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Edward Thompson: Wartime C.M.E. Discussion 2012 - 2019

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

  1. jma1009

    jma1009 Member

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    The Wallace simulator certainly can.

    Cheers,

    Julian
     
  2. jma1009

    jma1009 Member

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    Hi Simon,

    In something like Walschaerts valve gear, small alterations can make a lot of difference to the valve gear events. Problems with the design 'envelope' not being optimum can be compensated for in lots of cases. Lets call it clever tweaks to correct imperfect geometry or design restraints. W H Pearce on the GWR was the expert at this.

    A loco having different length conn rods is just one factor affecting good valve events, and to a certain extent, can be tweaked to avoid any discernable ill effects. It is not big factor with 3 independant sets of gear for 3 cylinders. Consider as an example the Jarvis rebuilds of the Bulleid Pacifics.

    Cheers,

    Julian
     
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  3. jma1009

    jma1009 Member

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    I am pleased to note that Simon in particular 'liked' the above.

    Unfortunately, the inevitable extension of my argument is that Thompson was wrong to insist on equal connecting rod lengths.

    He probably had as poor an understanding of valve gears as Bulleid and Gresley did... Gresley had to be shown the way with conjugated gears by Holcroft, and had to be shown the way by Bert Spencer for adoption of long travel valves. Bulleid, on the Q1, copied the hideous suspension offset of the Maunsell Q outside admission piston valve Stephenson indirect drive with rocker arms and loco links.

    By the 1930s and 1940s the CMEs of the 'Big Four' ought to have had a team of valve gear experts to guide them. Holcroft wasn't involved on the SR in the Maunsell Q class as is quite apparent, and the LNER valve gear 'guru' Bert Spencer was removed by Thompson from the drawing office at Doncaster.

    Thompson was left to formulate his own design precepts, that particularly with hindsight, in the matter of valve gear design and the factors that were or were not ideal, or could be corrected easily by an expert, resulted in the 3 cylinder locos he rebuilt.

    I am not too sure I agree with his big outside cylinders on his 3 cylinder rebuilds using high pressure A4 boilers that can only be accommodated in an 'ugly' position as the only alternative.

    I am not an LNER expert I hasten to add, but valve gear design is something that sort of transcends all this.

    Cheers,

    Julian
     
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  4. Jamessquared

    Jamessquared Nat Pres stalwart

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    I know you seem to have big animus against the layout of the Q / Q1 valve gear, but I've never seen any contemporary complaint about how it worked in practice, as against modern complaints against it in theory.

    If you look at the relative cylinder and boiler proportions of a Maunsell Q and, say, an N, you can see it was a bit under-boilered:

    Q class
    Grate: 21.9sq ft
    Firebox heating surface: 122sq ft
    Cylinders: 19" * 26"
    Wheel diameter: 5'1"

    N class
    Grate: 25sq ft
    Firebox heating surface: 135sq ft
    Cylinders: 19" * 28"
    Wheel diameter: 5'6"

    The grate of the Q class in particular is very small, effectively mid way in grate area between a Wainwright C and a Maunsell N.

    So fast forward to 1941 in the middle of the war: design capacity is limited, so Bulleid does an entirely pragmatic thing: take the basic class Q design which had proven itself to be basically sound, and concentrate his design effort on putting the biggest possible boiler on it. He didn't tinker about with the valve gear because I suspect he realised that the design effort needed to completely change the layout of cylinders and valve gear (and probably knock on effects on things like frame stretchers etc) would be out of proportion to what could be gained in performance, particularly since no-one was complaining about the valve gear!

    What he ended dup with was giving the 0-6-0 class 5 boiler power, with 23% more firebox heating area and 39% more grate area than the class Q.

    There are only really two things that regularly come up as criticisms when discussing the Q1 class. One is the poor access for cleaning the smokebox. The other (more serious) is poor braking performance. I've never seen contemporary complaints about the valve gear layout, despite your theoretical misgivings.

    Tom
     
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  5. Hermod

    Hermod New Member

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    What was the difference between Q1 and J39 crank and valve system?
    One not a bad word and the other a problem.
    External dimension limits more or less identical
     
    Last edited: May 22, 2019
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  6. Hermod

    Hermod New Member

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    Made as shown there would have been less front frameflex and steampipe leaks.

