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Loco musings ex the 71000 thread

Discussion in 'Steam Traction' started by m&gn50, Feb 25, 2013.

  1. m&gn50

    m&gn50 New Member

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    Sorry my message is a bit garbled, E.S.Cox speaks of GRESLEYs middle cylinders problems with valve expansion/contraction in the middle cylinder due to the extremes of temp(I'm not an engineer), I wondered if this may affect middle cylinder mechanisms such as poppets in general, as spindle wear was noted on the Claughton inside cylinder spindles (not a problem with regular overhauls); but it sounds like this can be adjusted. He has quite a lot to say on Caprotti from the 'Claughtons' and its slightly inferior cousin the Lenz and its most interesting in general. Anyone know of any books on the later version?
    I was wondering if modern materials could iron out the problems on Gresleys middle cylinder, with heat resistant big end and less variable expasile piston valve(it has all been proposed in the aboves papers some 60 years ago by someone who knew more about this than a modern engineer can do, has materials moved on such that his changes could be made to save wear? If anyone is going to be building a P2 if its Gresley gear this can surely be corrected nowadays(?) to make it improved and should be looked at, but if its Caprotti vs Lenz, go for Caprotti (it must surely sound similar?)!
     
  2. class8mikado

    class8mikado Well-Known Member

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    A lot of the Gresley Middle Cylinder problems were a result of the derived (conjugated) Gear which under certain circumstances (exarcebated by anything less than regular maintenence and accurate alignments) effectively worked the middle cylinder at a higher 'Cut off' than its outside counterparts. This overworking of the Middle engine combined with the split (and therefore the weakest) big end bearing led to .... problems.

    The Bearing design and general accuracy of alignment was much improved under BR by ex GW chap KJ Cook, this with regular maintenence checks almost eliminated the Gresley Middle engine problem.

    Concern for the Middle engine was the main reason that BR Caprotti was trialled on 71000 in the first place...

    Note BR Caprotti is a distinct step up from Caprotti / Lenz, both in Robustness and sophistication, though currently it isnt living upto its 'Robust' tag....which hopefully can be worked out because its a brilliant concept...
     
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  3. pjhliners

    pjhliners Member

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    The last two Pacifics at Crewe 20 April 2013

    At last, a Saturday with warm spring sunshine saw new-build A1 4-6-2 No 60163 Tornado passing through Crewe on a Cathedrals Express from Euston to Holyhead, on the same day as the last and most powerful Pacific built by British Railways, No 71000 Duke of Gloucester was on public display a few yards away in the Crewe Heritage Centre. The opportunity to photograph these two iconic locomotives during one outing was not to be missed.

    12 photos are at Zenfolio | Peter Hewitt's Transport Pictures | The last two Pacifics at Crewe 20 April 2013

    Peter, at the end of a fine spring day in the North West
    Zenfolio | Peter Hewitt's Transport Pictures
     
  4. 242A1

    242A1 Active Member

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    The fact that the BR Caprotti gear is showing signs of a lack of 'Robustness' will not be a surprise to some readers. The D.of G. people are going to have to find a way round this issue. It could be said that the gear is an expensive and overly complicated solution to a non existant problem. 71000 does not deliver a good mileage between failures. Imagine what fate would await such a locomotive if it had, in theory, to be relied on in traffic on a daily basis. It remains a one off prototype true enough but on the present showing 71001 would have done a 2002, so to speak, and would be fitted with piston valves.
     
  5. maddog

    maddog New Member

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    Just out of interest how did the caprotti standard 5's fare in service? 73129 is still around, so can't of been that bad surely? Has that had any significant problems in preservation?
     
  6. paulhitch

    paulhitch Part of the furniture

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    Don't know the answer but can observe that the "last hurrahs" of Andre Chapelon and Marc de Caso both reverted to piston valves. Everyone interested in steam locomotion should see de Caso's 232 U1 once in their lives and the sight ought to cause them furiously to think. Knowing British attitudes to "abroad" I fear such thought is out of the question!

    PH
     
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  7. Big Dave

    Big Dave Member

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    Some amusing concepts here.

    Logically the valve gear is a relative new to steam, but it works damn well in your car.

    Piston valves by their usage will always tend to wear in a barrel shape and require fairly regular reboring.

    I personally don't think the DoG is that far from being right. it has a good many miles to it's credit already, and what miles they are.

    I once thought the Duchesses were the be all and end all of British steam,.

    You probably cant compare the performance of 73129 as in my view they went backwards when they fitted single chimneys.

    The direct prototypes were 44686/7 which by all accounts were very fine machines and were used on class 6 turns.

