Steam speed records including City of Truro and Mallard

Loss of adhesion between the 5th wheel and rail at high speeds?

 

An acknowledgement is due to @Jimc , who picked up on this earlier.

 

well that’s a categoric position - I await the future book with interest to see who is right and look forward to revisiting this thread and this post in particular in due course.

If you’ve just topedoed the theory on the basis of a 60 year old memory and some light googling then you’ll have scored the hit of the young century.

 

Always a possibility but, if the drive to the chart and quarter mile markers is otherwise positive then that would not create this effect.

It would also mean that Mallard was actually going faster than 126 but I'm not going there!

 

Reading this, I'm reminded of a story my father told me of his time as a student in Dublin in the 1960s.

There is a scene in Ulysses where an image that comes up repeatedly. An American academic was preparing a paper on Ulysses, and had come up with an elaborate theory for the image. Within 24 hours of arriving in Dublin, he was shown a building which had a slogan painted on the end wall, which precisely matched the image in the novel.

With that cautionary tale in mind, I suggest that at minimum the original should be interrogated closely against the photographic images to verify the measurements and exclude the possibility of discrepancies due to imaging.

 

Read this one if you have the necessary maths.
https://www.asprs.org/wp-content/uploads/pers/1974journal/apr/1974_apr_493-500.pdf

 

It's not so secret. Anybody can ask the NRM for a copy, subject to the museum's contractural usual restrictions on sharing or publishing their copyright images.

(Amended as advised in #651 - thanks Jim!)

 

With reference to which, a recent court judgment has considerably weakened the ability of museums and galleries to assert copyright when reproducing images from their collection. I came across it in a Tweet from Bendor Grosvenor (an art historian) - https://x.com/arthistorynews/status/1733599719014687227?s=20

 

Whoever they are I'd bet they're not going to lose any sleep about that.

 

I think this is disappointing. I am agnostic as to whether Mallard broke 126mph, and I have absolutely no background in engineering, physics, maths or data analysis as some of those commenting on here quite obviously do, but I do find the whole conversation fascinating.

I certainly don’t see anyone grinding axes, but I do see some robust, but pertinent, challenges regarding your understanding and your methodology.

You appear to me to be confident that the data you have is uncorrupted (for want of a better word), that the data is an entirely accurate representation of what was happening during the run with regards to the speed of the train, and that therefore, if you can plot enough points from the data you have, you will be able to say for certain whether or not Mallard got to 126mph.

@Enterprise seems to be saying that this is an impossible task because the data in itself is too imprecise (this is before considering any of the points raised about margins of error). If I understand this correctly, it’s a bit like me taking an out of focus image (something I am still quite capable of doing, even in the age of digital cameras). It doesn’t matter how far I then zoom in on the image, and how much analysis I can undertake at a granular level, if the image is out of focus to start with, it’s not going to help me work out if I’ve taken a picture of an elephant or a combine harvester (extreme example, obviously).

@Steve and @Jimc have raised the issue of whether the copy of the roll that you have is accurate enough to do what you’re aiming to do. Nobody, unless I’ve missed it (or it’s gone over my head) has yet fully explained the inner workings of the Dynamometer car, which again has a bearing on the “precision” of the data.

@Jamessquared said something upthread about there being scope a lot of good new work to be done on high speed services in the 1930s (apologies if I’ve misrepresented), but that whether or not Mallard got to 126mph was a minor point in that. I’d agree with that. Stoke Bank is not the hill to die on.

Incidentally, I trained as an historian, and to me the interesting question is not what speed Mallard reached, but why when the speed seems to have been accepted as 125mph in 1938 (erring on the side of caution?) was 126mph put on the postwar plaque? I would have thought that that would have been a decision at board level, and I’d be interested to know if there were any discussions noted on that point.

 

A sense of proportion is necessary here.

There is an awful lot of analysis that can be done with a decent photographic image, especially with the sort of intrinsic cross checks that seem to be in the roll. AIUI Simon is proposing using the automated quarter mile ticks as a baseline. All that's going to happen by using the ticks as a baseline rather than taking measurements off a high resolution flat bed scan is that the error bars get a fair bit wider and the noise greater. This is not intrinsically an gamestopper, its just a question of working with it. I don't know everything Simon has planned, but from what I have gleaned it shouldn't be a major issue for what he has in mind.

