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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. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    And oh - the irony - of discussing Great Northern again on page 113 of this thread!
     
  2. PoleStar

    PoleStar New Member

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    Simon,

    I have just found the reference. OS Nock, British Locos of the 20th Century, Volume 1, page 201- 2. I think it is important. What do you make of it?

    If you don't have a copy I can quote it here.

    Tony.
     
  3. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    I'd be very interested Tony - yes please! Would make for an interesting discussion point here too. Many thanks.

    (On a side note, noting it is OS Nock making the comment - he has an entire section to himself in my book. The consistency of his commentary on Edward Thompson - or should I say inconsistency - is illuminating, in the round).
     
  4. PoleStar

    PoleStar New Member

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    Simon, Interesting what you say about Nock's commentary, but that is another matter.

    In the British Locos book he is discussing the problems of the Pickersgill 956, and then says this:

    "Many years later..........Edward Thompson told me of the investigations he made into the derived valve gear before deciding on a complete rearrangement of the front end of the Pacifics. At one time he was thinking of putting Stephenson's link motion in for the inside cylinder, and mentioned his idea to Stanier, who was horror struck! 'Whatever you do, don't do that', came his instant reaction; and Stanier went on to say that he had four big Caledonian engines like that (i.e. the 956s).....they were useless, and I had to scrap them.'"

    I don't think Nock would have made this up, and I think it shows that Thompson was having very real difficulties and Stanier was genuinely trying to be helpful.

    I think that Thompson had serious problems to tackle on the LNER , in wartime conditions, otherwise he would not have done all that he did. We tend to forget, too, that he was only doing his day job, and in common with other CMEs he had a life away from the railway, unlike some enthusiasts, apparently!

    All fascinating stuff, and if your writing and research is as good as it seems to be from what is on here, you need a publisher.

    Tony.
     
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  5. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Extraordinary. On so many levels. I simply can't see that this can be true. Nock must have misremembered.

    I say this because Thompson's intention, almost universally on every design he was ever involved with, was to simplify the design. Adding Stephenson's link motion is so out of character for Thompson, who had throughout his career fitted standard piston valve and walschaerts to virtually everything he touched on the LNER (whether at Stratford or Darlington or as CME).

    There was no precedent for fitting a different set of valve gear between the frames on the Pacifics and the original A2 proposal had a highly inclined centre cylinder as would become the standard under Peppercorn - and with three sets of walschaerts. The Thompson front end come about in part to utilise the advantages of three equal length connecting rods.

    This is actually the sad thing, during WW2 I don't believe Thompson did have much of a private life. His wife had passed away, his house was bombed, at one stage he was living out of his office in Doncaster works, surrounded by racks of his suits...! There is a passage, oft repeated, but most famously in Peter Grafton's book, where he looks out across the works and says to his secretary "what does one do, on a day like this, when one is retired?"

    Thompson's life, in parallel to Gresley, had tinges of tragedy where their spouses went before their time. Unlike Gresley, Thompson did not have children and therefore was lonelier.

    I can't speak for my writing (that's for others to decide) but I have been quite content to self publish at this stage. If someone comes along brave enough to want to publish a title on Thompson...! That's another matter.
     
  6. PoleStar

    PoleStar New Member

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    I feel I am repeating myself here. My argument is that if you wanted to replace a troublesome conjugated valve gear, then your first thought would be to fit an independent inside gear with as few other modifications as possible. There would be insufficient space to fit a normal Walschearts on the Gresley A1/A3 because the combination lever would foul the leading coupled axle. You would therefore look at alternatives which would clear the axle, but Stephenson's would be unsuitable because its valve events would conflict with those of the outside Walschearts - so what were the other possibilities? - as already discussed.

    I am sure that the use of standard parts was a factor in Thompson's thinking, and of course with divided drive and equal length con. rods there is adequate space for an inside Walscheart' s gear. You just have to redesign the locomotive to fit around it!
     
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  7. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Thompson's first thought was to remove the centre cylinder entirely for the small and medium locos (hence D class, B17 to B2 class, etc).

