If you register, you can do a lot more. And become an active part of our growing community. You'll have access to hidden forums, and enjoy the ability of replying and starting conversations.

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

    Joined:
    Aug 31, 2010
    Messages:
    5,591
    Likes Received:
    9,325
    Gender:
    Male
    Occupation:
    Asset Engineer (Signalling), MNLPS Treasurer
    Location:
    London
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    It's interesting: because my observation would be that Thompson kept most of Gresley's work intact, and tried to build on it: whereas Bulleid started with a blank sheet of paper and used virtually nothing of that he'd learned from Gresley when he went to the Southern Railway.

    [​IMG]

    [​IMG]

    I know which locomotive I think looks like Gresley could have designed it!
     
    andrewshimmin and Richard Roper like this.
  2. 30567

    30567 Part of the furniture Friend

    Joined:
    Aug 7, 2012
    Messages:
    5,608
    Likes Received:
    3,510
    ..... which is why I will be very interested to see your line on Bulleid when it is fully worked out. My instinct is that, if Thompson is characterised by simplification and Bulleid by innovation, they can't both have been right in the context of the 1940s.

    And with Bulleid, there will be a lot of interest in the rebuilding decision and the options considered and costs and benefits of that.
     
    pete2hogs and S.A.C. Martin like this.
  3. Eightpot

    Eightpot Resident of Nat Pres Friend

    Joined:
    Aug 10, 2006
    Messages:
    8,077
    Likes Received:
    2,264
    Gender:
    Male
    Occupation:
    Engineer Emeritus
    Location:
    Aylesbury
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    In the book 'A Gresley Anthology' edited by Geoffrey Hughes, J. F. Harrison wrote:-

    "On nationalisation, the Mechanical Engineering Dept. was completely dominated by LMS people. Somewhat naturally, they pushed their ideas on standardisation very hard, with the result that apart from some Gresley features, the basic designs were LMS and I felt we would never be able to continue Gresley's successful designs at all, until it was decided to design the BR Class 8 Pacific at Derby. So C. S. Cocks, ex-LNER via Bulleid and the Southern, who was Chief Draughtsman, was equally determined with me that we would produce a locomotive with as much Gresley as possible. We managed to get the rotary cam gear boxes of Caprotti design (thus avoiding any question of derived valve gear), a new forked end middle big end (thus avoiding hot middle big ends), roller bearing axle boxes (no hot bearings), new type carrier boxes replacing Cartazzi and giving a good ride, plus already standardised Gresley parts such as three-bar crossheads and new piston lubrication arrangements to reduce piston ring wear. The greatest care was taken to ensure streamlined steam passageways. I had been impressed by the need for this streamlining after examining the LM Duchesses which suffered from loose cylinders, and where the connections between the outside cylinders, frame plates and inside cylinders were like a minor staircase. This streamlining undoubtably helped 71000 to give 15.7% thermal efficiency, representing 86% of what is theoretically possible, and a steam consumption of 12.2 lbs per IHP hour, the lowest figure recorded by any steam locomotive, due to the Caprotti rotary cam gear and streamlined passageways.

    So I think it fair to say that Gresley's influence lasted right to the end of the steam era, and I am only too happy to say that those design features of No 71000 which we incorporated were basic Gresley thinking, improvements perhaps on his world beaters, but nevertheless improvements I am sure he would have carried out had he been in charge when 71000 was designed."
     
    Last edited: Jun 7, 2021
  4. S.A.C. Martin

    S.A.C. Martin Part of the furniture

    Joined:
    Aug 31, 2010
    Messages:
    5,591
    Likes Received:
    9,325
    Gender:
    Male
    Occupation:
    Asset Engineer (Signalling), MNLPS Treasurer
    Location:
    London
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Would you be surprised if I said that my personal opinion was that both engineers were trying to work out the same problem, and that both ultimately came up with a correct answer?

    Would you be further surprised if I said that I think Thompson's answer was overly conservative, and Bulleid's answer may actually have been right on the money, more or less?

    How about if I said that of the two designs, it was the top design that proved its worth as built as opposed the one below...which when rebuilt, was effectively what Thompson and his team built in no.2005 Thane of Fife, in the first place?

    Yes indeed.
     
    jnc, 35B, Richard Roper and 2 others like this.
  5. 30854

    30854 Resident of Nat Pres

    Joined:
    Mar 8, 2017
    Messages:
    12,172
    Likes Received:
    11,493
    Gender:
    Male
    Occupation:
    Retired
    Location:
    Brighton&Hove
    Heritage Railway Volunteer:
    No I do not currently volunteer
    By 'Bulleid's answer', I take it you're referring to pre-nationalisation developments? :rolleyes:
     
  6. S.A.C. Martin

    S.A.C. Martin Part of the furniture

    Joined:
    Aug 31, 2010
    Messages:
    5,591
    Likes Received:
    9,325
    Gender:
    Male
    Occupation:
    Asset Engineer (Signalling), MNLPS Treasurer
    Location:
    London
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Yes.
     
