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Steam speed records including City of Truro and Mallard

Discussion in 'Steam Traction' started by Courier, Jan 30, 2011.

  1. 30567

    30567 Part of the furniture Friend

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    Is that a bit similar to Rous-Marten, or rather the person on the train he quotes (he was on the footplate)? If it was 9 secs per quarter for four quarters then that's one thing. But 9.2 secs followed by 8.8 secs seems inherently dodgy.
     
  2. Hermod

    Hermod Member

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    As I read it both the 126 and 125 claim is regarded as un- physic by mr Andrews and Mallard ran with a steady speed of 124. (2to 5) before shutting steam and braking.
    If Mallard paper drum was .2 mm eccentric no further mudslinging is nessecary.
    The Germans had given up high-speed steam before the Mallard adventure and bougth diesel sets.
     
  3. Jimc

    Jimc Part of the furniture

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    Not so much if you figure the limitations of a 1/5 second stopwatch and the consequent rounding effects. For example 9.1 and 8.9 would be recorded as 9.2 and 8.8.
     
  4. 35B

    35B Nat Pres stalwart

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    No - but it does take us to the role of error bars, and how you interpret a graph between measurements.
     
  5. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    That’s not really true though. Yes they had a streamlined diesel set but they were developing the 05 and 06 classes and the streamlined coaches for the steam locomotives after the diesel set was in use.
     
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  6. sir gilbert claughton

    sir gilbert claughton Well-Known Member

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    Hi Michael.

    i read the 46255 claim in either a RM or TI , around 1959;; my uncle used to give them to me and i had a bit of a collection for several years as a result . after 65 years my recollection may well be imperfect and it is possible i am conflating 2 logs , but what i do remember is the ascent to Shap when 46255 was given full gear and "was keeping her feet " .......70% on a Duchess iirc . now i could be confused !! with another log where the train went over Shap and the controls were left untouched and a speed of 105 mph was recorded. - he infers it was more than that but does not claim it . . they don't sound like the same logs , i will agree . i think it is likely the 105 mph should be credited to 46251.

    my surprise at 96 mph thro' Harrow is because it was my local station and i spent a lot of time there . the fastest thing i ever saw there was D1 Scafell Pike on an Up train to Euston. maybe a Press Day , i don't know but it flew!!. i remember the leading axle hammering each rail joint . ....a precurser of troubles to come with broken rails
     
  7. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    As a sort of side project to my PhD work on high speed rail, I have been putting together some basic modelling on a budget. For £45 total I’ve created a reasonable (but not perfectly accurate) representation of the German high speed test train with 05 002 (portrayed by 001 here).

    The models are to HO scale (the loco is an un-powered Atlas Editions model, basic but the dimensions are good). The brown coach at the front of the train represents the German dynamometer car. All of the vehicles in the German train were clerestory vehicles of Epoch II, they’re represented by these coaches.

    IMG_2653.jpeg

    IMG_2655.jpeg

    IMG_2656.jpeg

    So the first thing which comes to mind is that the train is quite short overall, but weighed 200 tonnes according to secondary sources.

    05 002 was streamlined down to rail level, with a distinct but not extreme slope at the front end (for comparison, the LMS Coronation was flat fronted with a streamlined casing, Mallard conforms to a teardrop in profile by comparison).

    So the stats for 05 002 as a three cylinder 4-6-4 pulling a very short form train should have given it an excellent power to weight ratio.

    However, one thing the model really shows that isn’t apparent at a first glance is just how big the locomotives boiler was. It really is huge, at least 2/5ths longer than Mallards diagram 107 boiler.

    The casing is well designed in terms of covering up much of the running gear and making the locomotive streamlined from the railhead.

    However, unlike Mallard, the surface of the casing is broken up by more prominent boiler bands, the top feed, dome and more.

