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. Hermod

    Hermod Member

    Joined:
    May 6, 2017
    Messages:
    985
    Likes Received:
    283
    Gender:
    Male
    Location:
    Klitmoeller,Denmark
    Heritage Railway Volunteer:
    No I do not currently volunteer
    How fast and for how long was P2 timed on the level?
    If the Big Wheels means higher Speed is true, the P2 would be able to run 138 kmh from P10 measurement.
    A gentleman here stated that S15 were impossible to fire at/over 50mph and a mrBradley had a school comrade that timed S15 going to school during a year and they often ran 70.
     
    Last edited: May 8, 2021
  2. 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
    Surely the relevant numbers will concern the next series of measurements?

    There's something I'd have never expected to find myself saying, not so long ago! :)
     
    Allegheny and MellishR like this.
  3. Spamcan81

    Spamcan81 Nat Pres stalwart

    Joined:
    Aug 25, 2007
    Messages:
    35,121
    Likes Received:
    20,773
    Occupation:
    Training moles
    Location:
    The back of beyond
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    And Gresley himself was not averse to timing trains. He took his chronometer on board the press run of 2509 and informed the crew they’d broken 112 twice. No speedo on 2509 at the time.
     
    Johnb and Bluenosejohn like this.
  4. Spamcan81

    Spamcan81 Nat Pres stalwart

    Joined:
    Aug 25, 2007
    Messages:
    35,121
    Likes Received:
    20,773
    Occupation:
    Training moles
    Location:
    The back of beyond
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    The work for which the P2s were built did not require high speed running. The original remit was to replace double heading on the heaviest trains at the time.
     
    jnc and Johnb like this.
  5. Hermod

    Hermod Member

    Joined:
    May 6, 2017
    Messages:
    985
    Likes Received:
    283
    Gender:
    Male
    Location:
    Klitmoeller,Denmark
    Heritage Railway Volunteer:
    No I do not currently volunteer
    Big wheels are heavy,cost money and destroy tracks.
    Are You suggesting that Gresley used shareholders' money unwise?
     
  6. Spamcan81

    Spamcan81 Nat Pres stalwart

    Joined:
    Aug 25, 2007
    Messages:
    35,121
    Likes Received:
    20,773
    Occupation:
    Training moles
    Location:
    The back of beyond
    Heritage Railway Volunteer:
    Yes I am an active volunteer
    No. I'm suggesting that you are talking wee bit of nonsense.
     
  7. Hermod

    Hermod Member

    Joined:
    May 6, 2017
    Messages:
    985
    Likes Received:
    283
    Gender:
    Male
    Location:
    Klitmoeller,Denmark
    Heritage Railway Volunteer:
    No I do not currently volunteer
    Arguing about steam locomotive design is childish anyway,but interesting.
     
    Last edited: May 8, 2021
  8. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

    Joined:
    May 30, 2009
    Messages:
    21,065
    Likes Received:
    20,775
    Location:
    1016
    Heritage Railway Volunteer:
    No I do not currently volunteer
    Just so. However they were mostly used on curvy track in Scotland and I have read that this wasn't brilliant given the rigid four paired wheel arrangement. Two problems resulted: internal heating on axles and a tendency to spread track on curves.
    Neither was a deal breaker but would add to maintenance of loco and track. So in austere times this was not ideal.

    A high quality design/style CME might be less bothered than a maintenance/efficiency CME. Different times led to different priorities. And back we go to why probably Thompson was the right man at the right time for the LNER.
     
    MellishR, S.A.C. Martin and jnc like this.
  9. Hermod

    Hermod Member

    Joined:
    May 6, 2017
    Messages:
    985
    Likes Received:
    283
    Gender:
    Male
    Location:
    Klitmoeller,Denmark
    Heritage Railway Volunteer:
    No I do not currently volunteer
    A high speed passenger locomotive with tendencies to hotboxing,crankbreaking and track destruction was not an interwar deal breaker?
     
    ragl likes this.
  10. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

    Joined:
    May 30, 2009
    Messages:
    21,065
    Likes Received:
    20,775
    Location:
    1016
    Heritage Railway Volunteer:
    No I do not currently volunteer
    Not if it were to be used somewhere that wouldn't pose such problems. Fortunately the A1 Trust are not planning on running their P2 to Aberdeen or up Hemerdon, I hope. ;)
     