  7. 30567

    30567 Part of the furniture Friend

    Joined:
    Aug 7, 2012
    Messages:
    5,608
    Likes Received:
    3,510
    I think the best question to answer out of those is ' Was Bulleid right on the money, more or less'?

    I grew up on the lineside at Wimbledon C, Raynes Park and West Dulwich in the fifties. Until I saw an A4, I thought the Bulleids were fabulous, especially the ones which 73A kept in top external condition (34091/2 being two of them). And I'm quite sure my top speed behind steam was on the ACE, 35009 going down the hill from Buckhorn Weston.

    Looking back now, I am influenced by Winkworth's book, especially Chapter 4, provocatively titled 'How Bad Were These Engines?' and summarising his assessment on the following charge sheet --- slipping on starting/at speed ; poor steaming ; heavy on repairs ; poor availability ; uneconomical on fuel ; inaccessibility for repairs ; unsuccessful valve gear ; steam reverser. Obviously he finds no case to answer on some of those, and some of them (eg the valve gear, the reverser?) may be covered by your 'more or less' qualifier.

    What strikes me reading his book again is how qualitative the evidence base was nearly fifty years ago. On availability, for example, is it possible to do the same job on the Southern as you did on the Eastern? Do the same sort of records exist? A related question is whether the assumptions made about the displacement of older machines by the 110 light pacifics were borne out in reality. And, as with the B1s, would the SR really have been better off ordering a hundred Black 5s? Was 700k miles over 20 years a reasonable score in the context of the SR?

    Perhaps I haven't read the right books, but I'm thinking there are loads of interesting question marks here, so I wish you good luck in addressing these and others, Simon.
     
    MellishR, jnc and S.A.C. Martin like this.
  8. johnofwessex

    johnofwessex Resident of Nat Pres

    Joined:
    Apr 6, 2015
    Messages:
    9,185
    Likes Received:
    7,226
    Gender:
    Male
    Occupation:
    Thorn in my managers side
    Location:
    72
    Heritage Railway Volunteer:
    No I do not currently volunteer
    What though would the Bulleid Pacifics have been like if they had been fitted with Capriotti valve gear as he wanted?
     
    60525 likes this.
  9. Jamessquared

    Jamessquared Nat Pres stalwart

    Joined:
    Mar 8, 2008
    Messages:
    26,100
    Likes Received:
    57,416
    Location:
    LBSC 215
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I wasn't aware that Bulleid's intention was for the locos to be fitted with Caprotti valve gear. Rather, he wanted a miniaturised Walschaert's gear, as they eventually had, but with the rotating auxiliary camshaft shaft driven by gears. When that turned out not to be possible with wartime restrictions on availability of precision gear mechanisms (needed for the higher priority aero engine industry), the design was changed to have a chain-driven shaft.

    With that in mind, I think some of the issues of the Bulleid valve gear - notably chain stretch - might have been obviated; but others - notably the difficulty of sealing the oil bath - would have remained.

    Tom
     
    S.A.C. Martin and 30567 like this.
  10. S.A.C. Martin

    S.A.C. Martin Part of the furniture

    Joined:
    Aug 31, 2010
    Messages:
    5,591
    Likes Received:
    9,325
    Gender:
    Male
    Occupation:
    Asset Engineer (Signalling), MNLPS Treasurer
    Location:
    London
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    What strikes me as interesting about all of this is that we have the complete opposite being said in contemporary evidence about the Thompson Pacifics. Excellent steam circuit, great availability, low on repairs, reasonably economical on fuel (and better for the A2/2s than as P2s significantly), valve gear accessible and easily replaced.

    Slipping? All Pacifics slip. Total red herring. That's more about driving technique. I say that for all Pacifics.

    I think DW Winkworth's book is pretty much the authority at this point: he actually does use data analysis to back up his arguments. I have a few leads on the data required to do a similar thing for the Bulleid Pacifics compared to the Thompson Pacifics. I think the evidence might be quite surprising.

    I just hope that I don't take another decade to get a book out! Many thanks for your kind words and support.
     
