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35011 General Steam Navigation

Discussion in 'Steam Traction' started by GSN, May 15, 2015.

  1. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Bibby Line. The Crewkerne Incident prompted the rebuilding of the entire class under Jarvis' direction. I'm sorry, but it remains factual that the original Merchant Navy design was withdrawn on safety grounds, and part of their rebuilding was to ensure the like of that incident did not happen again.

     
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  2. class8mikado

    class8mikado Well-Known Member

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    The Crewkerne incident was 1953 ? ( by which time the Cabs would have already been changed )and prompted the withdrawal of the class for examination of crank axles, for safety reasons. The Locomotives were examined and subsequently reintroduced in their air smoothed form with a beefed up crank axle ( which other Bulleid involved loco suffered crank axle failures... ). iirc Mr Jarvis had already been asked to look at a redesign of the loco. and various schemes , including a 2 cylinder incarnation were subsequently produced. The first rebuild didnt happen until 1957 though and to the best of my knowledge the class did not sit idle for 4 years on safety grounds, the rebuild was primarily driven by economy/ availability ...
     
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  3. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Most of that is true: but the re-design was worked on by British Railways from 1953 and the first rebuild - British India Line - came out in 1956. The rebuilding was prompted by the failure of the crank axles, and the knowledge gained from running the two cylinder Standard Pacific types, from which we can see many similar design arrangements as a result.

    Jarvis' work on the Pacifics is well documented. The time frame for the re-design was contemporary with the developments on the Standard Pacifics.

    The safety aspect was not the greatest factor in deciding to rebuild the class. It was a significant one, which added to the already varied problems the originals had in terms of maintenance and reliability.

    Frankly - I think Jarvis did with the Bulleid Pacifics what Edward Thompson did with the P2s (just a decade later).
     
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  4. 30567

    30567 Well-Known Member Friend

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    Quick quiz question--- in 1960, which locoshed had the largest allocation of Pacifics after 34A?
     
  5. Johnb

    Johnb Resident of Nat Pres

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    I would Guess Exmouth Junction.
     
  6. Johnb

    Johnb Resident of Nat Pres

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    The difference being that the Jarvis Pacifics were a success. On the subject of 35018, it currently runs with the unique rebuilt self weighing tender. The tank was a stretched version of the 5250 gal version and I think it has a capacity greater than 600 gal. Can anyone confirm what it actually is. It does seem to be capable of very long runs between water stops.
     
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  7. Jamessquared

    Jamessquared Nat Pres stalwart

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    Simon - I don't think that timeline makes sense. The crank axle failure at Crewkerne was an immediate safety concern and caused the immediate withdrawal of the whole class for tests. Following those tests, new crank axles were made for 35001/12/23/24 (which were faulty) and 35025/26 (which were not faulty but changed nonetheless). The class was then returned too service.

    Subsequent to that, a new design of crank axle was produced and between late 1954 and mid 1955 fitted to 35010/11/19/23/26/27, presumably at overhaul.

    It was only after that the final decision about rebuilding was made, but that decision - which came down to a straight choice between rebuilding or scrapping and ordering the same number of "Britannias" - was made on cost grounds. the rebuild must have involved yet another crank axle design on account of the changed valve gear layout.

    So I think there are two processes going on here: a revised crank axle design, which was a safety improvement, but the kind of incremental development that almost all locomotives undergo from time to time; and the rebuild, which was about operating cost, not safety.

    Tom
     
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  8. nine elms fan

    nine elms fan Member

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    I thought it was Camden.
     
  9. std tank

    std tank Member

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    Well, Gateshead and Haymarket both had more Pacifics than Kings Cross.
     
  10. siquelme

    siquelme Member

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    The crank axles themselves that can still found in all surivivng Merchant Navys such as Clan Line are the same ones that were built post Crewkerne to be used with the Bullied valve gear. During the rebuilding program they were modified again however these changes were limited to fitting an eccentric sheave rather then a sprocket to transfer power from the valve gear.
     