    It is in theory possible - look at the rebuilt Bulleid Pacifics for a similar setup. Three sets of walschaerts driving onto the centre axle (which is what could have happened with Gresley's A3s, in theory, had any time been devoted to removing the conjugated gear and fitting walschaerts).

    The Thompson front end was surprisingly expedient in its original application on the rebuilt P2s, mind. It was virtually unbolting the front P2 frames and bolting on the new Thompson front frame and fitting three separate cylinders and their valve gear. You are absolutely correct in what you say there - standardisation as far as reasonably possible was the order of the day.
     
  8. Jimc

    Jimc Part of the furniture

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    Are you sure you're not getting over simplistic? Most big locomotives I've looked at are pretty tight for room for anything extra. I think unless one actually designs the gear and tries to shoehorn it in, together with all the supporting brackets and all the other bits and pieces, its a bit brave to say it could have been done. And its not enough to simply cram in any old implementation of Walschaerts, its got to match the events of the outside gear well, otherwise you get many of the same sorts of problems they were trying to resolve...

    As per footer I sometimes entertain myself by drawing fictional GWR locomotives, and I tried drawing a Castle with outside valve gear, only to discover it simply couldn't be done without either accepting irregular valve timing from valve rod expansion (and the GW were notoriously picky about that) or else completely redesigning the whole front end in the same way the Duchess was redesigned from the Princess, and for the same reasons.

    It seems to me that if Thompson's team could have found a way to get a third set of valve gear in without a major reconstruction they would have done it - you're making the case yourself with the work on availability. The very fact that they did try a major rebuild first suggests it may not have been an option. What are the LNER drawing office archives like? Would it be worth searching for proposals and outlines that went no further before GN was rebuilt? It might be instructive.

    Jim C
     
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  9. Jimc

    Jimc Part of the furniture

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    double post
     
  10. PoleStar

    PoleStar New Member

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    I am a model engineer, and I do design a bit of valve gear sometimes......Admittedly I haven't looked at this case in detail, but I think on the Bulleids the inside cylinder is mounted much higher than on the Gresley and is steeply inclined, so there would be more clearance. Even the original Bulleid gear had combination levers.

    I agree with Jim C. With his maintenance background, surely Thompson would have first tried to produce a (relatively) quick fix for the valve gear which could have been fitted during normal overhauls. The supposed advantage of equal length connecting rods may be a red herring.

    Tony.
     
  11. MellishR

    MellishR Resident of Nat Pres Friend

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    Do we know why Thompson was so keen on that? Granted connecting rods of different lengths would cause some differences in valve events, but surely no greater than from various other causes, less than those from badly maintained conjugating gear that was a main cause of concern, and nowhere near as great as the with supposed plan to fit inside Stephenson's (if there is any truth in that story).
     
  12. johnofwessex

    johnofwessex Resident of Nat Pres

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    I have no technical knowlege in this area but the post war rebuilding of the RHDR pacifics as two rather than 3 cylinders did not seem to reduce their performance............

    (Ducks)
     
  13. Hermod

    Hermod Member

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    Speed is the problem with two cylinder locomotives.
    At 5 revolutions per second ,either crew or permanent way staff will complain ,depending on percentage balancing in driving wheels.
    On three cylinder engines (or 4) this need not be a problem.
    Three 18 inch cylinders is easier to get through UK loading gauge than two 21.5 inch for same power.
    The downside to three is acces to middle cylinder and a 2-4% higher steam consumption.
     
    Last edited: Nov 12, 2018
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  14. PoleStar

    PoleStar New Member

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    I agree that differences in connecting rod length would only have a minor effect, and it didn't bother many other designers. Re the Stephenson story, I don't think Nock would have misquoted both Thompson and Stanier in print - Stanier, at least, was still alive when it was written -1962. My impression is that Nock is usually even-handed, and it is well known that Thompson trusted him.
     
