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British 8 coupled loco's

Discussion in 'Steam Traction' started by johnofwessex, Feb 16, 2020.

  1. Jimc

    Jimc Part of the furniture

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    It would be with perfectly rigid wheels and rails. What Steve is saying, I think, is that wheel and rail deform slightly under the load, and the net effect is that the contact patch ends up much the same area. I suppose the steel must deform if the pressure on it exceeds some particular value, and so if you have a 9.75 ton load in the wheel it will deform until the contact area is sufficient to support 9.75 tons, and it makes little difference whether its a 4'8 wheell or a 6'8 wheel, it will stop deforming when the pressure per square whatever reaches the same figure.
     
  2. huochemi

    huochemi Part of the furniture

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    Isn't friction the coefficient for that material x weight i.e. there is no contact area component?
     
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  3. Steve

    Steve Resident of Nat Pres Friend

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    But it doesn't simply take up a chord of a circle; it deforms, just like the car tyre does. The car tyre analogy is perhaps a bit simplified because the road doesn't practically deform, unlike the rail subject to the loading of a locomotive wheel. The steel of both have a similar modulus of elasticity so they will both deform until an equilibrium state exists. I've tried to find a simple explanation of Hertzian theory for rail wheels on rails on the 'net but failed as everything seems to consider either a soft wheel on a hard surface or a hard wheel on a soft surface. Wiki has this diagram, though.
    [​IMG]

    which can be found i: https://en.wikipedia.org/wiki/Contact_mechanics
     
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  4. class8mikado

    class8mikado Part of the furniture

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    Cool. The other positive with 8 versus 6 coupled is that for a similar length of wheelbase the 8 wheels sit better with less deflection in the axleboxes. Still think that a Brit or Clan boiler on a 2-8-2 wheelbase with 5ft to 5ft 6 wheels would have been the best heavy general purpose loco this country (n)ever had.
     
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  5. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    So a question that springs to mind is - do locomotives that remain static in museum permanently deform their tyres when static for long periods of time?

    Fascinating stuff this.
     
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  6. 5944

    5944 Resident of Nat Pres

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    Similar to the DB/DR class 41s. Same boiler as a two cylinder 03 pacific, but as a 2-8-2 with 5' 3" driving wheels.
     
  7. marshall5

    marshall5 Well-Known Member

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    As seen here (albeit an oil fired one so DB class 42) at Rheine in summer 1974. 'Always thought they were well proportioned locos.
    Ray.
    042 085 on trip freight at Rheine.jpg
     
  8. RLinkinS

    RLinkinS Member

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    Surely permanent deformation would only happen if the stress in the area of contact exceeded the elastic limit of the steel


    Sent from my SM-A105FN using Tapatalk
     
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  9. Eightpot

    Eightpot Resident of Nat Pres Friend

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    The USA S200 2-8-2s were built to the European/continental load gauge, and known as the Middle East' type. At 10' wide over the cab and 13' - 6" high over the chimney they are outside the UK load gauge.
     
  10. BrightonBaltic

    BrightonBaltic Member

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    At the risk of digressing - what is the widest steam locomotive ever built? Most of the big American stuff seems to be around the 11ft mark, with the N&W J-class 4-8-4 the widest I've found so far at 11ft 2in...
     
  11. Eightpot

    Eightpot Resident of Nat Pres Friend

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    Difficult to say without a lot of researching. It would appear in the USA that the New York Central had one of the smallest load gauge profiles, in fact little bigger than the German one, but it seems the further west one went, the load gauge got bigger.
     
  12. bluetrain

    bluetrain Well-Known Member

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    Very interesting question.

    USA locomotives were larger than those found anywhere else. The widest steam locos are likely to be those with the widest outside cylinders. Some compound mallets had enormous low pressure cylinders. The record appears to be 48-inch diameter on the Virginian Railroad 2-10-0-2 Class AE. According to Wikipedia, these engines were 12 feet wide. Given that the low pressure cylinders were mounted on the swinging forward power unit, the loading gauge must have even wider to allow for side movement.

    https://en.wikipedia.org/wiki/2-10-10-2

    I believe that the more general USA loading gauge width was/is around 11 foot. Similar widths are found in Norway & Sweden, Russia (5-ft gauge) and Spain & Portugal (5ft 6in gauge), but none of these countries had steam locos on USA scale. Even the infamous Soviet 4-14-4 only had 740mm (29-inch) diameter cylinders.

    https://en.wikipedia.org/wiki/4-14-4
     
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  13. LesterBrown

    LesterBrown Member

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    How wide was Fowler's Ghost?


    Edited: To answer my own question I have been carefully measuring the well known 3/4 front view comparing the buffer beam with the guard irons and came up with no more than about 10'6"
     
    Last edited: Feb 29, 2020
  14. 30854

    30854 Resident of Nat Pres

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    Brunel's BG never featured stock as wide (and certainly not as high) as might be expected. Mind you, that wasn't ever the aim. To my mind, the wonderful Fire Fly and stock at Didcot reveals the true proportions of BG far more readily than old photos or prints
     
  15. LesterBrown

    LesterBrown Member

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    It was just that, with the slidebars outside of the leading wheels I thought it might have been wider than any of Gooch's locos. The GWR Metropolitan Tanks, the only outside cylinder Gooch locos, had their cylinders inclined above the leading wheels.
     
