Edward Thompson: Wartime C.M.E. Discussion

Top man, thank you.

It's all about building an overall picture and I would never shy away from presenting both sides as best I can.

 

But are both personal resentment or professional disagreement? Thompson is not the only person to have questioned Gresley's engineering throughout history, yet the fact that he had the mandate and ability to make changes thereafter is why he is held up for such approbation.

 

I think the point is that the personal and professional fed off each other.

 

The evidence we have is the designs themselves - and it is not all people make it out.
Thompson clearly wasn't against everything Gresley did, mainly just the conjugated valve gear, and streamlined cab fronts. He also had strange ideas about equalising rod lengths which wasn't so much anti Gresley as anti everyone! You have to look at the other locos he rebuilt as well as the pacifics (including plenty of non-Gresley). They all took on a general LNER look which was Gresleyish. If he had been really anti Gresley they would all have received Belpaire taper boilers with low degree superheat and short travel slide valves! He also rebuilt some Raven machines, of course.

The Raven story sounds rather like nonsense. Raven wasn't in the frame for the LNER CME position - it was Robinson who was first choice, for good reasons, and he recommended Gresley.

 

A very magnanimous and far sighted move on Robinsons behalf

 

Maybe influenced by his age as much as anything else.

 

Not knowing what he had seen of your research and work, it's difficult to make a clear judgement of his response to it. It seems an exaggerated statement on the face of it, but then we don't know how you were expressing your support of Thompson, or how you were "putting things into context" or trying to explain away Thompson's failings.

Edit - 4470 Great Northern - and I have it from someone who was there in the drawing office at the time that Thompson had absolutely no say in the choice of the locomotive to be converted.
Who was that person? I feel sure I have read that Thompson was asked to change it but refused.

 

It was. Robinson also perhaps realised that his own more recent designs hadn't been in general as good as his earlier work or as good as good as that young Mr Gresley's first few designs. He was a very astute man, and not at all adverse to learning from others' ideas throughout his career. That is generally the mark of a fine engineer. Sir Nigel had that attribute too.

 

Hi Simon,

I suggest you look at the relationship between Holcroft and Maunsell.

Maunsell allowed Holcroft to apply his conjugated gear to a number of SECR and SR locos. Later Maunsell removed the conjugated gear substituting 3 sets of valve gear.

Holcroft had the highest regard for Maunsell, and never once took umbridge at the removal of his conjugated gear later on.

The Holcroft gear was better than Gresley's, but nevertheless there ought not to have been any 'anti' between Thompson and Gresley, apart from the stories of which you are well aware. From an engineering point of view Thompson was perfectly justified in wanting rid of the Gresley conjugated gear. However, construction continued on the V2s under his term of office with conjugated gear, which is an interesting topic of debate.

Holcroft appreciated the engineering considerations of removing his conjugated gear by Maunsell, despite it being better than the Gresley gear, so from a purely valve gear point of view I think your correspondent has rather missed the point.

Cheers,
Julian

 

I get the impression some posters and maybe some historical figures are/were over-thinking the possible animosity between Thompson and Gresley. There doesn't always have to be a reason, sometimes two people just inherently don't get on very well, or one person doesn't like another who is largely indifferent in return, as a quick consideration of any sufficiently large office will generally show. If both parties are professional it's not a problem and the work continues to get done, but when one gets the other's old job, well, there may be some changes.

Thompson's ideas about equal rod length weren't that strange, GWR/French four cylinder practice uses the same principle. The theoretical basis is sound, but it can lead to some less than optimal frame arrangements, and Thompson's team seem to have been a bit weak on that, the B17 to B2 rebuilds also suffered from the loss of the middle cylinder bracing the frames.

I suspect the reason Thompson kept building V2s was that there was a war on and the Traffic Department wanted more of them. Conjugated gear or no (and with the Gresley inside steam chest arrangement to suit the conjugated gear some creative disposition of the valve gear would have been required, if it were possible at all), they're a fine design and it would have been foolish to tinker too much in the circumstances. I think building the last four as A2/1s was slightly ill-conceived, they were always going to be non-standard orphans. What all the LNER three cylinder classes (including Thompson's) needed was the small modification to the big end strap implemented shortly after the war, which improved it considerably

Inside valve gear was a bit of a hot topic on the Southern during the war as well, with King Arthurs going out on Lord Nelson jobs when the four cylinder engines couldn't be prepared in time. When the LNER requested the loan of ten 4-6-0s the SR saw an opportunity and offered them Nelsons, which were refused in favour of some nice simple Urie N15s.

 

As they were five years apart in age, I doubt the social conventions of late-Victorian public schools would have permitted much socialising.

 

Wow, not sure how you come to that conclusion.

Holcroft gear - Rods outside the cylinders, multiple joints on a bar across the front, lasted a few years on a few locos before removal.

Gresley gear - two rocking levers, used on 400? plus locos including the world record holder, and in use on express traction until 1 year before the end of steam.

