Discussion in 'Steam Traction' started by Davo, Mar 22, 2019.
At the present time it is a 1 off loco with a 1 off monoblock casting.
To be pedantic, a “single surviving locomotive with a single surviving monobloc” would be more accurate.
That is my engineering background coming out.
Query-Where the K3s and O2s fitted with monoloc castings?
Is there some sort of lacuna in my knowledge: "a surging monobloc"?
Not sure it is something to do with a foundry pouring/teeming the metal from the ladle into the mould.
I think it's an auto-correct.... Should be "surviving".
Yes - very much auto correct - will now amend!
Good question. The answer according to my notes is no, they were separately fitted cylinders. The K3 had a very steeply inclined centre cylinder which probably negated the possibility of a monobloc at the time. I will check the RCTS green books when I get some time for a better answer.
It seems like nobody has quite answered your question. My take on it would be slightly different - it wasn't necessarily that Green Arrow was remarkable for having a monoblock per se. I don't actually know how many NER monoblocks were still around at the time Green Arrow was preserved, probably only the Q7s if they had them? The V2s were built with monoblocks, but by the time anyone thought to preserve one, quite a few didn't have them anymore. Problems with the monoblocks had led to them being replaced with separate cylinders on almost half of the V2s. However, Green Arrow did still have one.
You'll notice that class pioneers are somewhat over-represented in the NRM, and also that at certain times there was perhaps a drive for apparent originality over authenticity (hence 251 probably having very few parts that were on 251 at the time of withdrawal, and more 'original' examples of some SR classes being preserved over the first in class). I think you can also make a fair argument that the V2 is up there with the A4 in the ranks of Gresley's most successful classes. So a V2 was to be preserved because if you're going to preserve a Gresley engine that isn't an A4, it's an obvious choice, not necessarily just because they had monoblocks. Green Arrow was the first member of the class, and in reasonably original condition where many of its classmates weren't.
Three cylinders cast together in one monobloc casting was a N.E.R. practice and this was adopted by HNG for new designs where the arrangement of the front end, the disposition of the cylinders etc. permitted this. 2001 was built in 1934 and would be the first example of this practice since the O2 and K3 classes were in essence G.N.R designs even though they became Group Standard. The A1s again were G.N.R. and the disposition of the cylinders on this class continued through to the A4 and although this last design came out in 1935 there was little point in pursuing a monobloc in this class since this was a continuation of the development of the 1920 design and unlike the O2 and K3 the cylinder disposition was rather different to that to be found on the first of the passenger service Mikados.
Of the other classes the B17 and D49 again did not have a suitable cylinder disposition but the V2 design, which was first ordered in 1935, met the adoption requirements. The V4 class were also fitted with a monobloc. The three cylinder Mogul and Consolidation designs did meet the requirement but predated it and the remaining 5 examples of the P2 class are referred to as having conventional cylinders.
From a photo that I have it looks like the V1 2-6-2 tank locos had mono bloc cylinders.
V1s were 2 cylinders. V3s were 3 cylinders.
Sorry but the V1 was a three cylinder design. The V3 was effectively an uprated V1.
Yes, these three cylinder tank locomotives were also built with a monobloc. The design dates back to a proposal made in 1928 which steadily evolved from the original idea of a locomotive suitable to work over the widened lines of the Metropolitan Railway. The V1 first appeared in 1930 and 82 members of the class were built in batches up to 1939. The V3 first appeared in 1939. The cylinders were 16" x 26" producing a smaller block than that fitted to the V2 (and much smaller than that fitted to 2001).
I do not have much information about the V1/V3 classes. We are aware of the cracking issues which had an impact on some of the V2s and I wonder if the smaller casting fitted to the less powerful tank locomotives gave less trouble or even no significant trouble. These engines appear to be the first LNER design fitted with a monobloc and if these were deemed a success then it goes some way to explain the confidence felt in fitting such cylinder blocks to other designs.
Apologies if this is a daft question or has been answered previously, but does 'cracking issues' refer to the monobloc casting or the frame on which it's mounted?
In this instance the cylinder monobloc is being referred to. The frames on the V2 gave little trouble, we can carry out frame repairs and renewals if needed, the monobloc presented more of a problem though that is now solvable with a fabrication. There are those who would like to have the cast block removed from Green Arrow for a full assessment and inspection as part of an overhaul in order to discover the extent of what and where the problems lie. And dealing with the block in full isolation might allow more advanced repairs to be undertaken if this was found to be feasible.
I'd imagine today's better understanding of stress relief, coupled with CAD design and expanded moulding options moves things towards monobloc.
Of interest, is experience with monoblocs, as employed by Blodge, applicable to SG locos ... and vice versa
Absolutely. 'Originality' was just as much the fad in the 60s/early 70s as 'authenticity' is now. And doubtless the wheel will continue to revolve and old fashions will come back again.
CAD and polystyrene patterns aren't magic. They have their drawbacks and this would be a very large and complex casting. The physical capability and knowledge to actually get it right might not be there at a price that is affordable.
The monoblock cylinders on the Festiniog whilst impressive are probably 1/3rd the size of a V2 one at the most. The difference in scale is huge. Whilst they haven't shown any major flaws so far, they did have a quite a major issue with the removal of casting sand. This lead to damaged liners and rings. So it goes to show how you can miss simple things.
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