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P2 Locomotive Company and related matters

Discussion in 'Steam Traction' started by class8mikado, Sep 13, 2013.

  1. The Green Howards

    The Green Howards Part of the furniture

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    Does the Doncaster P2 LT have any representatives on this forum? It would be interesting to hear from them first-hand.
     
  2. Pesmo

    Pesmo Active Member

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    Fascinating seeing the P2 monoblock design. If the Franklin valve mechanisms are going to be similar in design to that shown in the 2015 edition of the communication cord the outer cylinders poppet valve gear looks to have reasonable access to maintain. However the central cylinder inlet valve mechanism looks to be an a very difficult place to access right under the saddle and looks like the exhaust valve mechanism would have to be removed first to get at it. Am I misunderstanding the drawing or perhaps the centre cylinder has a different valve design ? Are the Franklin valve mechanisms reckoned to be low maintenance items ?

    Looking forward to seeing how all this ties together including drive shafts etc.
     
  3. 242A1

    242A1 Active Member

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    Come on class8mikado, you must have access to enough information. Piston valves in the modern, Porta style are designed the way that they are with leakage avoidance as a fundamental objective. I call 80,000 km achieved a good result, particularly with respect to the gauge on which this was expected- 750mm. The multi-element packing are similarly impressive. So leakage on modern piston valve applications is of a very minor order. If you put a piston valve fitted new build into service today, or any other day come to that, and you find that leakage is in any way significant then you need to give the covanators and donators their money back with interest.
    I understand the P2 monobloc situation but they have made life difficult for themselves in pursuing a form of valve gear which, in the light of experience to date, offers little or no advantage over best piston valve application. Chapelon type OC poppet valves are not the ones in the final equation here. The British Caprotti application as fitted to 71000 is in question here. It has been matched by piston valves that are less than the best that this type are capable of. And I haven't raised the question of mechanical longevity yet.
     
  4. class8mikado

    class8mikado Well-Known Member

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    This is a Frustration is it not ?.
    Consider the few instances of British preserved locomotives needing a replacement cylinder. How many owners even briefly considered putting the other one on the market and having the design reappraised before casting/ fabricating anew.
    Most new builds have been pragmatic towards improving the known shortcomings of their chosen recreations but very little beyond that. Its almost seen as ' cheating' to look at anything that's come about post the time they we're in service. i.e. No doubt Patriot will have those LMS cylinder cocks that never seem to shut properly, it already has a Victorian smokebox and I suspect the prospect of changing the appearance of the chimney was a step too far for a possible improvement in draughting... but it will be a more accurate recreation for these very reasons.
    With P2 I would not have been happy if they had chosen the easy way out (Walshshaerts, cylinders, Gresley conjugated etc off the Doncaster drawing board), I am happy obviously that they've chosen a pertinently improved version of the Poppet valves on 2001. But im not that partisan that coming up with a new 'engine' based on redeveloped piston valves would have been a disappointment, far from it.
     
  5. Tim Light

    Tim Light Active Member

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    This is a bit of an aside, but 73156 obtained its Caprotti valve gear from a Malayan Class 56 pacific. This picture shows 564.21 "preserved" at Melaka, with a big gap where the valve gear should be. Was this the donor for 73156?
     
  6. JJG Koopmans

    JJG Koopmans Member

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    Outside the subject here, but one does not needs to change the appearance of the Patriot chimney, there are simpler ways for proper improved draughting!
    Kind regards
    Jos Koopmans
     
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  7. class8mikado

    class8mikado Well-Known Member

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    Patriots we're i understand quite good performers so they must have steamed quite well - but intuitively even on a three cylinder loco if a chimney that small is draughting well surely there s a cost for that in the system somewhere... PS your book is on my Christmas List.
    Not too sure but iirc only selective bits were required from Malaya (return crank gearbox... ?)
     
  8. Foxhunter

    Foxhunter Member

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  9. daveannjon

    daveannjon Active Member

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    I must admit I was a bit disappointed that the Patriot will retain the original small tube size which was reckoned to be slightly too big, with the result that when working really hard the superheater flues are a bit starved of their share of the hot gasses, but with a brand new loco in otherwise excellent condition it probably won't matter too much.

    Dave
     
  10. LMS2968

    LMS2968 Well-Known Member

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    It didn't at the time.
     
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  11. Tim Light

    Tim Light Active Member

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    I sometimes wonder whether people building replicas are motivated to recreate what once existed, or feel a need to iron out all the imperfections of the original class. We heard a lot about the design advances on Tornado, the various tweaks to 71000, and the need for Flying Scotsman to be in its most advanced form. I wonder how necessary this is? These classes coped OK in their heyday with heavier loads at higher speeds than are allowed today. Perhaps it's the creative engineers on the team that want to do more than just recreate the original design. I don't suppose it really matters so long as the engine looks right, sounds right and does the business.
     