  11. Hermod

    Hermod Member

    Joined:
    May 6, 2017
    Messages:
    985
    Likes Received:
    283
    Gender:
    Male
    Location:
    Klitmoeller,Denmark
    Heritage Railway Volunteer:
    No I do not currently volunteer
    In the good old steam locomotive days rails were laid further apart in curves to ease pasage of rigid wheelbases of 17 19 feet.
    Is that still so today where all vehicles are on bogies?
     
  12. 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
    Reply to Posting above No. 4312 by jnc.

    I'm not sure that anything could be done easily with the P2s as regarding the crank axle failures as originally built. Bearing in mind that they were built to the limits of the load gauge (they were 1-3/8" wider over the cylinders than an A3) , this gave no scope to make the rigid coupled wheelbase more flexible. If Gresley had opted to go for (say) 19-1/2" diameter cylinders and 250 psi (not brought in until a couple of years later with the A4s) the outside piston rod centres could have been increased by 1-1/2" to allow the coupled wheels to have some side play. As I understand it, the P2 Group have retained the design piston rod centres, reduced the cylinder diameters and upped the boiler pressure to 250 psi to compensate, this I understand, to reduce the overall width of the cylinders by 1-1/2" for route availability reasons. From the original Doncaster G.A drawing for 2001 there appears to be no thinning of wheel flanges to the 2nd or 3rd coupled wheel sets to help matters either.

    Having looked at their website (www.p2steam.com/design-study/) regarding the crank axle, it appears that there were anything up to five failures of them that has been attributed to the high torque that could be applied to the crank axle by the cylinders. The question I ask myself, and am uneasy about, is why did all these fractures occur at the 9-5/8" diameter axle behind the driving wheel rather than at the 8-1/4" diameter section adjacent to the inside cylinder crank web which I presume also has a key and keyway?

    My feeling is that with the rigid wheelbase like the P2s had, on going round curves a sideways pressure was exerted to the driving wheel rims and via the spokes to the hub, thus putting a rotating bending force on the axle just behind the wheel hub. To demonstrate this take a length of flexible hose and with both hands hold the ends and pull the hose into a curve. Now rotate it and it can be seen that any given point around the circumference is being alternately stretched and compressed.

    As the P2 Group website only refers to torque action it appears to me that they have not taken this rotating bending force into account at all, and that their 'stress relief groove' could indeed turn out to be a stress inducing one instead. In short, I don't think that they have fully investigated the problem which as currently designed and manufactured, could yet cause another failure.

    As an example of this effect that I have personally witnessed was on a Gardner 6LXB Diesel engine in a Foden lorry. Possibly though over tightening the timing chain, thus putting a sideways load on the camshaft sprocket, the 1" diameter steel camshaft sheared immediately behind the chainwheel. It is difficult to imagine this happening, but it did.
     
    Last edited: May 9, 2021
    jnc likes this.
  13. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

    Joined:
    May 30, 2009
    Messages:
    21,065
    Likes Received:
    20,775
    Location:
    1016
    Heritage Railway Volunteer:
    No I do not currently volunteer
    That is one of the most informed and thoughtful posts I've read from @Eightpot for some time. More to the point it raises questions we can't answer on here but strike at the heart of one of the weaknesses of the original P2 design.

    No doubt the A1ST is on a journey with this project and with its eyes wide open. Well we hope so.
     
    The Green Howards likes this.
  14. Cartman

    Cartman Well-Known Member Account Suspended

    Joined:
    Dec 14, 2015
    Messages:
    2,290
    Likes Received:
    1,672
    Gender:
    Male
    Occupation:
    Van driver
    Location:
    Cheshire
    Heritage Railway Volunteer:
    No I do not currently volunteer
    Given the problems which the long fixed wheelbase of the P2 appeared to cause on the twisty Aberdeen route, did 9Fs ever appear on it after nationalisation?
     