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  11. std tank

    std tank Member

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    The new crank axle, W11247, was drawn up in November 1953. The table on the drawing does not give the loco numbers this design was used on. It does indicate MN renewals, WC/BB renewals and the design was used on all the rebuilds, both MN and WC/BB.
     
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  12. siquelme

    siquelme Member

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    A section on the crank axles from the BR report which lists all the modifications undertaken during the rebuilding.
     

    Attached Files:

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  13. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

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    Well that's news to me. I agree that discussions about 'improving' the class to create more efficient and easier servicing arrangements had been going on for some time in the early 1950s when it became clear that these locomotives were definitely an asset for the Southern but also an expensive one when you factor in the on-costs. But I can't agree that the Crewkerne incident 'prompted' anything other than to deal with the crank axles.

    It was more significant data such as the Rugby Plant testing of 35022 in March 1953 that fed into the rebuilding project. For example it was here that it was established that a short cut off would tend to lengthen without any driver intervention and thereby affect any efficiencies that a crew might naturally wish to achieve. Add to that the fact that the steam reverser would also tend to creep and was therefore an unreliable indicator. Then there was the less than ideal blast pipe arrangement that was identified in the tests. Oh, and add to that the fact that oil from Holland America Line got onto the test bed rollers and caused slipping that was potentially dangerous at speed. This resulted in testing needing to be stopped to clean the rollers.

    Thinking about the rebuilding was in place soon after the Rugby testing. The Crewkerne failure may have added to the focus but it didn't determine it. I gather that there was some talk of scrapping the class and starting again, so the moment that Jarvis proposed a rebuild at half the cost of a new loco I'm not surprised that the powers that be jumped at the idea. And just look at what a beauty we ended up with!

    Of course that is not to imply that a reconstructed GSN is a bad idea. It will benefit from all the tlc that it may not have received in its time and, of course, a far less demanding existence awaits it in the future.
     
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  14. Matt37401

    Matt37401 Part of the furniture

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    Crewe North could be in with a shout?
     
  15. siquelme

    siquelme Member

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    We have never said it was a perfect design and there are things which we are going to change. You've pretty much listed most of them already which does make my life a bit easier in this reply. The original Merchant Navys weren't the most reliable design which is what led to there rebuilding in the first place. I do believe with the right modifications, care and attention 11 would be as reliable as her rebuilt sisters.
     
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  16. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Gents - fascinating stuff. Apologies if I have given any misinformation. Consider me corrected.
     
  17. siquelme

    siquelme Member

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    If your ever in Swindon, let us know and we'd love to show you around.
     
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  18. class8mikado

    class8mikado Well-Known Member

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    To my mind what we ended up with were what the Brits/ Duke(s) should have been, had the rebuild decision been made earlier ( at the time Mr Martin supposes) with more money in the pot the rebuilds may well have been Caprotti
    and the design in that respect at least would have come full circle.

    With the benefit of hindsight and the opportunity to re design and build one-off (a minor design tweak costs a lot when rolled out across a whole class or 2) there are no doubt lots of little tweaks that will help GSN be a worthy testament to the originals.

    Hope the front of cylinder fairings produced are more design typical that those odd bulbous ones she had, and that one of these days she gets the BR Blue ( which the original 'skipped')
     
  19. 30567

    30567 Well-Known Member Friend

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    Not 5A.
     
  20. Graham Muz

    Graham Muz New Member

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    I have to agree, the Full Report to propose the rebuilding was not published by the CM&EEs Office at Brighton until January 1955 and within the report with respect to the design of the original MNs had a single section titled "Performance" that had three sub headings , namely: i) Running Costs, ii) Reliability and iii) Availability. The word "Safety" does not appear within the report nor is the by then resolved post Crewkerne Crank Axle design even mentioned. The justification of the rebuilding program within the report was based on potential financial savings.

    It therefore can not be implied that rebuilding was down to "safety" and as such there should be no "safety" concerns, inadvertently implied or otherwise with the GSNLRS project to restore to original condition with a small number of caveats such as the post Crewkerne crank axle design and wedge shaped cab (that provided improved visibility from the cab).
     
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