    Loco wheelbase same (within inches) as BR Duke and LMS Pacifics
    Front coupled fourcylinder pacific from Romania still running
     
    Last edited: May 22, 2019
  7. sir gilbert claughton

    sir gilbert claughton Member

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    that , imo is what the Claughtons should have been
     
  8. Jimc

    Jimc Well-Known Member

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    To a certain extent is the key word though. The greater the inequality the greater the problem I imagine.

    The Castles and Stars had 7'10 inside and 8' outside rods. The Kings had 8'4 and 8'10, but my impression is Don Ashton considers the King implementation superior due to tweaks elsewhere.

    Don Ashton's website has a lot of information: I only wish I understood it all and I've been helping maintain it! This page http://www.donashton.co.uk/html/more_cylinders.html is probably the most immediately relevant.

    The interesting question is how much of a difference it makes. There were enough locomotives built with theoretically poor implementations right to the end of steam that you have to wonder. On the GWR the 57s and 94s, for instance, retained a 19thC layout of Stephensons which was theoretically inferior to the more modern arrangement on the Churchward standards and the 56s, but I've never heard it was a problem. Perhaps, like a lot of these things, it was only really an issue when you were hitting the limits of the technology and moderately powered locomotives running mainly at low speeds with moderate piston speed didn't push things hard enough to be a problem.
     
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  9. Jimc

    Jimc Well-Known Member

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    Cook says "complete white metal lining over the whole area of the bearings, machined to a close tolerance and fitted with feltpad lubrication. " He strongly implies the thickness of the white metal was reduced too. He says that although he did have some GW design rods made the Gresley Marine type, doubtless in its latest state of design, could be modified appropriately.
     
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  10. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    On the basis that I was using the "like" button to say thank you for responding to my direct question. It in no way is an indication I agree I am afraid!

    Robert Thom suggested equal length connecting rods and Thompson agreed. There was also, as I have explained several times, many stipulations on what Thompson and his team could do with locomotive design, including things such as having to reuse as much of a locomotive as possible in any rebuilding.

    There is absolutely nothing wrong with equal length connecting rods. That much is certain. The rebuilt Thane of Fife worked from 1943 until withdrawal by BR under dieselisation without any issues arising from crank axle failure or hot axleboxes on the driving wheels again. Three sets of walschaerts with divided drive and equal length connecting rods worked perfectly well on a day to day basis. That is a fact.

    We can argue the toss about whether or not it was the most perfect arrangement, or ideal, or whatever, but the fact of the matter is that it worked and worked everyday for a good twenty years.

    Not so. Thompson was specifically picked out by Gresley to sort out the B12s in the 1930s because of his theoretical knowledge regarding valve gears. I would however give a lot of credit for the B12/3 to his assistant A.E. English who helped develop the prototype 8579. Between him and Thompson they worked out the valve events on a wooden mock up.

    Bert Spencer was a conjugated valve gear specialist: Thompson had no intention of continuing with the development of three cylinder locomotives in anything but the biggest locomotives. He had a report which gave opinions on conjugated valve gear including not developing it further.

    You pick people for your team who believe in your vision, so removing Spencer was unsurprising. All CMEs change up their staff when they take over, Thompson is no different and given what he was tasked with doing, it is unsurprising he would want to add people to his team who would help him develop his vision for the future.

    At the end of the day, Thompson's Pacific designs worked perfectly adequately from 1943 until near the end of steam. They worked everyday, they were not incapable of doing the work asked of them, and contrary to the assumed party line, were not the worst locomotives the LNER ever owned by a long way.

    Until the advent of the double chimney on the A3s and A4s en masse, a double chimney Thompson Pacific was a more potent machine than the rest of the LNER fleet, second to the Peppercorn A1s, and the double chimney Humorist, A4s and few Peppercorn A2s fitted. If they became the effective second string of Pacifics in the mid to late 50s when steam was going anyway - so what? They were still usable and did good work.

    That at the end of the day is the truth to me. Not the best, not the worst, they were one way of doing things and had advantages/disadvantages to others like all engines.
     
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  11. Jimc

    Jimc Well-Known Member

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    Can you be a conjugated gear specialist and not know about all the rest? Isn't the actual maths and numbers for the conjugated gear pretty straightforward? AFAICS, all the difficulties are the other side of the cylinders.
     
  12. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    More to the point Jim - he disagreed with Thompson’s views and wasn’t prepared to support them.

