Bulleid 'Leader'

With a self-enforced stay at home I've been catching up on reading matter, currently books on the Southern Rly 'Leader'. The bit that puzzles me is that each loco had no less than 144 piston/cylinder rings for the sleeve valves - 24 for each cylinder. Plenty of photos showing the sleeve valves, but none with grooves to take the rings. So where did they fit? Enlightenment, anyone? A cylinder drawing would help - assuming one exists.

 

IIRC the rings fitted into annular grooves in the cylinder block, and contracted inwards onto the sleeve. The opposite of conventional piston rings, though bear in mind that rings for use with steam are not usually as "springy" as those in i.c. engines. There is a cylinder drawing in H A V Bulleid's biography of his father.

 

H.A.V.B's tome makes clear that construction techniques permitted much redesign work to be undertaken 'on the hoof', as work proceeded apace.

Initial steam trials on the butchered modified Marsh 'atlantic' were made without any rings, as Bulleid had hoped sleeve valves would prove sufficiently steam tight to not need them. The results were predictable. I don't know at what stage rings were added to Leader, or whether any initial drawings appeared ahead of their inclusion, but presume it was before the first completed bogie was steam tested.

 

If you read HAVB carefully, what it says is that provision was made for fitting rings to the Atlantic from the beginning. Therefore the ring grooves would have been machined in the components before final assembly.

It was initially tested without the rings in place. That seems quite reasonable for a new concept, and importantly, would have confirmed the working clearances for the sleeves when hot.

Do you have a source for your statement that Bulleid hoped the sleeves would be steam tight without rings?

 

The design wall pressure required for a piston or valve ring depends on the cylinder pressure. IC engines therefore require higher wall pressure.


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Miniature steam locos were often built without rings on the piston valves. They relied on a close fit between the valve and liner, oil grooves in the heads and reliable lubrication

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Haven't got that book, so is it possible for you to scan that drawing and put it on here, please?

 

Fair question. I should have taken more care to stress that comment actually reflected the only reasonable conclusion I could draw from HAVB's description of the test on the 'atlantic' (witnesses by OVSB's bother-in-law, Ivatt). It seems reasonable to suppose 'going mainline' with the loco thus equipped could only have happened had indications, the first time steam was raised, suggested the test was worth persuing.

If there's any alternative explaination for what seems an unduly 'visible' way of establishing a fairly obvious presumtion (i.e. rings keep things team tight), it escapes me. The description of the test records Ivatt's amusement .... and Bullied's lack thereof .... at the result, which I take to support my interpretation. I hope this clarifies my comment.

 

Bulleid's optimism about his innovations does seem to be reported elsewhere. Dusty Durrant, who was seconded to Ashford for a while, has a (second hand) tale in his book about an experimental smokebox ash chute for the Leader (fitted, he thinks, to a U class) of which he reports "...A large open duct in the smokebox seems hardly conducive to creating a satisfactory draught for the fire, and objections were raised. Bulleid's reaction was of typical super-confidence - 'My multiple jet exhaust system will easily counter the loss of draught', or similar'". He then goes on to say that the test loco steamed abominably except when handled by a particular driver, who kept his method secret. It turned out to be a 'bloody great turnip' stuffed in the ash chute to block it up!

But its correct too that we do need to very careful about documenting what are our own speculations. While writing my book there were at least two occasions where I constructed logical and not over elaborate theories to explain some design mystery, only for another source to turn up which made the theory quite untenable. Sometimes its very hard to let go a a splendid idea, and I've found myself hunting for reasons why I should allow myself to discard the contrary evidence. Dangerous!

 

What I find hard to understand is that the Southern Railway/ region, allowed Bulleid to design this type of engine in the first place, especially when other railways such as LMS, and GW had already developed their own DMU'S and Bulleid has already designed some EMU's and electric and desiel locos, so its clear the writing was on the wall for steam, the idea was to replace the shunting engines such as M7's from passenger and ECS work so why not design a smaller version of the mainline diesel, or electric, or better still do what BR did, design the 73 electro desiel

 

Around that period there were conflicting views on fuel sources. Oil was cheaper and more efficient but the Government wanted to cut imports so coal was encouraged as a fuel.