  15. Forestpines

    Forestpines Well-Known Member

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    I think you'd have trouble fitting three 18-inch cylinders into an RHDR loco. From memory of reading J B Snell's history of the railway, the major problem with the three-cylinder engines was that the centre valve gear was a slightly dodgy Greenly design that had a tendency to lock up solid now and again.
     
  16. PoleStar

    PoleStar New Member

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    And, um, Greenly probably used his own valve gear as there was no room for inside Walschearts!
     
  17. RLinkinS

    RLinkinS Member

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    For the record the 3 cylinder RHDR pacifics were rebuilt before the war. As Forestpines says above the main problem was the Greenly valve gear on the middle cylinder. It did not give the same valve events as the Walschaerts gear. Typhoon was modified by Davey Paxman in 1935 and Hurricane at New Romney in 1937. IArthur Binfield told me he carried out one of these conversions, so he must have dealt with Hurricane. He told me that the middle valve gear had failed and he was was called in to convert it to 2 cylinder. By this date he had moved away from the RHDR to work for HCS Bullock at Farnborough. Captain Howey arranged to have him flown down to New Romney and Arthur fitted a set of driving wheels from one of the 2 cylinder pacifics that was then out of service (I wish I could remember which one). After the work was complete Arthur had to make his own way back to Farnborough. Being flown to a job in 1937 was really out of the ordinary.
     
  18. Jamessquared

    Jamessquared Nat Pres stalwart

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    Holcroft notes that the inside gear in the N1 and U1 class was "similar to that" on the Z class.

    A few other points that might be germane in the consideration of putting inside motion in a class previously with derived motion.

    The first is that, in Holcroft's mind, replacing the derived motion with a third set of motion unavoidably resulted in less horizontal frame stiffness due to redesign of the stretchers to accommodate the gear.

    The second point is that as built, the N1 / K1 / U1 (three cylinder) had boilers pitched 3" higher than the equivalent N / K / U (two cylinder). No doubt that was to actually find space to get everything in, though was conceivably advantageous when they were rebuilt with independent an inner set of motion. In that context, the prototype N1 and K1 were built with conjugated gear, but they, along with the U1s and later batch of N1s were built with three independent sets of valve gear.

    The third interesting point - and this may have been a consideration for Thompson, with his workshop mindset - was that Holcroft is quite critical of the Gresley implementation of conjugated gear on the grounds that removal of the centre piston and valve required disassembly of the gear; by contrast, in the Maunsell variant, there was sufficient room to extract the centre piston from the front and the centre valve from the rear without upsetting the valve gear.

    He also predicted the issues due to uneven valve events as a result of heating of the inside valve spindles, discussing the issue directly with Gresley at a meeting in Gresley's office in January 1919, Gresley nonetheless feeling that it would be sufficient to control that by predicting the thermal expansion and making allowance during valve setting.

    Tom
     
  19. Forestpines

    Forestpines Well-Known Member

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    Thank you for that info! It does tell a lot about what sort of person Captain Howey was.
     
  20. Monkey Magic

    Monkey Magic Part of the furniture

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    This may seem a little bit macabre (and I apologise if I've missed it elsewhere in the thread) but I was wondering if anyone can shed some light on Gresley's death, I've never seen the cause reported - just that it was sudden and 'in harness'. What prompted me is that in my own work I've had two colleagues who died suddenly (now 15 and 5 or so years ago) - in both cases sudden heart attacks and those deaths have cast a very long shadow over us, quite often we still find ourselves wondering what they would have said or thought about a situation or problem, far more than colleagues who retired or colleague who died less suddenly (or prematurely).

    It was and is still quite traumatic for us and I wonder, if the suddenness of Gresley's death, traumatised some of his colleagues - after all he had been there for so long, and perhaps some of the hostile reaction towards Thompson was because some of his choices were seen as more disrespectful. (I am struggling for the correct words here).

    I appreciate that it is very easy to read meaning backwards and ascribe things that were not there. But while I've seen discussions about the aftermath of Lord Stamp's death and the shock it caused to his colleagues, I've seen little or nothing about Gresley's death.
     
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