    Whenever I see the DoG the operation of the valve gear strikes me as the optimum of elegance, no levers to thrash around.

    I've said my bit now so I will shut up for now.


    Cheers Dave
     
  8. 242A1

    242A1 Active Member

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    True Chapelon did revert to piston valves. There were two main reasons for this. Leakage being one (probably the most important to his mind) and the matter of training staff to maintain the new type of valves and associated gear being the other. Leakage is a huge problem on the steam locomotive as it can consume 50% of your evaporation. Piston valve liners do require reboring but in this day and age some 25,000 miles should be possible between rebores at 0.0012" of wear. That is with all other things being equal; quality of valve design, materials used, lubrication. There should be little leakage experienced and the valve rings should be good for even higher milages. Expansion and distortion of the cylinder casting (pressure and heat) was the cause of a large part of the problem with poppet valves so much so that the extra complication of elastic seating was introduced.
    The B.C. gear is an attempt to create something rather more complicated than what used to be found in a car (as you know some i.c. engines are fitted with variable timing) and the railway is not a place for less than robust engineering. There is another point. The generally accepted rule is that the steam chest volume should be as high as the cylinder volume and I am not sure how you achieve that with the B.C. gear fitted. Another factor to look at are the clearance volumes. These was a source of concern on 2001 and I wonder what they are on 71000? If anyone has the numbers could you please advise, thanks.

    I am with Paul Hitch, everyone should see 232U1 (and 231E22 - though if you wait a few years you might have a chance to see 231E41 in action)
     
  9. class8mikado

    class8mikado Well-Known Member

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    I like your bit Dave, the Caprotti 5's were judged such a success that the Gear was considered for more widespread use, however apart from a few 9f's and the Bulleid Pacific conversions, there were no new orders for BR Steam locomotives on which to apply it. The main plus of the gear was that valves did not need to be reset at intermediate overhaul.
    Have very little to say to 242A1 Other than to say he clearly doesnt understand the BC Gear and cannot distinguish between sophistication and complication. Seperated adjustment of inlet and outlet valves has been on the wish list of Locomotive engineers since stephenson, BC was the first reliable system to achieve this, that isnt to say other methods arent better or that poppet valves are better than piston valves.
    Where i can agree on a significant point is that the improvement in cylinder performance realised by BC gear is of a magnitude that a modern exhaust system such as lempor easily achieves and unless someone buys the Caprotti 5 and tinkers with its exhaust ( shame to loose that fantastic noise though... which clearly demonstrates the draughting is not right) that combination isnt available for appraisal or at least not in the UK
     
  10. 242A1

    242A1 Active Member

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    Well Class8mikado I have a rather good understanding of poppet valve gears and used to think of them as being something of a dream/final solution. However I chose to scratch a little deeper and then some more and so no longer see any need to have any great faith in them. They are interesting no doubt but consider this; for those people who have put so much in the way of time and money into 71000 would they rather see their locomotive at work or laid up awaiting futher analysis, development and repair? You can achieve the same cylinder performance using piston valves as you can with the BC gear. A more advanced exhaust system improves any engine regardless of the valve gear fitted. How many preserved locomotives with mainline certification, apart from 71000, have been laid low by unfathomable defects in their valve gear? I can think of the odd link being bent but nothing that could not readily be rectified. The components in a locomotive fitted with convensional valve gear have been developed to a good level of refinement and are far easier to manufacture than the components for BC gear, you can incorporate a variable lead function (see D & R G) if you wish to. It is not about sophistication or complication but rather about the search for the best solution. Chapelon, de Caso and Porta all gave up on poppet valves for very good reason. Check it out.
     
  11. class8mikado

    class8mikado Well-Known Member

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    Confused that you want to argue with me about the things we agree on as well as the ones we dont. (can you advise what D & RG is also)
    However imperious your technical argument and/ or well meaning your appraisal of the better solutions out there the chances of 71000 with anything other than the BC Valve gear it has is probably nil
    There are only two remaining engines with this particular variant of the gear and it is part of their identity for good or ill. You may as well say that Gresley conjugated gear is 'less than ideal' and suggest that flying scotsman be re built with three sets of walshaerts, or have the Joy gear on the G2a replaced or tell the owners of original condition spamcans to have them rebuilt as compounds.
    Whatever technical high ground you wish to defend its a pretty pointless argument - maybe you want to pick on 71000 as its held up as the best thing since sliced bread when in fact its simply an overboilered machine with quirky (but nevertheless very effective when it works) valve gear that has produced some excellent ( by British standards) performances. Its because i dont understand your motivaion that i dont care for your arguments however sound they may be...
     
