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Current and Proposed New-Builds

Discussion in 'Steam Traction' started by aron33, Aug 15, 2017.

  1. 30854

    30854 Well-Known Member

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    With hindsight, wasn't TGB's greatest acheivement to prove that the GWR didn't actually need pacifics?
     
  2. Copper-capped

    Copper-capped Active Member

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    Yes, Swindon were the original small chufferists.

    PH



    Lol, jokes aside, you could look at it like that when you consider the more than capable job that saints, stars, castles and kings did throughout and right to the end. I just think it didn't work well enough and became a dead end when compared to the promising locos already built and the potential for further development and improvement of proven design concepts.

    P.S. I'll rub @Jimc 's lamp as he is usually the man! :)
     
  3. Jimc

    Jimc Well-Known Member

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    Odd, thought I already posted this. But I suggest that the Great Bear's most significant achievement was to demonstrate that the GWR did have a use for a limited number of high capacity mixed trafiic/fast freight locomotives, which led to the 4700s. I've seen it said that although the Bear was nothing special at running express passenger, it was good at running fast fitted freight.
     
  4. Jamessquared

    Jamessquared Resident of Nat Pres

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    Oddly enough, over on the South Western, Drummond also found the best use of his shiny new passenger locos was hauling freight from Salisbury to Southampton - mainly coal, very slowly, at night, well away from prying eyes. :eek:

    How many of the wagons of coal were remunerative load and how much was an emergency supply in case the tender supply ran out somewhere in the Romsey area is unrecorded ;)

    Tom
     
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  5. paulhitch

    paulhitch Part of the furniture

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    Yes, I understand one class were known as the "gobblers" with an individual machine being called "the turkey"!

    PH
     
  6. clinker

    clinker New Member

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    'Gobblers' was a nickname for the Wordsel designed Great Eastern 2-4-2 T with rather poor Joy valve gear, the name tended to get put on any GER 2-4-2 T even the much improved James Holden versions with Stephenson valve gear. The current true new build F5 will have Stephenson gear but the larger F6 style glazed cab, in this form it will be a 'Glasshouse Gobbler'
     
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  7. Jamessquared

    Jamessquared Resident of Nat Pres

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    Yes, supposedly the P14s were “gobblers” or “turkeys”. The slightly later, though dubiously improved, T14s were “paddle boats” or “paddle boxes” on account of their looks, though there was a somewhat less polite nickname that was probably a truer reflection of a fireman’s opinion on the type. Not Mr Drummond’s finest hour...

    Tom
     
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  8. m&gn50

    m&gn50 New Member

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    The Great Bear i think was where the original design for a Castles front end draughting was done. As such it fits between Star and Castle and is far more significant than many think...
     
  9. LesterBrown

    LesterBrown Member

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    I've never heard that before. Wouldn't any improvements have been incorporated in the Stars, most of which were still to be built at the time the Bear was being developed? The later ones did indeed have their cylinder bores increased to the size of the Bear's.
     
  10. m&gn50

    m&gn50 New Member

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    Look at the drawings. You can put a Castle front end on tgb. But not a star.
     
  11. Hermod

    Hermod New Member

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    No railway in UK benefitted from having pacifics according to mr Ridless.
    4-8-0 with smaller wheels and wide fireboxes had been the way to go.
    Mr Beames was almost there ca 1930
     
    Last edited: Nov 10, 2017
  12. johnofwessex

    johnofwessex Well-Known Member

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    David Wardale and Peter Smith both don't seem enthused by Pacifics and reckon that the Standard 5 was the master of all jobs................
     
  13. Hermod

    Hermod New Member

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    Last edited: Nov 10, 2017
  14. 30854

    30854 Well-Known Member

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    AIUI it's the basic geometry and how applied forces affect the rolling chassis of yer bog standard pacific which leads to a tendancy to "settle back" on starting. Assuming for a minute I'm not barking, was Raven's format (i.e. drive to leading axle) any better in this regard?
     
  15. Eightpot

    Eightpot Part of the furniture

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    Yes, but the largest driving wheels that could be fitted in were the only 5' diameter ones of a 9F, and for passenger work one really needs something bigger than that.. Unfortunately, being the inventor of railways as we know them, we made the mistakes that we are stuck with, to wit, our restricted loading gauge profile.
     
    Last edited: Nov 10, 2017
  16. 8126

    8126 Member

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    Not really, in fact it may be worse. It's just a question of balancing the moments. Longitudinal force forward applied at rail height, longitudinal force backwards applied at drawbar height. Changing which axle the drive is applied to makes not a whit of difference to this. In reaction, the load on the rear axles is increased and that up front reduced. Pacifics don't necessarily lose weight in total off the coupled axles, since some of it will have come off the bogie (depends a lot on the relative spring rates), but a 4-6-0 (or anything with a leading bogie and no trailing truck) gets nothing but gain as long as it's going forwards.

    Now, on a Raven type arrangement, the driving axle is the leading coupled and that will be suffering from a reduced axle load. The driving axle is probably the one you'd least want to lose adhesion weight from; it'll slip more at the maximum torque points, leading to wear, leading to an increased propensity to slipping, leading to wear, leading to.....
     
  17. Hermod

    Hermod New Member

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    Not according to mr Ridless who acused Gresley of using to big wheels and Bulleid that used smaller when he got the chance down south.
    If a two cylinder 5 feet 9F could do 90 on demand a three cylinder be it 2 or 4 -8-0 could have run faster without selfdestructing
     
  18. Hermod

    Hermod New Member

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    A Raven three cylinder with no funny valve conjugation must have been miles more regular turning than A4s
     
  19. Jamessquared

    Jamessquared Resident of Nat Pres

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    Given the reputation of the A4s for sustained high-speed running, it's hard to justify that statement surely?

    Tom
     
  20. RLinkinS

    RLinkinS New Member

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    A 9F at 90 mph is running at around 500 rpm, the same as Mallard at 126. While this is fine for the occasional record attempt I consider that around 400 rpm was the usual maximum without causing mechanical problems. This would limit the speed of an engine with 5' wheels to around 75 mph. The wear on the pistons and valves of a 9F when running at 90 mph also proved to be a problem. I believe a wide firebox 4-8-0 suitable for express work is not feasible within the British loading gauge. I like the idea of a 4-8-0 but believe a better starting point would be to us the boiler design Chapelon used on his 4-8-0s
     
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