Steam speed records including City of Truro and Mallard

1 Long Ton (English/British Imperial) = 2240 pounds = 1016kg

1 Metric Ton (Tonne) = 2205 pounds = 1000kg

1 Short Ton (USA Customary) = 2000 pounds = 907kg

I haven't looked up Danish Tons, but I'm sure they will be lurking somewhere in Wikipedia.

Both the "Long Ton" and the "Short Ton" derive from historic English measures. The UK standardized on the Long Ton under the Weights and Measures Act of 1824 (conveniently just in time for the railway age). But the USA was by then independent and preferred the Short Ton.

 

OK
81000+40000+195000 kg running 40825 meter horizontal and 24meter down in 1011 sec.
Horizontal mean speed 40825/1011=40.4 m/sec
Verticl mean speed 24/1011= 0.023m sec
Rolling mean power price 9.81*316000*0.0015*40.4=188kW
Gravity mean power gift 9.81* 316000*0.023 = 71kW
Total length of train?

 

Apologies. Always assume Tom is correct,

Maybe try 20 metres loco plus tender and 20 metres per coach so 140 metres subject to improved precision.

 

So things to consider for any discussion of the Mallard run:

Positive factors:

• Short formed train (six twins plus one dynamometer car)
• Streamlined coaches make up majority of the formation
• Streamlined locomotive
• Double Kylchap improves draughting of locomotive
• Locomotive is a high speed Pacific locomotive
• Gradients on the run are 1:200, level and then 1:240

Negative factors:

• Dynamometer car provides drag (how much, difficult to say but not as sizeable as, for instance, any train formed of non streamlined coaches placed behind it)
• Rolling resistance of entire train
• Likely horsepower of the A4 - no indications given on run, may not have any reliable data from other runs if no A4 was indicated
• Mechanical resistances throughout

Known records:

• Primary evidence: Dynamometer roll for entirety of run
• This gives time recorded in seconds
• Distance, in quarter, half and full miles
• The regulator applications of steam
• Drawbar horsepower
• Secondary evidence: Much literature giving interpretations of the base data
• Dynamometer car was calibrated before and after run as per standard LNER practice

Things we could reasonably calculate:

• Aerodynamic properties of the train by way of modelling
• HP required to drag train at speeds recorded
• Overall friction of the train by way of knowing the drawbar pull and approx. weight of the train

Please let me know if there’s anything I have missed and I will add it to the above list.

 

With respect, No There are enough errors in calculating power outputs without adding to it.
(Errors are cumulative )
When calculating weights of trains we can count the Tare weight of the consist, (errors are
if stated weights on carriages are wrong ) the Gross figure is more difficult but 12-13 pax per
ton approximately.
The loco is more difficult I.e. how much coal and water in the tender etc.
But we are probably in the +/- 1-2% error.
Why would we want to add a 10% error by taking 2 pounds = 1 kg when actually 2.205lbs = 1kg.

Michael Rowe

 

I came across this paper today: https://steamindex.com/library/research.htm. Its titled "British railway research - the first hundred years", Text by Sam Wise; edited by A. O. Gilchrist and with a biographical note by E. S. Burdon.

Most of it isn't directly relevant to this discussion, but there is a short mention of Johansen and the NPL wind tunnel. One thing struck me. The paper says: "Worthwhile reductions in resistance could be achieved by a domed smoke box front and a fairing from cab roof to tender." Now we know whose streamlining experiment featured a domed smoke box front and a fairing from cab roof to tender. When exactly did Johansen did his work? Collet's streamlining exercise was in metal in March 1935. I wonder if Collett had some exposure to Johansen's work?

I also found this, although I don't have access to it. https://journals.sagepub.com/doi/abs/10.1243/JILE_PROC_1951_041_062_02?journalCode=jila which is a 1948 paper "Railway Wind Tunnel Work". What this link does give me is the Bibliography, and amongst other items it includes "Green J. J. “Wind Tunnel Tests of Locomotive Streamlining.” Railway Mechanical Engineer, Vol. 107, 1933, pp. 149–154 and pp. 204–211." Green, it seems, worked on the Canadian Railways.

Perhaps Collet's streamlining exercise, although undoubtedly it had much of the "quick and dirty" about it, was better founded in science than Nock would have us believe.

 

With respect Michael I didn’t take 2lbs as 1kg - I took 2.2lbs. Taking 1000kg as 1 ton is within your 1-2% error. So 195 imperial tons = 195 metric tons to within about 1,5%.

Tom

 

Apologies, more Senior moments !

Being picky, since errors are cumulative ( differential of UV) probably shouldn’t
even use 2200 for 2205.

Michael Rowe

 

Indeed but then you get to the fact that there is probably a bigger error between the quoted and actual weights of a carriage. Even diagram weights to the nearest cwt (5% of a ton) means a 30 ton carriage could be anywhere between 29.97 and 30.03 with a clear conscience, and that’s before you consider weight changes through things like tyre turning. So I suspect even a quoted tare weight of a train is probably no more accurate than a percent either side.

Tom

 

This may be a known unknown, but environmental conditions? In all the discussions about Ais Gill, I think---how hard was the wind blowing and from which direction? @Hermod should note that the GWR is W to E and the prevailing wind is from the west.

