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De-streamlined A4's

Discussion in 'Steam Traction' started by 26D_M, Oct 30, 2017.

  1. 26D_M

    26D_M Part of the furniture

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    Off topic but was de-streamlining A4s ever considered like some of the other LNER classes, Duchess etc? What would an unstreamlined A4 look like - a Peppercorn A1?
     
  2. Thompson1706

    Thompson1706 Active Member

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    Flying Scotsman.

    Bob.
     
  3. Fred Kerr

    Fred Kerr Part of the furniture

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    I was always led to believe that the A4 design was basically a streamlined A3 with minor improvements.
     
  4. Spamcan81

    Spamcan81 Nat Pres stalwart

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    Not in any books that I've read but conversely there were drawings of a streamlined A1 so Peppercorn obviously had ideas on that front.
     
  5. The Green Howards

    The Green Howards Part of the furniture

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    I think the only streamlined engines to have it removed (and not in the process of a rebuild) were the 4-6-0s used on some East Anglian services...
     
  6. Spamcan81

    Spamcan81 Nat Pres stalwart

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    I think you're right.
     
  7. The Green Howards

    The Green Howards Part of the furniture

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    Some of the engines used on the East Anglian service - B17s?

    ETA: Ah-ha! Streamlined B17 photo here. Courtesy of that page:

     
  8. Matt37401

    Matt37401 Part of the furniture

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    There were 2 of them I believe.
     
  9. The Green Howards

    The Green Howards Part of the furniture

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    Indeed - see the post above.
     
  10. Spamcan81

    Spamcan81 Nat Pres stalwart

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    East Anglian and City Of London.
     
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  11. S.A.C. Martin

    S.A.C. Martin Well-Known Member

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    No plans to de-streamline whatsoever. There were however rumblings from the LNER board about streamlining when Thompson and then Peppercorn took over.

    I had always been led to believe Thompson wanted the A1/1 streamlined, and the LNER board prevented him from doing this - however in my research, it turns out Thompson wanted to keep the A1/1 more conventional looking.

    There were a number of streamlined proposals of the various Pacifics including a semi-streamlined version of Peppercorn's A1 and A2 (which are the most famous ones as they were made as wooden models).

    On the "how much of an A3 was an A4?" question, you could consider the A4 an A3 GTI. However there's not that many actually standard components shared between the two classes, or were shared in steam days. Boilers were interchangeable but the A4s tended to keep theirs. A3s started being fitted with spare A4 boilers towards the end of steam.
     
  12. damianrhysmoore

    damianrhysmoore Active Member

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  13. 2392

    2392 Member

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    Indeed Gresley made great use of a wind tunnel testing during the design stage of the "Blue'uns". If you look at an A4 broadside on, though not up close, youll note that there's a decided "dimple" for want of a better term just behind the chimney in the casing. Gresley was having problems with the smoke not lifting clearly from the chimney and away from the boiler. The models used in the wind tunnel tests had a plasticine ridge along the top, as one of the models on one occasion was lifted out for modification somebody gripped it a bit harder than usual resulting in a thumb print dimple being made just behind the chimney. Nobody noticed until it went back into the tunnel for more tests and loo it changed the airflow and lifted the smoke clear. Who's thumb made the dimple was never found out......
     
  14. Eightpot

    Eightpot Part of the furniture

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    Just to add that the A4 boiler pressure was reduced to 220 psi when used on A3s.
     
    Last edited: Nov 1, 2017
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  15. Jamessquared

    Jamessquared Resident of Nat Pres

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    How much hinderance, if any, does the streamlining cause when preparing / disposing an A4? Clearly there were advantages (reduced power requirement at high speed, and smoke lifting). So to justify removing the streamlining, there would have to be some big advantage, of which prep/disposal would seem an obvious place to look. Or looked at another way, unless the hinderance was significant, there wouldn't be much justification in removing the streamlining.

    Tom
     
  16. S.A.C. Martin

    S.A.C. Martin Well-Known Member

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    You have to remember that under Thompson the valances - which were agreeably difficult to work with - were removed giving a “best of all worlds” scenario.

    The streamlinings greatest advantage was smoke deflection. No other LNER locomotive came close in this respect.
     
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  17. toplight

    toplight New Member

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    Wow interesting link, just had a quick look at a few of these films. Not seen this before. Looks to be a real treasure trove of old films
     
  18. Steve

    Steve Resident of Nat Pres Friend

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    IMHO, the only disadvantage when prepping/disposing an A4 over any other three cylinder loco was the need to open the cods mouth. Winding it open and closed is a chore and as bad as with winding the drop grate up and down. Not the best part of Gresley's design. Accessing the running plate is not wonderful but, if you use a ladder, as I tend to do when prepping any loco having oiling points on the running plate, it is no different.
     
  19. 26D_M

    26D_M Part of the furniture

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    Different mode of thinking on the LMS with the Princess Coronation class, ultimately. Makes for an interesting comparison in rationales?
    Just curious whether it came under consideration at the retro fitting Kylchaps in mid 50s. Perhaps a destreamlined A4 might have appeared like 60097 Humorist?
     
  20. The Green Howards

    The Green Howards Part of the furniture

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    Last edited: Nov 1, 2017
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