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Edward Thompson: Wartime C.M.E. Discussion 2012 - 2021

Discussion in 'Steam Traction' started by S.A.C. Martin, May 2, 2012.

  1. RLinkinS

    RLinkinS Member

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    The P2s pre-dated the A4s. I believe that the steam circuit was improved compared to the A3s and this improvement was carried forward into the A4s.

    Sent from my SM-A105FN using Tapatalk
     
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  2. 30854

    30854 Resident of Nat Pres

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    Interesting notion, though HNG also followed American developments closely. Did he perhaps regard the P2 as a passenger development of the P1, also constructed with one particular duty in mind? For that matter, was either P1 (or other 8-coupled loco) trialled on the Aberdeen line, ahead of work on the P2?

    Stylistically speaking, I'm aware of nothing vaguely close to the P2's original form, being so distinctive that (possible heresy warning) I've occasionally pondered Bulleid's precise involvement.
     
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  3. Hermod

    Hermod Member

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    Are there any written record of management or traffic department wanting 80 ton adhession 70 mph locomotives for Aberdean before design started or did HNG , who knew of Chapelon and the 4-8-0 in 1934, want to show what he could do?

    Same adhessive mass and wheel diameter.

    In 1934 crisis was really biting and not a lot of pe0ple in UK can have been able to pay for fast travel to a fishery harbour.
     
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  4. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    But Jim - I’m not arguing against the design concept of a mikado.

    I’m simply pointing out that at that time, the Pacifics were matching or in fact bettering the performances and utilization of those specific mikados at that specific time.

    6 non identical locomotives, versus nearly 100 pacifics of A10, A3 and A4 and the W1 which were all performing better than the P2s, even on the same work. If a pacific can do the job required - then the argument for a mikado falls away.
     
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  5. MellishR

    MellishR Part of the furniture Friend

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    Besides the documented much better availability (and lower coal consumption?) were they any better at pulling the trains when they were actually out on the road?

    Assuming all else equivalent (same boilers, crank axles not prone to breakage, etc) wouldn't the better adhesion of the mikado be beneficial at times (wet rails, leaf fall, a heavier than usual train or a driver who is less skillful at controlling a slip)?

    Thompson made them into better locomotives, but we're left wondering whether in principle they could have been better still as Mikados with their various faults cured or whether the information and ability to achieve that were unavailable at the time.
     
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  6. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

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    An off-thread comment but it is an interesting suggestion that maybe the P2 was an experimental locomotive design, if that's what you are implying. In common with Bulleid, I believe, Gresley was much influenced by European locomotive design and quite rightly paid particular attention to the work of Chapelon. Given that Bulleid built 140 of his design that can hardly be called experimental even though they contained elements that were untested but he was also providing a solution to a known problem/need of the time on the SR.

    With the P2 it's not clear to me what problem these locomotives were really meant to solve north of Edinburgh. It surprises me that there was demand on the line for trains of significant length and therefore requiring such a locomotive to handle load and terrain. So maybe Gresley was simply looking for somewhere to draw on continental experiences and try out a different design idea in the knowledge that if it were unsuccessful there were existing locomotives he could fall back on.

    He is not around to ask and as we have discussed already, getting access to truly objective assessments of locomotive design, use and performance is not always easy if anyone relies exclusively on commentaries from stock authors of the time.
     
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  7. Jimc

    Jimc Part of the furniture

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    Playing a bit of a devil's advocate here, but isn't that a bit of a circular argument? You design locomotives for the trains you want to run, but you run trains with the locomotives you have. So one presumes the 2-8-2s were designed with a view to running services that would be beyond the capabilities of the six coupled classes, else why bother. But when the 8 coupled locomotives turned out to be lemons, then surely the trains run must have been sized to be within the capacity of the smaller classes - if indeed, the trains were ever increased to the planned size. And "same work" is a very difficult thing to evaluate. Timetable, acceptance of late running, load, all these things could be subtly varied.
     
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  8. 62440

    62440 New Member

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    It would be interesting to see and compare the wordings of the operating instructions on size/weight for the P2s and the rebuilds.
     
  9. Spamcan81

    Spamcan81 Nat Pres stalwart

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    But the ECML south of Edinburgh is a completely different kettle of fish to that north of Edinburgh so some of the problems attributed to the P2s on the Aberdeen road my not have materialised. As for a shedmaster being "happy to have them'" being a laughable idea they didn't always get a say in the matter and do you have primary evidence for that remark? Do you also have any figures regarding such use as they did get out of Kings Cross before being sent to Scotland?
     
  10. 30567

    30567 Part of the furniture Friend

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    I don't know whether others would agree, but I find Townend a credible and authoritative witness. He says at the end of four pages on the P2s in typical careful fashion

    ' The P2s were restricted to certain roads in sidings and depots and despite thinner tyre flanges on the middle two pairs of coupled wheels could officially negotiate a minimum radius curve of 7 chains compared to 6 chains for the Pacifics. The P2s occasionally worked over the GN main line from KX, but their regular use would have caused some difficulty from this point of view as there were a number of tight curves in the KX station and depot area. When checked carefully in recent years due to frame management problems with more modern traction units, the sharpest curve measured over a short distance was found to be under three chains in radius, although negotiated by Pacifics for many years.'

    I agree that the ECML itself was a different kettle of fish, but that suggests other problems may have been a factor in the P2s not being given an extended trial down south. Surely in 1940/41 conditions with the loco starting 20 coach trains in Gasworks Tunnel, the combination of power and adhesion would have been, to say the least, useful.
     
