Steam speed records including City of Truro and Mallard

You’ve dropped this a few times now so go on then Tell us the subject/title/topic or waddevayacallit

 

I don't even know yet actually! It is very fluid but it is centred around the development of high speed rail. I am working on my first paper which is trying to define high speed rail in terms of its development, management and infrastructure development (including the development of high speed trains). CoT actually features in a small way at present.



It's allowed me some space to start collecting some data in terms of speed records - lots of interesting trends starting to come togther.

 

Oh well I've been almost irrelevant for most of my life so nothing new there Simon.

Actually I have been channelling my inner @Jimc because I found an earlier thread where he was putting a similar question. I think it is an interesting question how, for example, Mallard's speed compares with Tornado's. What I take from @Maunsell907 is that 126mph down the hill converts to around 105 or 106 on the level all else constant.

Obviously I don't know the literature but it strikes me that much of the presentation is from the pre-computer era. So wouldn't it be nice to have a multivariate model on a spreadsheet based on theoretical mechanics and parameter values from wind tunnels and testing stations etc? Then, to me, overlaid on that, you want some observations (calibration if you like) out on the road. From what you say about dropping four out of five for excessive noise/optimism bias, it sounds as though that might be what you are doing.

Within that family of curves, you would want some uphill, some downhill, some moving 200 tonnes, some moving 750 tonnes (9Fs etc), different air resistance coefficients, wind effects etc. One bit of the family would be on the level. For that bit of the family I would rule out the LSWR (undulating road). The obvious level racetracks would be Brunel's railway (?Sonning, Wantage) and York to Darlington. I definitely agree on the need to distinguish between dynamometer car data and Trains Illustrated/ Railway Magazine type logs

 

With my sincerest apologies, no offence was intended!

Hmmm, not sure that is true actually. The gradient for the section where 126mph was actually attained is 1 in 200 and in the grand scheme of things, gives a small advantage towards attaining higher speeds.

Given Mallards acceleration on the actual run uphill and drawbar horsepower recorded, it is very clear that in a scenario “on the flat” with perfect conditions that it is likely she would have still achieved speeds in excess of 120mph. Tornado is not streamlined and therefore has to do significantly more work to achieve 100mph compared to the streamlined A4.

Yes, almost exactly, though I am trying to approach it from a different angle, by creating a theoretical framework and model by way of scale for the likely required horsepower/evaporative rate and then working out the other variables like air resistance, rolling resistance, etc.

Put it this way, it’s been a significant point of discussion with my supervisor. We’re both fascinated by the development into high speed rail here and abroad and one of the things we think we may accidentally demonstrate is that, by way of modelling, most of the timekeepers logs of the day were just not accurate enough, on balance of probability against the “ideal situation” for a locomotive and train.

Its all highly speculative at this point, of course.

 

None taken Simon, I'll get my old t-shirt out.

Well if your model demonstrates conclusively that the gradient effect is 'small' and the streamline effect is 'large' then that will be a useful contribution.

If the gradient effect is small, I think I'd be asking why all the observed 100mph pluses happen to be going down hills. I'd expect to find more of a mixture.

Edit--plus if the gradient effect is small and the streamline effect is large, what magnificent locos the rebuilt MNs were. But then we knew that......

 

JOOI, what's the earliest logged run for which records survive?

Presumably with the development of high speed, you are talking relative to regular network trains? Would a %age above usual speed/below standard times be a means of helping define "high speed"?

 

I never find power discussions about max speed as very easy to follow, preferring personally to think in terms of forces. We know from Newton's laws that an object will continue to accelerate all the time there is a net force on it: therefore, in any case, the peak speed (i.e. the point at which acceleration stops) will be whatever speed the loco has attained when the tractive effort developed at that speed just balances the sum of the various resistances (rolling resistance, drag) plus whatever force is donated by gravity for trains going downhill. The resistance formula obviously varies with speed (drag increases with speed etc) and the TE developed also varies with speed, so finding the point they balance is essentially an exercise in iterating over various speeds - something a spreadsheet is well suited to. (*)

Of course, such an analysis does require good data on both train resistance and the variation of TE with speed.

(*) Typically, at low speed, TE is high and train resistance low because there is negligible drag, so the train accelerates. As speed increases, the tractive force at the rail decreases, and the overall resistance increases. Plot the point where those two curves cross and you get the peak speed, i.e. the point that the train stops accelerating because the force it is able to apply just balances teh resistance it is experiencing.

I'd like to see the calculation. What's the total train weight for Mallard's run, including loco? I believe around 400 tons - down a 1 in 200 gradient that is giving you somewhere in the region of 4,400lbf knocked off the train resistance that the loco has to balance through its tractive effort. It is I would suggest quite a considerable help.

Tom

 

Gravity gift is per definition equal to force times velocity

Force was 407000*9.81 newton downward
Horizontal speed was around 56 meter per second on a 200 grade.(or 240?)
That is 56/200 meter=0,28 m per second downward.
Power Gravity Gift was then(force times velocity )=1118kW or 1499 horsepower
The maximum measured (indicated) cylinder-horsepower ever on latest V2 was 1990 indicated horsepower.
Calling gravity gift insignificant is not OK

 

This is an excellent summation that everyone should read and pay attention to.

Hi Tom, happy to send you the data privately.

I think I should have explained better: overall in terms of the gains in positive factors, the falling gradient is not as significant a factor as the streamlining and the total power output of the whole train. My stats look lower than that you’ve produced there, but we’re both what I would call “in the ballpark” for the gradient.

 

I never said it was “insignificant”, only in that specific case of Mallard there were other factors at play that are greater, to be clear.

