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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. Jamessquared

    Jamessquared Nat Pres stalwart

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    Feel free ... (Royalty payments can be sent to the usual places ;) )

    Tom
     
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  2. 2392

    2392 Well-Known Member

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    With used low denomination notes in plain brown envelopes under the 5th rock on the left:rolleyes::Saywhat:!
     
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  3. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Noted! ;)
     
  4. Hermod

    Hermod Member

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    The ultimate european steam locomotive was probably a three-cylinder compound 4-8-0.
    In UK with narrow loading gauge etc discussions at the moment is centered on what pacific scheme was best using past examples as guidance.
    It is my unpaid duty to argue for a Webb compound three cylinder 5 feet 6 pacific front wheel drive would have been best .
    Looking much like the Raven (My Hero) A2 but a couple of feet shorter boiler.

    It will be up against running preserved engines

    Big Wheels (6 feet 9)

    Gressley
    Undivided mid- wheel-set drive.

    Thompson,Stannier divided drive
    (Seeing Tornado as a Thompson with more inacessible mid- engine)

    Sensible Wheels (6 feet and smaller)
    A lot of MN,BB,WC were undivided mid wheel

    Riddles Std 8 and Pebbercorns Blue Peter were divided drive

    Brittanias are not considdered being two cylinder selfdestructors.

    I went back to pages 105-110 and enjoyed reading but did not find anything about war time availability Sandringhams versus B16s.
    This would illuminate the all important question who was best of the Raven,Gresley or Thompson ?
    Sandringhams and B16 were same power and mass and the Sandringhams went first.

    On post 2083 it is mentioned that some standards had alligator crossheads and some LNER style.
    The Alligators were used on pony truck engines because they build narrover and do not get hit by leading driver coupling pin.

    When the Thomson story has run to end I for one look very much forward to the LNER wartime statistics.
     
    Last edited: Nov 15, 2018
  5. pete2hogs

    pete2hogs Member

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    Just as a comment. Having bought a Hejlan O2 i was consulting Yeadon v9 and had realised I'd previously just skimmed over the gratuitous insults to Thompson. Why on earth should he not fit his standard boiler to the O2's when it was easy to do? And what right has a supposedly technical author to write - and I quote -
    'No wonder a knighthood never came his way'
    because he had the temerity to rebuild the P2's.
    I never noticed this clear bias when I first read the volume, and since Yeadon was a major contributor to the supposedly definitive 'green guide' one must be apprehensive that similar unjustified dislike may unfortunately influence that work too.
     
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  6. Forestpines

    Forestpines Well-Known Member

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    Yes, I recall noticing that there are some rather anti-ET asides in some passages of the green bible.
     
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  7. jma1009

    jma1009 Well-Known Member

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    Re PoleStars' comments,

    And that quote of O S Nock.

    There is no way that Stephensons gear could be fitted to a Gresley Pacific at all, and any other valve gear for the middle/inside cylinder.

    Stephensons would not fit at all, though it would probably give very good events compared to the middle cylinder valve events 'overrunning' on the conjugated gear when not in tip top condition.

    Note that Holcroft did not approve of the Gresley arrangement of conjugated gear.

    It was Holcroft who showed Gresley how the middle cylinder could be inclined, which was adopted on his Pacifics. Holcroft showed how the conjugated gear could be compensated for this, which Gresley was unaware of. (Query if Gresley had any understanding of conjugated gear at all, compared to Holcroft).

    To convert the Gresley Pacifics from conjugated gear to a separate additional 3rd valve gear was quite problematic. Thompson must have been aware of this, if not of his own accord, via LNER valve gear supremo in the LNER drawing office - Bert Spencer.

    Look at the Gresley Pacific inside cylinder block with conjugated gear. The piston valve is placed to match with the conjugated gear lever and horizontal. The middle cylinder bore is inclined. Neither make fitting a separate valve gear possible.

    At the very least, a new cylinder block was required for the middle cylinder, and a new crank axle if an independent valve gear was to be fitted to the middle cylinder.

    An SR 'Z' class Walschaerts valve gear could possibly have been fitted, as worked out by Holcroft, many years previously, and Drummond had done something similar much earlier still (the combination lever function being supplied by an eccentric out of phase in both cases).

    I don't think that Gresley understood valve gears - he copied a Prussian loco for his first conjugated gear loco (Hermod will no doubt confirm), and Holcroft had to show him how to do it properly, to an extent!