  16. Dag Bonnedal

    Dag Bonnedal New Member

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    The Virginian AE Mallets were so high and wide that they had to be transported from Alco to the railway with the LP cylinders, cab, chimeny and other stuff transported separately.
    As you say, the Scandinavian countries have loading gauges over 11 ft. The Norwegian built cl. 49, the Dovre Gigant filled this profile (3400 mm) and I think the Swedish F and R classes are close as well.
    Indian broad gauge railways has a width of 12 ft, but I don't know the size of the steam locos, but some of them are BIG.
     
    Last edited: Mar 3, 2020
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  17. bluetrain

    bluetrain Well-Known Member

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    Indian broad-gauge locomotives generally followed British practice and were similar in size to our home main-line engines. But although there were numerous independent Indian railways during the period of British rule, many of the locomotives were to standard Government designs. These culminated in the 1920s in the introduction of heavy passenger 4-6-2s and heavy freight 2-8-2s. After independence, the Indian Railways introduced the WP-class 4-6-2 and WG class 2-8-2, which blended British and American design features. At around 100 tonnes, they were of similar size to typical European 4-6-2s and 2-8-2s. The WG class 2-8-2 eventually totalled 2450 locos, which must make it one of the world's most numerous types.

    Only a small number of larger engines were built. The Indian North-Western Railway had some Baldwin-built compound mallets, which certainly looked massive, but not on American scale (see attached picture). The largest Indian locomotives appear to have been some 4-8-0+0-8-4 garratts built for the Bengal-Nagpur Railway:

    https://en.wikipedia.org/wiki/BNR_class_N

    https://artsandculture.google.com/e...ves-national-rail-museum/IgJClH4eKKhGLQ?hl=en
     

    Attached Files:

    Last edited: Mar 7, 2020
  18. andrewshimmin

    andrewshimmin Well-Known Member

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    Illustrated in "Locomotives that never were" by Robin Barnes.

    Sent from my Pixel 3a using Tapatalk
     
  19. bluetrain

    bluetrain Well-Known Member

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    This thread has not so far considered 8-coupled tank locos. Most British companies made only limited use of heavy freight tanks, possibly because the extra weight of a tender was seen as useful for controlling unfitted trains. At the time of grouping, the GNR and LNWR had built modest numbers of 0-8-2 tanks (41 and 30 respectively). Around 1930, Gresley considered the production of a new 3-cylinder 2-8-2 freight tank, with at least 6 designs being sketched, using 4 different boiler types. This project did not proceed. The LMS built 30 0-8-4Ts to LNWR design in 1923-4. But all these GNR and LNWR engines were eventually scrapped without direct replacement, their duties apparently taken over by tender engines. No 8-coupled tanks emerged within the LNER and LMS standard ranges, nor was a freight tank included in the later BR standard range.

    The GWR provided the exception to this general pattern. The GWR had always liked tank engines for goods trains to a greater extent than the other major British companies, a tendency reinforced when the GWR took over the South Wales lines. The GWR 4200 class 2-8-0T was the only British 8-coupled tank to be built in large numbers - 205 of them, with 54 later rebuilt to 2-8-2T. The class was not only successful in GWR and BR service, but has continued to do good work for a number of heritage railways.

    The 4200 does not only stand-out as Britain's most numerous type of 8-coupled tank. Its 2-8-0T wheel arrangement appears to be almost unique. I can find only three other examples:

    (1) Firstly, a type built for some Swiss local railways, starting with the Lake Thun Railway. After electrification, they were sold to Austria, where they became Classes 279/379. At only 54 tons, these 2-cylinder compound engines were much smaller than the 4200-class, comparable in size to GWR 4400 2-6-2T.
    https://de.wikipedia.org/wiki/BBÖ_279

    (2) A mixed set of 2-cylinder compounds and simples was built for the 3ft 6in /1067mm lines in German South-West Africa (now Namibia), with dust skirts for desert operation:
    https://en.wikipedia.org/wiki/South_West_African_2-8-0T

    (3) Finally, a pair of 750mm gauge 2-8-0Ts were built by Henschel in 1938 for a German local line. The pair have survived in heritage use on the island of Rügen.
    https://de.wikipedia.org/wiki/DR-Baureihe_99.480

    I am sure there must be some more 2-8-0T types lurking somewhere. But they are certainly elusive. The GWR 4200 reigns almost unchallenged!
     
  20. johnofwessex

    johnofwessex Resident of Nat Pres

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    The 42XX's were designed for use in the South Wales Valleys where the design fitted the bill exactly. I have heard it said that the 2-8-2T's would have been much better as tender loco's as they would have been lighter and have had a longer range.
     

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