V2 4771 green arrow to return?

No surprise there although for all my grasp of CAD, it might as well be witchcraft! I was wondering how the practicalities of managing the effects of the manufacturing process (specifically rates of cooling) on the very different masses involved. I noted the fabrication vs. casting debate regarding the 'spider' on 6MT 72010.

Query: Given the sort of fallout you describe and with the range of 'scopes' now available to raise inspection to levels undreamed of in the not so distant past, I'm surprised to hear casting sand removal is still such a bugbear. What's the old saying about an ounce of prevention? At what stage and how is it currently removed from complex castings?

 

I am going to be contrary and say that the monobloc was not the best engineering solution for a three cylinder locomotive.

Why? How it was mounted on the Gresley classes meant that you couldn’t remove the bloc without lifting the boiler on all of the classes fitted with it. If there was any issue with any of the cylinders, requiring specific repair that could not be done in the frames, in situe, the monobloc would be required to be removed.

The availability figures I have for the LNER seem to indicate that those with monoblocs were in works for longer at each heavy general than those classes fitted with separate cylinder castings, where it was possible to remove cylinders and valve gear in isolation without lifting the boiler. It is somewhat telling that as the monoblocs became life expired on the V2 class the solution to the issue of not manufacturing further monoblocs was fitting many of the class with separate cylinders, which required fitting of outside steam pipes.

No other railway in the UK utilised monoblocs like Gresley did and I think this was an Achilles heel which really didn’t need to exist. Some might also argue that three cylinders for the V1/V3 class where two cylinders were considered adequate on other railways might also be something to discuss.

Gresley was a genius in so many different ways, and he has remained a favourite historical figure of mine ever since I first laid eyes on my first steam locomotive (60103 Flying Scotsman), but the fact remains that he focused on areas of ultimate performance, PR and innovation without necessarily paying as much attention to other aspects of the CME role (workshop organisation, spares, standardisation) as he could have done. Whether you feel that detracts from his reputation or not, there is no denying his excellence where the high speed train is concerned and his articulated streamlined trains and locomotives are undoubtedly among the finest creations that the world has seen in the steam age.

 

With my Devil's Advocate hat firmly in place .......

Surely the need to remove the boiler to dismount the monobloc assembly comes down to questions of design, no? The frames as designed by HNG were no massive departure from convention (and he had Bulleid to cover that particular base!). If looking at an entirely novel design, intended to employ a monobloc, other than the special case of a Fairlie, surely it would make more sense for that component to be removed from below.

I realise these considerations are very different in detail, but my point regards design thinking:

Anyone seeing a FfR England in a state of undress for the first time will be surprised (if not shocked) to realise the outer firebox wrapper forms part of the load bearing chassis, frames attached. fore and aft. Unconventional? Yes .... but with nearly 170 years under it's belt, I'd suggest the design has proven reasonably sound.

Anyone given to performing their own car repairs who's owned a 1960/70s Dagenham Dustbin after a BL A55/60 Oxford type car will be aware servicing is made a lot more difficult by Ford's practice of including a cross-member under the engine block meaning you have to remove the entire ruddy engine to effect removal of the sump, adding many hours to what, on the Leyland vehicle merely involves some basic yoga.

I noticed during construction photos on Corris No.10 that the design facilitates removal of cylinder assemblies forwards from the main frame, once the buffer beam is removed.

Older technology especially seems to perpetuate design features long after the rationale for doing something in one prescribed manner had passed and for the most part, change has come in incremental baby steps. You only need look at the occasional ding-dongs on here about the relative merits of superheating to realise how new fangled anything from the 20th century still is to some!

 

How many visits to the works would have involved lifting boilers off anyway?

 

More than you would think. The fact is most locomotive visits to works on the LNER were boiler related over and above everything else. In wartime, boilers were the major issue for Gresley and Thompson as CMEs, mostly responsible for the long queue of locomotive at works, awaiting to be worked on - to the extent that additional boiler inspectors were ordered by Thompson to conduct assessments to determine if a locomotive should continue in service or not.

But the monobloc took up additional time for locomotives where a boiler lift would otherwise not have been required, which is the crux of the point here.

