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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. Eightpot

    Eightpot Resident of Nat Pres Friend

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    Just wondering if this was a repeat of what Thompson did earlier on the GE section by modernising B12s and D16s with more modern piston valve cylinders and a re-designed valve gear to improve them when the existing cylinders needed replacing anyway.
     
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  2. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Precisely. Thompson applied the same methodology to most of his work.
     
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  3. Jamessquared

    Jamessquared Nat Pres stalwart

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    Cylinders were certainly a consumable item, particularly on older locos. I haven't done any form analysis, but a rough sort of figure for pre-grouping Southern locos (and I don't suppose others were very different) was that they might have life of around 1/4 million miles. So over a lifetime, a loco might easily have four or five sets of replacement cylinders, so provided you timed it right, a rebuild with extensive modification of design (for example replacing slide valves with piston valves) could happen at relatively little marginal cost, since the cylinders would need replacing anyway, as @Eightpot says.

    With regard the later J11 retaining Belpaire fireboxes: was the intention that they were a lightweight 0-6-0 with greater route availability? I note from lner.info that a J11 was around 51T (i.e. 17T axle load); a J39 was 57T (i.e. 19T axle load). It's certainly possible to imagine that putting a J39 boiler on the J11 frames made it too heavy; and trying to design a smaller, lighter round-topped boiler runs into the issue that the most expensive part of having a new boiler is making new flanging blocks. So just a hypothesis, but conceivably the "round top J11" may have foundered because the version with a J39 boiler was too heavy, but redesigning a smaller boiler was too expensive when the flanging blocks already existed for a Belpaire firebox. Just a theory.

    Tom
     
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  4. RLinkinS

    RLinkinS Member

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    They could have used the same flanging blocks as for the V1/V3 tanks. The boilers on these were 5' diameter rather than the 5' 6" of the J39s.
     
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  5. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    The Cox report was published internally to the LNER Emergency board, and discussed that summer, with Thompson's overall standardization plan approved and in place prior to approving the rebuilding of one P2 type locomotive. It should be noted that although the wheelbase change wasn't mentioned, Cox's report recommended rebuilding some conjugated valve gear locomotives with a third set of walschaerts.

    I think Thompson, after ordering the W1 to work alongside the P2s on test and seeing the results of that locomotive's work, probably decided a rebuilding to Pacific format would be a more logical outcome. Bear in mind, there wasn't much time or desire for experimental testing; everything had to meet certain criteria including using as many standard parts as possible.

    The conversion to a Pacific format was further simplified by the P2's original design in that it split the main frames between the front driving wheels and the second set in the mikado format. Fitting the Thompson front end on was as easy as unbolting the original frames and bolting on the new one.

    The boiler was shortened and a new smokeboxe made, together with using some modified LNER cladding to replace the original (egg shaped) P2 type cladding.

    Thane of Fife was in so many ways, highly simplified from the P2 design, when rebuilt as a Pacific. A "Ronseal" rebuild. High tractive effort, Pacific locomotive, easy to maintain and more readily available for work. It was a success.
     
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  6. Hermod

    Hermod Member

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    Thank You or some interesting facts about frames before and after.
    Did Gresleys pacific also have split frames and what (standard?) cylinders was used for A2/2s?
    Is there a website place where one can see the general frame arrangement of P2s?
     
  7. andrewshimmin

    andrewshimmin Well-Known Member

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    I've just discovered another overseas use of what appears to be Gresley conjugated valve gear: on some massive metre gauge 4-8-2 and 4-10-2 locos on the Sorocobana in Brazil.
    Just in case anyone is interested!
    I make no remark about whether they should have been rebuilt with independent valve gear...

    Sent from my Pixel 3a using Tapatalk
     
  8. lewi73050

    lewi73050 New Member

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    And this monster also used the conjugated valve gear... you can see the 2-1 lever clearly[​IMG]

    Sent from my SM-G960F using Tapatalk
     
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  9. jma1009

    jma1009 Well-Known Member

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    Hi Simon,

    The P2 new build project is progressing well, and you are a supporter of this worthy project.

    I don't myself subscribe to your view that the Gresley P2 design was inherently bad, and I should imagine neither do those behind the current P2 new build.

    So there is a dichotomy here, I would suggest, that you have not explained.

    What are we to believe? A P2 rebuild by Thompson was better than the original P2, and those involved in the current P2 new build ought to do a 'Thompson' on it into a Pacific?

    Alternatively, could the current P2 new build project be on the right track, so to speak, and by a few minor alterations produce a jolly good P2?