    Rightly or wrongly, Spencer wasn’t part of his plans.
     
  13. Jamessquared

    Jamessquared Nat Pres stalwart

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    Maybe "champion" might have been a better word than specialist? Regardless of your knowledge, you are going to be a bit of a square peg in a round hole if the new boss has a fundamentally different philosophy, regardless of whether that new philosophy is right or wrong.

    (Consider in IT the situation of an application specialist working in an environment in which the boss is a keen advocate of in-house development on open source platforms. If a new broom comes in changing direction to Commercial Off The Shelf, the second-in-command probably has the technical acumen to adapt, but maybe isn't going to be the best lieutenant to the new boss).

    Tom
     
  14. bluetrain

    bluetrain New Member

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    Nice video from Hermod. I once had a calendar that contained a photo of the Romanian pacific, and it was startling - the cylinder placement was quite unlike any other 4-cylinder engine that I know about.

    As an LNWR man, perhaps I can remind you of the events of 1849, when "Mac's Mangle" went into battle with the platform edges at Euston station. The "Mangle" was an experimental 2-2-2 built by James McConnell, with both outside frames and outside cylinders, the cylinders being set at the unusually wide spacing (for Great Britain) of 7ft 6in. The overall locomotive width is not known but,with 18in cylinders, must have been well over 9ft; probably near to 9ft 6in.

    The Claughton class, the LNWR's largest engine, by contrast had cylinder spacing of 6ft 6in and overall width was only 8ft 8in.

    In the Romanian pacific, a wide cylinder spacing will be necessary to allow for sideways movement of the front bogie wheels. If the Claughton design had been like that, it is likely to have collided with the LNWR loading gauge, if not with an actual platform.
     
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  15. jma1009

    jma1009 Member

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    A few points to pick up on...

    Bert Spencer was a LNER valve gear expert, and not just as Simon has stated a 'conjugated valve gear expert'. We all know the story of the original A1s with short travel valves, and Bert Spencer advocating long travel valves. That is not per se a conjugated valve gear issue but an understanding of an expert like Bert Spencer of how short travel valves would and did hamper the original A1s. The point was proved most conclusively.

    Tom picks up on my comments on the SR Maunsell Q class valve gear. He states that there was no criticism at the time - but in fact there was - by Bulleid - as to why an antiquated Victorian style loco should have been built in the 1930s. (See Steam Index). Then he copied the same chassis for the Q1! If Bulleid had any expertise in valve gears, and Stephenson's gear, he would have known (and Holcroft would have told him had he been asked by either Maunsell or Bulleid, which he was not) that replacing the loco links with launch type links would have solved the design mess of the valve gear on the Q and Q1, and having made a bit of a study of this myself (as has Don Ashton) I cannot see that any alterations were required to the chassis components whatsoever, other than pretty much re-designing the expansion links, and redesigning the eccentrics with a beneficial reduction in throw and friction.

    The GWR 57XX valve gear is pretty much what 'City of Truro' had with top suspended links and slide valves doing 100mph in 1904, except with longer travel and a big underneath steam chest and a very free exhaust, and with the centre line of the valve gear slung downwards.

    Gresley, Thompson, and Bulleid ought also have taken a leaf out of the GWR's book so to speak with regard to loco smokebox draughting. The Thompson B1s used the Gresley arrangement which was very far from optimum.

    Thompson's B1 was pretty much a copy of the LMS 'Black 5' but with a round top boiler, and flimsy frames and inadequate axleboxes that wore quickly, and a very poor smokebox draughting arrangement. I personally, as a result, would not consider it a 'good' design - or at least it could have been much better.

    It is interesting that Thompson copied the defective Gresley smokebox draughting arrangement on the B1s - it seems to me to indicate someone who was not quite up with the niceties of design, and was ignorant of lots of stuff that had been known and applied in other companies for at least 20 years.

    Cheers,

    Julian
     
    Last edited: May 22, 2019
  16. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    I don’t think you quite grasp the issues of WW2 I’m afraid Julian - those issues much repeated on this thread countless times. That much is clear from your description of the B1.

