Edward Thompson: Wartime C.M.E. Discussion

Though to be fair, when you write (as you have in earlier posts) about Thompson's "criminal butchery" of Gresley locomotives, you aren't exactly showing much objectivity and judgment yourself either!

I still think the historiography is interesting: why is it that in one and a half centuries of steam locomotive development, encompassing designers with a huge range in competence, yet it is seemingly only Thompson who attracts such a level of vitriol? I'd suggest the Gresley Fanboys are scarcely doing themselves or Gresley's memory many favours by their seeming incapability of realising that, on occasions, even Jove nods!

Tom

 

Yes, but an inside Walschaert needs an excentric and -strap which are very heavy parts. The remaining parts certainly are not divided in total over the two outside gears and one does not need all of them. Please note that the change from Bulleid gear to three independent Walschaert gears added 5 tons to the MN/BB/WC class.
Kind regards
Jos Koopmans

 

hi simon,

it is not for me to produce you with primary source evidence to counter your argument. im not the one writing a book about Thompson! however on the evidence in particular of the Stanier/Cox report you seem to have difficulty in interpreting this objectively and understanding the correct interpretation of the report.

Lplus (with extremely well argued posts) and many others and myself have arrived at a contrary view on this report to you. you see the report as carte blanche and justification for what Thompson subsequently did, but i hasten to point out you are in the minority and many of us regard the report as strong evidence of Thompson's failure to do what he ought to have done at the time based on the report's contents.

at no stage have i expressed any view that Thompson was anti Gresley. i have instead tried to approach this matter from an engineering and design standpoint. the question in my mind is what would a reasonably competant CME have done in the same situation, and in wartime, and with the financial constraints of the LNER at the time. my conclusion is that anyone else would have made some small but significant changes and avoided rebuilding 'Great Northern' and the P2s.

cheers,
julian

 

(and in reply to Tom's above post, if one arrives at a considered view that what Thompson did to 'Great Northern' and the P2s was unnecessary, then the hideous results of the rebuilds could indeed be regarded as 'criminal butchery'! but perhaps i used over emotive language to press home a point - in which case i apologise!)

 

hi simon,

i do have a copy of the Rugby Test report on the B1 from 1951 if you havent already seen it.

makes very interesting reading as primary source material.

cheers,
julian

 

I don't think that is quite true. A rebuilt WC/BoB is about four tons heavier than an original, but that is by no means all in the valve gear. Instead, it is lots of small additions, none of which is huge but collectively add up: a much more robust smokebox, running plates, balance weights, reversing screw etc. I haven't got the figure to hand, but I seem to recall that Bulleid estimated that the minaturised inside motion would save about 1200lbs, so presumably that is the sort of figure that is directly ascribable to adding a third set of valve gear - it's certainly not five tons; nearer half a ton.

Tom

 

Phew, found it:
"By January 1943, the Running Department had requested a modern version of the LPTB L2 2-6-4Ts. All orders for the V3s were cancelled or postponed, and plans were prepared for the new 2-6-4T. The boiler was based on the V3 but with a larger firebox and longer water tanks.

Attempts to widen the boiler diameter were made, but this proved impossible without reducing the water capacity. A tapered boiler design was prepared, but was quickly rejected by Thompson. A 5ft parallel boiler was used instead.

For the pony trucks, Thompson departed from Gresley's preference of a double swing link suspension. Instead, he chose a design using helical control springs copied from the LMS-designed O6 2-8-0.

Thirty of these new L1 locomotives were authorised in April 1944, and the first locomotive (No. 9000) was completed in May 1945."

Taken from the LNER encyclopaedia. Other evidence may contradict this.

Intuitively it is the rigid part of the wheelbase which will impact the ability to negotiate curves, not leading or trailing trucks or bogies.

Fair enough on the Jinty, it just surprised me that the wheelbase of a small tank engine is so close to that of the P2. I would argue though, again intuitively, that the fact that on the mikado there is not an axle at the mid-point due to the even number of axles will actually help the P2 on tight curves.

