A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 60


Hello Chums

Long Lap/Travel Valves, Direct Steam Circuit, Higher Pressures and Superheating - The Big Step Forward

OR:

GJ Churchward - An Appreciation.

Before our discussion moves away from valves, I thought a brief recap on Edwardian developments might be helpful. King Edward VII reigned from 1901 to 1910 and his brief reign, like that of William IV seventy years earlier, witnessed a notable advance in steam locomotive development.  In fairness, the late-Victorian contributions of JF McIntosh's introduction of large-diameter boilers and WM Smith's development of piston valves should be noted.  Both have been acknowledged in previous postingtons.

Although some locomotive engineers were happy to accept developments - Mr Worsdell (NER) and Mr Johnson (Midland) with piston valves and Mr Hughes (L&Y) with superheating - there appeared to be a reluctance from many to move away from what they had always done.

Which makes me wish to acknowledge the remarkable achievements of GJ Churchward on the GWR, over a period corresponding almost exactly to Edward VII's reign.  I occasionally detect a certain antipathy towards GWR locomotives from some railway enthusiasts - a sort of 'anything except Swindon' - a view which I do not share.  Let's take a few minutes to discuss how Mr Churchward can be reasonably described as the father of the modern British steam locomotive.





There was much made at the time of alleged GWR secrecy, suggesting Mr Churchward deliberately withheld information about his work from his contemporaries. I accept he did not publish full drawings of his locomotives, but I believe he was open about what he was doing. And I'm in good company:-

'Swindon had the reputation of being the most secretive place. Yet there was little that could not be discovered about GWR locomotives by some mild espionage, and one hardly need go so far as that when GWR locomotives could be observed in action in half the counties of England. A knowledgeable observer could spot the long travel of the valve spindle as one of Churchward's engines moved off, and hear the sharpness of the exhaust. Passing at speed, the barely-audible beats and the wide sweep of the connecting rods gave clear indication of the high expansion ratio. The higher than average boiler pressure of 225lb was a published figure. On each side of the smokebox, large steam pipes took a direct route to the outside steam chests. No patents covered these features.'¹


And:-

'The so called secret could hardly have been more clearly disclosed: long lap, long travel, small clearances, high piston speed, ample ports and passages. So obsessed however were other contemporary engineers that valve travel was something as firmly fixed as the laws of the Medes and the Persians that this exposition had absolutely nil effect upon Churchward's colleagues [...]'²

Unlike his successor, CB Collett, Mr Churchward was supportive of the learned institutions.  He read few papers but was a frequent contributor to the discussion of those read by others. I'd like to include several quotes. The first one is from Mr Churchward's only important paper to the Institution of Mechanical Engineers, the second and third are from his contribution to papers read by others:


On Boiler Pressure

"The higher pressures now common have undoubtedly produced more efficient locomotives both in respect of hauling power and coal consumption. [...] By employing  225lb in simple expansion engines and by making the necessary improvements in steam distribution enabling shorter cutoffs to be used, corresponding improvements in efficiency and economy of fuel have been obtained. Great increase in drawbar pull at high speed has also resulted."

Large Locomotive Boilers, Institution of Mechanical Engineers, 1906.


On Piston Valves

"On the Great Western Railway, piston-valves have been tried and have given considerable trouble; they are undoubtably one of the most troublesome pieces of mechanism with which anyone can have to deal. I have before me the task of curing the defects, if possible; feeling quite sure that engineers will never have a chance of utilizing to the utmost the power of the locomotive , and bringing it, in economy, within like reach of the compound*, without the use of piston-valves.'

American Locomotive Practice, Institution of Civil Engineers, 1903.


On Superheating

"It has been found on the Great Western Railway, in the course of a considerable amount of work with superheating, that the question of lubrication must be specially attended to, and unless the lubrication is not only effective and sufficient, but also continuous, there is certain to be trouble with high superheat."

Compounding and Superheating, Institution of Mechanical Engineers,1910.

 
George Hughes of the L&YR was also supportive of the institutions and was a good and innovative engineer. He was second in Great Britain, after Mr Churchward, to introduce superheating but made the error of using it to keep boiler pressures no higher than 180 psi. His 4-4-0s, mentioned earlier, with high superheat and long lap, long travel valves could have transformed his locomotive practice if only, like Mr Churchward, he had persevered and overcome the inevitable lubrication difficulties.