    MellishR and andrewshimmin like this.
  11. Jon Pegler

    Jon Pegler New Member

    Joined:
    Jun 30, 2014
    Messages:
    42
    Likes Received:
    30
    Gender:
    Male
    Heritage Railway Volunteer:
    No I do not currently volunteer
    Bulleid may have been influenced in his use of a miniaturized Walschaerts valve gear by looking across the Atlantic.
    The Franklin poppet gear employed a small gearbox containing a miniature Walschaerts valve gear, driven from the outside crossheads with a crossover arrangement.
    This was first revealed in 1937 and put into service by 1938.
    Andre Chapelon was know to have seen this valve gear in action.
    Together with the welded boilers, disc wheels etc., I would imagine Bulleid have been fascinated with American locomotive progress, to the extent of employing some of their ideas on his new designs.
     
    pete2hogs, MellishR and S.A.C. Martin like this.
  12. Jamessquared

    Jamessquared Nat Pres stalwart

    Joined:
    Mar 8, 2008
    Messages:
    26,100
    Likes Received:
    57,416
    Location:
    LBSC 215
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I think the criticism of the Bulleid Pacifics was not that they slipped on starting (which pretty much all locos can be induced to do), but rather that they slipped at speed. That is a more serious flaw.

    My working assumption about that is that it was primarily related to the reverser problems (lack of fine control; very rapid operation given the lightweight valve gear; poor maintenance regime caused by constricted location). The consequence of those was that if you were working hard at speed and tried to adjust cut off by a small amount (as can be done on a loco with a screw reverse), it would be very easy to over adjust. If that error goes towards full gear, the likelihood of slipping due to a sudden large increase in power is considerable.

    I think in due course most of the serious reverser issues were designed out (primarily a redesign and relocation for the Light Pacifics, elements of which were retrospectively fitted to the first series Merchant Navies and incorporated from new in the later Merchant Navies). However, you are never going to get really fine control with a steam reverser. Probably just as significantly, drivers adjusted their technique to drive on the regulator rather than drive on the reverser, as would be possible on other locomotive types - which reduced slipping at speed, but meant the locos were never being driven at peak thermal efficiency. Still, Bulleid was (probably correctly) of the view that passengers don't notice thermal efficiency, but they do notice poor punctuality.

    My sense is that the steam reverser was always going to be problematic on a big pacific. Fine on the Q or Q1, but less so on a Merchant Navy. Interestingly, as well as the Ashford and Eastleigh pattern reversers(*), the Southern drawing office also had the Brighton pattern air-operated screw reverser available. Potentially that would have given the precision of a screw reverser but the desired labour-saving of a power-operated reverser. I don't know if they ever tried to get it to fit, but the general opinion seems to be that they couldn't get a working arrangement of a screw reverser in combination with the miniaturised valve gear, so I guess not. Had they been able to get it to fit, I'm sure it would have been a small change to make it power-assisted, Brighton style.

    (*) The Southern type reverser fitted to the Bulleid Pacifics was an incrementally developed amalgam of the best features of both - not as is often erroneously stated the "Eastleigh pattern" unchanged.

    Tom
     
    Last edited: Jun 7, 2021
  13. Richard Roper

    Richard Roper Well-Known Member

    Joined:
    May 22, 2006
    Messages:
    1,310
    Likes Received:
    1,355
    Gender:
    Male
    Occupation:
    Librarian
    Location:
    Just up the road from 56E Sowerby Bridge
    Heritage Railway Volunteer:
    No I do not currently volunteer
    This was a problem that also occurred with the Stanier Pacifics, particularly the Princess Coronation class.

    Richard.
     
    S.A.C. Martin and Jamessquared like this.
  14. bluetrain

    bluetrain Well-Known Member

    Joined:
    Mar 3, 2019
    Messages:
    1,326
    Likes Received:
    1,460
    Gender:
    Male
    Location:
    Wiltshire
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I certainly see Thompson's designs as Gresley derivatives, but stepping back to Gresley's GNR years before he became committed to conjugated gear and 3-cylinder solutions for almost everything. As you indicate in your later post, Thompson's approach was a fundamentally conservative one.

    Bulleid was of course a radical, but if you look underneath the air-smoothed casing, Bulleid Pacifics retain a lot of Gresley features. Tapered boilers with combustion chambers and high superheat. Three cylinders with drive concentrated on the centre axle. There seem to have been only a few hundred 3-cylinder Pacifics across the planet, but the most obvious design variation was between those with unified drive (usually on the centre axle) and those with divided drive (usually with Peppercorn-like cylinder layouts).

    Will be interesting to see your book on Bulleid if it goes ahead. There is definitely a GNR linking theme here, so I further look forward to your book on Archibald Sturrock!
     
  15. S.A.C. Martin

    S.A.C. Martin Part of the furniture

    Joined:
    Aug 31, 2010
    Messages:
    5,591
    Likes Received:
    9,325
    Gender:
    Male
    Occupation:
    Asset Engineer (Signalling), MNLPS Treasurer
    Location:
    London
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    I have thought about this post a lot since reading it in the 5025 thread, and I think we are in danger here of using one example of a 410 strong locomotive class as a stick to beat a whole class with.

