with Edward Thompson, who was interviewed at least twice, by Nock, and one other, on the subject of the conjugated valve gear and made no mention of the internal report he had commissioned which, to be brutally honest, did not pull its punches in the description of the performance of Gresley's valve gear during wartime.

    You could certainly read into that a different slant. Different time, different people, different conditions and different conceptions of what is right. I do not judge Gresley or Thompson on the context of today against that of the past, but within the context of the past. In that we find a closer "truth" I feel.
     
    Last edited: Nov 19, 2018
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  11. Eightpot

    Eightpot Resident of Nat Pres Friend

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    For all that, the LNER was not alone with inside big-end problems. According to A. F. Cook's 'LMS Locomotive Design & Construction' published by the RCTS in 1990, the LMS/LMR also had its share of trouble in these components in that they issued a modification Job Number 5555 on May 9th, 1950 to fit all their 'Pacifics' and 3-cylinder 4-6-0s with the LNER type heat detectors/stink bombs - a total of no less than 364 locomotives.

    Re the difficulty of fitting a 3rd set of Walschaerts valve gear for the inside cylinder on V2s, it appears that there was a scheme for the LMS to build a 3-cylinder 2-6-2 during the war. I wonder how they would have overcome this problem had the locos been built?
     
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  12. flying scotsman123

    flying scotsman123 Resident of Nat Pres

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    That's the spirit, open minds, new ideas etc.... :rolleyes:
     
  13. Jimc

    Jimc Part of the furniture

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    That's maybe a bit strong. Holcroft wasn't the first to design a conjugated gear, Joy had designed one for marine engines, although Holcroft worked his out independantly. Holcroft's gear was rather different to Gresley's, more symmetrical, and laid out for the valve being right in the centre of the locomotive, but I think with more bearings.
    After Gresley had built his first conjugated gear, which was very complicated, involving rockers, to deal with inclined inside cylinder, Holcroft then made a suggestin for a simplification.

    Interestingly Holcroft's N1 for the SECR used the Gresley layout with the offset valve.
     
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  14. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Comments like these used to bother me greatly. Mostly because they were then justified by calling me a liar, or revisionist, or whatever...

    Now I see them for what they are. The commentary of people whose world view is threatened by research, examination and debate.

    It is a shame that your first post in this thread is such an unpleasant one. I encourage, or try to encourage, debate as much as I can and robust debate has happened in this thread for the most part.

    You do not attempt to put across why you feel that way, or discuss it. You merely wish to disregard my work out of hand.

    Your loss.
     
  15. Wingsandwheels

    Wingsandwheels New Member Account Suspended

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    No loss to me.
     
  16. flying scotsman123

    flying scotsman123 Resident of Nat Pres

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    I'm not interested in your opinion but I am going to post specifically to say so without explaining why. ;)
     
  17. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    One has to ask though, why you feel the need to be so deeply unpleasant towards me?

    I have not, as far as I’m aware, ever done anything to you personally, so why do you post here to make such comments?
     
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  18. Wingsandwheels

    Wingsandwheels New Member Account Suspended

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    I was in no way unpleasant towards you. Merely stated my opinion on ET and said I wouldn't be bothering with your book.

    Snowflake generation?
     
  19. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    You rubbishing my work out of hand without seeing or reading it, coming onto this thread to “merely” state your view...

    No, I’m done arguing. :Yawn:
     
  20. 35B

    35B Nat Pres stalwart

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    Given the discussion that’s gone on upthread, I’m interested in why you feel that way about Thompson, and are seemingly so determined to avoid considering whether received wisdom may be incorrect.

    As an aside, @S.A.C. Martin (whom I have never knowingly met) may be many things, but he does not strike me as a snowflake, whichever generation he belongs to.


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