Whilst other locomotive engineers used some of these developments, it took about twenty years before they realised the key to success was to adopt them all and, by then, Mr Churchward had retired.  During his term in office, only Mr Maunsell on the SE&CR came close. Mr Maunsell was a clever chap and engaged three exceptionally good engineers to help him - one from the Midland (high superheat and general appearance of the locomotive) and two from Swindon (boiler, cylinders, valves and steam circuit).

Mr (later, Sir Nigel) Gresley was rather slow off the mark but the exchange trials, in  May 1925, between his 'A1' 4-6-2 and a 'Castle' 4-6-0 (effectively, an enlarged 'Star') convinced him of the superiority of the Churchwardian approach.

Incidentally, it has been suggested on occasion that the opportunity was taken to measure the valves of a 'Castle' when one was in the custody of the LNER and unattended by its own crew. There were two opportunities for this, both in 1925.  Pendennis Castle took part in the locomotive exchanges and then Windsor Castle was at Darlington for the Centenary celebrations.

The late Terry Miller, Vice-President of the Gresley Society, was a former LNER locomotive man and was requested by the society to advise on the feasibility of removing a valve.  He concluded, from his experience, two skilled fitters could have removed a valve, taken the necessary measurements, and put it all back together in a couple of hours.³

Let's end with a quotation from Sir Nigel Gresley, included in his vote of thanks for WA (later, Sir William) Stanier's Presidential Address to the Institution of Locomotive Engineers in 1936:

I was pleased to hear Mr Stanier refer to his old Chief, Mr Churchward, because I have always thought, and still think, that locomotive engineers in this country owe more to the ingenuity, inventiveness and foresight of Churchward than to any other chief mechanical engineer.


* Compound locomotives. A fitting subject for a subsequent postington, methinks.

¹ The Arthurs, Nelsons and Schools of the Southern, SC Townroe, Ian Allan, London, 1973, ISBN 0 7110 0434X, Page 31.

² Speaking of Steam, ES Cox, Ian Allan, London, 1971, SBN 7110 0236 3  Page 54.

³ A Gresley Anthology, Geoffrey Hughes (Ed), The Gresley Society and Wild Swan Publications, Didcot, 1994, ISBN 1 874103 19 4, Page 35. Incidentally, Terry Miller was the engineer who proposed the concept of the High Speed Diesel Train to the British Railways Board in 1969.

The quotations from the Proceedings of the institutions can be found in Speaking of Steam and:

Master Builders of Steam, HAV Bulleid, Ian Allan, London, 1963.


ENDNOTE

I mentioned Mr Collett's 'Castle' 4-6-0 of 1923 as being, effectively, an enlarged and more powerful version of Mr Churchward's 'Star'. However, many enginemen found the 'Star' to be a smoother-running engine.  The 'Star' had four 14 1/4 inch diameter cylinders (later increased to 15 inch) while those on the 'Castle' were 16 inch, and when rebored could be enlarged up to as much as 17 inch.  However, the 'Castle' shared the same 8 inch diameter piston valves as the 'Star'.

The late Kenneth Leech, an authority on GWR locomotives, remarked:

'By modern standards the steam and exhaust ports [of the 'Castle'] were on the small side and tended to restrict free running.'

Portraits of 'Castles', Bryan Holden and Kenneth H Leech, Moorland Publishing, Ashbourne, 1981, ISBN 0 903485 89 3, Page 19.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Toodle-pip

John

Amazing stuff, as usual, John.    

This is certainly a fascinating series.
And particularly well written I might add

There was another post-Grouping CME who used long travel valves, but it's not that easy.

George Hally, CME of the Metropolitan Railway, designed a class of 2-6-4T around parts made by Woolwich Arsenal to a design closely based on the SECR 'N' class moguls. These parts were made as part of an unemployment relief scheme after WW1: these had long travel valves from the original N design. The boilers were built by R Stephenson & co, also resembling the SECR boilers, so that the Met locos had a decidedly SECR/Maunsell look about them. They were class G on the Met.

