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Bluebell Motive Power

Discussion in 'Steam Traction' started by Orion, Nov 14, 2011.

  1. 8126

    8126 Member

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    I'm not sure whether the thermic syphons were a bonus or a cause of the steel firebox, but I think it's likely that the steel firebox was a design decision independent of the wartime economic conditions. Look at the Q1, the most austere design Bulleid did and yet there's a copper firebox. Now of course that allowed re-use of the Lord Nelson flanging blocks, so maybe that skews the economics a little, but then the Pacifics also had solid bronze axleboxes as built; again, if you're looking to save every scrap of copper that's not what you'd do.

    With the high pressure of the Bulleid boilers as built, a steel firebox very quickly becomes just a sensible design choice - it can (and needs to be) thinner than a copper box, which combined with the all-welded firebox saves a useful chunk of weight. The thermic syphons then add weight back in, but recent experience on the LMS among others had shown that radiant heating surface was all-important in giving a free steaming boiler and Chapelon was using steel fireboxes and thermic syphons on his locomotives, of which Bulleid was probably more aware than most British CMEs.

    I am of course speculating...
     
  2. 30854

    30854 Well-Known Member

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    I'd love to see today's computer modelling applied to thermic syphons. From what I've seen, they all tend to fail in the same place (the outside obtuse angle). Even with Porta's work on GP systems, it strikes me that there remains work to do within the firebox. Add to this my personal peccadillo (torrified biomass) and there's scope for some serious research. "Fenchurch" on pellets? Effit, why not?

    Am I raving? Check it out and see what you think:

    http://csrail.org/torrefied-biomass
     
  3. Jamessquared

    Jamessquared Nat Pres stalwart

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    I'm sure it would be an interesting discussion on another thread ...

    Tom
     
  4. huochemi

    huochemi Well-Known Member Friend

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    I too was puzzling over the Bulleid Society Chairman's precis of the reasons behind the choice of steel. I attach the relevant extract from Bulleid's paper to the ILoco E (1946), in which he prioritises weight saving. He ranks the use of steel v. copper as desirable in connection with material availability, and the pressure factor is mentioned, although slightly obliquely. Cost does not appear. Neither is the ability to repair fireboxes at sheds mentioned (I assume that comment is aimed at repair of plates rather than stays, as stay changing must have been routine). Now it is possible a more thorough exegesis of available material would support cost as a factor, but it does not seem to have been uppermost in Bulleid's mind at the time.
     

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  5. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    That is technically correct - copper welding was not possible at that time. I do not know if this was Gresley's reasoning for the design on the V4, however.

    It would be fun to see one of the Bulleids pulling the Golden Arrow one day :)
     
  6. torgormaig

    torgormaig Active Member Friend

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    To my knowledge The Bulleid Pacifics and the one V4 were the only locos in the UK to use thermic syphons and they all had wide steel fireboxes at a time when copper boxes were the norm in this country. Another type that used a wide steel firebox was the WD 2-10-0 and these incorporated a simpler version of the thermic syphon, namely welded arch tubes. The narrow firebox WD 2-8-0 version on the other hand I think stuck to a conventional copper firebox. Happy to be proved wrong on any of this if others know more than I do.

    Peter
     
  7. Kylchap

    Kylchap New Member

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    Can someone please explain why thermic syphons were used in locos with a steel firebox but not in copper ones? Thanks.
     
  8. 30854

    30854 Well-Known Member

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    See post #2885 (above), but if your question was aimed at syphons formed from copper, I'd be interested to know too (even if I end up feeling a bit daft, should the answer be glaringly obvious!).
     
  9. huochemi

    huochemi Well-Known Member Friend

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    Bruce (The Steam Locomotive in America) actually covers Arch tubes, Syphons and Circulators (e.g. as in the SAR Class 25) in one diagram titled "Three methods of fire-brick arch support" i.e. focusing on this rather than their circulating characteristics. Arch tubes seem very common in wide boxes (other than in the UK).
     
  10. torgormaig

    torgormaig Active Member Friend

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    That's because most parts of the world used steel fireboxes. I'm sure we would have seen far wider use of such devices here if the technology of the day had permitted their construction in copper boxes.

    Peter
     
  11. twr12

    twr12 Active Member

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    When a very experienced Bulleid fitter (preservation era): 35027, 34072, 34028, 34070; looked into 60163s firebox, he said “what holds up the roof?”

    You had to know Frank to appreciate his sense of humour!
     
  12. Jamessquared

    Jamessquared Nat Pres stalwart

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  13. Jamessquared

    Jamessquared Nat Pres stalwart

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    paullad1984, S.A.C. Martin and 30854 like this.

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