    Ergo, proving that what Thompson did to the P2s was unnecessary?

    Cheers,

    Julian
     
  10. Jamessquared

    Jamessquared Nat Pres stalwart

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    Julian - I think you are conveniently ignoring two things: that the team building the modern P2, with the benefit of hindsight, spent years doing extensive computer simulation work to design out the original faults, particularly in valve gear design and track holding / stability.

    Thompson didn’t have years available, and didn’t have computer simulation.

    Its perfectly consistent to believe that under wartime pressure and with a class of demonstrably low availability, rebuilding as a Pacific was logical and low risk, while simultaneously holding that free of time pressure and with modern analytical methods, the original design could be improved upon.

    Tom
     
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  11. Fred Kerr

    Fred Kerr Resident of Nat Pres Friend

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    Julian

    As a lifelong admirer of Gresley and his works I am aware that Thompson developed the LNER fleet in directions different from any ideas that Gresley may have had BUT Thompson did so in the environment of both WWII and the continuing poor availability of the LNER locomotive stock. These factors also affected Gresley BUT he died (in harness) before being able to provide his solutions thus leaving Thompson - as the LNER's choice as successor - to provide the solutions. Your continued criticism suggests that your admiration for Gresley accepts Thompson as being anti-Gresley but IMHO your continued carping merely says more about you and your opinions without adding to the evaluation of a CME caught between the rock of needing to improve locomotive availability and the hard place of not diluting the reputation of his predecessor. The fact that the LNER Board considered him fit to succeed albeit for a short spell until retirement and then appointed Peppercorn to succeed Thompson and Peppercorn continued along the path that Thompson initiated should surely suggest that Thompson's achievements be both fully analysed and given greater credit than hitherto.

    There is also the considered opinion that Thompson may have discussed some of the matters with Gresley hence included some of his thoughts within his actions; that is only hearsay but I cannot imagine that both Gresley and Thompson didn't't discuss such matters especially since Thompson deputised for Gresley at some of the LNER Board meetings in Gresley's absence.

    In terms of the current P2 project you are obviously overlooking the fact that the A1 Team has had the benefit of CAD to test out theories whereas Gresley and Thompson only had main line running as the test arena; even the Rugby Test Plant - which could have answered many of the design problems - wasn't available until after WWII and the solutions couldn't wait until then as they were needed DURING WWII not after it !

    I would suggest that you cease your criticisms of the "what if ...?" kind as you seem to be ignoring the consequence of both the death of Gresley and the needs occasioned by WWII. In that context perhaps it is worth asking "what if there was no forum such as this to discuss the Thompson era and Simon simply produced his book through the normal publishing channels; how would that affect both your opinion and counter-arguments to the treatise produced by Simon ?"

    As an admitted Gresley admirer I look forward to reading Simon's analysis but I will read it in the context of the times in which Thompson was in charge hence taking note of the factors affecting both his ability to make decisions and the consequences of the decisions that he took.
     
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  12. jma1009

    jma1009 Well-Known Member

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    Hi Fred,

    You have gone off on an unnecessary 'rant' that quite avoids the points I was attempting to make.

    I am not a Gresley 'fan' either.

    I posed a simple straightforward question without any bias whatsoever.

    As to one of Tom's points, H S Gowan and Don Ashton were able to do their analysis of valve gears in the 1970s, [initially in Don's case without computer simulation and he went on later to do this with computer simulation many years later] ; just as Bert Spencer and Harold Holcroft would have done; no computer simulation available then. I have not heard of any issues with the P2 valve gear as originally designed, so one part of Tom's riposte is without foundation.

    If Simon suggests the original P2 design was so bad and Thompson was justified in rebuilding it, why on earth are the P2 new build group (of which Simon is a supporter of) building essentially the Gresley design?

    It is quite a simple question, that only requires common sense!

    Cheers,

    Julian
     
  13. Jimc

    Jimc Part of the furniture

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    It is indeed an interesting question, but isn't the answer that whatever the flaws of the design its the one they were most likely to raise money for? Its scarcely the only new build project for a locomotive that might be described as not very good, which in itself says something about the preservation movement.
     
  14. 2392

    2392 Well-Known Member

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    I'm glad to see this thread has returned to a more reasonable debate back and forth, with regards to Mr Thompson's efforts compared to Sir Nigel Gresleys.........
     
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  15. Jamessquared

    Jamessquared Nat Pres stalwart

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    Julian - in concentrating yet again just on valve gear, you have ignored the point about the substantial computer modelling work done by the modern P2 team on vehicle dynamics, crank axle design etc - techniques that weren't available to Thompson.