    If Thompson knew anything about valve gears, his comment to Stanier was clearly a throw away remark about fitting Stephensons to Gresley locos as the inside gear to replace the conjugated gear. It was probably an 'in joke' deriving back to Churchward's use of Stephensons gear as perfected by Willy Pearce, the GWR valve gear supremo. Pearce also designed the inside Walschaerts gear for the Stars, Saints, Castles and Kings. The 'in joke' - the nuances of which O S Nock ought to have appreciated, but at the time missed!

    Anyway, that is my own slant on things for what it is worth.

    Cheers,

    Julian
     
  8. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Scales lifting from eyes...



    There’s no “if” about it. Thompson was technically minded. His work on the B12/3 with AE English must rank as one of the most complete and perfect rebuildings of a locomotive class - and his decision to remove the lentz gear for piston valves must surely be the correct decision?



    Entirely possible, and yet there is no other anecdotal evidence for such a thing.


    As I say, pinch of salt.
     
  9. jma1009

    jma1009 Well-Known Member

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    Hi Simon,

    Hmm..

    There were lots of people in the 1930s who regarded Churchward and Collett's adherence to Stephensons gear as very 'old hat'. Actually, modern valve gear simulators have shown the Churchward arrangement of Stephensons gear as designed by Willie Pearce to be well nigh perfect.

    If you don't understand the intricacies of designing Stephensons and Walschaerts valve gear then please give me a bit of slack..

    Very few CMEs understood locomotive valve gears in any detail. Holcroft (ex-GWR, then SECR and SR), Bert Spencer (LNER) understood these things, and the GWR had Willie Pearce from the early 1900s till the early 1940s. None were CMEs and all were of lower rank but in each case their CMEs relied heavily upon them for their expertise.

    Gresley had a very poor understanding of valve gears, and Holcroft had to show him the way with the conjugated gear. Holcroft states Maunsell's initial designs for the SECR were 'Inchicored' with short travel; one is left with the impression that Maunsell then left all valve gear design to Holcroft until the Q class in 1938 which shows nothing of Holcroft's input. Collett left all the valve gear design to Willie Pearce, as did Churchward.

    Gresley initially ignored Bert Spencer's advice with the A/1 valve gear.

    What do we learn from the above? The CMEs left valve gear details to subordinates. I have no doubt from the above that no more Thompson understood the niceties of locomotive valve gears anymore than Gresley did.

    Cheers,

    Julian
     
    Last edited: Nov 16, 2018
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  10. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    If you base your view of Thompson on the history of others you will come up short.

    In the B12/3 rebuilding Thompson has a full wooden mock up made of the valve gear and he personally worked on the valve gear events with AE English - even turning the handle to make the valve gear move. See Graftons biography for more details.

    Thompson at almost every turn of his career on the LNER when presented with a locomotive class looked to use a tried and tested walschaerts valve gear design. He used piston valves wherever he could.

    He may not have understood the full intricacies of valve gear design but he was much closer to the process than any of the CMEs you’ve mentioned above, particularly at the maintenance level when head of Stratford works.

    I fear you underestimate Thompson’s knowledge and experience greatly by not being as au fait with his history as the others.
     
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  11. 8126

    8126 Member

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    I agree that Spencer was the valve gear man on Gresley's design team. In fact, he had to campaign long and hard to get the long lap valve gear which so improved the A1s and was used pretty much unchanged on the A3 and A4. There had been an earlier attempt, but it was a bit of a bodge and performed accordingly (thus reinforcing Gresley's initial belief that long lap gears weren't worth the effort), whereas Spencer went all out to optimise the valve events for 15% cutoff, while not making massive changes to the existing gear.

    All the above is in the relevant green books, and strongly suggests the valve gear on the Gresley Pacifics could have been better if there had ever been the opportunity for a full re-design. Possibly a slightly contrary opinion here, but I don't think the valve gear was the fundamental weakness of the type from the improved A1s onwards. What they had was an inside big end problem, exacerbated by some of the characteristics of the valve gear. Once the big end problem was solved, the 2:1 gear was a damn sight easier to work with than a third set of valve gear.

    Vaguely linked, but while wiki-wandering I came across the Australian three-cylinder 4-8-4 no. H220, built with a Henschel 2:1 type gear which appears to have used rotating shafts instead of pivoting levers to obtain much the same effect.
     
