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Bulleid Pacifics - Past or Present

Discussion in 'Steam Traction' started by 34007, May 13, 2008.

  1. 8126

    8126 Member

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    In terms of pin loading and amplification of errors in rocker driven valves, there are two things to consider. One is the degree of amplification - the Bulleid gear is doing quite a lot at 3:8 (2.66x increase). Even in the fairly common examples of Stephensons gear originally arranged to drive slide valves below, instead going through rockers to drive long lap piston valves above, I think it would be pretty rare to see a ratio of new valve travel to old as high as 2. The GWR inside-to-outside rocker drive on the outside cylinder engines drives the valves in the same direction, so the pivot only needs to provide the additional load due to the increase in travel, not a full reversal of the increased load.

    That said, I was mostly commenting that the 3:8 levers in the Bulleid gear have a lot of opportunity to mess things up with the valve events, and perhaps not the most maintenance friendly.
     
  2. Allegheny

    Allegheny Member

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    Still on the subject of tensioners, for a chain which can run in either direction, you could have a two ended tensioner arm, pivoted at the center, with one end acting on the "forward" side of the chain and the other end acting on the "return" side. The spring would need to supply sufficient torque to the arm to ensure that the chain remains taut under all foreseeable operating conditions.
     
  3. srapley

    srapley New Member

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    Whilst there is a thread dedicated to all things 35011, a lot of what we're discussing here is relevant to all Bulleid pacifics. We also have our own website where one can become a member (https://www.35011gsn.co.uk/membership.html) or even a shareholder (https://www.35011gsn.co.uk/shares.html) in our project
     
  4. Wayne

    Wayne New Member

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    There are a number of people falling into the age old trap of repeating things that other people have written, that those people have erroneously written that previous people have commented on. Wrongly.
    Any locomotive is built for a reason, any railway. An engineer doesn't just come up with something and says 'I'm building this!'.
    The Merchant Navy's and there smaller cousins where no different.
    The Southern railway wanted their new engineer to design a locomotive that was able to keep out of the way of it's new electric trains and cut down on dwell times at stations. This last bit is often ignored when discussing the Merchant Navy's.
    They didn't want a driver spending ten minutes or more oiling around the locomotive at a station stop. Particularly the time consuming inside valve gear on a three or four cylinder locomotive. If I remember correctly a Castle has 126 oiling points.
    This is one of the reasons our man went for an oil bath. Yes they leaked, but only a small amount and then generally through poor maintenance.
    An oft repeated error by many that the oil bath caused the issue of oil being flung about.
    The real culprit was lazy driver's!
    There were two oil trays located in the cab, these had quite a number of trimmings for the running gear. These were put in the cab for ease of filling and keep the oil warm.
    Problem was they should have been removed at the end of a journey. Some didn't, and the oil kept feeding to the running gear. Next journey it was flung all over the place. Not the old wives tale of the oil bath. This fact was known by railway staff, but totally ignored by people wishing to put down the locomotives. Then miss reported for years.

    The stretching of the chains has also been miss reported. They did, but only as much as they were allowed within tolerance. Again checked on maintenance. Generally it wasn't an issue, only occasionally it got the wrong side of what was expected.

    If there had been a fundamental flaw with the original locomotives, they wouldn't have still been around at the end of Southern steam in July 1967.

    Having both fired and driven 34067 on the mainline, I personally know what an original light Pacific is like. If maintained, like anything else, they top draw.

    The Driver's loved them, fitters hated them. Most of the tales of wo come from fitters, not the Driver's.
     
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  5. Spamcan81

    Spamcan81 Nat Pres stalwart

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    Excellent post. Our chief engineer has said the same about the oil trays being the culprits.
     
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  6. 35B

    35B Nat Pres stalwart

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    Thank you for that view from the footplate. It does however raise a question.

    If Bulleid designed his Pacifics to be easier to maintain, why did some fitters hate them so?


    Sent from my iPhone using Tapatalk
     
  7. RLinkinS

    RLinkinS Member

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    Because working on the valve gear or middle cylinder crosshead, connecting rod, etc, was made much more difficult as it required the fitter to climb inside the oil bath. I learned this from a fitter who used to work at Ramsgate shed.

    Sent from my SM-A105FN using Tapatalk
     
  8. Dave Williams

    Dave Williams New Member

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  9. srapley

    srapley New Member

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    Very interesting post Wayne, well said. With your experience of 34067 on the mainline, is there anything you would change about it that we could consider for 35011?
     
  10. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Fitters or drivers. There’s some people missing there. The accountants.
     
  11. Dave Williams

    Dave Williams New Member

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    Reality check?
     
  12. Spamcan81

    Spamcan81 Nat Pres stalwart

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    Ever needed to do work inside the oil bath? That's a big reason for being unpopular with a fitter. They're a dream to prep though.
     
  13. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    This sort of is what drove the changes in locomotive engineering over the second world war for a number of railways, including on the continent. If you break it down ala the LNER records:

    The main aim is to get the number of days off for repairs down as much as possibly and to maximise the time the locomotives are in use. If you're spending more time on prepping locomotives than using them, your availability for work goes down. So reducing prep time from the driver's point of view is a sound way to go. The compromise is time spent at sheds, whether that is longer prep or longer repairs. If the locomotive class reduced its time spent out for repair by way of design, then that's a win. If it didn't, then you'd argue the time offset by way of design against prep wasn't a net gain but potentially a loss.

    This is why, fundamentally, having statistics like the above to play with can really change how we view a class of locomotives. Getting the full picture by way of the statistics allows us to examine more fully if the secondary evidence supports the primary or not.

