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

I feel people get very hung up on the "completes the Gresley circle" without stopping to question what that actually is.

Thompson and Peppercorn continued the Gresley line. That is factual. Round topped boilers married with recognisably Gresley components and the only major change was to discard the conjugated gear and to fit a third set of walschaerts to the largest engines, and reduce the number of cylinders to two for medium and small locomotives. Otherwise, the LNER design house carried on virtually as is.

On the Southern, Bulleid discarded virtually all Gresley thinking for his Pacifics, save for idea of the derived motion to the middle cylinder (but done with chains instead) and Harrison for the British Railways' 8P kept the three cylinder layout for the Duke too, but again fitted Caprotti and walschaerts instead of anything reasonably Gresley in outline.

In both cases, they discarded the round topped boiler for a belpaire, which Gresley did not like and in this, from a manufacturing point of view, had a point.

The final development of line of Gresley's thinking was the Peppercorn A1, no question about it. That it ranks as one of the most reliable and high mileage performers of British Railway's 8P Pacifics indicates the excellence of the design.

It is perhaps unpalatable to some, but Gresley's legacy was carried on by Thompson and then by Peppercorn, and both of them were assisted by Bert Spencer in that regard.

Bulleid and Harrison went off to do their own things (as engineers are wont to do, and so it should be).

 

In the opinion of some maybe but there were marked differences between Gresley's and Thompson's thinking so I think it's stretching it a bit to claim that Thompson carried on HNG's legacy.

 

Whilst I don't disagree with your analysis of both Thompson's and Peppercorn's contribution to the Gresley stream of development I feel that Harrison, although following his own line of development, still contributed to a Gresley line of development - albeit different from the Doncaster-based engineers. To this "amateur" mind I feel that bringing LNER practice to the place where Gresley began his career - especially in an environment dominated by LMS practice - should see greater credit being given to Harrison for his work with 71000 and I would be interested to see a comparison between 60163 and 71000 once the latter returns to the main line.
IIRC I have read that Gresley was interested in Caprotti valve gear but the cost of licence fees ruled out its use on his locomotives hence the situation at Harrison's time (i.e. out of patent hence no licence fees) encouraged him to consider it in deference to his admiration for Gresley and - presumably - looking to see if Gresley's interest was worth further consideration. Perhaps it was the LMS thinking / processes that failed the production of 71000 (much as Fowler's imposition of LMS axle-boxes on the LMS Beyer-Garratts) but the efforts of the present owning group to iron out the foibles of the "Duke" have over time produced a locomotive that has shown a performance level that many did not expect it to achieve.
Perhaps I am naive in my thinking but I feel Harrison is worthy of greater credit for developing Gresley's ideas albeit in a different direction from that attained at Doncaster by Thompson and Peppercorn hence my interest in a comparison between 60163 and 71000 once both are returned to main line duty; perhaps even look at comparisons with 60532 once that Peppercorn development returns to main line duty.

 

And just how much of Gresley's design thinking was incorporated in 71000? LNER three bar crosshead slidebar perhaps but IMO precious little else.

 

From the Office of the Devil's Advocate:

Can a 'derived motion' which is no more (or less) than an impressive exercise in animated geometry be classified as a 'valve gear', when the key components controlling timing are precisely those functions of the (Walschaerts) radial gear from which the motion is derived?

In similar vein, wasn't the valve gear used by Bulleid on his pacifics 'merely' a derivation of Walschaerts, the difference being in the use of chains rather than eccentrics and cranks?

I'm not about to argue Lentz, Caprotti et al aren't a significant departure from radial valve gears!

 

Was it truly a derived motion? If I read the drawing I've been looking at correctly then its basically standard Walschaerts, except that instead of return cranks the required movement is taken from a chain driven crank. The only design of locomotive ever to have 3 sets of motion between the frames?

 

Thompson Peppercorn (and Bulleid) (and the GWR/LMS/SR) all preferred the so-called "De Glehn" bogie (which designation seems to be based on the weight transfer arrangement through side bearers - on the Gresley bogie, the weight transfer was via a circular pad around the central pivot), and the weight transfer / side control arrangements for the two wheel front truck was also changed by his successors, which seems to me to be a significant design change too.

