V4 2-6-2 No. 3403

which was more common than you might think - the story of the Clans being disliked because they were repeatedly rostered for Class 7 work is well known (both the cases where it was done through ignorance, but also during their foray on the Eastern Region where at least one of the players strongly hinted it was deliberate so that they could keep their Brits IIRC) but there were others.

A classic, and a new one on me until I heard it recently from the horse's mouth (a horse who still bears the scars...), was the J15s transferred to Neasden, for sub-allocation to Aylesbury, to work the Watlington Branch. While at Neasden, and also apparently at Woodford, there were multiple outbreaks of 'it's an 0-6-0 tender locomotive, clearly we can give it J11 work'!

 

I would understand the terms to be taken in isolation of the intended duty.

In other words - if you drive the loco hard, the cylinders consume steam at a given rate; and the boiler can produce steam at a given rate. If they are not in balance, the loco is under-boilered or over-boilered as appropriate.

Then you can look at the duty, at which point it may be desirable to deliberately design a loco to be under- or over-boilered. In other words, the term has an objective meaning, but not a pejorative one: a loco being under-boilered may be an entirely rational design choice.

As an example, by design, shunting locos are ideally under-boilered, because the duty cycle has short periods of high-output work, during which you can mortgage the boiler safe in the knowledge that very soon you will have a pause during which time you can recover water level and pressure. A GWR small prairie always looks under-boilered to me (judging its grate area and heating surface against locos with comparably sized cylinders) but again I suspect that is not a bad design choice for loco subject to the stop-start duty cycles of branch line working. You wouldn't want to do a long sustained run with one though, or at least if you did and worked at the boiler limit, the cylinders would not be doing as much as they could. That's the 43xx "can't work an excessively fast and heavy train" problem.

The flip side - I'd suggest a Merchant Navy is over-boilered: the boiler can produce more steam than the cylinders can use. But again, that is useful for the desired duties, rather than a flaw. It means that even if the boiler performance falls off towards the end of a long sustained run (clogged ashpan, clinkered fire, dusty coal etc), the driver can still get a level of performance out of the engine that has not diminished - because even with a degraded fire, the boiler is still capable of keeping up with the cylinders.

So to me, the terms have an objective meaning around the relationship between sustained steam production and sustained steam consumption in ideal circumstances; and the designer may then choose deliberately to bias one way or the other based on intended duties. My understanding with most BR Standards was that they were deliberately designed to be a bit over-boilered, but that is erring on the right side in a situation where you don't expect you'll be able to maintain coal quality or crew skill to the levels expected pre-war.

Tom

 

John that is most definitely one for another thread

 

The LMS Stanier Class 3 2-6-2T had a boiler of almost identical size to the GWR small prairie (length 10ft 10in, diameter tapering from 4ft 2in to 4ft 9in). But the LMS engine had a laden weight of 71 tons, compared with only 61 tons for the GWR 4575 class.

Some of the Stanier engines were later rebuilt with larger boilers, while the subsequent BR 82xxx Class 3 2-6-2T got a substantially larger boiler for only a small overall weight increase.

 

The two J15s which went to Neasden to be sub-shedded at Aylesbury were transferred in 1957 from Bury St. Edmunds and as the Y14/J15 first appeared in 1883 and withdrawals of the class were well underway by 1922 - these were elderly engines. They had developed from the early days a reputation for outstanding haulage abilities and even as late as 1953 one was witnessed working a train of 11 LMS corridor coaches. It was nothing unusual for them to be pushed outside the envelope of what might be expected of a rather modest 0-6-0. In good condition they could work what might be called miracles but transferred off territory in 1957 - that was never going to do them any favours.

 

Shortage of steam could be due to a variety of reason of course, "under-boilered" rather implies that there was no cheap fix to improve steam production. The Standard Class Five's draughting and steam production capability was improved by a minor adjustment (reducing the blastpipe cap diameter slightly), as it was for a number of other loco types (including the V2s) although those mods usually involved changes to several dimensions including chimney size, taper, height of choke above blast pipe etc. In his 1954 paper to the ILocoE, "Experiences with BR Standard Locomotives",- Cox in response to a question about the Clans said "They had found....that it would benefit from some sharpening up at the front end, as had been found with the Class 5 as described in the Paper [i.e. the modification noted and described in the BR Test bulletin], and the necessary small modifications would be made shortly.". Which sort of suggests that there was a recognised case for and scope for increasing the steam production of the Clan.