    I really don't get why you see the rebuild as so controversial. Take the situation Urie had when taking over from Drummond. He had small numbers of non-standard four cylinder 4-6-0s that were known to be heavy on coal and had unreliable fireboxes and insufficiently large axle boxes that meant they spent considerable time on shed undergoing repairs. They ran low annual mileages relative to the 4-4-0s on the railway. So Urie rebuilt them completely, in the the process setting the design template that was followed by his successor for rugged, simple two cylinder 4-6-0s. In many ways, the change of wheel arrangement from mikado --> pacific disguises the fact that there was far more Gresley remaining in the P2 rebuild than there was Drummond remaining in a Urie rebuild.

    All Thompson did is what any competent CME would have done, and indeed routinely did do, in the same situation.

    Tom
     
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  16. andrewshimmin

    andrewshimmin Well-Known Member

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    Julian,
    You are being rather disingenuous, whether intentionally or not.
    This whole endless thread has shown that there clearly were issues at that time with the valve gear (inter alia) on these locos, and that some sort of major attention was needed.
    But also that the valve gear was only part of a wider problem.
    Whether Thompson's solution was the best one available at the time is what we're all discussing.
    The new build P2:
    - will be a one off toy (no disrespect intended with that term), not part of an operating commercial fleet
    - was chosen for new build because of sentiment about its impressive appearance and romantic early disappearance, rather than its engineering excellence
    - will, in any case, differ in many important respects from the originals, which were a hotch potch themselves. In fact, the differences are so great there's no way the LNER would have classified it as P2!
    As such, nothing about the original P2s can be inferred from the new one.
    Any more than the merits or demerits of Earl of Merioneth or David Lloyd George can be used to argue for or against the decision to scrap Little Wonder in the 19th century.

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  17. andrewshimmin

    andrewshimmin Well-Known Member

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    Beautifully put!
    I wonder how much controversy there would be if Thompson's A2/2 had been more beautiful or indeed the P2s and 4470 less elegant?!?!
    (I quite like the looks of the A2/2 and A1/1 personally, but it's hard to deny the especial good looks of a Gresley A1. I think the RHDR ones are perfect!)

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  18. Fred Kerr

    Fred Kerr Resident of Nat Pres Friend

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    Perhaps the question should be put to the A1 Group - could Gresley have made a success of the P2 fleet had he had the current level of computer software to hand ?

    In respect of your comment re the work of Messrs Gowan and Ashton note that they were (a) not subject to the demands of WWII and (b) not responsible to the LNER Board hence coming back to the basic fact that you seem to be ignoring viz. the demands of the LNER Board for better locomotive availability and the needs for WWII production did not provide time for experiments hence the need for tried and tested solutions - in Thompson's case a rebuild to a 4-6-2 using "conventional" 3-cylinder valve gear. Your proposals that Thompson ignored / overlooked design elements require TIME and that was something that neither the LNER Board or the LNER CME had hence Simon's considered view that any analysis of Thompson's work as CME HAS to take note of the conditions in which his work took place hence his analysis and the thrust of the book he is writing to re-assess Thompson's contribution to the LNER history.
     
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  19. 30567

    30567 Part of the furniture Friend

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    Just an amateur here, but my limited reading is that the decision to rebuild was not made purely on mech eng grounds. Maybe the P2s would have worked fine between Chicago and Omaha, but they were not suited to the curvy Aberdeen line and could not be transferred to KX because of the sharp curves in the vicinity of 34A. So civil eng and operational flexibility considerations played a part in the decision.
     
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  20. MellishR

    MellishR Resident of Nat Pres Friend

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    Adding my two penn'orth to answers already offered; the appeal of the P2, especially the first version before the A4-style nose, is that it was a very handsome locomotive with great potential but lost to the world because of its flaws. Building a new one identical to the original would indeed be a bad idea, but the Trust is building a new improved version, largely the same as the original and looking the same but with the flaws designed out.

    Simon's intensive digging through the documents has shown that the P2s' availability in the circumstances of WWII was even worse than that of most other LNER locos, so something had to be done about them urgently. Thompson did a quick and dirty rebuild which provided both a first stab at a design for after the war and a more useful loco for immediate needs. Another CME in the same circumstances might have done something different, but Thompson's choice certainly wasn't a bad one.

    As for the valve gear; both before and after the War the Gresley gear was satisfactory, but in wartime conditions it was one of the causes of trouble. Supported by the Cox report, Thompson decided not to use it for future designs but also not to bother rebuilding the existing fleet except for a few as prototypes for new constructi0n.
     
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