    In the interests of balance, I’ll repeat myself.
    • WW2 saw large shortages in foundry capacity, materials and skilled workers to work for the LNER in many key roles
    • Thompson and his design team were heavily restricted by the war office and by the LNERs emergency board as to what they could build new, and how
    • Therefore any new locos would have to be built simply (see WD designs)
    • Due to a lack of foundry capacity, all B1s built during the war had fabricated axleboxes
    • The B1 was made up of pretty much entirely standard LNER parts, to the extent the first ten used V2 driving wheels (later rebalanced) and the boiler/smokebox arrangement was made similar to the existing and satisfactory B17 setup
    I’ve never heard anyone describe the front end of the B1 as “defective” and certainly not the Gresley front end draughting arrangement either.

    I’d be interested to find out if there’s anything accurate here (because to be honest, it reads like a fairly petty jibe).

    There were 410 Thompson B1s built and run by the LNER and later B.R. - two survive today. Their good work is well recorded despite their austerity design and, tbh, it’s not an understatement to say the B1 was a good engine.

    Regarding being a “valve gear expert” versus “conjugated specialist” - me saying he specialised in conjugated valve gear does not in any way denigrate, or preclude, that he was also a valve gear specialist.

    The point is, and remains, that Spencer disagreed with Thompson’s approach and - like any CME who was building a team around a design philosophy - he would only keep those around him who bought into it.
     
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  17. jma1009

    jma1009 Member

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    Hi Simon,

    Perhaps you ought to do a bit of research into good smokebox draughting before launching off - Jos Koopmans could give you the heads up on all this.

    The Gresley arrangement was quite peculiar having an enlarged lower portion of the petticoat pipe then a restriction and a section above that was tapered and too short in length. It was a far cry from the GWR modified '10 standards' based on Goss that Holcroft prepared for Churchward before 1911, and later other well known research from WW1, and of Young after WW1. Thompson and Gresley could have phoned up Holcroft and Sam Ell over all this and much more besides, or invited them over for lunch to discuss.

    Just as an aside, in so much as Bulleid did not understand the niceties of valve gears, he also did not understand correct smokebox draughting, and Jos has suggested for sometime alterations to the Bulleid version of the Lemaitre draughting on the preserved Bulleid Pacifics.

    The Gresley Pacifics had flimsy frames, and despite Thompson, who ought to have been aware of this deficiency, nevertheless continued this policy of thin frames. GWR and SR locos built during Thompson's period in office had thicker frames, so it wasn't due to WW2 shortages, but LNER expediency, that arguable did not pay off.

    Cheers,

    Julian
     
  18. Hermod

    Hermod New Member

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    The Romanian Pacifics were downrigth ugly.
    They were very strictly axle load limited and Maffei of Munich had to move bogie very close to drivers to have a bigger share.
    Conflict with Romanian loading gauge was not an issue.
    The interesting thing is that they were well liked and and ran to end of steam.
    Multicylinder frontcoupled 6 feet pacifics were a possibility.

    http://www.dampflokomotiven.net/Html/231000neu.htm
     
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  19. Hermod

    Hermod New Member

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    Claughtons had four cylinders,6 feet six drivers.
    No end of trouble
    B16 had three cylinders,five feet 8 drivers.
    Lots of ton-miles.
    A lot of CMEs had not understod that multicylinder meant smaller wheels were OK.
     
  20. Jamessquared

    Jamessquared Nat Pres stalwart

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    That quote by Bulleid seems to have been something he said years later - that he was dubious about building such seemingly antiquated-looking locos but was powerless to stop it as the materials were already at hand. It isn't however borne out by the facts, since the first set of frames were cut only in December 1937 and work on the first boiler only started on December 14th; and nothing happened at all on the frames, cylinders or boilers of the second and third locos before April 1938. So Bulleid had ample opportunity to call a halt while a redesign took place had he wanted. To me it comes across therefore as a bit of rose-tinted hindsight on his part - whatever misgivings he had, they cannot have been very strong at the time the locos were built. They weren't, in any case, expressed specifically about the valve gear.

    As for the Q1s, you seem unable to grasp that companies exist to deliver value for their shareholders, and what they do - or don't do - needs to be seen in that light. Design resource is severely limited at the best of times, even more so in the middle of a war when the loco works were taking on external jobs (other locos, munitions, tanks and landing craft etc.) for the war effort. In those circumstances, you fix the things that need fixing. No-one was complaining about the Q class valve gear, so it was left unchanged on the Q1. Ashford certainly wasn't in the business of making changes just to satisfy latter-day theoreticians, when the men on the ground were not saying there was anything wrong.

    Tom
     

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