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34046 Braunton

Discussion in 'Steam Traction' started by 92143, Oct 18, 2011.

  1. class8mikado

    class8mikado Member

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    Any of You B'lleidophiles Know what the Nozzle diameter on a WC/BB lemaitre is ?
     
  2. Richard

    Richard New Member

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    2.75 inches diameter x 5.
     
  3. david1984

    david1984 Well-Known Member

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    I'm nicking that to describe the Southern mob in future :D
     
  4. 34007

    34007 New Member

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    Then I guess I am a B'lleidophile and a one of the Southern Mobs!! Or just call me 'Mr Bulleid'.... :D
     
  5. Footbridge

    Footbridge Member

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    I doubt supporters of the P class locos would approve of similar descriptions :eek:
     
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  6. Steamage

    Steamage Member

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    Yes, two separate sets, but probably with a large intersection
     
  7. class8mikado

    class8mikado Member

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    2.75 inches ?that is a lot of blast tip area ... is that the size of the hole or the size of the bit of metal with the hole in . is it the same as the MN'S ?
     
  8. Richard

    Richard New Member

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    I can confirm that all drawings have the holes marked 2.75 inches dia, the Merchant Navys are the same, giving an area of 29.68 sq in - if my maths is correct!
     
  9. Jamessquared

    Jamessquared Nat Pres stalwart

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    DL Bradley gives five nozzles of 2.625" for a Merchant Navy, situated 15.625" below boiler centre line and discharging through a 25" choke.

    I'm only skim-reading and can't find an equivalent figure for a WC/BB, but the fact that he doesn't explicitly mention a different dimension might suggest the proportions are the same?

    Tom
     
  10. Sheff

    Sheff Well-Known Member

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    But is the nozzle parallel / cylindrical internally or is like a venturi with a choke point somewhere below the tip, which would be of a smaller diameter?

    For interest, from the DoG website ...... The total area of the plain blastpipe nozzles of No 71000, at 25sq in, was less than either the five-nozzle unit of the 'Merchant Navy' at 27.5 sq in, or the twin-cloverleaf pattern of the 'A2' Kylchap blastpipe at 29.5 sq in.
     
  11. class8mikado

    class8mikado Member

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    162cm Sq ? I work that back to 2 x 4 inch ' Nozzles' on ex works 71000, same as a 9f? which is acceptable......for a 9f (or a clan....)
     
  12. std tank

    std tank Member

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    The bores on the blast pipe cap for the Bulleids are 2-3/4" dia at the bottom and 2-5/8"dia at the top.
     
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  13. Richard

    Richard New Member

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    Yes, my error, I was reading the measurements off the blast pipe drawings instead of the one for the cap!
     
  14. class8mikado

    class8mikado Member

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    How does it work Vic....?:confused:
    Ah dunnoh, but it does.:rolleyes:
     
  15. Jimc

    Jimc Part of the furniture

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    in AE Durrant's book "Swindon Apprentice" he writes:

    "Always eager to learn new techniques, I was most interested to discover how Bulleid's modified Lemaitre exhaust varied according to locomotive size, and extracted the relevant drawings for study. [he was seconded to Ashford at the time]. To my amazement they were all virtually the same, five jets of 2 5/8 inches diameter on closely similar pitch circle. Only much later did the significance of this emerge. The original design was probably prepared for the 'Nelsons' and worked well. On the Schools, it was really too big, which is why no definitive results were obtained in its favour. When these same sized jets were applied to the far larger 'Merchant Navy' class, they created too much back pressure, as confirmed with the tested high fuel consumption, but also created so much draught that the boilers were unbeatable! By coincidence the identical arrangement on the smaller Pacifics provided a less extravagant draught and back pressure, giving them their popular acceptance. It seems amazing that the jet and chimney dimensions were not varied according to locomotive size, this being one of those little mysteries which make locomotive history so rewarding."
     
    Last edited: Apr 14, 2014
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  16. class8mikado

    class8mikado Member

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    So there you have it, if you have a MN it might benefit from a renozzling ( is that a word ?)
    Will keep a look out for that book.
     
  17. Spamcan81

    Spamcan81 Nat Pres stalwart

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    If what Mr.Durrant said is correct, why weren't the draughting arrangements modified during the rebuilding process?
     
  18. 8126

    8126 Member

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    Apparently there was a proposal from Swindon test plant to modify the draughting of the rebuilds, with the nozzles opened up to around 30sq in and the petticoats modified to be longer with a tighter choke. My reference (Rogers, Bulleid Pacifics at Work) doesn't say whether this only applied to the MNs, or all the Pacifics . Nothing to do with efficiency though, they'd been asked to suggest a way of curbing the extravagant fire throwing of the rebuilds, although apparently the probability of fuel savings was noted. But by then it was 1961, and nothing was done about it. I'm sure I once read (rough quote): 'Anyone who thought the Bulleids threw a lot of sparks from the chimney hadn't seen a Nelson at night.'
     
  19. Big Al

    Big Al Resident of Nat Pres Staff Member Moderator

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    All I can recall on such matters is a memorable night when it was decided that Woking to Waterloo should be attempted in even time on one of the semi fasts from Salisbury. As we took off from Woking (and that is probably the right turn of phrase) I remember the scene at the petrol filling station on Albert Drive (now a Citroen dealer) that is next to the railway on the north side of the line about a mile out. Motorists were diving for cover as hot red cinders bounced off the roof and into the forecourt. So much for spark arrestors....and yes we did make it to Waterloo in 24 ish minutes.
     
  20. david1984

    david1984 Well-Known Member

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    It is rather curious after reading that interesting quote, certainly chimney and blastpipe dimensions can make a big difference, especially since Bulleid would have been aware of the difference the double Kylchap made on Gresley Pacifics.
     

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