Edward Thompson: Wartime C.M.E. Discussion

None that I know of.

 

Through the many exhausting years of following this marathon thread there is a certain question which keeps coming into my head, so maybe it's time to share it. Let's imagine for a moment that Edward Thompson had not succeeded Sir Nigel Gresley. Instead, a different person took on the job of CME after Gresley's death. No speculating about who that person might have been, let's keep it to A. N. Other.

Given the circumstances of the time, what do you think would have happened, if anything, to Great Northern and the six P2s? What would have been the course of steam locomotive development between the demise of Gresley and the commencement of the BR era, assuming that the new CME lasted till then? If we can exclude emotion and formulate ideas about the most likely strategy, this might help put into context what Edward Thompson actually did. Over to you . . .

 

Preserved locos lead very sheltered lives though in relation to their original service; in particular the ratio of preparation time to hours run in traffic is way different.

Perhaps a pertinent counter-question might be: if conjugated valve gear was no trouble given adequate maintenance, why did Peppercorn not perpetuate it on his locomotives?

Tom

 

Would it actually be that bad? Oiling up the shaft, on a two-cylinder loco you have four eccentrics and two big ends, so six places to oil. On a three cylinder loco you'd have six eccentrics, but only one big end, so seven places - more, but hardly much more, and the slow part of oiling a shaft is finding a comfortable position to do it! The tops of the expansion links are easy; the bottoms slightly more challenging. The tricky one I can see would be oiling the die block of the middle set of gear, though that depends a bit how they are arranged (are they three together, or two together and one separate? Anyone have a drawing? My hunch is it wouldn't be much worse than doing a two-cylinder loco, provided the previous driver left it in a position well set for oiling - as is the case with a two-cylinder loco.

Tom

 

Taking that little lot into account, the demise of Mr Paget's 2-6-2 mightn't be considered such a loss.

 

Having oiled up a Raven 3 cylinder loco (63460), I can assure you that it a lot harder than an relatively small inside cylinder loco with Stephensons gear, which most survivor are. You can get the middle big end out of the way but the adjacent eccentrics limit the room available for you to squeeze up between the shaft and the firebox. The waggly bits are also a bit of a challenge. It's been suggested to me that drivers used to simply pour oil all over from the top, knowing that some would find its mark and lubricate the difficult bits. It's a technique I never tried but I can see its advantages.

 

And another question would be, if conjugated was so much trouble, why did Gresley's successors not convert all locos so fitted to three independent sets of gear? The fact that they remained in service until 1966 answers that IMO.

 

OTOH, Maunsell did exactly that on his own three-cylinder locos with conjugated valve gear.

There are lots of design ideas that are less than optimal, but which continue because they aren't so problematic as to be worth the difficulty of converting them. I suspect Gresley's three cylinder locos were in that class.

Tom

 

It is very difficult to fit a 3rd set of valve gear into a loco where the inside cylinder drives onto the second coupled axle because the first coupled axle gets in the way. On the Thompson pacifics the inside cylinder drove the front coupled axle.

Sent from my SM-A105FN using Tapatalk

 

It's probably easier said than done. Unless, like the Southern locomotives with Holcroft gear, where AIUI the capability was designed into the locomotive, then trying to retrofit inside gear would also mean relocating any items that are in the way of the gear, not to mention designing in a gear that has reasonable events. Most likely once the war was over it was not worth the trouble. And quite probably there were higher priorities - like building B1s.

 

Oh come on. BR found the time to rebuild over half the Bulleid Pacifics so if the Gresley 3-cylinder locos were so bad, I'm sure they would have found the time. 34A and 64B turned A4s for high speed work on the ECML, including the non stops, until dieselisation saw them moved elsewhere and even then they remained in front line service until replaced by diesels in 1966.

 

The fact that you choose not to solve a problem doesn’t mean there is no problem: it just means the cost-benefit analysis works out on the other side. Bear in mind the Bulleid Pacifics were much younger and therefore on the estimated lifetime left after rebuilding, there were more years to recoup an investment in rebuilding; and the maintenance problems were more severe so the annual savings would be higher. (The working assumption was that locos rebuilt ca. 1960 would carry on in service until about 1980 - twenty years to recoup the investment). The combination of the two tipped the balance towards rebuilding in the one case, whereas the balance of costs wouldn’t justify it on the Gresley locos with fewer years left to recoup any such investment.

Tom

 

Would it be just as difficult on a B16?
For the present discussion (Gresley v Thompson) the B16/1 B16/2 B16/3 engine cards can probably give lots of further information.

 

Keep on ignoring the facts. The Gresley Pacifics lasted until 1966 and were replaced by dieselisation, not retired in favour of more modern steam designs. During the dieselisation process on the ECML they were able to match the accelerated diagrams introduced for the diesels. When their ECML days were over, some were transferred to Scotland on the Glasgow - Aberdeen expresses. Not only working the accelerated diesel timings but replacing the damn things because they were so unreliable. Hardly a damning verdict on this “unreliable” derived motion. If you care to read a bit more, rather than mire yourself in pre-grouping Southern matters, you would find out that the Achilles’ heel of the Pacifics was the middle big end. Once that was redesigned post-war, the rate of failures plummeted.

 

This is interesting - Bulleid Pacifics were being rebuilt right up to 1960, with an estimated withdrawal date of 1980-ish... Yet the Modernisation plan had already been put into place in 1956. As we also know, the building of BR Standards continued up until 1960 too, with estimated working lifespans of 45 years. The two situations (continued building / rebuilding of steam locomotives, and concurrent rapid dieselisation) don't sit very well together as a sound economic plan, to me...

Richard.

 

Which, viewed through a slightly different lens, helps interpret why rebuilding might not have been chosen to be value for money. If availability of parts and labour rose post war, then the constraints of wartime would no longer have been so extreme and the balance of advantage would have shifted.

A further thought. I think it was Top Shed that recognised the value of kylchap exhausts on their locos, but were unable to get BR to permit widespread installation of them because of the limited payback period. That was a relatively minor change, unquestionably of value, but which fell foul of the accountants’ assessment of value for money. Wasn’t the same plausible for the Thompson rebuilds, especially a decade earlier when cash and materials were tightly controlled?


Sent from my iPad using Tapatalk

 

Crewkerne broken cranks versus hot middle big ends?

 

I think, from my reading around the subject, that the word 'plan' in 'modernisation plan' was in more than a few places, wishful thinking. Certainly it fell a long way short of most people's definition of a plan.

It was, also, overtaken by the rapidly deteriorating financial position of the railways and the poltical pressure that placed on the railways to cut costs and lines and to accelerate the elimination of steam.

 

The Beeching cuts need to be factored in too, the reduction in services and closures meant less locos were needed so steam could be phased out more quickly

 

Not forgetting the rebuilding of many of the LNER O4 class variants into O4/8s, using Thompson's 100A boiler. This continued well into the 1950s.