 

There's lots in your post to consider, but I'll just comment on this bit for now. Perhaps, I wasn't very clear on this, previously; the point Iwas trying to make was that discarding a successful system isn't necessary just because others are discarding less successful versions of the same type of system. I think the Gresley conjugated gear was a particularly elegant way of eliminating between frames valve gear on three cylinder engines, despite not being the most precise, and despite being sensitive to poor maintenance. I don't know the details of the conjugated gear used elsewhere, except fo the Holcroft gear, but just because others couldn't make it work isn't a reason, in itself, for abandoning a successful system.

 

Well I dunno, I 'm not a steam engineer, my education being more in the pure sciences and my work with software, but I really don't understand how you and lplus reach the conclusions you seem to from that report. I don't altogether agree with everything SAC concludes from it, but he seems to me a lot closer than you two. I thought this was actually one of the more important posts :

 

But that inherently is the point - the LNER was in a wartime scenario and poor maintenance was rife because they simply didn't have the manpower or the provisions for the high standards of maintenance normally required. We're talking about failures across a range of tank locomotives, mixed traffic and freight and express passenger locomotives. In the context of the time, Stanier and Cox reported on the problems as they saw. Pre-war, with manpower higher and with supplies of specialist lubricants available, for instance, the report could have gone completely the other way and stated that, though it wasn't something they'd use, the gear was adequate. That's not the case in the report.

So as I see it, the report is accurate if we take it in the full context of the time it was written in. We may disagree inherently with its conclusions but we can understand and respect why they were made, surely?

 

It is if you are disagreeing! Providing evidence for your claims is absolutely necessary. Otherwise you could - as you have been doing - make some pretty baseless accusations based on things you've heard down the railway pub and present them as fact!

I must confess I wouldn't put you and Lplus in the same bracket of debate.

And yet somehow I find myself struggling with understanding where the engineering is in your viewpoints.

Perhaps - but then he asked for an independent report and that report is pretty damning. The language used is pretty clear in its conclusions:

 

Just for a bit of light relief, here's another markedly unsuccessful loco with Gresley valve gear:



Though for the avoidance of doubt, the poor performance of the class was mainly for reasons other than directly the valve gear. Each loco in the class was quickly rebuilt as two pacifics, with new boilers but retaining the three cylinders and conjugated valve gear, but those locos weren't much better and were rapidly superseded by a new class of simple rugged two-cylinder 4-8-2s. The rebuilt locos soldiered on into the 1950s before being scrapped in very run-down condition.

(Look up "NZR G class")

Tom

 

Had to chuckle at this bit - "The '2 to 1' valve gear although theoretically correct is, in practice, incapable of being made into a sound mechanical job."

So for something described thus, it's interesting to note that it remained in front line use for another 25 years after the report and locos so fitted were entrusted to the highest profile jobs on the former LNER network. A little bit of "not invented here syndrome" perhaps.

 

I agree that in light of what happened afterward, that sentence seems ridiculous: but if we are putting it into context they were making the report in the middle of a war, with reduced levels of maintenance available and higher than average failure rates, and if the statistics in the report are anything to go by, six times greater than on the LMS with comparable locomotive stock. So is it such a ridiculous assertion if we put it into the context of the time?

That's the nub of the issue. Looking at it in retrospect, and putting the circumstances into context - not just picking out the one sentence and stating it's a nonsense based on results which hadn't happened at that time. How could Stanier and Cox know what was round the corner? They were writing of the time, not the future which hadn't happened yet.

 

That's what happens when you stray from what Beyer Peacock would have designed. 2 x 3-cyliner Garratts were not common and none seemed to have been as successful as most of their 2 x 2-cylinder cousins.

 

You are quite determined to ridicule the Gresley gear aren't you? How many people have to tell you that the problem with the Gresley middle big end was the big end itself? Even the Cox report didn't put the blame for that solely at the feet of the derived motion.

 

Not at all. I've even agreed with you on the basis of history after that event.

However the reports conclusions clearly state that there was a case for not perpetuating the valve gear. Point number 1 - as above.

That is a fact: don't shoot the messenger because Cox and Stanier wrote that, I didn't.

I'm not arguing - at all - about the engineering of the valve gear and its suitability before or after the report was written. I am pointing out what the report says and also the context of the time in which it was written.

At that specific time, Stanier and Cox wrote a report independently of the LNER and recommended that the valve gear not be perpetuated.