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  12. jma1009

    jma1009 Well-Known Member

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    Hi Simon,

    I have actually provided you with lots of stuff that supports your stance, on Thompson, but there we go!

    The nuances were lost on you as they were on O S Nock, who was similarly ignorant of such niceties!

    Cheers,

    Julian
     
  13. huochemi

    huochemi Part of the furniture

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    From an engineering perspective, prima facie, using only two sets of valve gear seems like a good way to go and probably explains why Gresley gear was used globally in the 1930s. What seems to have killed it off was the lack of three cylinder locos as much as anything. The only instance I know of where Gresley gear was replaced on the same class of locos was the Thai Baldwin Pacifics, where the later locos were fitted with two sets of Walschaerts on one side. Whether Heavy Harry's gear was superior, I don't know, but I suspect there were issues of multiplication of slack and possibly whip in the rather flimsy drive shafts from the outside valves, which would have been exacerbated on high speed locos. A geared drive such as Caprotti seems a rather more elegant solution.

    Were I writing the book, I would be inclined to include a short section on other gears available at the time, and their popularity, and if known, their disadvantages, to put Gresley gear in context.
     
  14. Hermod

    Hermod Member

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    Considering GWR policy of inside eccentrics driving outside valves ,it is hard to believe that some kind of a short armed rocker was impossible on Gresleys.
    Has someone a drawing or CAD model of the combat area?
     
  15. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Julian if that’s the case perhaps you wouldn’t mind being more direct in pointing this out.

    There’s nuance and then there’s nuance. The internet and the written word rarely help in identifying such nuances.

    I re-read your post before writing myself and my initial reaction was that you were being rather mocking of me, which felt unfair. I read it again and cannot make up my mind now on that point.

    I prefer to be more direct because subtlety is lost on the Internet.
     
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  16. 8126

    8126 Member

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    Eight of the eighty-eight UP 9000 class 4-12-2s had the Gresley gear replaced with a third set of Walschaerts gear driven from an additional return crank and expansion link on one side. The remainder had roller bearings installed throughout on the Gresley gear and remained unconverted. Given the relentless focus of US railroads on availability and maintainability, I'd suggest this implies that replacing the Gresley gear (with a much more accessible solution than a third set between the frames) did not have any significant benefits.

    It could be argued that real replacement for the Gresley gear in the case of the 9000s was two sets of outside cylinders on a high-speed 4-6-6-4, in the form of the Challengers.
     
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  17. Jamessquared

    Jamessquared Nat Pres stalwart

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    I just looked up the NZR G class 4-6-2+2-6-4 Garratts. They had Gresley gear; when they were rebuilt (for other reasons) into pairs of pacifics, they retained the Gresley gear. For various reasons they remained unpopular, though interestingly Sean Millar notes that they had the second lowest per mile operating cost of any New Zealand pacific. I suspect the difficulties of getting - and even more, servicing - a third set of independent valve gear between the frames on a 3'6" gauge loco may have been a challenge.

    There's a very fine photo here: https://en.wikipedia.org/wiki/NZR_G_class_(1928)#/media/File:NZR_g_class_garratt.jpg of one them as built, which shows the Gresley gear with a cover protecting the workings. When rebuilt as pacifics, that was initially retained but it seems that during the war it was removed and they ran the last 15 years or so with the gear exposed; presumably a modification to help servicing. (see e.g. http://www.trainweb.org/nzsteam/g_4-6-2.html)

    Tom
     
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  18. Hermod

    Hermod Member

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    Conjugated valve gears are maybe usefull for low speed three cylinder locomotives of which there was not very many.
    The Prussians made a G12 2-10-0 in 1915 because they feared problems on connecting rod big end if made as two cylinder.
    The two outside valve gears were conjugated and this worked OK.
    For high speed locomotives ,that is more than 5 rps,it was not tested in Germany I think.
    Gresley did in England and the jury is still out.
    UP was a fast freigth engine and was not develloped further but this was maybe due to the BIG inside big end.
    We must all be happy that Gresley tried or we utterly superfluous steam lovers would have to watch TV or cook more.
    Rather steam than dishonneur.

    .
     
