'Britain's Most Powerful Steam Locomotive' - The P2?

Discussion in 'Railtours & Preservation' started by alexl92, 18 Sep 2018.

  1. alexl92

    alexl92 Established Member

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    The A1 trust/P2SLC, for whom I have massive respect and admiration, have been selling the P2 new build as 'Britain's most powerful steam locomotive'. I don't wish to question their integrity, but I have to ask - is it really more powerful than a BR Standard 9F? What would its' power classification have been, under BR?

    Thanks!
     
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  3. etr221

    etr221 Member

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    I believe yes, the P2 is more powerful than a BR standard 9F.

    But on an all time basis, I think Britain's most powerful steam loco would be the LNER U1 class 2-8-0+0-8-2 Garratt
     
  4. theageofthetra

    theageofthetra Established Member

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    What about British built Garretts for the Colonial market?
     
  5. Flying Phil

    Flying Phil Established Member

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    I suspect the A1 Trust mean the most powerful steam locomotive in Britain...now. The three cylinders would give it the edge over the 9F, although the latter's smaller driving wheels count in it's favour.
     
  6. Eyersey468

    Eyersey468 Member

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    How did Big Bertha that was used on the Lickey Incline compare to that one?
     
  7. 70014IronDuke

    70014IronDuke Established Member

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    Surely the smaller drivers of the 9F are an advantage in terms of theoretical tractive effort (other things, boiler pressure, cylinder volume, being equal), but I believe they make no difference to the power output. I'm not even sure if the three cylinders are an advantage in terms of power, at least in theory - though the use of three cylinders properly designed will reduce unbalanced forces, especially at speed - saving damage to the track and the loco tearing itself apart.

    The power output has to be based on the ability to produce high-energy steam, which depends on the ability to burn a lot of coal (hopefully efficiently), so you need a big grate - and transfer the resultant heat into the steam (so you need plenty of surface for heat transfer, meaning tubes and superheater surface). A chunk of that energy will then be lost as the steam is delivered to the cylinders and the exhaust is blown up the chimney. I suppose three cylinders will produce a more balanced steam flow, and a less pronunced exchaust blast, which serves as a better basis for better front-end efficiency - so in that sense three cylinders helps the power output. But that still needs good design of the steam passages - or I suspect it comes to naught.

    In terms of speed, glory and spectacle, the P2 must be up there at the top. But as somebody else has mentioned, in terms of brute, if rather utilitarian and unglamorous power, I doubt a P2 could outperform the U1.
     
  8. sprinterguy

    sprinterguy Established Member

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    I'm not sure in terms of horsepower at the drawbar (For which 6234 "Duchess of Abercorn" holds the official record of 2,511hp set in 1939), but in terms of nominal tractive effort the P2 will be the most powerful steam locomotive in Britain at present, as Flying Phil states.
    I believe you would be correct, here's some comparative tractive efforts, for the curious:

    HEAVY FREIGHT
    LNER U1 2-8-0+0-8-2: 72,940lb
    LMS 2-6-0+0-6-2: 45,620lb
    LMS "Big Bertha" 0-10-0: 43,313lb
    BR 9F 2-10-0: 39,667lb

    EXPRESS PASSENGER
    LNER P2 2-8-2: 43,462lb
    LNER A2 4-6-2: 40,320lb
    LMS "Princess" 4-6-2: 40,300lb
    GWR "King" 4-6-0: 40,300lb
    BR "Duke of Gloucester" 4-6-2: 39,080lb
     
    Last edited: 19 Sep 2018
  9. pdeaves

    pdeaves Established Member

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    Or the GER 'Dcapod'?
     
  10. 70014IronDuke

    70014IronDuke Established Member

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    Tractive effort is a force. It does not equate to power.
     
  11. sprinterguy

    sprinterguy Established Member

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    Hence my caveat that I don't know the drawbar horsepower. If anyone has anything more substantive then feel free to add, but I thought it a reasonable rule of thumb, and quite possibly where the A1 Trusts' claim stems from.
     
  12. Spartacus

    Spartacus Established Member

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    I do believe that with 8 smaller drivers that a P2 should be able to trump a Duchess's efforts.
     
  13. AndyY1951

    AndyY1951 Member

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    Do not confuse Power, measured in Horsepower, and Tractive Effort, which is a force, measured in pounds. Basic O-level physics!
    In principle a locomotive could develop its full Tractive Effort whilst stationary against the buffer-stops (of course in practice it would slip), whilst developing no power!
    Power is the Tractive Effort multiplied by Speed, so a locomotive such as Big Bertha had a high Tractive Effort but could only run at low speed, so wasn't very powerful.