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  11. Eightpot

    Eightpot Well-Known Member Friend

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    Wasn't the idea behind the P2s to eliminate double-heading on the Edinburgh to Aberdeen route?
     
  12. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

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    Just more than a bit of drum banging with that comment along the lines of 'I'm going to pick at anything you say to ensure you have concrete evidence for that remark"

    It's a pity that some of the authors who have gone before were not subject to such scrutiny. It might have prevented some of the contentions on here being repeated.
     
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  13. 30567

    30567 Part of the furniture Friend

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    That's what Townend says, but there are then a couple of pages about the problems with the crank pins, possible remedies etc. He also says that slipping and failure to restart a train uphill were unknown with the P2s.
     
  14. Hermod

    Hermod Member

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    Continental six feet(or thereabout) driver Mikados had some kind of KrausHelmholz or Zara truck up front.
    When Chapelon rebuilt a six feet pacific to 4-8-0 this was not a possibility so he thinned the flanges of mid drivers.
    HNG wanted to employ his conjugation (patent) and Swing-link front truck (patent) and so selected to follow Chapelon with thinned mid drivers but on a big wheeled Mikado.
    Chapelon 4-8-0 low pressure inside cylinders yielded almost as much power to a two bend front crankshaft as did the three P2 cylinders to the second driver single bend.
    This extreme care for the crank was the excuse for the conjugations.
    Cab and footplate looks nice on HNG locomotives and the rest was so so.
     
  15. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    There is no doubting the material benefits of an eight coupled wheelbase over a six coupled wheelbase. That is not the issue here. The basic line of contention isn't "were the P2s capable of prodigious acts of haulage" - it's whether they could do their day job efficiently and with minimal expense to the company. Which - with respect - we have proved beyond all reasonable doubt on this thread that as P2s, they did not, and without major modification, could not. So the bottom line is that the six coupled locomotives, including classes A10, A2/2, A3, A4 and W1 all did their work and had better mileages and availability.

    But the point Jim is that the six coupled machines were found to be up to the task on all the trains the P2s were rostered for. That was why the A4s supplemented them, why the W1 was compared to them, why Thane of Fife as an A2/2 was compared to the 5 P2s for a year. The report from the emergency board minutes is explicit:



    Bolded for emphasis.

    That's very speculative. We simply don't know, and won't have anything comparable bar the new locomotive which will incorporate all of the fixes that the P2 Trust have decided is necessary for the design to work reliably on the national network. I think however the work done by the P2 Trust in their new P2 suggests strongly that where the original P2s ran was secondary to the design deficiencies: if it was simply the route, given how Network Rail tends to smooth out curves in design these days, if it was just the route, the design wouldn't have been amended as much as it has.

    We do not have quotes from relevant shedmasters saying they would not take them on: however I challenge you to find a single locomotive shedmaster in the whole of human history who would be presented with a locomotive class whose availability is under 50% and mileages less than a third of that anticipated in a year who would be willing to take on such a locomotive to add to their fleet, and thus skew their own numbers by way of reducing the overall availability and average annual mileages at that shed. Can guarantee you that nobody - nobody - would have taken the P2s on aside from those sheds they were already stationed at.

    I do in fact, but I have to have the figures verified independently before publishing (I intend on putting them into my Gresley book). Suffice to say, you'd expect the figures to be better than their work in Scotland. Not the case I am afraid, only proving that the best of the class, really, was Wolf of Badenoch as a P2 and that the worst was Cock O' the North and Thane of Fife together for different reasons.
     
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  16. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Yes, but double heading was gone anyway for the work they were doing by the time of the second world war, and with the Pacifics and W1 proving fully capable of the work the P2s did, we are left with the question of necessity for an eight coupled wheelbase again.
     
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  17. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    He absolutely is, which is why he is mentioned by name and thanked in my book's special thanks section. I discussed over email the availability statistics with him last year and we both came away with a greater understanding of the P2s in particular. I dare say that we changed each other's minds on certain aspects of the arguments for and against.

    But by 1941, there had been several crank axle failures, availability was poor, mileages were down, more V2s were coming into service and the Pacifics were proving superior in every way. The additional adhesion of the P2's wheelbase does not somehow eradicate their other issues and that there were similarly powerful locomotives that were doing the same or similar jobs better. In addition, there were only 6 of them: compared with nearly 100 Pacifics and by the end of 1941, over 100 V2s. Moving the entire class would have made minimal difference to the ECML, in my opinion.
     
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  18. Jimc

    Jimc Part of the furniture

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    Which is interesting really.
    Bearing in mind the theoretical superiority of the 8 coupled its possible to make a number of guesses as to why that should be. But speculation not useful without evidence.

    Its hard to avoid thinking that from a technical viewpoint the A1 trust should have built a second A1 rather than to try and fix the flawed P2 design, but of course the P2 would be a lot better at the critical factor of attracting cash donations.
     
  19. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    I once said (jokingly) to a member of the trust that they should have built a Thompson A2/3 Pacific, given the commonality of parts between the development of the classes (P2 > A2/2 > A2/3 > Pep A2 > Pep A1).

    The fact remains that I am a founder member of the P2 Trust (no.103). So there's my bias on show!
     
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  20. Hermod

    Hermod Member

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    The cabs of the A2/2 make them look faster than the 2/3s
     

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