As for copyright, the NRM has not used copyright law to restrict redistribution of material I have received from them. Instead they require you to agree a contract about how you will make use of the material. This is significant, because unlike copyright, contract law doesn't have an intrinsic expiry.

And finally, I *still* am completely unconvinced of the usefulness of critiquing a piece of work before its been done.

 

This is what is on the locomotive, It's good enough for a lot of us.

 

Even more interesting is if Gresley himself believed in 125 mph based on the quarter mile speeds shown that was manhandled by his own merry men?

Mallard by Hermod posted Dec 5, 2023 at 10:03 AM

 

Some of those writing in the thread are unquestionably doing that and I have no problem with that. They know who they are and I have PM'd them to share what I can as they have contributed positively (if robustly) at times.

There are some for whom I can do no right and I have noted similar commentary on other threads. The thing that incenses me is:

• They haven't got sight of the documents I have
• They haven't had the discussions I've had

Telling me I would be better off doing something else is a nonsense.

I've never said it is "uncorrupted", I am aware of the roll's limitations and that of my copy.

I have my own concerns with a previous analysis as I think the reasons given in that analysis may be wrong.

I think I will say politely that you need to go back and re-read the thread to understand where I am coming from.

I have pointed out what I have, what I am seeing, where I disagree, and fundamentally I am more interested in the start of the roll (which rarely gets analysed, if at all) anyway. I have said this multiple times in multiple posts.

Is there an element of invisible ink here or are people reading what they want to read?

Deja vu. The copy I have is, as above, of a very high quality and set against certain standards I am satisfied with. People who have been shown a copy of the roll by way of sample on this thread are welcome to give their views as to whether they feel it stands scrutiny as a copy.

I have repeatedly said it's not my main interest in analysing this.

I understand it from notes, board minutes, a report on the fitting of the plaques prior to being sent out for the exchange trials in 1948, and examining the dynamometer roll, 126mph was an instantaneous speed calculated from the roll within one of the 5 second intervals taken by the LNER team on the roll.

The question that has been posed for me is whether the speed recorded is down to a defect in the equipment, or something else, and I am leaning to "something else" based on the approach I am taking, as, again, I can only report on what I am seeing and doing.

And as Jim has said above, I've not finished the study yet and am getting to grips with it. Part of my write up will be strengths and limitations of the study in any event.

 

It is a small job for an honest angle grinder to
remove the W ,
cut open top of O and R
and remove L and D.
Five minutes max?

 

May I suggest

I am sure that it would be possible for @S.A.C. Martin to access the original roll and base his work on that rather than the copies/

I am sure that if someone is kind enough to pay for this Simon would grab the opportunity with both hands.

Until this happens however we are where we are, and I await the result with great if untrained interest.

 

It doesn't necessarily add a great deal though. Personally speaking when working in archives I always feel under a great deal of time pressure. I prefer to photograph as much original material as possible and then analyse it when I get back to base. In some ways, too, you can get more from images than you can from the originals since you can do so much more with them. There's also the responsibility thing. All this stuff can only be handled so many times and is going to get more delicate with age. If you don't *need* to handle the originals you shouldn't.

 

The clamour for "use the original roll" is, I feel, at odds with conservation needs and practical reality. Mr Andrews may have had the time and monetary support to work on the roll in his own time: I do not. I am therefore doing what I can within my own parameters and needs of the project.

The dynamometer roll is over 40ft long, end to end. There's practical considerations in undertaking an examination of the roll.

The photos I paid for the NRM to do on my behalf are, I believe, now accessible for a fee from the NRM's search engine facility. So, whether you agree with my approach or not, I and the NRM's search engine team have provided enthusiasts and academics with a full digital copy of the roll to analyse: something that wasn't available before and has enabled this discussion.

 

Remember the glory days of the National Archives/PRO where both ink and photographs were banned?

you basically had to make notes, at speed, with a pencil then stand or fall on your analysis of said scrawl at a later date! Or go back to London and check the documents again….

Both my undergrad and post grad theses were written under such conditions - pretty sure my handwriting has never recovered!