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Current and Proposed New-Builds

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

  1. M Palmer

    M Palmer Guest

    Speaking of the GER Decapod, I recall a photo in the GERJ of the 0-8-0 "rebuild" next to the substantial remains of the Decapod itself. I always thought it looked quite purposeful if someone could dial down the steam pipes! Apropos of nothing, there is a rather attractive drawing of a 3-cylinder 0-8-0T in J. Holden's connecting rod patent of 1903 if anyone is interested.

    https://worldwide.espacenet.com/pub...=D&ND=3&date=19031203&DB=EPODOC&locale=en_EP#
     
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  2. class8mikado

    class8mikado Well-Known Member

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    So the connecting rod is a big flatbelly in it with a big 'Eyelett' hole in it to clear an intermediate axle ? yep . perfect sense. Bit of a Tw*t for the assembly shop....
     
  3. Jamessquared

    Jamessquared Nat Pres stalwart

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    The Stockton and Darlington Railway got there more than half a century earlier ...

    william-bouch-commerce.jpg

    (Via: https://www.gracesguide.co.uk/File:Im1890IME-pl053.jpg)

    Tom
     
  4. estwdjhn

    estwdjhn Member

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    What was the supposed virtue of this arrangement with the connecting rod under the coupling rod? Was it just to get an extra inch of side clearance for the cylinders, allowing them to be bigger diameter?
     
  5. Hermod

    Hermod New Member

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    Very likely as they could not angle the cylinders Crabwise due to the low boiler centerline gospel.
    Another benefit is that the locomotive must have a yawed very much due to short wheelbase and long boiler.
    In 1846 it was not widely understood how balancing works.
    Making cylinders closer together was maybe a hope that it would run a little more like an inside cylinder locomotive.
     
    Last edited: Jan 23, 2020
  6. LMS2968

    LMS2968 Part of the furniture

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    It wasn't that uncommon to put the coupling rods outside the connecting rods. The Midland Compounds had this arrangement, but being 4-4-0s with the drive to the leading wheels eliminated the need for the circular connecting rod.
     
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  7. MarkinDurham

    MarkinDurham Member

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    As did the NER's H1 4-4-4Ts

    Mark
     
  8. Jamessquared

    Jamessquared Nat Pres stalwart

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    I don’t know, though presumably whatever benefit wasn’t seen as worth it in practice, since I believe the class only ran to three examples.

    Tom
     
  9. Jamessquared

    Jamessquared Nat Pres stalwart

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    I doubt that is the reason - the loco probably never went much above 10mph or so in traffic, so I doubt stability was much of a concern, either in practice or in the designer’s thought process. Bear in mind that at that time the S&DR was still building Hackworth-type locos with the cylinders elevated at 30 degrees or so high up the boiler sides. (See e.g. https://en.m.wikipedia.org/wiki/Derwent_(locomotive)

    Tom
     
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  10. 30854

    30854 Part of the furniture

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    Indeed and not just on std gauge, as a quick gander at FfR's Linda and Blanche reveals.
     
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  11. Jamessquared

    Jamessquared Nat Pres stalwart

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    Just thinking about this a bit more: all the early S&D locos I can find pictures of seemed to have the connecting rod inside the coupling rods. That wasn’t a problem with vertical cylinders, nor as they migrated down to angled along the boiler sides. It became an issue with horizontal cylinders mounted conventionally at the front of the loco.

    So a hypothesis is that this was an interim solution on a very early design with horizontal cylinders, but before the conceptual leap to swapping round the position of coupling and connecting rods. Possibly there was a concern - later shown to be unfounded - about the strength of crank pins and trying to get the piston thrusts as close to the wheel as possible? The fact that this loco was built in 1846, only a year after Derwent with angled cylinders, might be suggestive of a design in transition.

    Tom
     
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  12. Dunfanaghy Road

    Dunfanaghy Road Member

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    I take it that you are referring to 6-coupled engines? Mr. Adams's 4-4-0s had horizontal cylinders and con rods inside coupling rods, didn't they? Of course, under Mr. Urie it all went the other way and the frames were joggled to keep the cylinder centre line (and O/A width) within bounds.
    Pat
     
  13. pete2hogs

    pete2hogs Member

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    It's not the only desirable thing, however. Both 4-4-4T's tick a lot of boxes. OK, a standard 3 or 4 tank is maybe the ideal, but surely you aren't suggesting that every line should be running identical locos? The fact that there are still unrestored Std 4's (or there were last time I looked) suggests not everyone sees them as ideal.
     
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  14. bluetrain

    bluetrain Member

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    So no chance for a new-build Cowes & Newport 2-2-2 tank?
     
  15. paulhitch

    paulhitch Guest

    Too much W.I.B.N. hankering after express types perhaps?
     
  16. pete2hogs

    pete2hogs Member

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    While 4-4-4T's are in the frame I recall that Swindon rebuilt one of the M&SWJ 4-4-4T's with a taper boiler. A job for Didcot maybe? I can't find a picture of it anywhere on line but I seem to recall it was a reasonably presentable job, unlike some of the other Swindon attempts to update their inherited stock before the Depression hit.
     
  17. pete2hogs

    pete2hogs Member

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    I will grant you that! Some amazingly short preserved railways have got themselves involved in restoring equally amazingly unsuitable large mainline locomotives. I don't think i'm in that category or I would be soliciting your donations towards my L&YR Highflyer :)
     
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  18. Jamessquared

    Jamessquared Nat Pres stalwart

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    This one? The picture is nearer than you might think!


     
  19. pete2hogs

    pete2hogs Member

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    That's the one! If the boiler had been pitched a couple of inches higher it would be really handsome.
     
  20. 30854

    30854 Part of the furniture

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    Paint 'em different colours. Simples!


    Wot?
     
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