 

Which has been checked out, designed and will be implemented on this one complete with a higher boiler pressure and welded boiler etc, (read the project website for all the information, very interesting)

 

Inadequate exhaust systems remain a problem on locomotives and people still point the finger at the boiler as being the problem. SSC figures can be too high too and the boiler gets the blame. One well known locomotive used excessive coal and water and the boiler got the blame. A little thought would have raised questions. Fuel was being consumed and water was being evaporated. So why was so much evaporation taking place, where was all that energy being lost? In terms of evaporation rate per unit of fuel being used the boiler was not performing too badly. It took years for the penny to drop and for questions to be asked. Never assume your valve gear design is adequate. And as for other losses these are seldom negligible.
We have moved on a long way from Cox and know that the exhaust system is the key component and can design systems that BR could never dream of. And so we should, our charges deserve it and we should strive to be the best custodians. Don't forget an exhaust system change is always reversible so when waiting for the next overhaul the engine can revert to its original state if desired and be displayed as such.
To be honest I don't mind if the smokebox fitted to the Clan looks similar to that fitted to 25NC 3454, or class 26 3450 or perhaps like 19D 2644 so long as the engine is given the chance to drive its boiler as well as possible.

 

Where does this negative Clan stuff come from? All of the people I know who worked them say they were fantastic. Free steaming and strong. Almost always had class 7 and 8 work thrown at them, which they naturally struggled with. On class 6 work perfect and much easier to work on than a Jubilee and just as good.

Whether they were needed is a different question but they were definetly capable.

 

That was my understanding as well. Because they looked like Brits they were expected to perform like them too, which was never going to happen.

 

The Clans suffer in a similar manner to the Thompson A2/1s - some writers of the 20th century have been overly critical without understanding what work they were intended for and on what lines.

Frankly, I think the primary evidence for both shows two classes that were free steaming and fully capable. Much of the criticism expects them to do class 7 and above express passenger work, which is at odds with their designers intentions.

 

Possibly the issue with the Clans is why? What was the point of producing a loco between the very capable Standard 5 and a Britannia, I think even Cox questioned the need. The only reason I can think of for inflicting them on the Southern was a long term plan to cut losses and scrap the Bulleid light Pacifics. Thankfully Jarvis came up with a much better solution. This latter point is pure conjecture on my part of course.

 

Even E. S. Cox remarked about a 'Clan' that he was at the controls of experiencing a 'wooliness' that was absent in the other BR 'Standards'.

 

E.S. Cox was not a driver. There are a lot of questionable things in his writing that need looking at, IMO. Besides which, even within a class of steam locomotives you will have some which are not as good as others, not least maintenance issues and usual wear and tear. I wouldn't put too much stock in one particular run, either.

 

Maybe, but he followed this by saying -

"Certainly the draughting proportions were not quite right, and these were subsequently rectified, but what was called for was a searching analysis on the Stationary Test plant of the whole air, gas steam cycle. We never got round to this, however, due to pressure of other work and there was no demand for further engines of this kind to make it worth while."

'Locomotive Panorama - Volume 2', by E. S. Cox, page 22.

 

It seems there was still a lot of "suck it and see" in those days and insufficient reason to do much of that to improve the Clans, so they were never as good as they could have been. The new one should be better still.

 

I think that's a bit dismissive and patronising. There is a fair amount of evidence from the autobiographies of various senior folk in the locomotive engineering community that they had plenty of experience in footplate work - and as Premium Apprentices, which is how most started out, were provided with footplate passes and were encouraged to use them. It might not have been their daily job but I suspect most had a reasonable amount of experience.

 

When you’ve read as much of Cox as I have done in the last ten years you tend to feel a bit weary reading some of his more subjective views, I’m afraid.

But with respect, I wasn’t being patronising to anyone on this thread. Dismissive, sure, as some of Coxs views on locomotive classes are questionable to me based on the evidence.

Please don’t misrepresent my views on Cox as somehow relating to everyone who was a premium apprentice, by the way. That’s not particularly fair and I was specific to Cox in my original post.

 

Couldn't agree more! Cox had his biases and was wont to flaunt them in his books, usually being very selective in the supporting evidence he presented.

 

Em, if you were to restrict the acceptable works of railway authors to those who seem to be unbiased I think you would be left with a very short reading list. I don't think company loyalties are exclusive province of lay enthusiasts!