    There's a few things which stand out to me:
    • Boiler not being able to make steam easily - this boiler was a higher pressure version of that used on the B12/3 classes, and as Diagram 100A was used on 410 B1s, B17s, B2s, B3/3, O1s, O4/8s, shortened and then used as a basis for classes K1/1 and K1. This particular boiler is based on Gresley practice and has never really been described as anything other than free steaming.
    • The axleboxes on the B1s were fabricated, not cast, and different oiling arrangements are a hazard of the time they were designed and built in - WW2.
    [​IMG]
    • The firehole door is virtually identical to every other LNER locomotive with a round topped boiler,
    • Can't comment on the sanders but they're the same type used on virtually every other LNER/Gresley loco of the same time period
    • The injectors are the same type as on other LNER classes of the same period. If you've been on any of the Gresley designed locos, you'll have seen these
    • The design was completed in 1942, worked out of the box, and by 1948 they were pushing ahead with production examples with minimal updates (new wheel centre castings, better balancing, and more)
    • No further updates to the LNER stock was really considered after 1948 aside from those which made business sense (e.g. O4 into O4/8 or O1)
    • The plan to "replace B1 boilers with standard 3MT boilers" appears to be on paper nothing more than a draughtsman's suggestion, for which strengthening plates to the firebox flanges were used instead (which makes much more sense)
    I respect your views Steve, but I think where the B1 is concerned, it was a design engineered down to a specification and price that was achievable. Pound for pound, the L.N.E.R. and then BR got their money's worth out of the 410 B1s and that's really the measure of its success. Having sat on 61264 myself at the NYMR some years back, and having the GCR's Black Five 45305 for comparison in my university days, my personal view is that I understand why the Black Fives are so loved - but I'd take the Thompson B1 instead, every time.

    It's austere, basic, with a comfortable cab set up and gets the job done. I love it as a design. I dare say it's probably right up there as one of my favourite locomotive classes. Are there locomotives with better specs? Yes, there are, but I am not sure any other class did what the B1 class did, which was very quickly replace a huge array of pre-grouping stock and take on the work of engines larger than itself reasonably well too. It's not a Rolls Royce, it's very definitely a Ford: and it did that role well.
     
    Last edited: Jun 11, 2021
    pete2hogs, Romsey and Richard Roper like this.
  16. MellishR

    MellishR Resident of Nat Pres Friend

    Joined:
    Apr 16, 2009
    Messages:
    8,068
    Likes Received:
    5,164
    Also three cylinders and 6'2" wheels. (I'm catching up after spending little time here in the last few days.)
     
  17. Spamcan81

    Spamcan81 Nat Pres stalwart

    Joined:
    Aug 25, 2007
    Messages:
    35,121
    Likes Received:
    20,772
    Occupation:
    Training moles
    Location:
    The back of beyond
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    Whilst I agree that judging a whole class from experiences of a single example is not entirely reasonable, I’d argue that praising a whole class after having “sat on” a single example is equally unrepresentative. Having said that, a former 34D fireman friend of mine liked the B1s, even though they could be rough riders at times, and would take one over an L1 any time.
     
    S.A.C. Martin likes this.
  18. 30567

    30567 Part of the furniture Friend

    Joined:
    Aug 7, 2012
    Messages:
    5,608
    Likes Received:
    3,510
    That's interesting because one of the authors, possibly Harvey, says that Hitchin was the depot that got the best out of the L1s. Not inconsistent, mind......
     
    S.A.C. Martin likes this.
  19. S.A.C. Martin

    S.A.C. Martin Part of the furniture

    Joined:
    Aug 31, 2010
    Messages:
    5,591
    Likes Received:
    9,325
    Gender:
    Male
    Occupation:
    Asset Engineer (Signalling), MNLPS Treasurer
    Location:
    London
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    My personal views on the loco design aren't the driving force of my argument: rather the fact that the 410 locos were built quickly, went into service, did the job required and quickly replaced a vast number of older locomotives that, in reality, weren't as good as the B1s by virtue of age.
     
    pete2hogs likes this.
  20. Spamcan81

    Spamcan81 Nat Pres stalwart

    Joined:
    Aug 25, 2007
    Messages:
    35,121
    Likes Received:
    20,772
    Occupation:
    Training moles
    Location:
    The back of beyond
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    That's loco crews for you. I recall reading one article in which a driver stated his preference for an original Patriot over a Royal Scot, even the rebuilds, when logic would dictate the Scot would have been a better choice.
     
    35B and S.A.C. Martin like this.

Share This Page