GWR 111 "The Great Bear" and Surrounding Controversies

AIUI the number of 5X's and 6P's required was dictated by the Traffic Dept. No more Jubilees were converted simply because there were no more 6P's needed.
Ray.

 

Correct! The number of (BR) Class 7s needed was deemed to be 91, i.e. 71 Royal Scots, 18 Rebuilt Patriots and two Rebuilt 5X Jubilees. That's the alternative theory, but 91 does seem an exceedingly precise figure.

 

I suppose you can start with the services on the timetable, and calculate what locomotives are required to run the services, which gives you the active fleet required at any one time. Then allow for availability, and something for contingency and I suppose you have the size of the fleet required. There's a voice in my ear suggesting that its going to be much more complicated than that though.

 

When and what locomotive types Please?

 

Continued from US Boiler design thread here:

So I'm wondering, then, if one may guess that Churchward's combustion chamber boilers in the Krugers were an experiment to deal with the tube problems that so concerned him by distancing the tube plate from the grate, rather than any concern for excess tube length. So more of another 19thC experiment than a precursor to the very large combustion chamber boilers of the 20thC. So if I hypothesise that Churchward's thinking in 1907 when the boiler for the Bear was designed was that combustion chambers didn't offer anything much towards protecting the tube plate - or at least caused as many problems as they solved, and that very long tubes were not an issue if the proportions were right.

Interesting to note, as I picked up from the Mallard thread, that 23ft tubes were made to work very successfully on the DDR05 streamliner

 

Or were the Krugers a case of too many innovations at once? A boiler with a combustion chamber, increased piston stroke of 28" and first time use of piston valves on the GWR. True the boilers started at 200psig, then lowered to 180psig and finally to 165psig. Was this because of the combustion chamber though? The firebox/combustion chamber appears almost longer than the barrel. The boiler is also parallel, so was there a problem with circulation, particularly in the area of the combustion chamber? One of the boilers, with pressure reduced to 100psig survived in use at Swindon until 1965.

 

Holcroft tells us that there were problems (unspecified) with the combustion chamber. The Large Locomotives paper includes a design for a new boiler for the Krugers, tapered, but no combustion chamber. But yes, too many innovations seems fair.

As I like doing that sort of thing, here's a quick 4-6-4 version of the Bear with a 25% bigger firebox. An outside framed trailing bogie might make more sense, and there are a number of other things that could be done better. Ought to have an 8 wheel bogie tender, but I didn't have one handy.

 

I think the trailing bogie could allow you to give the footplate crew a slightly more spacious cab… always one of the odder elements of the Bear…

EDIT your version does look better proportioned already though!

Simon

 

Yes, that's a Star sized cab. The Bear one would have looked ridiculous!

 

Thank You

I am very well aware of LNWR Ramsbottoms importance for the last 150 years world history as creator of the split piston ring .
I thougth You was refereing to first application of many small section piston rings on piston valves when superheating took over.
In Germany it was first employed by firma Wolf in portable steam engines around 1900 and the norm all over superheated steam locomotives before 1914

 

How close was The Great Bear chassis (well, the first ten wheels of it ) to a Star? AIUI it was rebuilt into a Castle; was that comparatively straightforward, or a "raise the whistle, replace loco, lower the whistle" job, or something in between?

Tom

 

The boiler barrel of the Kruger does appear very short; the firebox/combustion chamber is about equal in length. If the cladding reflects the shape of the firebox, perhaps the front top corners are too square? The cladding on the firebox side also looks a bit odd.

 

John Ramsbottom is certainly credited with the invention of the cast iron piston ring, still used in internal combustion engines. However, these were fitted to the pistons; the valves in his day were almost always and possibly always flat slide valves. The single piston valve ring which came with superheating was courtesy of Schmidt and, as I understand it, was part of and indivisible from the superheater package.

 

Very close. The difference between Bear -> Castle and Star -> Castle conversions was that the frames were cut after the second pair of driving wheels, not the third. Also presumably the Star boilers could be reused.

I'm sure you're right. There are photos of the Kruger boxes about and they are very square indeed, quite different to the subtle curves of the standard boxes.

 

I guess that makes sense in that the main difference from a frame point of view will be in relation to different dimensions of boilers (and cabs), and how they fit at the rear end, so makes sense that the differences are from behind the middle axle.

Tom

 

Getting more like du Bousquest's Nord 4-6-4 of 1911. The 4-6-4 tender loco became quite prolific in North America but remained a comparative rarity in Europe.

Britain's next Pacific design after Great Bear might have been John McIntosh's unbuilt Caledonian Rly loco of 1913. Would have had 4 cylinders, grate of 37 sq ft and tube length 22 ft. I think I saw a diagram in one of Nock's books.

Wonder if Dugald Drummond ever thought about a Pacific for the LSWR? Was his F13 4-6-0 not the largest engine in Britain when introduced in 1905?

 

Cook says in Raising Steam on the LMS p.81 that the "existence of such a large pool of [G9 1/2S] boilers [ i.e. the boilers for the unrebuilt Patriots] was one of the factors which prevented H G Ivatt from obtaining permission to rebuild further [Patriots]".

 

Fixed it for you

Tom

 

From AE Durrant's book 'Swindon Apprentice' this is a Kruger firebox about to be scrapped in the 50s. Superficially it doesn't seem a very sophisticated design.