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35011 General Steam Navigation

Discussion in 'Steam Traction' started by GSN, May 15, 2015.

  1. Allegheny

    Allegheny Member

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    This comment really related to the P2, which has now been transferred to the GSN thread:eek:

    I take it that, back in the day, the advantages of a Pacific over a Mikado outweighed the points raised above. I guess the original P2 didn't go over Shap too often!
     
  2. Hirn

    Hirn Member

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    Actually I was catching up and at that stage had not read what had come in lately on the P2, Thompson & New Build threads.

    It is true,though, that composing and finalising my reply I found myself unsure which thread I was replying to. It is indeed pertinent to all three however happily by sheer accident.
     
    Last edited: Oct 19, 2021
  3. MellishR

    MellishR Resident of Nat Pres Friend

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    I still think it's a shame that they're not going for the (cardan shaft?) system that Bulleid originally intended for the valve gear until wartime conditions forced him to use chains, but it's their project.
     
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  4. srapley

    srapley New Member

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    Hello all,
    I've been off this thread for a while due to some IT issues (change of laptop so needed to reset my password for this account and simply haven't got around to it until today). To answer or quash a few points around what we're doing (or not):
    1. the crank axle will be the same geometry (more or less) as the design fitted to GSN in 1955, the balanced design, which was fitted to all rebuilt Bulleid pacifics, as well as 6 original MNs prior to rebuilding (including GSN). The main difference will be in the material, as the original steel isn't available in large enough billets for our purposes, any geometry differences (if needed) will be subtle, related to balancing. The other, related, difference is we will likely keep the maximum boiler pressure to 250psi, as this is what the supporting analysis assumed for the crank axle (280psi would increase the forces on the axle by ~12%)
    2. the crank axle failure on Bibby Line occured at high speed, due to high cycle fatigue essentially. My understanding of the failure on the P2s is it happened at low speed, where the extra axle reduced the tendency of the wheels to slip compared to a Pacific, so there was an opportunity for a higher bending moment to go through the crank axle before the wheels would slip, leading to failures. The redesign of the MN crank axle after Crewkerne was done to eliminate the HCF by reducing the load at high speed, producing a design that is very similar to that on 71000.
    3. the chain driver sprocket on the crank axle will be to a new design, that will be informed by the design fitted to the existing original Light Pacifics as well as the inside eccentric fitted to the rebuilt locomotives. We're producing the new design because (1) the sprocket for the unbalanced crank won't fit the balanced axle and (2) the drawings for the sprocket fitted to GSN in 1955 are not in any collection we know of (such as the BPLA or NRM).
    4. the balancing of the motion will be to a new design, that will be informed by the design fitted originally to the MNs as well as to the locomotive when rebuilt. We're producing a new design because (1) none of the existing balancing designs will balance a MN with bulleid valve gear & balanced crank axle, and (2) the design that was fitted to GSN in 1955/6 is not in any collection we know of (such as the BPLA or NRM).
    5. the rest of the valve gear will be the same as the original design, although the chain material may be different (our friends with LPs have managed to reduce chain stretching with the use of modern materials).
    6. the oil bath will be the same as the original design. We'll take advice on whether to keep the original welding design or modify it, as we believe with modern welding techniques we may be able to reduce the tendency for the bath to leak
    7. we won't be looking at implementing any alternate design of valve gear, as we are trying to recreate a Bulleid Merchant Navy, and the valve gear is a fundamental part of that. In my opinion, there are two things we're trying to recreate-how a Merchant Navy originally looked (air-smoohted casing), and how it originally worked (chain-driven valve gear with outside admission), though the latter impacts on the former. Whilst the idea of some "what-if" using gears/cardan shafts etc. is nice to ponder, it would take us away from that vision of the original Merchant Navy, and would bring in significant extra costs, as more-and-more of the locomotive would be new design, so would need designing & certifying accordingly. I understand why our friends with 2007 are looking at different valve gear to the original, they have a completely new machine, so presumably whatever valve gear they use will need to be accepted & approved for very similar costs. If we use the original design we can say (1) this is what was originally fitted, and (2) it's the same as is fitted to Tangmere & other LPs that have been mainline certified, so our case for grandfather rights is strong.
    8. the tender will be a 3 axle design, the rest is to be determined. It's likely to have the long wheelbase of a 6000 gallon tender, but we may well change the fuel/water ratio (I read in a book that one of the 6000 gallons was fitted with a new tank in the 50s/60s which brought it up to 7000gallons for example). It will have raves, which may hide changes to the upper profile of the tender.
    9. the exhaust & steam circuit: we are exploring the idea of modifications to the steam circuit & exhaust to improve the performance & efficiency of GSN. The steam nozzles are aguably undersized, and probably not pointing in quite the right direction, so there's potential for some improvement there with minor tweaks. For the more radical changes, with a clean sheet of paper, a locomotive our size would have some form of twin exhaust (Kylchap, Kylpor, Lempor etc.), but we want to maintain the aesthetic of the loco with a single large exhaust with 29" diameter outlet. We're conducting some aerodynamic studies looking at essentially a squat Lempor or stretched Bulleid-Lemaitre to see what can be done in that respect as well, does it bring any benefit, and at what cost? The rest of the steam circuit, if we can make changes that don't undermine the grandfathering case (and don't stress the existing parts of the steam circuit by creating some imbalance), then we may look at incorporating them.
    10. the reverser will be the original design of steam reverser (we have one of these in our possession now), replacing the screw reverser. Our understanding from our LP friends is if it is well maintained the tendency for it to creep & the other historical issues experienced are reduced or disappear.