  12. Big Dave

    Big Dave Member

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    Comparing the Duke as it is now to Chapelon's era is illogical Chapelon was dead before the Duke reapeared in the form it's present form so he could not comment on it.

    I totally agree that good steam passages both to and from the cylinders are an ideal to aspire to.

    Less than ideal valve events will nullify advantages gained in good steam passages.

    BC valve gear is a holy grail for engineers the gear is altered to provide torque at low speeds and is adjusted to optimise as speed rises.

    This lack of variation was the probable cause of the early caprotti 5's lack of guts.

    Simply put if you have a car whose valves have too great a dwell angle it will exhibit the same characteristics poor low speed performance but great speed once the rev's rise.

    Incidentally Sentinel thought enough of poppet valves to use them.

    Incidentally is the Duke's present situation due to mechanical problems or political nones.

    Come on guy's get it sorted so we can all see this magnificent piece of British engineering doing what it does best.

    Cheers Dave
     
  13. class8mikado

    class8mikado Well-Known Member

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    Ironically Chapeleons comments on the original 'choked up' 71000 and the valve gear settings have subsequently been put into practice and are one of the reasons that it can now raise 50,000lbs/hr steam. and probably evaporate its own firebox in the process

    Does anyone else on here think that 71000 should be rebuilt with conventional Piston Valves/ walshaerts gear or similar ( and how theyd derive the valve events for the middle cylinder ) ?

    Afaik the recent problems would need a strip down of the motion to investigate fully. Since one of the tube plates (and a couple of other bits) are nearly expired ? so the decision has been to combine the strip down with the overhaul - for which there is insufficient funding at present - which puts 71000 in the same Hiatus as quite a few locos, Blue Peter for example.
     
  14. detheridge02

    detheridge02 New Member

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    I think the chances of converting the valve gear on the Duke are a non-starter. Even if the owners wanted to do so the engineering required to convert would be cost prohibitive. New cylinder blocks, new design to control the middle cylinder, new motion, new exhaust arrangement and new control linkages to the cab.

    At the end of the day even if all these could be achieved it would reduce the Duke to an over-boilered Brit. As she is she's a unique prototype from a class that was never fully developed by BR just as the Clans were never fully tested and improved.

    Blue Peter is a complex issue, a shame as it would be great to see A1,A2,A3 (eventually!) and A4 together in steam just as it would be great in a few years to have a BR Standards line up of 2MTT*, 2MT, 3MTT*, 4MTT, 4MT 2-6-0, 4MT 4-6-0, 5MT, 6MT*, 7MT, 8P.

    *denotes not yet complete. There were rumours of a 3MT 2-6-0 new build but nothing seem to have been heard in years.
     
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  15. 61624

    61624 Part of the furniture

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    Don't think 60532 is a complex issue at all. From what I've heard it's just a case of an owner who can't afford to overhaul it himself, but thinks it is worth silly money as a result of what was paid for 4472. If he was willing to part with it for a sensible sum I think the rate limiting step on it running again would be the speed at which it could be overhauled.
     
  16. class8mikado

    class8mikado Well-Known Member

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    Suspect tha 60532 needs quite a complex / expensive overhaul. So whoever wants her will need to spend that silly money and some more silly money for the overhaul.
    As a supply and demand issue if youve got a few million quid you can buy an 8p Steam loco, if you havent - you cant. they dont grow on trees. Even a new one costs silly money and takes years to build so if Blue Peters owner doesnt need the money... at least shes under cover, in one piece and on display.
    Clans i think will prove excellent Value for money in comparison and the order book is open; available in a wide range of colours*
    can be supplied with a range of tenders, valve gear, draughting Gizmos, whistles bells etc (* Green mostly, Green cylinder covers, no lining out and cabside stripe as required... )
     
  17. MarkinDurham

    MarkinDurham Well-Known Member

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    Whilst I don't want to go OT, 60532 is believed to require a new middle engine cylinder block, which is a big expense, of course, although not a big issue technically.

    Back OT, I agree that converting the Duke to conventional Walschaerts gear is not the way to go. I await the revealing of the cause of the valve problems with interest; as do many others, I suspect. Here's to a successful return to service of 71000 in due course.

    Mark
     
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  18. b.oldford

    b.oldford Member

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    Dave

    I think the general consensus within the 82045 team is they would assist anyone seriously contemplating a Class 3 mogul with advice and the use of tooling but view building one engine as enough.
     
  19. daveb

    daveb Active Member

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    and 9F?
     
  20. detheridge02

    detheridge02 New Member

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    And 8F for that matter :)
    Dave
     

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