  12. 242A1

    242A1 Active Member

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    I have read more articles than I would care to fully remember. But I would ask if you have read Porta's proposal to the A1 Trust, any of Porta's published papers, David Wardale's "The Red Devil and Other Stories of the Steam Age", details of the design of the 5AT, Chapelon's "La Locomotive a Vapeur" - I could go on.

    The "free exhaust events" means what exactly? RC gear to date has offered little or no thermodynamic improvement over readily achievable piston valve practice. And don't believe that piston valves cannot be improved further. You have to be very careful with exhaust events, you do not want to have a deleterious effect on the firebed. The phenomenon of carry over should be minimised, you want your fuel to be subject to combustion and not launched in raw, uncombusted form out of the chimney. Poppet valves can achieve this wonderfully well, and so can more conventional valve types.
     
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  13. Steve

    Steve Resident of Nat Pres Friend

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    In the case of the Patriot, especially, I think that it needs to be exactly as the original, warts and all. If you set out to improve it, you may as well be producing the taper boiler version. After all, that was improving on the original.
     
  14. Gav106

    Gav106 Active Member

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    With regards to the Patriot we have always said we are building one as close to original as possible. We are not out to break records or show what can be achieved if you change this this this and this. Just here is a patriot with an original boiler built to traditional designs, with British engineering to keep the skills alive in the UK using locations that do apprenticeship schemes. The originals had a good reputation when in good condition and that's good enough for us. We did for a while look at the draughting but decided that if we produce a loco that doesn't even sound like a patriot then we wouldn't be happy. People liked the look and sound of a Patriot and have given us money to produce that so we are doing what our members want as they are the people giving the money
     
  15. LesterBrown

    LesterBrown Member

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    From my point of view 2999 will have too many improvements already with the use of an existing boiler.
     
  16. Spamcan81

    Spamcan81 Nat Pres stalwart

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    But that is historically correct as she is running in the mechanical condition that is accurate for the latter days of her BR career. In preservation she was fiddled with but AFAIK those "improvements" have been removed. Whilst I'll agree that the locos mentioned above did indeed cope with heavier work in the past, they had the backup of a major railway works with a large workforce, an almost inexhaustible supply of spares and the deep pockets of a large railway company so if something did go wrong rectification was relatively simple and affordable. These conditions do not apply these days so I can understand fully why loco owners won't want their locos worked to the limit on a regular basis.
     
  17. class8mikado

    class8mikado Well-Known Member

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    An Interesting Point. The Tornado Boiler and the original P2/1 differ in a couple of respects, 1) the so called Combustion chamber which might be of some help, 2) the longer smokebox which again might be of some help and a tube bank that is 2ft shorter which may not.
    Expect that the same Kylchap dimensions (Tornado) rather than the Original P2 are being used ? However the Larger Cylinders and very free exhaust may, certainly at starting, produce a serious pull..... shame if all that power and adhesion cant be exploited at starting because of having to pussyfoot around the exhaust throwing the fire... having said that on todays relatively light trains performance at 30mph plus on a 1 in 70 is the main focus
     
    Last edited: Dec 23, 2016
  18. 242A1

    242A1 Active Member

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    I suppose it depends on what what you are building and the work that you are expecting of it. A replica should be as historically accurate as can be achieved, warts and all. It doesn't matter if it is restricted to preserved lines only or has only a modest haulage capacity. Poor cab layout, difficult to prepare and dispose of, indifferent steamer, needful of regular attention to some design weakness that you might wish didn't exist - it doesn't matter so long as what you are creating fills an important historical gap. Whether the machine would see much use is another matter.
    Tornado was not proposed as a slavish copy of a 1940s design. You could call it a Peppercorn A1/2, a modestly modernised machine more suitable for late C20/early C21 construction better suited to mainline running than existing types.

    71000 was a one off prototype that was hindered by some poor design decisions amongst other things. It is a fortunate survivor, the enthusiast community is so very lucky to have it. It remains a work in progress and it remains to be seen quite what will have been done to the finished article and how it will differ from the original as produced by BR.

    Flying Scotsman in a more advanced form (not the most advanced) was at one level worth achieving. Better and more forgiving steaming with a far higher power output is very much needed on the modern mainline. However if you were going undertake such a project in a more successful and balanced way, well you could, but you would need to carry out more work on improving the chassis of the machine. If the frame design had been improved then the some of the problems faced by the NRM would not have existed. But the owner would have needed far more money and much of the LNE heritage would have disappeared. Actually an owner with that much in the way of resources would still own the engine.
     
  19. ragl

    ragl Well-Known Member

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    With all of the ongoing discussion regarding the fitting of Poppet Valves to 2007, I don't see the problem; historical precedent can be followed and it could be re-built in due course with piston-valves and Walschaerts valve-gear and then............... into a Pacific???

    Cheers,

    Alan
     
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  20. John Stewart

    John Stewart Part of the furniture

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    Even if dedicated to total authenticity it would be normal to improve the specification of things that had a reputation for wearing out rather quickly. That could be a design change, a superior material or the use of modern lubricants and delivery systems.
     

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