    I hope this has clarified some points. There is a lot going on with this project in the background, to all of you I would say if you are interested in putting the steam back in General Steam Navigation, in seeing Bulleids magnificant Merchant Navy design return to the rails, please join our society (https://35011gsn.co.uk/membership.html), donate to our appeals (https://35011gsn.co.uk/funding-campaigns/) and/or buy shares in the project (https://35011gsn.co.uk/shares.html)

    Steve

    Dr Steve Rapley MIMechE

    Chief Mechanical Engineer

    35011 General Steam Navigation Locomotive Restoration Society
     
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  5. MellishR

    MellishR Resident of Nat Pres Friend

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    Thank you. It is very helpful to have an explanation not only of what you're doing but of why you're doing it. Even if some of us might have preferred some different decisions, we can respect the ones that you have made.
     
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  6. Martin Perry

    Martin Perry Nat Pres stalwart Staff Member Moderator Friend

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    Many thanks for providing a comprehensive update of the plans for the loco restoration.
     
  7. 30854

    30854 Resident of Nat Pres

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    Superb summary and very much appreciated. Many thanks for taking the time to add some considerable detail concerning the many complex issues involved.
     
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  8. siquelme

    siquelme Well-Known Member

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    On Friday our CME took a group of students from Loughborough University to look at the smokebox and exhaust of 34039 Boscastle. This was to aid their understanding of the geometry they’re studying as part of developing the Internal Aerodynamics and draughting of 35011. Thanks to Andy Morgan and Mike for hosting us.

    [​IMG]
     
  9. Flying Phil

    Flying Phil Part of the furniture

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    It is good to see such co-operation between organisations and education. Well done to all concerned.
     
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  10. siquelme

    siquelme Well-Known Member

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  11. siquelme

    siquelme Well-Known Member

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  12. Bikermike

    Bikermike Well-Known Member

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    Good to see!
    As a thought, is it worth trying to build in post-coal burning tech? Clearly this is finger-in-the-air stuff, but more options as to damping, adjustable firebar configurations, spark arresting, large number of AA batteries in place of coal, etc might be worth designing in - in keeping with OVSB's pioneering spirit.
     
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  13. 30854

    30854 Resident of Nat Pres

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    Given Bulleid's well known enthusiasm for making tbe most of new techniques, you have to suppose he'd have been like a kid in a toyshop with today's CAD technology, computer controlled machining and sacrificial mould casting capabilities.

    In an excellent update, I was particularly struck by the work being done on internal streamlining and ejector arrangements. Seeing this level of symbiotic relationship developing between the engineering team and a universtiy is fantastic and bodes extremely well for all involved.
     
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  14. JJG Koopmans

    JJG Koopmans Member

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    It took me some time to think this over! In general a 8-orifice jet unit should be slightly better than a 7 jet type. However a single chimney of diameter D compares favourably with 2 chimneys each of 0.71D because
    the total wall area is related to D and for the double chimneys to 1.4D, bad for flow friction. The original Bulleid is imho a proper concept with wrong dimensions and could easily be improved.
    Kind regards
    Jos
     
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  15. siquelme

    siquelme Well-Known Member

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  16. Flying Phil

    Flying Phil Part of the furniture

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    I see, from the website, there has been continued progress but not much has been posted on here, which is a shame.
     
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  17. Flying Phil

    Flying Phil Part of the furniture

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    The website has been updated again with an August Update.
     

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