    I challenged the assertion that the P2 could develop more power than a Duchess in a letter to Heritage Railway magazine maybe a year or more ago, David Elliott from the P2 Trust put forward an analysis supporting the P2, but the bottom line is that the capability of the Duchess was measured, whereas the P2 power never was measured. I don't retain my old magazines, perhaps somebody could dig out his reply.
    I wasn't convinced by his analysis...…………..

    Andy
     
  14. mushroomchow

    mushroomchow Member

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    Quite remarkable that it even outperforms "Big Bertha". Can't wait to see it in action slogging over the S&C!

    Well hey, we'll have a chance to finally put the issue to bed once 2007 gets up and running, since we'll be lucky enough to have mainline certified, working examples of both.
     
  15. AndyY1951

    AndyY1951 Member

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    We won't ever know, unless their owners, with Network Rail involvement, can operate them both to the limit of their abilities whilst hauling a dynamometer car and a heavy train. Or somebody recreates a Test Plant akin to the ones at Rugby or Vitry. I don't think either scenario is likely, unfortunately.
     
  16. chorleyjeff

    chorleyjeff Member

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    I reckon an average of three standing starts from Hellifield then flat out to Blea Moor by each engine with equal loading would tell the story.
     
  17. Spamcan81

    Spamcan81 Member

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    You’d need identical weather and rail head conditions for that method to give meaningful results.
     
  18. chorleyjeff

    chorleyjeff Member

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    And a whole host of other variables not least of which are human factors of driver and fireman or firemen. But it would be a good indicator. After all in steam days conclusions were drawn between loco capacity by comparing runs at different times such as post war loco trials between locos of different Companies on each other's lines. I suspect that actually the comparisons were not much use e.g. Some engines driven for minimum coal consumption but others flat out.
    Even today there are forums where comparisons are made between steam loco classes, and sometimes between diesel and steam locos, using runs made at different times with different loads and timings and conclusions about relative performances made.
    But the exercise mooted in the first place would be a rough and ready way to do a comparison using the same route and load and give enthusiasts much to argue about!
     
  19. XDM

    XDM Member

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    I am not sure you are right.
    I am not an engineer, but I remember schoolboy mechanics.

    The key thing about a steam engine is that it can store power. A diesel can't.

    So if one of the Hellifield engines sets off with maximum boiler pressure but the competitor sets off below max pressure, the max pressure engine has an advantage.
    It may deliver more HP, power, till its boiler pressure is drained by the work & falls to that of its competitor.
    Then all else being equal it will deliver the same HP .

    Again, all else being equal(a very big if) providing each engine set off at its maximum boiler pressure then chorleyjeff's test would still not be perfect.
    A small wheeled engine with high TE would win over a short distance. A greyhound with large wheels & lower TE would win over a long distance.
    Please correct me if wrong. I enjoy learning from my mistakes.
     
  20. Monty

    Monty Established Member

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    Therein lies the problem, to my knowledge nobody has been able to 'max' a Princess Coronation in terms of power output, even using two fireman during trials was not enough. You would probably need to use a mechanical stoker to get even close, the locomotives have similar sized firegrates but the Stanier Pacifics are miles ahead when it comes to both heating surface and areas. Both engines have large cylinders but again the Princess Coronation have an extra one compared to the P2. I remain to be convinced that this claim is nothing more than a way of generating more interest in the P2 project, it's what the A1/P2 trust(s) do and they are very good at it.
     
  21. Spartacus

    Spartacus Established Member

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    With many excursion's taking on their steam loco at Helifield, if the loco wasn't at or very close to blowing off pressure either there's something quite wrong with the loco or the fireman is only good for chucking on the fire o_O:D

    From Hellifield the climb and is quite long and a bit varied too, perhaps the only big external variable beside the weather would be fuel, you'd have to hope the coal would be the same quality, though both having wide fireboxes would mean one wouldn't have a particular advantage over the other if quality wasn't to that design's liking.

    A good thing that will come from standardised steam paths (not that they aren't to an extent already) is that it should make it easier to compare performances. I'm hoping 2007 & 6233 do something comparable, given time for 2007 to get properly run and and footplate crew to get a proper knowledge of her, after all there might be nobody alive who's been crew on a P2 by the time she runs.....
     
  22. AndyY1951

    AndyY1951 Member

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    I'm not sure that comparative runs would answer the question 'which is the most powerful' unless as I said above, each is operated to the limit of its ability, which would not be at all easy to organise.
    We need a new stationary test plant!
     
  23. chorleyjeff

    chorleyjeff Member

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    I would assume each loco would be driven and fired by highly skilled people who would know how to get the max. performance from each engine. After a little while boiler capacity to make steam and engine efficiency to use it will show up. It is unlikely a railway steam engine will perform exactly the same two days running so any comparisons can not be exact. In any case it is unlikely that such large engines could be manually fed enough coal for any extended time so theoretical performance is compromised and theoretical only. In other words it is nice to speculate but it is no more than speculation. More interesting is the possible day to day performance over an extended period.