On what basis is the Holcroft gear better?

 

Agreed. "Socialising" is maybe missing the point. 8126's first para above probably gets to the nub of the matter.

 

It's possible that both designs were flawed for use in day-in, day-out service, but the conversion costs of the Maunsell locos - which had been designed from the outset to allow a straightforward conversion to three independent sets if required - made that conversion feasible when the inherent problems of conjugated gear started to reveal themselves; whereas the LNER had to persevere with conjugated gear because there wasn't a feasible conversion available without replacing significant parts of the locos.

In other words, the maintenance and wear lead to sub-optimal performance on both railways, but the design of the SR locos meant that the balance of costs favoured a simple rebuilding to three independent sets, whereas the balance of costs on the LNER favoured retention as the conversion would require far more replacement and therefore higher costs.

Tom

 

Fewer problems with valve timing for a start. Every engineering solution has pros and cons. Its often not sensible to categorise A is being definitively better than B. It would be interesting to compare the service experience of those LNER locomotives with the conjugating gear behind the cylinders where the valve timing problems are arguably fewer. Of course this was't an option for the A4s etc.

 

Really? Given the number of pivots on the system, I'm not sure that would be correct. The layout may have led to less movement of the middle valve rather than more, but even the excess movement of the Gresley centre valve wasn't a problem until the gear wasn't maintained. It wasn't even seen as the primary cause of the middle big end failures when poorly maintained. I'd like to hear what jma1009 says since he was the one who said it was better. Maybe there's some test data?

I think I'll stick to the numbers used and for how long, as a measure of ability. There's no doubt Holcroft was a clever man - I feel sure I read he pointed out to Gresley that the cranks could be offset so the cylinders didn't have to be in line - but I don't believe his gear was better than Gresley's.

Edit - Changed wasn't to was. Finger trouble.

 

Quoted in F A S Brown: "it has given me the key to the whole situation."

 

Yes, one of the problems with the A4 layout was that the centre valve timing was affected by heat expansion of the outside valve rods. What the Holcroft gear did was ensure everything was from the cold side of the valve rods (there's probably a better technical way of describing that).
Another example: one of the advantages of the Star inside valve gear layout was that again everything was driven from the cold side and the mechanism was all quite short rods. With outside gear they would have either had to drive the rockers from the hot side of the valve rods, with consequent poor valve timing control, or else, like the Duchess, have a very long run from the rockers to the valves. Every solution has pros and cons.

 

Compared to the effects of wear that was minor, and could be taken into account so that when warm the timing was correct. Bearing in mind that the valve gear would be hot for most of the journey, it was hardly a problem.

 

Hi Lplus,

I am very happy to reply to your comments.

Can I please suggest you read part 2 of Holcroft's article in The Engineer 1946 February 22nd.

It is now online on Gracesguide.co.uk

http://www.gracesguide.co.uk/images/5/5c/Er19460222.pdf

Holcroft's arrangement was better because it was driven direct off the valve crosshead, so avoiding expansion problems when valve setting compared to the Gresley version. The valve could be withdrawn for examination without the need (unlike the Gresley gear) to dismantle the gear, and upsetting the valve setting. The potential for 'whip' in the long lever remains, but the SECR and SR engines never suffered from the same problems in this regard as the Gresley gear. Indicator tests proved this.

Gresley was keen to use light materials, and initially objected to the cast steel stretcher for the conjugated gear for the long travel valves on the A1s after the interchange with the GWR. The SECR had no such qualms. It is quite clear I think that Gresley had only a partial understanding of the gear, hence Holcroft's involvement early on in showing the crank settings did not have to be all at 120 degrees and the cylinders did not all have to be inline. Holcroft went on to design a conjugated gear for 4 cylinder locos.

I personally hold the view that if Holcroft had been successfully head hunted by the Gresley/the GNR (It was unsuccessful due to Maunsell's intervention), Holcroft would have ended up as Gresley's successor, but this is pure speculation on my part.

Holcroft was one of the very few UK designers who understood valve gears. W H Pearce, whom he worked with at Swindon was perhaps the most brilliant.

I have an article of the visit by the SMEE to Kings Cross shed in the late 1940s where much time was spent dealing with how the Gresley gear was set. It is quite illuminating. I also have Don Young's book describing his time as a premium apprentice at Doncaster setting Mallard's valve gear in the 1950s. Again quite illuminating. It was all a bit 'hit and miss' and up to the judgement of the individual chargehand.

Swindon practice was quite different, and Holcroft was ex GWR drawing office.

Holcroft knew the middle cylinder valves could overrun especially at high speed or long cut off. I think you will find the dimensions of the conjugated gear on the SECR and SR locos were quite massive compared to the Gresley gear, notwithstanding Gresley's use of high tensile steel.

I probably havent covered everything, so many apologies to Lplus if the above is not as comprehensive as he would wish!

Cheers,
Julian