More generally, I feel there is a need to specify the type of model being estimated here. As discussed just above, many of these variables should really be represented in a mean/variance type of way. That suggests a simulation approach-- running the Little Bytham experiment 1000 times, what does the cloud of results look like?

 

Total length of train 140m according to 30567

140*.13=18.2 squaremeter eqvivalent drag area.
airwork= drag area*dynamic pressure*speed over ground

18.2*0.5*1.23*40.4**3=738kW

Nessecary indicated horsepower (738+188-71)/0.746=1146 cylinder horsepower

WP_20180721_003[1] by Hermod posted Jul 21, 2018 at 3:24 PM

The graph is from Britania .
Castle boiler can boil 5-10 % more than a modified Hall that is more steam frugal
A modified Hall made 1541 ihp as short time max power on test stand.
For lack of better measurement let us assume Tregenna Castle could make 1541 ihp mortgaging boiler and ca 25% less as very hectic one hour rating (Like Britania).
I estimate from Hall test plant data and projecting from Britania values that a Casstle can make
1160 IHP as one hour rating on a lucky day.
My very exact scientific train estimator says 1146 IHP.
Stokholm are You reading?

 

When we know the conversion factor why bother approximating in the first place? It’s only a couple of finger taps on a calculator. I’d only approximate if I was doing mental arithmetic.

 

I was doing it in my head

I guess the wider issue is you can get hung up on whether a ton is 1000kg or 1015kg, and forget about all the inaccuracies such that a 30 ton coach could be anywhere up to about 35 depending on how many people are sitting in it! My take home from Mallard's run is that (1) it ran very fast (2) gravity was a big help and (3) such speeds were clearly impractical, based on the fact that the locomotive didn't survive the journey intact!

Tom

 

What do we really know? Not that much, really. We have the dynamometer trace but even that doesn't tell us much. It tells us the speed the train was doing and this shows a very high speed for a steam loco. Without examining the trace in detail I'm not in a position to argue what that speed was. Other than that, it tells us the drawbar pull on the dynamometer car and, with the knowledge of the speed, we can deduce the HP required to drag the train along at that speed. From the drawbar pull and knowing the weight of the train, the gradient and acceleration we can deduce the overall friction of the train, but not the individual elements of wind and mechanical friction. But a lot of this probably involves guesswork. The only way we'll know the true weight of the train is if each vehicle was put on a weighbridge as part of the testing and, sticking my neck out, I'll say this didn't happen as it was an articulated set and I doubt there would have been a weighbridge in the country (perhaps world) that would be capable of doing that without recourse to dismantling the set. Do we know the rotating inertia of the wheelsets? That's not an insignificant factor on this train when looking at acceleration. Gradients are an interesting one. When the line was built it would have been surveyed and the gradients known but, as time goes by that aspect will vary due to relays and general maintenance. The average gradient between the original changes of gradient may be accurate but there can be significant differences in the detail. As an example, the gradient on the NYMR's Goathland bank is widely quoted as 1 in 49, which the average is but there is at least one section of a ¼ mile that is 1 in 42/3 which, in the context of what we are talking about is quite significant. After all this time we've no idea of the accuracy of the permanent way detail.

Let's come back to the dynamometer trace. I don't know so I'm asking; was there a calibration check before and after the run and does it exist as part of the trace? Without that information, we've no idea how accurate everything was and thus its validity. There's a well known instance of one railway's dynamometer car being found to be inaccurate when borrowed by another railway. I forget the circumstances and don't have time to go looking.

Of Mallard, we probably know even less because a dynamometer car tells us very little about the loco. We know it did the same speed of the train and we know the drawbar pull was also the same but very little else. I'm guessing that the loco was fresh out of shops so piston and valve rings would be good but I don't know. Worn rings can account for significant steam loss. We've no idea of how much steam was being used to drive everything. I believe we know the boiler pressure but little else. We've no idea of internal friction, cut off being used, steam chest pressure, superheat temperature, water levels and a host of other factors, both major and minor. As has also been said, we don't know the total weight of the loco as we don't know the coal and water levels in the tender. Nor do we know the amount of coal on the firebed. An A4 supposedly weighs 167.1 ton but after some time out on the road 2-3 tons of coal will have been used and possibly 2-3000 gallons of water. In extremis that can account for 14 tons of variation, perhaps more. That's about 9%. You can argue that quite a few of these points are relatively minor but, added together could become quite significant.

 

Nothing wrong with that. See my post above.

 

England needed heroes and greatness back in 1946.
Upping speed claim from Gresleys 125 to 126 and casting it in brass was affordable.
Everything else was dissolving,rationed,american or much to expensive.

 

And in 1938?


Sent from my iPhone using Tapatalk

 

Waiting for some not steam loving Articifial Intelligence to read the roll after digitizing

 

As I recall, Gresley borrowed the LMS one to calibrate the NER one. It turned out the LMS one was not calibrated properly. I need to go and check that.

The LNER dynamometer car was calibrated before and after each run, it was recorded in the running instructions. I will add to our list of "knowns". For the sake of interest and accuracy, I need to find out what that entailed.