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Tornado

Discussion in 'Steam Traction' started by Leander's Shovel, Oct 20, 2007.

  1. Jamessquared

    Jamessquared Nat Pres stalwart

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    I suspect you need the aerodynamic shell as well as the free-running steam circuit: power required to overcome drag scales with the cube of the speed, so, for example, an increase from 100mph to 125mph requires almost double the power absorbed by air resistance. (Not necessarily double the total power of course, but by those speeds, definitely significant).

    It might be interesting to think what impact different carriages have: pulling a train of Mark 3s might make a considerable difference relative to the train that Mallard pulled. Which probably just goes to show that speed records with uncontrolled conditions are a bit silly as a concept ...

    Tom
     
  2. Bikermike

    Bikermike Member

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    If you were really going for it, it would be tape over all the small bumps and handles etc, diaphragms in the joins between coaches, possibly a beaver tail to reduce turbulence in the exit, valances over the driving wheels (starting to look like a coronation set) Then there's weight loss (not so coronation set - replace the wilton carpet with carbon fibre)...
     
  3. 30567

    30567 Well-Known Member Friend

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    .... as in my 1 in 200 down stretch is longer than yours and doesn't have a 20 mph crossover at the bottom. What is the speed on level track equivalent to Mallard's feat?
     
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  4. MellishR

    MellishR Part of the furniture Friend

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    There are indeed many variables. It has long seemed to me that the very small difference in the peak speeds between Mallard and the German contender going downhill are outweighed by the latter's sustained very high speed over an undulating road. But as for a hypothetical future attempt, what should be the parameters? You might not want to do it light-engine for the sake of braking capability, but how many coaches do you need? Or what about running stationary in a wind tunnel? Blue Peter ran very fast while stationary, against the friction between the wheels and the rails, thus delivering a fair amount of power; until something broke.

    Returning to what may actually happen, there is a prospect of Tornado being allowed 90 mph occasionally when specially arranged, but sadly not helping with the pathing on ordinary trips.
     
  5. Bikermike

    Bikermike Member

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    a measured mile in each direction along it within an hour of each other on a salt flat, is the recognised test in other spheres...

    Anyone got a few miles of track to stick down at Bonneville?

    It's a shame the Tornado high speed running failed, faster paths would open up a lot more running options.
     
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  6. S.A.C. Martin

    S.A.C. Martin Part of the furniture

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    But this isn't the case. The Peppercorn A1 is a development of the Peppercorn A2. Which in itself, is a development of the Thompson A2/3, the rebuilt P2s, and the P2s at the start of the chain.

    The end of the A4 development is the A1/1, Great Northern. Peppercorn chose to develop the 6ft 2in loco into a 6ft 8in loco and thus we have Tornado.
     
    Last edited: Oct 1, 2020
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  7. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

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    Maybe so, maybe not. The Tornado 100 mph run was really just a vanity/publicity operation and a sense of needing to show that the locomotive was capable of such things when on paper there was little doubt that it was possible. Other classes had already gone before and 'got the tee shirt', so to speak, but remember that it was only possible to do it in the dead of night.

    On the wider point, Network Rail would need a lot of convincing about higher speed running and TOCs would be very wary of suggesting paths that demanded such speeds. As it stands nearly every path I can think of involves quite a wide margin amongst other services for all the delay attribution reasons we know.

    In practice, I personally think it does no loco any good at all to push it along in order to get up to magical speed numbers as I understand was necessary on the Tornado run because earlier locations were lost through routing/tsr/signalling issues. In that case it was a last chance opportunity before York when the best location down towards Croft Spa had been lost. (Remember the Bittern run when the loco was eased at 95 mph on that same stretch when an effortless 100 could have been achieved if allowed.)

    There is a lot to be said for steam to be allowed to capitalise far more on the natural undulations of the line down and up hill thereby improving the efficiency of operating the train and in the process taking up less track time. For that, all you need is a bit of common sense to be applied. For example, the Southern limit was 85 mph and Merchants could happily cruise at 80/85. I see no reason why that shouldn't be allowed for all big Pacifics......if the owners think that is sensible. There is nothing 'special' about 90.

    Whether that would in practice free up more running options is another matter. I think not. But it would definitely make for more efficient and economical operating.
     
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  8. 30567

    30567 Well-Known Member Friend

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    Going back five years, wasn't the one identified commercial opportunity doing KX to York in four hours on a regular basis as a tourist train? To get that to work required a genuine 75mph schedule with no padding (eg Potters Bar to Grantham 93 miles in 80 mins), which obviously requires running in the 80s, which is what the A1s did week in week out in the 50s and 60s. From that point of view what was needed was 90 max not 90 actual.

    Whether that commercial opportunity would have proved successful we will never know.
     