They give reasons, chief amongst them is the big end strap - agreed? - but nevertheless they stated based on the information they had available at the time, that they felt the LNER should not continue with the valve gear.

So please explain where by contextualising that, I am in any way "ridiculing" the Gresley gear? In fact, I would like you to pick out where - in 41 pages of this thread - I have directly or indirectly ridiculed the valve gear. I have not: I have tried to contextualise the feelings of the time based on the evidence available.

Please stop being quite so dismissive and aggressive. You sometimes post some very helpful information but the manner in which you write does not become you sir.

 

I don't think it is ridiculous. It just depends on the use of words, and even in 70 years the shades of meaning may have changed. I was transcribing some 130 year old newspaper reports of races the other day, and it repeatedly struck me that I would not have used a given word in quite the way the author did.

I think Cox/Stanier are talking in engineering design terms. To extract what I see as the critical sentences with my emphasis.

So, what do they mean by incapable of being made into a sound mechanical job? Well, what they cannot mean is that they think its going to fall apart. As they were well aware the gear had already been running much of the LNER's work for the previous 15 years or so, and they don't ascribe the unacceptably high failure rate of big end bearings to it. So logically they can't possibly mean sound in the sense of not breaking, nor, in my opinion, is there anything in the report that says they do think that. All they say that there will be an increased rate of wear over components in separate valve gear. Are any of us in a position to dispute that?

I think the key point is the magnification of the play that must have existed in a mechanical device of that era. That inherent defect is where they see the design as unsound, and that's why they think it shouldn't be replicated on new construction. The fact that the design continued to work for the next thirty years as well as it did in the previous 20 would be of no surprise. Whilst Stanier/Cox do suggest *consideration* being given to replacing the conjugated gear in *certain* classes, at no point do they recommend replacing it in all classes. That must mean that they envisaged many of the classes, and possibly all, completing their full working life with the conjugated gear on.

If you are going to say they were right or wrong to say there would be extra wear on the conjugated gear over three sets of valve gear then you need to be armed with the detailed maintenance records of all the classes, including the time spent on each one for routine shed maintenance. And I doubt that data has been put together, even if it exists. Has anyone tabulated the complete maintenance records for all the Pacifics? Do the record cards even hold records of shed maintenance time on each loco?

But isn't it characteristic of enthusiasts that when we see a document from professionals which doesn't match our preconceptions then our first instinct is to rubbish it?

 

as quite a lot of mention has been made of Harold Holcroft,

it might be of interest to compare how the SECR and SR dealt with the Holcroft conjugated gear.

only 2 locos were so fitted. SECR 2-6-0 N1 822 completed 1922, and SR 2-6-4T K1 A890 completed 1925 (later converted after the severnoaks accident to U1 2-6-0). no other SR 3 cylinder locos had conjugated gear fitted having instead 3 sets of walschaerts gear.

both locos were converted to 3 sets of valve gear in 1930 and 1932. the design specifically provided for easy conversion.

the reasons given for the gear's removal was increased maintenance costs (same problem as on the Gresley gear but many years earlier), Ashford having to make non-standard spares for just 2 locos, and the removal of weight restrictions.

in a debate of the Institute of Loco Engineers in 1948 following Clifford Cock's paper on 'History of Southern Locomotives to 1938' the minutes record some very interesting observations by Holcroft as follows:-

"The remedy for over-travel or other irregularities of the third valve is to make the primary gears as rigid as possible, consistent with their weight. The deflection of the levers of the conjugation is small but could be further reduced by using a deep I section of aluminium alloy. It does not seem to be grasped that corrections can be applied by departing from the rigid 2 :1 ratio of the levers; the valve events can be advanced or retarded and also the travel can be adjusted by slight alterations in the proportions of the levers. In other words, the possibilities of the conjugated gears have not been fully explored: they can take many forms, there is no need to adhere to those forms so far employed."

cheers,
julian

 

You are correct there, quoting from the head is dangerous practice. I started checking on motion weights,both Phillipson and Johnson say nothing, the German Eckhardt has an inertia calculation with weights, boils down to about 300 kilo, the eccentric has to be added, 150 kilo extra? So half a ton is quite near.
Kind regards
Jos Koopmans