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

Well you'll have to be more thick skinned if you post comments like yours and expect no comeback. My remark was based on your avatar "Osmium"...it seemed strange

 

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All sorts of things will work to a greater or lesser extent. Cost effectiive might be another matter. I suspect though, if you managed to train your shed staff to the level where they could successfully maintain high pressure hydraulics, it might be easier to drive all the valves directly from cams rather than have a derived gear from two sets of walschaerts. But at that point one starts thinking about poppet valves and and and...

 

The LNER did try poppet valves the surviving B12 8572 being one of them.

While the Lentz fitted B12's were not a success the 'Shires' were so perhaps Lentz rather than Conjugated was the way the LNER should have gone.

 

I am not sure that Gresley's preference for conjugated valve gear can be seen as either right or wrong. It was a design option with both advantages and disadvantages - which are discussed in a number of books as well as in the Gresley and Thompson threads in this forum. I would make the same comment about the wider issue of 3-cylinder drive, where again there are pros and cons. But I do note that, outside of Britain and Germany, 3-cylinder locos (both simple and compound) were fairly thin on the ground in most countries. In the USA, I believe that you had the Union Pacific 4-12-2 (88 units) and Southern Pacific 4-10-2 (49 units) as 3-cylinder types, but not mush else?

The Britannia may have been our largest 2-cylinder loco type, but it was not the widest. 22-inch outside cylinders were used on some of Urie's LSWR engines, plus the 4-6-4Ts of the LBSCR & GSWR. But I think the widest standard-gauge loco bodies were 9ft 2in over side tanks on the LSWR (Classes G16 & H16) and GCR (LNER Classes A5/1, L1 (later L3) and S1), compared to only 8ft 9in width for a gauge-friendly Britannia.

 

Urie locos had a joggled frame behind the cylinders, setting the centre line of the cylinders a couple of inches nearer to the loco centre. The overall width at the cylinders may not have been unusual, however the width over the tanks of the 516 (or H16 class) was.
Pat