    The deflectors that were added around the chimney underpin the the fact that the front end is not optimised for air flow around the loco. The chimney has a bit of streamlining but retains a lip, which is bizarre given the use of stovepipes on other streamlines.

    So, does some things better than Mallard, does some things worse. If you have a copy of my Gresley book, you will note that the tender behind the 05 closely resembles one of the LNER proposals for the A4 Pacific tender, with stepped sections of streamlined casing.

    Its definitely helped visualise what the loco and train would have looked like, and raised some questions, so worth the modest expenditure, IMO.
     
    Last edited: Jan 16, 2024
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  8. Bill2

    Bill2 New Member

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    I don't believe that's correct. As a model, think of a pendulum clock: start the pendulum at one side and it has to complete a swing before releasing the escapement so the hand can tick on. I think the same applies to a mechanical stopwatch, i.e. a 1/5 second stopwatch will show 8.8 seconds until 9 seconds has elapsed, when it will tick up to 9.0, and will then show this until 9.2 seconds has elapsed when it will tick up to 9.2. It's not really a question of rounding at all. Thus timing a quarter mile in 8.8 seconds with such a watch means the time is actually somewhere between 8.8 and 9.0 and therefore the speed is between 100 and 102.3 mph assuming everything is accurate. This is (partly) why one should time over a longer distance than a quarter of a mile, and also why one should not quote decimals.
     
  9. Jimc

    Jimc Part of the furniture

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    That's a very interesting observation, I think you're right about that, and I'll have to give a good bit of thought to the implications.
     
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  10. Jamessquared

    Jamessquared Nat Pres stalwart

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    Off the top of my head, it suggests the magnitude of the error is the same, but all on one side rather than equally distributed either side.

    So (hypothetically) given 0.2s is about 2% at those sorts of speeds, previously you might have said a 9s quarter mile = 99 - 101mph; and now you’d say 9s = 98 - 100mph.

    Tom
     
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  11. johnofwessex

    johnofwessex Resident of Nat Pres

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    My immediate comment is that while Mallard is hauling - Dynamometer car excepted a streamlined train the German one is anything but
     
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  12. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    F50977BA-46D3-4B82-86B6-F79F00ED889B.jpeg

    C64698C2-6F31-49AC-856D-77F44FF26484.jpeg

    This books seems to suggest that 05 002 was damaged far more after its speed run than Mallard was - a complete boiler tube replacement suggests a lot of damage.

    Mallard only required its middle big end remetalling, by comparison.
     
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  13. flying scotsman123

    flying scotsman123 Resident of Nat Pres

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    Probably a silly question, but whilst I can see how very high speed beyond expected design would knacker big end bearings and such like, how would it affect the boiler? Is it simply vibration etc., or am I missing something?
     
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  14. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Not a silly question. I don’t know either. It’s really intriguing.
     
  15. 35B

    35B Nat Pres stalwart

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    Was that work solely due to that one run?


    Sent from my iPhone using Tapatalk
     
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  16. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    Cross referencing it with the other book, it seems to suggest not as a result of one run.The locomotive had been pushed very hard over a series of runs.
     
  17. Jamessquared

    Jamessquared Nat Pres stalwart

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    Holcroft mentions in his book that he, along with a party of other British visitors from various railways, had a run at over 100mph behind it only a few days after its record run.

    Tom
     
  18. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    The dates I have are:

    11 May 1936 - Record run.
    30 May 1936 - Run for the English party.

    Inbetween - in works.

    Holcroft, as ever, an unreliable commentator to these proceedings (and others).
     
  19. Steve

    Steve Resident of Nat Pres Friend

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    Is that an opinion or a fact that you can back up?
     
  20. Jamessquared

    Jamessquared Nat Pres stalwart

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    Hang on - why are you saying Holcroft is unreliable?

    I probably paraphrased his words (because the book is elsewhere in the house). But I can't see what's wrong with the statement that the party had a run behind the loco a few days after its record run.

    Tom
     
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