Steam speed records including City of Truro and Mallard

I’m not being capricious. I have consistently said I disagree with Andrews’ interpretation of the data.

I can’t put it any more simply than that.

I believe I have answered Toms questions directly and moreover I’ve gone out of my way to explain my position and provide screenshots of my work to Tom privately.

If you don’t understand even after all of the above, I can’t help you. Sorry.

 

I don't know why the photos don't show up for you. They are there on my machine. Just click the link https://www.lner.info/forums/viewtopic.php?f=11&t=9331&start=75 and it will take you to the article, with pictures, on the LNER forum. Last post on that page, then following page.

 

I didn't say that you were capricious. I said that your reply suggested your understanding was capricious. There's a subtle but important difference.

 

In both cases I believe I am not being capricious or providing a capricious response.

I hope that is clear?

You are welcome to reach out via pm to ask any specific questions if you so wish.

 

Simon - I'm grateful for the screenshots you provided which show the general form of what is recorded on the roll. Obviously (and correctly) you have only provided fragments, so not enough to carry out any kind of detailed analysis on.

You are also correct in saying that because the roll has marks for both time and distance, then the precise speed the chart moves doesn't matter. However, obviously if the chart is moving at a constant rate per distance travelled, it makes subsequent analysis easier, since you can measure direct from the roll, rather than having to reference back to the distance markers. That would make analysis quicker and it seems logical to me that the NER / LNER would have designed that to be the case - if so, the mile markers would then just provide a calibration check and reference points.

I am though still troubled by your assertion that "in reality the distance between each quarter mile on the graph paper is going down as the speeds increase and increasing as speeds decrease" whereas Andrews finds "over a long stretch (12 miles or 24 feet of paper) [...] this showed the paper was moving at an average rate of 24 inches per mile with an error of less than five parts per ten thousand". He is saying that regardless of where he measured, a quarter mile was 6 inches long. You are saying different.

So I ask again - what measurements have you got for disparate speed regions of the roll? And as a follow up - are you measuring off the roll, or off a photograph of the roll? Those two things are not the same.

I don't think this proves anything about the underlying accuracy of the dynamometer car; nor is it evidence that either proves or refutes Andrews' work. Essentially the LNER have taken (by measurement from the roll) the distance travelled in a five second interval; and you have taken the time taken to cover a 1/4 mile distance in the same location, and you have both arrived at answers that are close to each other. That proves nothing about the accuracy of the dynamometer car; the one interesting thing it does do is set a rough limit on the precision that a method based on visual measurement from inked lines on a chart can give. That two people get a result about 1/4% apart gives some kind of upper bounding limit to the precision about which you could state the speed. This whole sub-thread started with a question about where you should set the error bars. Well, there's the first thing to feed into that discussion: the limit of precision on taking measurements by hand is probably about 1/4% (there will be other errors of course, and they are cumulative). But what that calculation doesn't show is anything about the accuracy or consistency of the underlying mechanism of the dynamometer car.

Tom

 

Let's focus on that one. Which data is he not looking at and how does that affect his one-per-mile fluctuation?

Lets get this clear. You are saying that the movement of the paper does speed up as the train goes faster (so the seconds marks get further apart), but not in proportion (so that the quarter mile marks get closer together).

Could it be that the paper drive is from the take-up drum, so the paper speed increases as the thickness of paper on the drum increases? That would have a much easier way to built the recording system than trying to achieve a constant paper speed. On this particular run, the paper speed would have been increasing as the train speed increased, but by coincidence because both were increasing (until steam was shut off), not because the paper was linked to the ninth wheel.

 

Thank You and very interesting.
The paper is advanced and speed-controlled by a polished thinwalled cylinder of ca 200mm diameter that is 24 inch cirkumference.
One turn of copper roll is one mile travel

Please disregard from ??????? to ?????????????

Blurb and I got wiser




??????????
can be adjusted to very fine limits
The counterroll can have contrapressure adjusted and thereby deform main roll into an ellipse.
If the wall and the two endplugs are not tottaly uniform and central we have one and four distortion automatically and we can adjust paper speed travel to rail speed ratio after purpose of upcomming test,moon-phase,temperature etc.
The one and four wave distortion will be phaselocked.

??????????????



