Steam speed records including City of Truro and Mallard

Hi Michael - I really don’t understand the problem. I agree with your approach. I think it is a “good starter” for anyone trying to delve more into this - I was trying to be complimentary, my apologies if that didn’t come across.

I think you still need to up the figures for air resistance, which is what I was getting at. The reason I posted my graph (which is derived from Spencer’s stats - important distinction, Spencer did not make the graph) is to show what a direct comparison between a streamlined and non streamlined locomotive is. The horsepower difference is significant between two mechanically similar types of locomotive.

My apologies for previously misunderstanding your point (about a month ago?) - I wasn’t aware that learning was a problem. How does anyone improve without asking questions, debating and discovering?

I am grateful for your recent inputs and I think your theory has merit.

 

Simon: My R includes air resistance and was dependent on data from road
Tests; Ell (twixt Swindon and Slough) and Andrews ( March Norwich and a
turntable in N.Wales inter alia ). I added 20% to their figures’ based on Road
tests of the late Victorian/Edwardian period, this is probably high but I was
covering an ignorance. What is your statement that I need to up the figures
based on please ?

Michael Rowe

 

Was Coronations speed of 114 mph on the approach to Crewe in 1937 accurately recorded and verified? It was still doing over 100 only a mile and a half from the reverse curves at the entrance to the station which had a 20 mph limit, and the brakes had to be slammed on, but it was still doing 57 mph when it got there and only just made it.

 

I believe that several stop watch types all logged 112.5 but all agreed it was still accelerating and were happy with 113 m.p.h. The speed recorder on the footplate touched 114 and it was on that basis the LMS claimed that speed. 113 seems to be reliable.

 

Hi Michael - it’s covered in my Gresley book, but there’s been a different approach to calculating air resistance and optimum forms for streamlined shapes for some time with railway vehicles. I recommend Chapter 4, page 53 of Train Aerodynamics: Fundamentals and Applications.

Baker/Johnson/Flynn/Hemida/Quinn/Soper and Sterling’s work on railway aerodynamics goes through a full modelling and drag reduction method description, together with the appropriate equations (which are too numerous to list here but worth reading).

The point I am making is that Spencer’s work points towards a real world scenario where streamlining actually makes a significant difference to the locomotive’s power requirements, and modern day modelling is more complicated and in depth these days. Applied more rigorously to older forms, you can get a clear sense of the real world problems with some of the high speed claims.

 

If we're concerned about terminology, then strictly "Indicated Horsepower" is calculated from indicator diagrams of pressure in the cylinders, which were not made on the runs in question (and in Mallard's case would have made even more mess of the streamlining than the dynamometer car). But I think it is reasonable to use that term for the amount of power developed in the cylinders, even if that can only be estimated from other measurements.

As for CoT's maximum speed; estimates of what it theoretically could have achieved, taking account of many factors including air resistance, are subject to substantial uncertainties in most of those factors. I think those uncertainties are much greater than those appling to R-M's stopwatch timings.

 

So going back to one of your earlier posts, just supposing there was a 20mph south westerly wind that day. What is the hp equivalent of that?

 

Good question. I am not aware of any Test figures ( although there may be some within
the various post WWII tests ) for a 20% following wind but I think undoubtedly it
would afford at least a 10% reduction in R. ( whether directly behind or at an
angle, whether the train was on a flat open route eg Taunton to Bridgwater, or
in a cutting eg leaving Whiteball UP or on an embankment will effect how much ).
Having said all of that I think it would have afforded COT a bonus of at least 100-200HP.

As an aside it is generally accepted that some of the more memorable performances
twixt Swindon and Ealing Broadway and Andover to Hampton Court Jct benefitted
from a South Westerly. (. particularly KA 777’s effort in the early 1930s. Salisbury to
Waterloo in 72mins 41 secs with 90mph at Byfleet and 345 tons gross)

Similarly Doctor Andrews after initial tests on the ECML recognising the prevalence
of South West trade winds carried out further testing on an East West route i.e.
March to Norwich.

Sorry the answer is somewhat vague but wind resistance is, stating the obvious,
a moving target.