I was not trying to downplay the significance of going downhill, I am just trying to be clear in what all of the different factors are and how they may have contributed to the data we have.

 

That’s precisely what I am trying to define, to be frank!

You could argue that the earliest high speed locomotive, for example, was Rocket - it virtually doubled the top speed attained by railway locomotives overnight. Honourable mentions to Sans Pareil and Novelty who also did speeds significantly in excess of that achieved at the time.

There are clear distinctions to be made and that’s actually been part of the fun of the early research, the questions behind high speed rail, and all of these high speed claims are fun to examine.

 

Simon, you seem very keen on considering the Tests at NPL as being the gospel . They followed
AFAIK similar Tests at NYU and MIT in the USA.Subsequent testing work on the real thing,
rather than 1/40 th models ( particularly under Andrews on the Western Region and Ell on
the Eastern Region ) suggest Johansen figures were up to 20% adrift.

In terms of stream lining and HP savings, bearing in mind that AFAIK the ‘Silver Link’ ‘Coronation’
and ‘West Riding’ WTTs were predicated on 90mph maximum speeds, the saving of 139HP max
at any time on the journey when traded off against more difficult access at wash outs, shed checks etc
seems marginal. I understand why Stanier thought the stream lined casing superfluous, and
emphasised his indifference by having five ‘Coronations’ built without stream lined casing.
I also understand why BR ( if not LNER ? ) removed the lower casing sections of the A4s.

I am firmly of the view that whether in the USA or here the chief motivation for streamlining
locos was the Art Decoratif. movement.
( The Southern caught the mood in its new stations etc, the LNER in its high speed trains and
the LMS, begrudgingly I feel, in the Coronation train. )

To the question by 30567, “Are there any authentic 100mph on the Level’ I think not. I am not sure about
the 100mph by Tornado, At the time I think the suggestion was that 100 was nearly reached on the
favourable 1/629 south of Northallerton and it required an all out effort to reach 100mph. The
only record I have seen is a picture of a smiling Commercial Director by a speedo registering 100mph.
If there is either a GPS trace and/or quarter post readings it would be interesting to see.

Whatever occurred it would have required c. 3000 IHP bearing in mind the load. ( Interestingly
when locos were being driven all out up to Stoke. The late Mike Nottley recounted how when he
was on the footplate of Tornado, whilst at 70mph they were normally limited to RFO and 45%
cut-off on this occasion permission had been given to increase the cut-off further. Similar
heavy handling ( I am resisting using the emotional ‘thrashing’ word ) of an A4 indicated a
slight advantage in power to the A1 of c 100-150 HP.)

I am not aware of any other candidates for 100mph on the level. Indeed 97/98 seems
to have been tops ?

100mph was rare behind steam. They required a favourable location. On the Southern for
instance Wallers Ash, Andover. Big Al has referred to Bert Hooker’s effort on a special.
Interestingly, he quotes 102mph, other logs give 101 and 100. (The limitation of one tenth
even one fifth of a second stop watch. At 100 mph a 9.0. second reading could be anything
from 8.96 to 9.94 i.e. plus or minus .45%. I.e simplistically 100mph could be 101 )

Continuing with locations Axminster on the Southern and on the Western Dauntsey and
Honeybourne, both at the bottom of 1/100 gradients and at Little Somerford after nine
miles down at 1/300. The GWR examples with King 4-6-0s at Dauntsey and Little Somerford
and Castle 4-6-0s at Little Somerford and Honeybourne.

I have gone on too long but a final thought, I think dismissing 4 out of 5 historic logs is
perhaps revisionism taken to a new level. Yes on a particular log one passing time may
appear odd, similarly a rogue speed but to reject the whole log. Consideration of a
large number of logs ( as per the RPS Archive ) enable a good picture of day to day
and maximum performances to be achieved.

I cannot help with saying Simon that four out of five logs can be ignored but the NPL
Tests on a 1/40 scale model are acceptable.

Michael Rowe,

 

Hi Michael,

I’m not taking them as gospel. As mentioned earlier I am hoping to re run the tests in the modern day.

We have to treat each on their own merit and the science of one has informed current science and the other hasn’t.

If I may be so bold Michael, but your understanding of streamlining of railway vehicles isn’t informed enough. The LNER/LMS did with the NPL some very extensive testing and experimentation which led to the shapes chosen, both of which are aerodynamically superior to non streamlined locomotives and those which were “industrially designed” as part of the overall streamlined movement.

I would suggest reading Frederick Johansens paper on it - very compelling reading and gives a better idea of what was being done by NPL at the time.

Best wishes

 

Are you please referring to the Johansen paper to the Mechanicals in 1936. If so I
quoted from the paper in post 1768 on the Gresley forum.

Michael Rowe

 

Yes, and what do you think the outcome that his paper opined?

Because I saw you quote it originally and your views you have given since are at odds with the facts on streamlining.

 

If you don't mind my asking, do you use a GPS app, or a device?.

 

My model predicts that Tornado must make 2400 indicated horsepower to propel a 190 meter long train at 45.4m/sec and with a mass of 485 tons on level road.
V2 made maximum 1990 at test stand fresh coal,payed firmen etc.
Boiler on Tornado is basicly the same but for the grate and this must somehow be countered by being not fresh from shed.
The V2 was most efficient at 80 mph or more or less as Tornado doing 100mph.
There is thus no reason to believe Tornado can make 2400,but if the 629 gradient holds water it is another matter.

190 meter long train used 1421kW as air resistance
A485 tons train got 343kW from gravity and spended 324 on rolling
and 1990 ihp is 1484 kW

You have saved my day and model.

If it is worth the effort to use the numerical model on CoT please give me numbers.