Sir Nigel Gresley - The L.N.E.R.’s First C.M.E.

That is a bold and rather sweeping claim. The LMS was for instance unique in having a substantial (staff of around 150+) Scientific Research Department, based mainly at Derby, whose responsibilities covered a wide area, not just locomotive related matters such as water treatment. (You may recall that when a new laboratory was opened in Derby in December 1935 by Lord Rutherford, the eponymous Jubilee 5665 disgraced itself by running short of steam hauling the great and good to the opening ceremony from London).

 

The pens are weighted differently Steve.

 

I stand happily corrected. LMS isn’t my area of research (yet!)

 

Not relevant to the precise speed (however defined or determined) of Mallard but this LNER.info thread has some more photos and details of the dynamometer car and its history - last used in 1951.

https://www.lner.info/forums/viewtopic.php?f=11&t=9331

 

Weighted differently or weigh differently due to the method of operation used to transfer the element being measured to the pen?

You have obviously convinced yourself about the origin of the so called ticks so we'll just have to agree to differ.

 

Weighted differently, look at the pens themselves.

To be frank Steve it’s in the photograph. I’m not disagreeing with you on the basis of a religious belief, it’s there in the photograph and the different types of pen and their weighting matches what we find on the mallard roll.

 

I’m sorry, but that is not at all obvious to this lay observer. Working solely on the photo, and without the roll, we ordinary mortals are at a significant disadvantage in interpreting the picture.


Sent from my iPad using Tapatalk

 

With my electronics engineer hat on, the little 'ticks' on the square wave are overshoots in the pen mechanism (as per jimc's explanation in post 1591). In servo terms, they're slightly under-damped in order to achieve a faster rise time of the pen; if they were anything else the timing would be compromised. Were such a waveform presented to me on an oscilloscope, I'd be taking measurements at the HAD (Half Amplitude Duration) point.

 

To this old LNER enthusiast, the cutting of two Gresley Pacifics were an utter travesty: 2509 Silver Link and 2750 Papyrus, the latter being a test bed for so many ideas.

 

Okay, fair comment.

When you look at the pens, you can see that some are more heavily weighted from the top than others. The reason for that is that this (together with the mechanism attached to them) are designed to give a specific movement and a specific weighting on the paper roll.

It’s more obvious with two of them - the time and distance pens which actually give similar shapes on the roll. The ones which give constant results (e.g. drawbar horsepower) over the whole roll are not so heavily weighted.

These will be calibrated as the rest of the mechanism and dynamometer car was.

For the most part I am still here because I think it’s really important to have a publicly available space in which to discuss historical topics of interest, and Nat Pres does things much better than most places available.

There have been times where I have found myself utterly exasperated though. Sometimes it has felt like if other writers had presented their findings, they might have found a different kind of debate. It feels exhausting sometimes to report back on primary evidence found. When I originally presented David Andrews compared to my own work, it felt (and potentially this is my perception) like his work was accepted without question and mine was questioned first. Both in reality should be questioned (and that’s fine, that’s how it should be).

I don’t know, writing on Thompson and then Gresley has been both an educational experience and a heartwarming exercise and also utterly infuriating and heartbreaking at times. I still find myself remembering a moment at the Bluebell when accosted by an anti-Thompson individual verbally and some of the emails I have received over the years (which included one poorly written and ill thought out death threat) haven’t helped my mental health at all.

Maybe I haven’t helped myself at times (sorry everyone for that - I am trying to work on my tone. I know I don’t always get it right), but it has been good that we have some very knowledgeable people on the thread who keep me on my toes too (Jim, Tom, Steve, the list goes on).

I am hoping that some of my research and work will be able to go towards further education, but that’s a by the by. One thing is certain, when we’re at our best in this thread and forum is when we’re discussing things. We don’t always agree, and that’s fine, but if we are all able to have a place to discuss it rationally then that can only be of benefit to better historical study for everyone on the topics we choose.

 

Interesting, thank you for this. I did a quick google of HAD and this has become another rabbit hole to go down…!

I think I had better bow to the superior knowledge and acknowledge Steve was right.

 

Not Papyrus for me - Humorist. That no Gresley A3 would be included within the National Collection is still bonkers to me. Yes, you can’t save them all, but arguably Gresley’s first Pacifics set a trend that other railways followed.

 

So just noting the above, please accept a humble apology from this enthusiastic but sometimes obtuse researcher.

 

Numbers from mr Andrews paper .
126mph blue claim is at mile 90.12 and energy content of a 400 tons train is 634 MJ.
11 seconds before train was at mile 90.5 ,speed 123.4 mph and kinetic energy was 608MJ.
26MJ on 11 seconds are roughly 322 horsepower more for acceleration .
Mr Martin can maybe try to use his short wave analysis method on the let us say 20 seconds of interest?

 

I can certainly have a go, but my working week starts shortly. I can have a look at the weekend.

 

Moving on a bit - were there any people on the footplate (other than the driver and fireman) and has anything ever been written from that perspective?

The reason for asking is really thinking about water levels and braking. Looking at the graph in post 1565 (and ignoring the inconsequential wobbles in speed ) the loco slows from 124mph to 110 mph in about 2/3 mile. At those speeds that's 14mph speed loss in 20 seconds - and presumably a similar deceleration continues for quite a period afterwards as the loco slows down to more normal speeds.

That's a pretty severe deceleration sustained for quite a long time. As anyone who has been on a footplate would know, brake hard on a downhill and the water gets thrown forward, which on the footplate you see as the water dropping out of sight in the gauge glass. Presumably with the loco having been worked so hard in the run up to the peak speed, the real water level may have been gradually dropping anyway in the minutes leading to the peak speed.

It's one of those situations where I would actually have quite liked one of those O.S.Nock footplate descriptions with the carefully drawn graphs showing progression of regulator opening, cut off and water level! Quite likely that when the driver put the brake in, the water disappeared out of sight and remained so for a heart-stoppingly long period!

It would be interesting to know if there are any first hand descriptions of the enginemanship shown in the attempt.

Tom

 

The closest I have is Eric Bannister’s account from his book, and he was in the dynamometer car. I have cited this in the book. Bear in mind it was (in a secondary aim) a braking test for a high speed train.

Or, there’s Duddington’s account you can hear here:



There’s also this, which is his last run as a driver - and with Mallard - in 1944.

 

I will check the roll for you when I get a moment later on Tom.

 

More horsepower
If the train gets 1400 horsepower from gravity at 123.4 it gets say 1428 at 126.
If air resistance eats 2500 horsepower at 123.4 it needs 2661 at 126.
We need 330hp for acceleration and say 70 mean hp to combat rising air resistance that is 400 extra hp to go from 123.4 to 126 in eleven seconds.

 

I think Jimc is the one you should be bowing to.

there's no need to apologise to anyone. As you have said on more than one occasion the debate is always interesting and it is a learning curve for us all.