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Gresley's proposed 4-8-2 locomotive

Posted: Sun Aug 12, 2018 10:40 pm
by ShroomZed
Most of us have the general knowledge that Gresely had at one point (I think 1938?) proposed a 4-8-2 design that never went through due to the war. It seems though that detailed information on this 4-8-2 is nearly totally elusive. Can anyone supply me with information about this design, such as the context for it, where it was meant to run, and any known or estimated technical details?

I just find the idea of a 4-8-2 design running on LNER lines quite fascinating not just due to the imagined size of the thing, but because Britain had built so many 4-8-2 locomotives for foreign networks (particularly for South Africa) and so it would have been interesting to see ones running at home.

Any thoughts or estimates on how these 4-8-2s would have done and further what would have happened to them are also quite welcome. Thanks guys.

Re: Gresley's proposed 4-8-2 locomotive

Posted: Wed Aug 15, 2018 10:36 am
by Atlantic 3279
I imagine that it was intended for the very heaviest passenger trains on the main line, as opposed to the fastest ones which were the responsibility of the A4s. I've only seen drawings by the well-informed (and a painting) of the 4-8-2 as a non streamlined loco looking very much a stretched A3. That did not stop me from building a model of a streamlined version! One or two decent models of the "proper" version exist too. Things that we don't know of course include boiler and firebox proportions. Would, in 1938, the large grate already in use on the P2s and about to feature on the W1 rebuild have been incorporated in the design, would a long combustion chamber be used and would the design have adhered to the established tubing pattern of Doncaster's large, wide-firebox boilers? It has been suggested that as grate sizes increased, as draughting characteristic changed, and as barrel lengths were progressively altered over the years, the standard tubing arrangements became less thermodynamically efficient but that this was ignored simply because the desired extra power was being produced. Ten years later the Peppercorn boilers still stuck to the same general plan...

Kylchap chimney with payment for use of the design, or another attempt at tweaking a more basic chimney and blastpipe to get decent results?

The cylinders and valves are another unknown. Would the wisdom of large valves for free running at high speeds, as on the A4s, be adopted? Could the cylinders of A4 pattern be bored out to a sufficient size to allow the larger 4-8-2 to produce enough tractive effort? Would the loco instead just use A1/A3 cylinders bored out to maximum diameter (rather like the W1 rebuild) even if that meant smaller valves that restricted performance at higher speed?

220 psi or 250 psi?

Would duties include the non-stop services, justifying a corridor tender?

There are more questions than I have time to consider.

Re: Gresley's proposed 4-8-2 locomotive

Posted: Wed Aug 15, 2018 1:49 pm
by Pyewipe Junction
This loco is described and illustrated in Locomotives That Never Were by Robin Barnes, who cites Nigel Gresley Locomotive Engineer by F A S Brown as his source.

Dimensions given by Barnes are: cyls (3) 21 x 26"; pressure 250 lbs/sq in; driving wheels 6' 8"; TE 45,700 lbs, grate area 50 sq ft.

The illustration (presumably the one referred to above) shows the loco as rather like an A3 on steroids, with a slightly tapered boiler and a sloping, not curved, front. No smoke deflectors and no streamlining. To my mind rather old-fashioned looking for 1938.

According to Barnes, the main problem with the design was its length, and here Barnes correctly asks why 6' 8" driving wheels were preferred, as Gresley had already proved that 6' 2" wheels were more than adequate for express passenger duties. The larger drivers added 2 feet to the overall length and the firebox still protruded 3 feet into the cab.

Barnes's opinion is that the design would have had a limited life post-war because of decreased train weights and the proposed LNER ECML dieselisation. That's funny, I thought that train weights actually increased after the war.

Both the LNER and LMS toyed with 4-8-2 and 4-8-4 designs but nothing actually materialised. Harrison is on record as saying he would have pursued 4-8-2s had he taken over from Peppercorn. As things turned out however it does seem as though the ECML requirements were met by the post-war 4-6-2s.

Re: Gresley's proposed 4-8-2 locomotive

Posted: Tue Aug 28, 2018 4:41 am
by sturrock
Spencer, as ‘Technical Assistant Locomotives’ under Gresley was in a perfect position to observe, even participate, in most of the latter’s schemes. In a paper given to the Institute of Locomotive Engineers in 1947 he mentioned an “elongated A3” as a 4 8 2 with 21inx26in cylinders, 250lb/sq in boiler and a 50 sq ft grate. This would give a nominal tractive effort of 45,684lb with its 6ft8in wheels. Later other proposals were apparently made for several updated prototypes. Eight coupled express locomotives reached outline drawing stage in 1946 before Thompson had retired, with 6ft8in, 6ft6in and 6ft4in wheels. Three outlines , one 4 8 4 and one of 4 8 2, were prepared, in outline similar to the original P2, the other of the 4 8 4s streamlined with the full curving A4 streamlining, not just the ‘added front’ of the later P2s. Geoffrey Hughes in “The Gresley Influence” (Ian Allan 1983) has outlines of all four types.
Following is a summary of the several possibilities mentioned.

Gresley 1939 3cyl 21x26in cyls 250psi boiler 6ft8in wheels, nom.te 45,684lbs.
Thompson } 1946 3cyl 21x26in cyls 250psi boiler 6ft8in wheels 45,684lbs.
Peppercorn } 6ft6in wheels 46,856lbs.
or } 6ft4in wheels 48,089lbs.
Harrison? } Followed by a Chapelon inspired 400psi 4 cyl. compound??

It looks like all were intended for express work, not necessarily for significantly heavier loads, but to increase schedules by ‘evening out the banks” as it were.

Jon. H.

Re: Gresley's proposed 4-8-2 locomotive

Posted: Tue Aug 28, 2018 8:50 am
by Hatfield Shed
I cannot help but feel that had eight coupled express traction been really required for widespread application, then considerably more effort would have gone into getting the P2s fully sorted as vehicles. With a small group of big wheel 2-8-2s available there's your test bed for the problems of the yet longer proposals. Once the P2s were mutilated, that opportunity was gone.

The 2-8-2 was a major success in North America, France and Germany, shame that it didn't get the full developement required for the UK. Hopefully we get to see what it needed for 'track kindly' operation with the new build.

Re: Gresley's proposed 4-8-2 locomotive

Posted: Tue Aug 28, 2018 3:42 pm
by Pebbles
Who knows what form any 4-8-2 may have taken, or indeed whether it would have eventually been required. Bert Spencer's presentation presumably addressed design studies which could be seen in the same light as those preceding the eventual emergence of the A1, which I seem to recall included a 2-6-2. At the design study stage all options would need to be explored including the wheel diameter and indeed whether 3 cylinders remained the best option. An interesting aside is why the 4-6-4 configuration was retained when 10000 was rebuilt, as it would have been quite simple to have grafted the rear end of a P2 onto the frames. I can only think of two reasons, firstly face saving, or secondly the long wheel base would enable the engine to be used as a test bed for a larger boiler/firebox.

Re: Gresley's proposed 4-8-2 locomotive

Posted: Thu May 23, 2019 10:03 am
by Bantamcock
I have s few sources of information on this that I can drag out at the weekend for you.