    The Green Howards likes this.
  15. torgormaig

    torgormaig Part of the furniture Friend

    Joined:
    Jul 17, 2007
    Messages:
    4,444
    Likes Received:
    6,546
    Surely the 9F wth 5ft drivers and a middle roller wheel was a very different beast to a P2 with 6ft 2ins drivers.

    Peter
     
  16. jnc

    jnc Well-Known Member

    Joined:
    Apr 3, 2012
    Messages:
    1,511
    Likes Received:
    2,706
    Gender:
    Male
    Location:
    Western Atlantic
    Heritage Railway Volunteer:
    No I do not currently volunteer
    Thanks for that considered reply. It's a little scary; the thought that the 'new' P2 could also break axles is fairly boggling. I had assumed that with the wealth of advanced simulation tools at their disposal, the Steam Locomotive Trust could have put their finger on the exact cause of the original failures (something which might not have happened back in the day, from my admittedly poor knowledge of them), and tweaked the design to rectify it. It will certainly be extremely eye-opening if the new P2 breaks an axle (if so, that will certainly cast an interesting light on the potential wisdom of the decision to rebuild them). Although it may take a while (especially if your suggested cause is accurate), as it's apparently a long-term fatigue thing (given the infrequency of the original failures). Well, I hope for the best, but whatever happens, I'm sure it will cast some illumination.

    Noel

    PS: By "decision to rebuild them", I mean the one back in the 40's.
     
    Last edited: May 10, 2021
  17. 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
    That's some impressive analysis. Scarey, but impressive and sent me straight to the lined page on the P2 site. Like everyone else, I've been unquestioning of the computer modelling done, forgetting that computers will only provide answers to questions posed in the first place. The linked page mentions an increase to 10" diameter, but given the nature of @Eightpot's case, that leaves an unanswered question.

    Another point elsewhere, just yesterday, got me mulling the 'duplex' layout, as per the Pennsylvania T1, where, if I'm understanding what's on their website (big "if", I'll grant you!), this very point underpinned the original rationale of that design i.e. two independent 4-coupled units on one rigid frame. That, of course, is a very different kettle of fish, design wise and not vaguely applicable to the P2, but indicative of an all too real problem, as described by Eightpot.

    I'll watch this one with some interest and not a little trepidation.
     
    jnc likes this.
  18. Fred Kerr

    Fred Kerr Resident of Nat Pres Friend

    Joined:
    Mar 24, 2006
    Messages:
    8,239
    Likes Received:
    5,250
    Gender:
    Male
    Occupation:
    Freelance photo - journalist
    Location:
    Southport
    Maybe not 9Fs but surely the Grangemouth-based ex WD 2-10-0s 90750-774 with their 4' 8.5" driving wheels and their 34215 lb tractive effort would have been a regular sight.
     
    Cartman likes this.
  19. MellishR

    MellishR Resident of Nat Pres Friend

    Joined:
    Apr 16, 2009
    Messages:
    8,068
    Likes Received:
    5,165
    We're back to the claim that the P2s' long rigid wheelbase caused problems on the Aberdeen road, but was that really so, or did the idea arise from a combination of hearsay and misunderstandings? If there really was a problem, was it due to the long rigid wheelbase alone or to that in combination with inadequate guidance from the pony truck (which is one of the design flaws that have been addressed in the new build)?

    Can Simon please remind us whether the P2s' very poor availability (which was the reason for Thompson absolutely needing to do something with them) was mostly due to the crank axle failures (which is the other major design flaw addressed in the new build) or by other faults besides?
     
  20. Jimc

    Jimc Part of the furniture

    Joined:
    Sep 8, 2005
    Messages:
    4,052
    Likes Received:
    4,665
    Occupation:
    Once computers, now part time writer I suppose.
    Location:
    SE England
    Heritage Railway Volunteer:
    No I do not currently volunteer
    It seems to me that speculation that the A1 trust have forgotten to consider a particular design flaw in the original is at the far reaches of internet guesswork. I doubt the trust or the regulators have missed the potential problem.
    But in any case we now have effective ND testing and the locomotive will be running low mileages by historical standards so there's plenty of potential for an inspection routine to catch anything early.
     
    MellishR, 35B, Llwyngwern and 3 others like this.

Share This Page