    It's why I am expecting my dip into the southern railway's archives to likely show there were salient reasons for developing the Bulleid Pacifics as is, and I am becoming more confident that their original design was fit for purpose and probably the key issues highlighted were overplayed.
     
  14. 35B

    35B Nat Pres stalwart

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    No. Neither been on footplate nor under the frames - which is why I asked.
     
  15. Jimc

    Jimc Part of the furniture

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    Well that depends. On the GWR prep was a piece work task. So reducing prep time made no difference to the bottom line unless the locomotive department was going to renegotiate all the rates with the union. There were, incidentally, just two rates, large engines and small ones.
     
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  16. 8126

    8126 Member

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    The bottom line isn't necessarily the only factor here. If you consider a time saving as the difference between getting your loco out on time or not, the advantage perhaps reappears. The Southern experienced this in wartime, with Arthurs subbing for Nelsons, not because the Nelsons weren't available but because the Arthurs were quicker to prepare. Both would have attracted the large engine rate, under a comparable system, but if resource constrained which would you rather be trying to get out on the road?

    Admittedly, I have read of P&D crews on piecework going home once their allocated number of locos for the shift was met, regardless of the time actually taken or the number of locos still waiting for disposal on shed. In that case you still arguably win with a loco that's quicker to prepare and dispose, because you get the same number done but they're still ready sooner.
     
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  17. Jamessquared

    Jamessquared Nat Pres stalwart

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    In principle high availability is a good thing, because it reduces your overall loco requirement, and therefore your capital requirement. For example, if you have duties requiring 24 locos at any one time and Class A has 80% availability and Class B has 60%, then you would need to build 30 locos of Class A or 40 locos of Class B to ensure always having 24 available, i.e. Class B offers you a net saving of 10 locos.

    The issue is complicated though due to the capability of locos. The SR - particularly on the Eastern Section - had a combination of particular difficulties on its main routes to Dover and Folkestone. Weak bridges, heavy gradients, often approached via extreme speed restrictions so they couldn't be rushed (Sole Street Bank was 5 miles of 1 in 100 approached via a 15mph curve at its foot) and heavy boat trains. The result was frequent recourse to double-headed 4-4-0s. In that regard, if a Pacific with 60% availability can substitute for two Wainwright 4-4-0s with 80% availability, the Pacific may still end up being cheaper to operate, not least in terms of crew.

    SR loco availability and mileage is also complicated because the traffic was very "peaky" and older locos were kept for use during the summer but then rusticated over the winter. So the nominal availability and mileage may be harder to interpret: a loco that is winterised in the back of a shed and therefore not available for service may not be an issue provided it could be got ready for use by Easter. And the winter boat train headed by an L1 4-4-0 might become a summer train double-headed by an L1 and D or Stirling F1; which then get replaced by a West Country that is under-worked during the winter on a light load ...

    In other words, the figures will be really interesting, but you will need to interpret them "in the round" rather than just comparing numbers. With Bulleid pacifics, I think a lot of the thought process needs to be around "by building them, what were they able to replace?" and the flexibility that that drove.

    Tom
     
  18. Cosmo Bonsor

    Cosmo Bonsor Member

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    I find this sort of technical discussion interesting, partly because I used to work in a factory that made gears. I was a machinist, then in QA.

    Firstly TL;DR, the chain driven gear was not the big problem it has been made out to be.

    The chains lasted until the end and as has been said, Drivers liked the original WCs. It must have been great for the traffic department to have light, powerful and free steaming engines at their disposal, especially in the West. Tom talked about the reversers being more of the villain of the piece earlier up thread. This is from a document produced by my former colleague Tony Deller. He ended his BR apprenticeship with six months in the valve setting gang at Eastleigh. He was there and wrote it down. Is that primary evidence Simon? I hope more of his papers come to light. I will ask a mutual friend about them. I was more interested in picking his brains on Stephenson’s gear while working with him. There were others more interested and knowledgeable about the pacifics than me. Also I only drove an original once as a Fireman, so not much direct experience there, I’m afraid.

    It would be interesting to see a set of cylinder diagrams taken when an engine was put into traffic after overhaul, then just before it went back, just to see how much the valve events had changed. I would be surprised if this ever happened though. My mildly glib remark about other three cylinder gears was referring to Bulleids earlier work. He must have known how the conjugated gear performed in day to day service and understood the practical issues that arose. How unlikely is it, that this experience didn’t feed into later designs?

    The original idea for shafts intrigues me because of the gears needed. You must have running clearance between gears, known as backlash. The only error this induces in a valve gear is between forwards and backwards running. The wear over time would be very small indeed. The phasing of the crank shaft to the jockey shaft is set at construction. There should only have been two UJs and a splinted joint on the first cardan shaft and six bevel gears in total as I envisage the drive to work. A pity it was not done, but as we know, the gears were needed in machines to drop things on people. I really would like to see a digital or actual model of this.

    Lastly, any one running a Bulleid on Ovoids at the moment? It’s when you need a big engine to cope with not such good fuel.
     
  19. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Incredible stuff and just the sort of "hands on", and "there at the time" evidence we should be looking at.

    Primary evidence is defined as:
    • archives and manuscript material.
    • photographs, audio recordings, video recordings, films.
    • journals, letters and diaries.
    • speeches.
    • scrapbooks.
    • published books, newspapers and magazine clippings published at the time.
    • government publications.
    • oral histories.
    If it comes under any of these, then it's primary evidence.

    I'd be very interested in reading them too, and happy to remunerate accordingly for the privilege.
     
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  20. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    This is a really interesting and insightful post. As a driver of the locos in the modern day, do you feel the miss reporting of the issues with the locomotives is mostly down to apocryphal stories?
     
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