 

There are a number of factors to consider here. However it did reach the stage where boiler feedwater treatment was so good it was felt that a boiler should not need to be removed from a locomotive within its economic life. It was also appreciated that the removal of the boiler, should it be necessary, did take an unacceptable length of time.

The boiler ought to be tied to the locomotive for its working life, which was good because it acknowledged that the need for boiler repairs had become far less frequent but in the event that you did need to remove it you would want to do it quickly. The question is how quickly could it be done? The "zip-on" boiler concept was developed, credit Col K. Cantlie, which would allow for a boiler to be either applied to or removed from a locomotive in about 15 minutes.

Francis Webb was very interested in the use of steel as a locomotive frame material. The first cast steel locomotive bed was produced in 1929 so far as we can tell and these were preceded by cast steel sides with bolted cast steel stretchers.
Gresley began his apprenticeship at Crewe in 1893 and served under Webb during the Race to the North. When Grouping came about Gresley would have been well aware of the constituent N.E.R. and its abilities. I have read that Robert Absalom Thom was the member of what we might call the 'Gresley Team' who was involved in overseeing the production of the large and complex castings.

We had no equivalent to the General Steel Castings Corporation in the UK. Bolts and rivets remained the order of the day; the French benefited from the cast steel bed and so did some of the UK's export customers.
So back to the monobloc. Once you have started combining the components of a locomotive together which would ideally be best if they were permanently joined into unified structures why stop before you you have combined everything possible into one? We know it works and maybe someone else had a dream.

 

It should be pointed out that to just remove the single inside cylinder of a Thompson or Peppercorn 'Pacific' would also require the boiler being lifted. On the GWR the position is even worse with all those 4-6-0s, 2-8-0s, 2-6-0s and 2-6-2 tank locos needing just an outside cylinder being changed, also needing a boiler lift as the (outside) cylinders incorporated half of the smokebox saddle as well.

 

Different question, I realise, but would I be correct in supposing the 'divided drive' four cylinder layout preferred by "The Churchward School of Design" doesn't lend itself to a monobloc casting?

 

The inside and outside cylinders are not in line so a monobloc cannot be used.

Sent from my SM-A105FN using Tapatalk

 

As I suspected. Thank you.

 

That is somewhat missing the point. You can remove the outside cylinders and valve gear without the boiler being lifted. That is the crux of the issue of the monobloc where you don't have that choice.

 

I'm not really sure if the issue of a boiler lift is such a big deal - yes, it's a lot of work, but boilers were swapped routinely and with more frequency than cylinders were swapped, so in the vast majority of cases, if the overhaul was big enough to warrant new cylinders, you were likely having the boiler out anyway.

I think the bigger issue telling against a mono-bloc is that any accidental damage of a cylinder (i.e. something outside the normal run of wear and tear, such as a casting fracturing) would require the entire casting to be replaced, rather than an individual cylinder.

The other consideration is that for locos with plate frames (i.e. the vast majority of British locos), casting inside and outside cylinders together; or equally the GWR design of outside cylinder / inside valve chest cast in one piece, requires the frames to be cut away in the vicinity of the cylinders and then re-inforced by some means. For example, the Maunsell 3 cylinder moguls had left-hand and inside cylinder cast as a single casting (that being the biggest unit that could be made in the Ashford foundry); the frames have a deep slot into which the combined casting is placed, with a splice plate then riveted over the top. There is a discussion of the design considerations that went into selecting that design in Holcroft's book.

Tom

 

V1 frames awaiting cylinders.

 

V1 frames, now with cylinders fitted.

 

That's a superb find - where do you find those?

Does put it into perspective how big the monobloc is!

 

In 'The London & North Easton Railway In Focus' by John Crawley, ISBN 1-899597-12-3 (published .in 2001)

 

Fettling a V2 cylinder block. Note the waistcoats, natty headgear and questionable safety boots.

 

And machining it.

 

Simon, in the nicest possible way, is there anything on Standard Gauge that’s small apart from the pay packet?

 

There are some very good photos of monobloc cylinders for the V2 and P2 locos in the book Gorton Tank by David Gosling.