 

Martin - if you look at fuel economy and maintenance costs, the Adams O2 was considerably cheaper to run than an M7. So really what Bulleid should have done about the “M7 problem” was just build more Adams O2s ...

Tom

 

Or do as the Southern Railway/Southern Region became forced to do in desperation a little later, build to the perfectly satisfactory LMS Classes 2 and 4

 

These decisions at the time are rarely as clear as they appear in hindsight.

 

Good question. The general view of the production order, signed off just prior to nationalisation, is that it was a last grand gesture from the board. Although likely part of the story, this discounts overriding factors at the national level.

To understand just how so novel a project got backing in the first place is another matter entirely. Taken at face value, OVSB's aims of near universal route availability with just four classes was admirable and the objectives of the Leader project reasonable enough. The fly in the ointment was, of course, the degree of novel and/or untried technology, in both the loco and its construction.

Bulleid accurately assessed the shortcomings of Stephensonian steam, including its labour intensive nature and questioned whether steam could match the advantages, real and perceived, of internal combustion.

Recall that with perennial 'balance of payments' considerations very much exercising governement in the postwar era, use of domestically produced fuel was seen as infinitely preferable to spending vital foreign currency reserves on imported oil, then as now priced in US$.

Whatever one's political stance, the Atlee government didn't have the luxury of being unquestioningly profligate for no good reason. Had the project borne fruit, the advantages in terms of massively reduced costs, across the entire national network, would have been on an almost inconceivable scale. With the hindsight we can employ, Leader clearly encompassed some questionable decisions, but, whether or not - with better qualified oversight - they could have been, by no means all of those were at all obvious at the time.

 

It would be important to establish at an early stage that the sleeves did not seize in the cylinders when hot, either through expansion or lack of lubrication. To eliminate confusion with the rings which might be doing something similar, one way would be to steam the engine without fitting the rings. That seems quite practical to me, and I doubt that anyone expected it to be completely steam tight. In fact if it had been, the sleeves would surely have been too tight for service use. It was all new technology, and the working clearances required were not known. The number of broken rings later experienced tends to confirm that.

 

So why didn't he go down the pulverised , or semi liquid coal fire approach ? and a modification of his oil bath motion, that could have allowed firing, from a central cab, similar to Garrett 's

 

Although it pre-dated Bulleid, the SR had prior experience of a pulverised coal trial where I am sure Bulleid would have been aware of the outcome; it was not the economy that was hoped, primarily I believe because a lot of fuel was drawn unburnt through the tubes by the draught. (There were also handling problems that led to minor explosions). I think pulverised coal was not readily amenable to burning economically without significant other changes to the design of boiler used.

Tom

 

It is a wild shot but in Brigthon the firm of Ricardo had made an interesting observation.
They had wasted a lot of tax money on a two stroke sleeve valve configuration during the whole war.
They had all kind of problems sealing the sleeves on the outside with contracting rings,labyrinths etc.
(As had Bristol with fourstroke aero engines.)
In pure desperation or by accident they had a very thin and flexible sleeve with no arrangements for sealing and that worked.
Difficult to start but working like a dream when hot.Calculation showed that pressure could not do it and the explanation was that combustion heat expanded sleeve into very closeness to cylinder and the gap regulated the heat transfer.Selfregulating.The firm Junkers in Germany had exploited the same effect somewhat earlier in some opposed piston diesel engines with undivided piston rings.
Bulleid lovedwild things and Brigthon is in SR territory?

 

I'd question the desperation in that statement.

A lot of the existing pre-grouping passenger tank locos - whether class O2, M7 or H - still, as it turned out, had 15 to 20 years more remunerative life left in them at the end of the war, most of them continuing in use until the early to mid 1960s (and in some cases the late 1960s). That rather suggests to me that comments about their being worn out may have been somewhat exaggerated.

That rather suggests to me that the "M7 problem" (for want of a better phrase) was somewhat illusional - an illusion for Bulleid, but also I am not convinced that the SR actually needed the LMR class 2 and 4 locos, good as they were. With a combination of electrification, closure or development of the DEMUs, I think BR(S) could have kept going quite happily into the 1960s with the locos it had, gradually withdrawing them as required. The building of LMR locos at Brighton Works immediately post war smacks to me more about an attempt to keep industrial workers in jobs following the rapid winding down of munitions work, rather than because there was a demonstrable need for new locos.

Tom