Edward Thompson: Wartime C.M.E. Discussion

What are the best sources to read for the Bulleid Pacifics rebuilding decision? I was thinking that could be Simon's next project but maybe it has been done already.

 

The licence fee for Chapelon's patent on the Kylchap would also have been an issue.
Going back to the conjugated valve gear, the levers move in a horizontal plane, so supporting their weight would have applied twisting stresses to the various bearings. This doesn't apply to Walschaerts (or other types of) valvegear, where the components move in a vertical plane.
I'm not a mechanical engineer, so I don't know how much of a problem this would have been.

 

That would open a whole new can of worms. If you think Thompson v Gresley can get a bit heated, it would pale into insignificance compared to Bulleid v Jarvis.

 

You're in danger of playing the man not the ball again.

It seems to me that neither view point (that the motion was an issue and that it was good enough to soldier on) is mutually exclusive. In the conditions during the war the conjugated motion couldn't be maintained well enough not to give the problems that are well known and I think beyond argument? Post war with more resources the valve gear could be made to give good service.

With LNER and the country on their knees between 41 and 46, it doesn't take a huge leap to think that rebuilding lots of locos was not possible. Which might explain why Thompson focussed on other matters. More locos would have been the big driver given the build up to D day which was in preparation from 42 onwards and involved a lot of extra traffic in 43 and 44. The existing locos simply had to plod on. Then the immediate issue eases probably from about early 45 as the war effort started to wind down and the amount of goods traffic and troop movements reduced. More locos and less work means less pressure on reliability and anyway there was no money.

The southern situation with the Bulleids was different. These were the bulk of the new locos and the rest of the fleet was often ancient. The unrebuilt engines being a nightmare to maintain they were rebuilt because the alternative would be new locos, and why would you do that when the cylinders wheels frames and boilers were new and the last at least, excellent. If dieselisation and closures hadn't intervened my own view is that they would all have been rebuilt.

In summary the conjugated gear was not a big enough issue after the war to justify rebuilding program on the scale of the southern pacifics. This doesn't mean the gear wasn't a problem and the fact that later LNER designs didn't use it suggests it was enough of an issue to abandon its use. Which it seems is precisely what Thompson recommended.

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I believe that the Chapelon patents for the double Kylchap system expired around 1941. With the A3s and A4s being so fitted in the late 1950s the coal saving paid the cost of fitting it in something like three weeks according to Peter Townend.

 

That would certainly explain Thompson using the system for his Pacifics from the outset.

 

Withdrawal of A3s started in the late 1950s. The majority of A3s, A4s and V2s were withdrawn in 1962-63.

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Because of dieselisation of their core routes on the ER and NER, not because of any inherent unreliability.

 

...... unlike certain of the 1st gen diesel classes intended to replace them.

 

They were reliable but they did not achieve the mileage between overhauls that the Peppercorn engines did. I think this was evolution. A good designer such as Peppercorn would aim to improve on previous designs by changing the areas that caused problems.

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So why the inconsistency to the Thompson Pacifics, if that was the case?

 

And there is only so much resource available for design and build. Once the war was over it seems that conjugated gear issues were manageable. But also on the sheds in the late 40s/50s was a large stock of pre group locomotives, a good number of which were well past their sell by date due to be kept on in WW2, and which we may assume were all running lower mileages between overhauls and lower availability than more modern designs. So which do you do first?

 

Must see.
When and where?

 

I can't help but think that the situation in 1942-46 and 1956-60 is so radically different to render a comparison between the Bulleids and the Thompson locomotives incoherent. It is a poor comparison because the starting point is different, as well as the end point. They were rebuilt/built for different reasons with different short and long term objectives in mind and in completely different political and economic situations. It is just whataboutery to invoke it.

 

In Scotland the A4s were drafted in to replace the NB diesels that had replaced LMS steam.

 

But the contemporary comparison between a Thompson Pacific built in 1943 and a Bulleid Pacific built in the same time frame (from 1941 onwards) is reasonable. Total number of Thompson Pacifics produced: 26 (four classes). Total Merchant Navy locomotives: 30 (one class).

The Thompson classes only saw some minor changes to their design - full length deflectors for the A2/1s and A1/1, and eight wheel tenders for the A2/1s fitted. Boiler types became standard with the Peppercorn Pacifics (A2/2, A2/3), Gresley A4s (A1/1) and Gresley V2s (A2/1s).

 

This post, frankly, hits the nail on the head.

 

Keeping it classy!

 

Just want to put in a supportive word for Mr Bulleid here.

It's 1941 and he's well aware of the lack of manpower and maintenance available to his railway. Strangely enough - Mr Thompson recognises this too.

The two men order 6ft 2in Pacifics between 1941-45, as "mixed traffic" machines: both designs have been designed to reduce downtime, albeit in different ways (chain driven valve gear and oil bath versus three sets of walschaerts). Both men recognise that some austerity thinking is required and all of their designs incorporate some utility thinking.

Bulleid, unlike Thompson, actually needs another 110 Pacifics for the issues on the Southern (accelerating of services/length of trains/axle weights/etc) - Thompson looks to solve the issues on his railway with a range of standard locomotives for specific tasks, using standard components.

Ultimately the two men were trying to resolve the same issues in different ways. Do we think they did a good job? Well - I used to think less of Bulleid. It may surprise you that the more I've learned about Thompson, the more I have warmed to Bulleid's approach to steam locomotive design.

Ultimately I am biased in one specific way: I think the Jarvis rebuilds of the Merchant Navy class are magnificent. They are in effect what Bulleid could have done, had he followed Thompson's way in 1943 with Thane of Fife. That's perhaps the most surprising thing about all of this, really. Jarvis did to Bulleid's Pacifics a more extreme rebuilding than Thompson did to either Great Northern or the P2s.

 

I'd also suggest that what we are looking at is at least a five sided die and that every single wartime CME instigated a major design departure from previously established practice.

• Fairburn and Ivatt at the LMS - there are different needs - there is not a big engine need but there is a need to deal with the elderly tank and 0-6-0s and which does produce fairly radical design - certainly unlike anything else seen before and the precursor to the standards. I notice that no one takes Fairburn/Ivatt to task for rebuilding the Patriots. And of course, the very radical solution to the 'pacific' issue is 10000
• Hawksworth - the Modified Halls and later 1500 represent a radical design shift. Also the investigation into Gas Turbine locos.
• Riddles - with the 2-8-0 and 2-10-0. First 2-10-0 in Britain, designed to be cheap, go anywhere locos, I'd suggest not designed with a long life intended.

I'd suggest that in design terms, Thompson was the least radical of the designers in terms of departing from established practice.

I don't see Fairburn/Ivatt, Hawksworth or Bulleid accused of campaigns to rid their lines of their predecessors work even though they embraced in war time conditions, radically different design solutions.