Michael Rowe

ps Dr Andrews is not David Andrews. Dr Henry Ivan Andrews gained his PhD in 1946 !
( MSC in 1931 ) He worked for English Electriv pre WWII and then the LMS. Hermod
may be interested to know he was a follower of Professor Nordman.

ppss Dr Andrews also carried out wind rests on a locomotive. He placed it on
a turntable in N.Wales and observed wind effects in different positions !

 

My contribution to human welfare is a cheap and dirty model for estimating power versus speed of trains.
If someone will supply total length of train and mass we can try it on the CoT run with and without following wind.
Measured wind velocity vary very much with placement of probe.

 

I can't find anything to link to, but have heard this is done as a way to reduce the impact of the floor of the tunnel, while also having wheels that the air can't simply go under... I think it's in one of my books, if i find it i'll post a quote from it.

 

Were there any other high speed runs at 100mph plus with Duchesses? The Coronation one is the only one I've heard of

 

Not many, but there had to be the coincidence of the 100 m.p.h. and someone on board recording it. On the same day as the 113/114 run, 6220 took the train back to Euston in 119 minutes start to stop, apparently hitting exactly 100 at Castlethorpe, 99 at Kings Langley and 96 at Harrow, with much of the distance at well over 80 m.p.h. It had had a hard day!

On 5 September 1957 6244 took the Caledonian from Glasgow to Euston and arrived 37 minutes early. The time from passing Crewe to Euston was 118 minutes. It is assumed that this was an arranged run if only to keep the sections ahead clear, but no detailed logs were made, only the guard's journal, but speeds over 90 would have been needed and the 100 must have been a possibility.

But the only other claimed 100+ - actually 102.5 - was achieved by 'Lizzie' 6203 at Milepost 39 south of Leighton Buzzard on 3 May 1936. with seven bogies, weight including engine 366 tons. The gradient is 1 in 1330. Reported in the LMS Magazine, March 1937.

 

I have a suggestion regarding the "mirrored 05s" wind tunnel test. Could they have been looking to quantify the significance of the floor/ground effect? Bearing in mind the probable absence of moving floor wind tunnels in those times, how do you quantify how significant the inaccuracy in your fixed floor model is?

Well, if you do a mirror symmetry model, you now eliminate the effect on the airflow from that non-moving floor (which will tend to slow the airflow close to it). The models are symmetric, so in theory no streamlines should cross the virtual floor, barring turbulence, eddies, etc, and the virtual floor is quite possibly a closer approximation to the real ground (receding rearward at approximately airflow speed) than a fixed floor.

 

OSNock has given details in three of his books of a log behind 46251 with 13/444/465 tons
between Glasgow and Carlisle on the ‘Mid Day Scot’ The 10 miles of Beattock bank
were descended in 6 minutes 36 seconds with 64mph at the summit, 91 past Greskine
and105mph at Beattock. I do not know who recorded the run, the log as published has
speeds consistent with passing times throughout. It is I believe the claimed fastest
speed on the WCML other than the pre WWII tests. I think it was made in 1957.

Also in 1961 RM but again no recorder given. ( not unusual with Mr Nock who was
not over generous with his acknowledgements. )

Michael Rowe

 

Do we have weather records for the days when any of these runs were made?

 

In 1956, when in the RAF, I used to travel from Paignton to Taunton leaving at midnight. Having changed at Newton Abbot to a Plymouth train we usually arrived at Taunton around 2.30 am.
I have often wondered what speed the train achieved down the bank from Whiteball Tunnel as it was certainly very fast with the coaches rocking very much indeed. It was apparent that it was a high speed. The trains brakes were applied in earnest as we approached Taunton Station.
It is unlikely that timings by train speed enthusiasts were made at those hours.......but you never know.

 

I used to wonder what the class 504 units got up to on the descent from Whitefield to Radcliffe when I was coming home from school and later work.. It was straight for about two miles and down a 1 in 46. It was probably no more than about 65 to 70 at a guess, but they used to bounce around like mad!

 

It was pretty ropey in a tram.


Sent from my iPhone using Tapatalk

 

at least the trains had comfy seats, in those trams it's like sitting on an ironing board.

back to steam, I tend to think of the A4s as intended for fast running and speed with the Duchesses as more of a heavy haulage machine, built to cope with big loads on Shap and Beattock, also the East coast main line is flatter and less curvature and better suited to fast running

 

Thameslink Class 700: "hold my beer."