As conspiracy theory it hits all buttons and save me proving the sheer impossibility of the 1938 speed claims.
Warp drive and ABS braking for UK steam was not yet working.

 

I am saying different, because I have found differently. Our approaches and methods are different.

I can only report on what I’ve found Tom. And it is factual that the roll is set up to 6 inches per quarter mile at the start of the roll, and by the end of the roll there is an obvious variation in the high speed sections. I have to report on what I find. Isn’t that the point?

You’ve used the word “average” in relation to the length of the quarter mile lengths on the paper - as has Mr Andrews - whereas I’m looking at and measuring each quarter mile on the roll individually.

But again it doesn’t change the price of fish. The point is the time period between each quarter mile mark. Ultimately that’s the period that needs to be clear.

But - and this is a really clear difference between the two approaches - I’m not the one clamouring for the dynamometer car being inaccurate. I’m recognising the dynamometer car as designed has limitations when exposed to the extremes of high speeds.

 

But Andrews doesn't just give an average: he also gives the variation "less than 5 parts per ten thousand". In each six inch length, he is saying he found that length to vary by less than 3 one thousandths of an inch across 24 feet of roll. So what is the variation that you are seeing - how long is a quarter mile at one end of the roll relative to the other? What are the longest and shortest quarter miles that you have measured? All you have said is that you are seeing a variation that is - presumably - much larger than Andrews' has seen. Which isn't just a question of disagreeing with his analysis: you are fundamentally disagreeing with the data on which he has based that analysis.

And I'll ask again - are you measuring from the roll, or are you measuring from a photograph of the roll?

You ought to be able to answer those questions very easily, surely?

Tom

 

Hi Tom,

I’m not sure why you’re being quite so aggressive in your last round of questioning - I don’t believe I have exactly been so defensive in my answers as to be evasive.

But yes, I am working from a photograph of each section of the roll. I thought I had made that clear in my PMs to you. If not, my apologies. However there are some advantages to working from a digital copy.

Working from the photographs of the roll will of course also give us more to write on in terms of the limitations of the study and the analysis. However I am using specialist software that allows me to do these measurements by way of scale. This will be part of my write up.

I have limitations on my time that means I am not able to study the actual roll at the museum. There’s also a question of cost and museum support for being able to do the study in person.

I hope that you now have all the answers you need?

 

I hope you don’t feel this is aggressive but I think it would help if you say just what is the variation you are seeing and how this conflicts with Andrews.

 

If I may be so bold, maybe I am trying to be diplomatic by not giving an exact answer.

If it would help this part of the debate, yes I think there is enough of a variation that it has concerned me when I have been doing my own analysis.

I am also subject to having my analysis peer reviewed and I don’t want to necessarily prejudice that.

I think I have given more than most would in terms of answers, data and photographs.

 

Thank you. I respect your reasons but, for me, I think it draws a line under this particular part of the debate for now.

 

It seems we may need to await Simon's thesis to see the details of his measurements from the roll, his analysis of them, his conclusions, and how those conflict with the Andrews paper. I am not convinced that pre-publication of snippets of the work would prejudice acceptance of the thesis, but it's his project so it's his call.

 

I think critiquing his work before he's done it is a somewhat futile exercise.

 

Kind of like a high-brow livery debate! Par for the course….

 

I had to laugh. Good luck Simon, the community here has given you some pointers. Looking forward to the finished article.

 

I can’t quite remember how we got here because a lot has been said, but my issue with all of this is that I’m currently studying the whole roll, so I have a point of view based on what I’ve been doing.

I feel happy to share what I can and I think I’ve gone to quite an extreme to try and explain myself and my views that perhaps I should have stepped back from and left alone.

Part of why I think some of what has been said about my posts has been so robust is because the paper I have referred to was couched in very absolute terms and presented a lot of graphical representations which don’t actually show the core underlying data, which is what I intend to do as part of the PhD together with my own analysis.

Andrews’ paper being very absolute in what it was saying makes it difficult for anyone who comes after (myself included) to question what’s been said.

From my point of view, I’m looking at the same base material, I’ve spotted some things I am not sure about in Andrews’ interpretation and have also realised I can do something different with the data.

 

Did Andrews write his paper based on examination and measurements of the original dynamometer roll, or did he use photographic images provided by the NRM? I would not necessarily classify photographs of the roll as 'base material'.

Andy