  9. Steve

    Steve Part of the furniture Friend

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    Back longer than I can remember when I was an engineering trainee there was a book in the office on steam engine design and by engine I mean just that and not a locomotive. One parameter mentioned and which I have always remembered is that a reciprocating steam engine should be designed for a maximum speed of 360 rev/min (6 rev/sec). If you translate this into steam locomotive maximum speed this works out at about 85 mph for 6'-8" drivers and 77 mph for 6'-0" driving wheels. I think that these are sensible maxima.
     
  10. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

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    Sounds sensible. As with road speed limits, the limit is the maximum not the target! But running up to 80/85 when the gradient leads to that is not the same as pushing the loco to get to those speeds when on the level or a slightly rising grade. There is a useful safety indicator in the cab and it isn't the regulator but the reverser, imo!
     
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  11. guycarr360

    guycarr360 Member

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    looking back at the video from the weekend, it seems the wish, is for the opportunity to run up to 85mph ish, when conditions dictate, and not as an advertised standard.

    Think this is a sensible approach.
     
  12. John Petley

    John Petley Well-Known Member

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    I think this would be a sensible approach to the 75mph+ question. Presumably little extra would need to be done by a given loco owning group in terms of maintenance if we were talking about giving a big pacific its head on a downhill stretch compared with aiming for 90mph on the level. This does mean that the shorter schedules such as KX-York in less than 4 hours may be out of the question, but in terms of the enjoyment factor for those on board, I would say that a downhill dash at 85mph could well be far more exciting than 90mph on the level. I was on the ill-fated Ebor Flyer and know that we reached 90mph before disaster struck, but what struck me at the time is that it did not feel exceptionally fast because the acceleration was so steady.

    If people won't mind me bringing mention of a diesel into this thread, I recall taking a circular trip from Bromley South in the 1980s when there was a regular 47-hauled diagram from Liverpool to Dover and back, out via Tonbridge and Ashford, back via Chatham. We must have been running at 95mph for mile after mile on the relatively straight section from Tonbridge to Ashford, but the highlight of the journey for me was the acceleration from the summits on the switchback and much more steeply graded London Chatham & Dover line (i.e., after Shepherdswell, Selling Tunnel and Sole Street) I doubt if the top speed was any higher than on the racing stretch on the outward leg, but it certainly felt faster. I would therefore maintain that allowing 85mph for steam downhill from , say Shap or Grateley would be just as satisfying to those who enjoy fast running aregular 90mph running on the ECML while being much less demanding on the loco.
     
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  13. Kylchap

    Kylchap Member

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    I don't think there was ever any intention to thrash Tornado along at 90mph for mile after mile on a routine basis, but rather to be permitted to run up to that speed on occasions if conditions and the demands of the path allowed. It seemed to me that the lack of excitement travelling at 90+ on the Ebor Flyer was due mainly to two things: the nature of the coaches we were in; the fact that Tornado seemed to do it effortlessly. I hold the, probably controversial, view that the standard to which the loco was being maintained was not up to the demands of running at 90mph, not that the loco per se was not up to it. Its legendary reliability had led to complacency.
     
  14. LMS2968

    LMS2968 Part of the furniture

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    So how did it achieve that 'legendary reliability'?
     
  15. MellishR

    MellishR Part of the furniture Friend

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    Thank you for putting me straight on that. I do find the evolution of the many classes and subclasses of LNER Pacifics confusing, even disregarding the versions that never got past the drawing board.
     
  16. Big Al

    Big Al Nat Pres stalwart Staff Member Moderator

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    Oops. Can of worms time although I wouldn't argue with any of that comment. But that was then and hopefully as they say, lessons have been learned. They just need to be remembered as 70, 80, 90 all bring with them the same issues. It's just the scale that changes. As for 'legendary reliability' you might perhaps expect that a new locomotive after running in and the ironing out of any teething problems - stays anyone? - should be reliable. But then so is 5043...there is a list.
     
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  17. D1002

    D1002 Part of the furniture

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    ‘Legendary reliability’? Surely that award should go to 35028.........?
     
  18. 242A1

    242A1 Member

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    The AAR rules use 504 rpm. Why be so conservative?
     
  19. Steve

    Steve Part of the furniture Friend

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    Well, I wasn't aware of that but now I am, if you want an honest answer, it would be because I don't think 504 rpm is realistic. That equates to 108mph with 6 '-0"drivers and 120 mph for 6'-8". Just how many locos have actually met those criteria on a day to day basis?
    I've just had a look in Phillipson and it has this to say on the subject.
    ".....an empirical rule which states that the diameter of the coupled wheels at the tread, in inches, should equal the maximum speed at which the engine is required to run, in miles per hour, still finds acceptance in many quarters. This rule implies a maximum rotational speed of 336 revolutions per minute, and it is not desirable that this quantity be greatly exceeded, although for purposes of design a maximum speed of 360 r.p.m. is generally assumed; it should be mentioned that some continental designs allow for the exceptional maximum of 420 r.p.m."

    I'll stick with 360 rpm as being sensible.
     
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  20. Romsey

    Romsey Member

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    But please don't tempt fate!

    Cheers, Neil
     
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