    PS It must be obvious I am no engineer.
     
  24. penrithsteve

    penrithsteve Member

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    Out of interest, how would the 'Chinese' KF locomotive preserved at the National Railway Museum, compare?
     
  25. mushroomchow

    mushroomchow Member

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    That's easy, the weather in Hellafield can be simply categorised as "awful" 90% of the time. :lol:
     
  26. sprinterguy

    sprinterguy Established Member

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    Again I don't know the sustained power output, but if Wikipedia is to be believed, the maximum tractive effort of the KF class is similar to that of the P2, at 43,396lb.
     
  27. 70014IronDuke

    70014IronDuke Established Member

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    While comparing standing starts from Hellifield to Ribblehead with equal loads would indeed be "interesting" - I don't think it would be a true test to compare maximum power outputs - even if the locos were worked to the maximum attainable (while, of course, observing any line speed restrictions).

    The reason is that the maximum speed attainable with a 10 coach load + passengers (say, 375 tonnes gross trailing load) would be - guess - something like 55 mph, and the average speed significantly less - at around 45 mph? (IF anyone knows better, please correct my assumptions.)

    Such a run would favour the P2, which, with its smaller driving wheels, would probably be able to reach its maximum power output at around 50-55 mph. I suspect the Stanier pacific, with 6'-8" drivers, will probably be at its maximum theoretical power output around 60-65 mph.

    I'd posit that a fairer practical comparison would be on a run from (Newcastle)-Darlington-York, with Darlington passed at a controlled speed for both locomotives of (say) 60 mph with trailing loads of 400 tonnes, and both trains permitted to exceed 75 mph south of Darlington.

    Is there anyone alive today who worked a P2? The last locomotive running as a 2-8-2 would have been 1942? Assuming the fireman at the time would have been, say, 20, that would make him 96 or so? I suppose it is possible, but not much chance. Fantastic challenge for the P2 boys to find someone!
     
  28. Warwick

    Warwick Member

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    On the naughty step again.
    If anyone thinks that tractive effort equates to power just compare the tractive effort of a 1,250 hp class 25 with a "Merchant Navy" Pacific.
     
  29. theageofthetra

    theageofthetra Established Member

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    If we are looking at foreign locos then some of the last and biggest of the three and four truck geared Shays must be right up there in the tractive effort 'Top Trumps'

    If just looking at UK based loco's what about the Aussie Garrett at that museum in Coatbridge or the Saffer one in Manchester?
     
  30. etr221

    etr221 Member

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    On searching for "steam locomotive power formula" I found - among others - http://www.smex.net.au/reference/TractiveEffort02.php - which gives
    and also has a power (and tractive effort) calculator.

    Putting various classes into this gives - at 60 mph, with K=0.85, and in no particular order - the following: 9F 2-10-0 6350 hp; GWR King 6450 hp; LMS Duchess 6400 hp; LNER (Peppercorn) A1 5980 hp; A2 (Blue Peter) 6470 hp; P2 (Gresley as built with 220psi boiler) 6950 hp; P2 'Prince of Wales' (new build with 250 psi boiler) 7900 hp; Gresley proposed (1939) 4-8-2 7310 hp; BR Duke of Gloucester 6250 hp; Hypothetical design with 3 21"*28" cylinders and 6'-2" wheels 8510 hp @ 250psi, 9530 hp @ 280 psi (exceeding anything built, but practical max for Britain? taking max figures from different designs; freight version with 5' wheels 10500/11800 hp respectively, to indicate what might have been achievable).

    But all these are very much theoretical figures for rough comparison purposes only: in practice would be affected and restricted by the ability of the boiler to generate enough steam for long enough (and crew ability to get it do so), the valves' ability to get the steam in and out of the cylinders, the adhesion to get it through the wheel/rail interface, etc, etc. So large spoonful of salt required...

    But they do indicate that the P2 Trust claim is not without justification.
     
  31. E&W Lucas

    E&W Lucas Established Member

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    Would suggest that the formula quoted is fanciful.
    The figures produced suggest steam locos having a similar power output to a Class 91. Common sense indicates that this is wide of the mark.

    You’re close to the reality with your later remarks though. The thing’s ability to boil water is the key to its true power output. Also the ability to employ what it boils efficiently. High pressure gives high temperature gives high superheated gives more work produced for each pound of water boiled. Then add in the ability of the loco to get rid of exhaust steam; the less effort required to do so, the more power available to do work. The higher the temp and pressure of the exhaust steam, the easier this becomes. One look at the steam passages on Big Bertha or the LNE Garret, both low pressure locos, helps you realise what a nightmare they must have been in this regard. The fact that Bertha was regarded as unfit for normal train working, indicates that its boiler was incapable of supplying the engine for more than a short distance.
     

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