  19. Fred Kerr

    Fred Kerr Resident of Nat Pres Friend

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    Having read through the latest collection of postings I hesitate to add some thoughts - but in the interest of providing a focus I offer :

    1. References to OS Nock by some commentators have compared Nock to Tuplin in that they failed to understand the full nuances of engineering hence were liable to conjecture in their writings. Note that Nock's field of expertise was in braking hence his interest in engineering but locomotive engineering is a field that needs the level of comprehension that I believe - as do others - that OS Nock didn't have.

    2. CMEs tend to operate as part of a team with themselves at the head. The discussion about valve gears suggests that this was one area where the CME would delegate the task to an expert - even if the solution was ignored - as with Gresley and the initial reaction to suggestions of long travel valve settings. I venture to suggest that Thomson's problems at Doncaster are centred on the possibility that he disagreed with the Gresley team that he inherited given his (possible) view that the conjugated valve gear had problems that his economy minded mindset found difficult to solve. I return to a previous posting where I referred to Harry Knox who wrote that Haymarket maintenance standards undertook gear maintenance at a lower mileage than specified by the CME but that the CMEs never updated the maintenance manual(s) based on that experience. Was this a case of (a) simply allowing depots to act on their experience given the level of responsibility accorded by the CME (b) ignored because it conflicted with the CME who saw this as a running sore or (c) not made known officially to the CME.
    It beggars the question (considered in your thesis ?) of the changes made by Thomson and the opinions of the individuals within both the Gresley and Thomson teams - especially for the Gresley team members who did not become Thomson team members.

    3. I believe the CMEs had a dry sense of humour hence suggesting that both Nock and other observers failed to understand the nuances of comments and in-jokes. Given the problems with today's internet regarding the nuances of any posting (was that irony / sarcasm / serious comment ?) I suggest that interpretation of written texts in the early part of the 20th century may need to be reviewed in the same light as this may have been part of the mis-understanding that led to queries about their published writings. Sadly the passage of time suggests there is now little context in which to judge the quality of that interpretation.

    As usual I temper my thoughts with the opinion that your own work is also going to be objective but readers will temper their opinion by their own level of bias towards Thomson hence my best wishes for your endeavours.
     
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  20. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    I completely agree.

    (On a side note I have worried - and continue to worry - that despite the strides I have made in my own understanding, I am not qualified to pass comment or judgement on the engineering myself, hence most of my analysis in the book is levelled at evidence, context and asking questions - not necessarily able to answer the most technical ones).

    I will have to PM you privately when I am able to consult my notes from Kew, but Thompson sent out information and instructions regarding maintenance to all the mechanical engineers regularly as a result of investigation, according to that I have seen (and am happy to share with you privately, if you like - as I cannot publish such archive material online).

    In the latter years of Gresley's tenure, I am afraid I have not found the same level of attention, and would suggest your thoughts regarding local knowledge on maintenance to be correct where Gresley/Thompson are concerned. In short - two different approaches, where Gresley was more content for local knowledge to take precedence and Thompson - noting availability issues - would look for solutions to be sent out.

    There is no doubt in my mind that Thompson changed the makeup of his team members because he did not believe they would follow the direction he felt compelled to take. The change of roles for, as an example, Bert Spencer were made almost directly after the Cox/Stanier report was given to the emergency board. There was about thirty five years of Gresley's work and belief in Gresley's work in the LNER and GNR and the depth of feeling for their old chief was undoubtedly strong.

    I think it can be both true that Thompson was trying to do his best in a difficult situation, exacerbated by poor availability and set against a backdrop of wartime austerity and destruction, and that he was also more forthright and potentially thoughtless in terms of the perception others held for the work he was doing. I note from the LNER Emergency Board minutes that he amongst others paid tributes to Gresley on his death, and in interviews Nock and others took after Thompson's retirement, he repeatedly praised Gresley's work on the one hand whilst quantifying what he felt was Gresley's greatest weakness (conjugated valve gear).

    I can see - and I am sure everyone else can to - that Thompson's approach may be seen as accusatory or denigrating Gresley, but equally if trying to look objectively at Thompson, you can see a firm belief in the work he felt he had to do to improve the LNER's lot, and an attempt at balance potentially.

    I completely agree with you, hence my reluctance to give Nock's quotation regarding Stephenson valve gear much credence. Even if it was dry wit on Thompson's part, we can't be sure of the context - and it isn't corroborated by much else.

    On the other hand, it is clear he had a close working relationship with Stanier over the latter years of his career and perhaps it may be worth me looking into Stanier more at a later date.

    Much appreciated Fred, thank you.
     
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