 

The only marked difference is the choice of conjugated valve gear instead of a middle set of valve gear for the Pacifics.

Thompson and Peppercorn, I said. That should be clear. Undoubtedly Thompson's designs carry forward Gresley's work, as does Peppercorn's.

To ignore the obvious facts is to be at odds with them, I'm afraid!

 

Which has always been my argument - there is next to nothing in 71000 that is "LNER" however the Standard 5MT, drawn at Doncaster Works, is very clearly LNER from the running plate downwards.

 

That is a fair point.

 

I've seen OVSB's arrangement described as 'reduced Walschaerts', so in that sense, I suppose 'derived from' (as opposed to the 'derived drive' of the Gresley conjugated motion). With the GW (and Stanier's) arrangement relying on rocker arms, the only examples I know of employing more than two full sets of valve gear were fitted with sleeve valves (and here, imagine two full stops!).

Does anyone please know how Webb went about things with his compounds?

 

Point of order. Many NER locos had 3 sets of Stephenson's valve gear between the frames.

Sent from my SM-A105FN using Tapatalk

 

And Thompson/Peppercorn's Pacifics all had a third set of walschaerts between the frames.

 

While that may be true in terms of valve gear and motion, is it true for the frames, axleboxes etc?

Sent from my SM-A105FN using Tapatalk

 

A fair point and I couldn't tell you I am afraid. I suspect you are likely going to tell me it has more in common with the LMS practice?

 

Are we coming dangerously close to discovering the reason for the 1948 exchange trials?

 

Fair enough. Not an expert on those. Three pairs of eccentrics and a connecting rod!? Must have been busy!

 

Have to disagree I’m afraid. Taking the V4 as an example, Thompson ditched the design completely and developed the B1. Apart from being steam locos they were as different as chalk and cheese. I just cannot see how the B1 could be described as taking forward Gresley’s work. As for the Pacifics, they had the mark of Doncaster about them I agree but divided drive, equal length con rods and that long wheel base don’t say Gresley to me, they say Thompson. Turning to Pep, I’d argue that he took ET’s work forward and refined the designs with ideas of his own.

 

But by 1940 how much of Gresleys work - conjugated valve gear, 2-6-2's etc was what was needed?

The B1 on the other hand was just the job

 

Really? You truly can't see how it's taking forward Gresley's work?

Gresley boiler (100A), Gresley V2 wheel centres on the prototype, Gresley cylinders, Gresley valve gear, standard LNER tender, slightly modified, but Gresley, standard Gresley control setup, Gresley frame design, virtually.

Your problem is that you're thinking of this in a very anti-Thompson esque way without looking at what actually happened.

The V4 was cancelled because it was too expensive and complicated to make with the design and materials specifications. Cut and dry, the LNER couldn't afford the V4 as a mass market answer to their problems.

So Thompson and his design team put together a locomotive made up of standard Gresley parts, but two cylinders. The result was the most numerous LNER design and the most successful 4-6-0 on the railway and the design which undoubtedly became the maid of all work going forward.

Which only came together because Thompson and his design team took all of the best assets and designs Gresley and his team had produced for the railway, and put it together in a workable design.

Just because a Gresley locomotive design didn't continue being made does not mean Gresley's legacy was not carried forward. Thompson's successes are also Gresley's, because Gresley trained him.

And I agree with you on that specific point. I even said that above. The rest is Gresley's legacy with Thompson's team doing what they could in difficult conditions.

The only changes that were made to the Pacifics was the wheelbase by way of the connecting rods, and position of the front bogie by way of steeply inclining the centre cylinder (a reversion of sorts to Gresley) and the cab front which became a sort of semi-wedge shape like the A4s.
Peppercorn continued building B1s, K1s (with minor mods), L1s (with even more minor mods) and O1s/O4/8s and probably if time had allowed would have continued the withdraw and replace scheme of the pre-grouping stock.

Thompson carried the ball forward, Peppercorn provided the touch down with the A1 design. That's the Gresley legacy, in a nutshell. LNER design from 1923-48 is Gresley's legacy which two great men continued and refined to the needs of the railway they inherited. Nothing more, nothing less.