The six locos were built in 1925, and taken over by the LNER and reclassified L2 in 1937; they were withdrawn between 1943 and 1948. They principally worked freight over the Met, with rare use on passenger; after Stratford took over their shopping in 1938, they could occasionally be seen on duties in that vicinity whilst running in.

Martyn

 The RCTS LNER locomotive series has a bit to say about measuring the Castle valve travel and general arrangement of the valve gear. Once was, IRRC, during the trials against the A1, and the second at the Stockton and Darlington Centenary exhibition. Need to check. The valve gear settings were replicated on the design office 'model' used to measure the valve events at various cut offs, and Spencer was eventually able to persuade Gresley to try, and then change to, long travel valves after the resulting economies in coal and water mentioned already by John earlier.

Martyn

What a fascinating series! It must take hours of work to research and type up. I admire and very much appreciate the effort John is putting in to help all of us who are beginners to understand the mysteries of the steam locomotive. I really hope there will be the possibility of getting a document of all parts of the series when it does finally conclude.
Keep it coming John!!!
Cheers 
PS If you are going to be at TINGS on the Sunday please come and find me on a layout called Haversham Central (I think this is the correct name) as I am helping run it on the Sunday. If I've got the name wrong I'll post the correct one later.

QuoteWhat a fascinating series! It must take hours of work to research and type up. I admire and very much appreciate the effort John is putting in to help all of us who are beginners to understand the mysteries of the steam locomotive. I really hope there will be the possibility of getting a document of all parts of the series when it does finally conclude.
Keep it coming John!!!
Cheers 
PS If you are going to be at TINGS on the Sunday please come and find me on a layout called Haversham Central (I think this is the correct name) as I am helping run it on the Sunday. If I've got the name wrong I'll post the correct one later.

I got the name correct, so I will be on Haversham Central on the Sunday at TINGS.

Quote from: Firstone18 on January 28, 2025, 10:14:51 PMWhat a fascinating series! It must take hours of work to research and type up. I admire and very much appreciate the effort John is putting in to help all of us who are beginners to understand the mysteries of the steam locomotive. I really hope there will be the possibility of getting a document of all parts of the series when it does finally conclude.
Keep it coming John!!![..]

Thank you very much indeed for your kind and encouraging comments.

The initial research doesn't take that long because I tend to write the first draft more-or-less from memory. It's the fact-checking that takes the time; making sure I have remembered correctly. Even so, an embarrassing error sometimes slips through and I'm hugely grateful to those who point these out.

I like to dig out some appropriate quotations as well - this can take some time.

One thing has become clear - it would be much easier to write a 'Coarse Guide to the Steam Locomotive' for an audience comprised of those who already know how it works.

My assumed base-line knowledge of a reader is familiarity with toy trains in 'N' gauge.

Also, and most importantly, the ultra-brief mini-series is written to (hopefully) entertain. If it informs as well, so much the better. In my view, this requires a anti-textbook writing style. Unfortunately, I expect this puts some people off.

Perhaps worth mentioning is I don't normally use the internet for research or fact-checking, but YouTube is a useful source of helpful videos.

The mechanical contraptions that move the valves are coming up next, although we had better have a quick think about cranks first. After that, I'll bore you with a discussion about more than two cylinders, compounding the tediousity  with a diversion into compounding. Then we'll move on to something that was still a work in progress at the end of steam - getting the exhaust out of the chimney in the most useful way. We'll meet a clever French chap and, as mentioned before, finish with a Finn.

As for what happens after the mini-series is complete - I have no idea.

Thanks again for your lovely post.

With all good wishes.

John

Just a little more on long travel valves and the LNER trials.

Spencer tried to interest Gresley in early 1925, but was rebutted. However, prior to the Castle trails, Gresley did permit a loco to be fitted with long travel valves. But this was a bodge with existing valve gear components; Spencer said it would show no improvements, and wanted nothing to do with it. It did show no improvement.....

Later in 1925, after correspondence between the Doncaster and Swindon chief draughtsmen, a second design was made (but no loco altered), and again, Gresley was not impressed and nothing came of it.

Spencer persevered throughout 1926 refining his own version, and finally, in December, #2555 'Centenary' was fitted with the new gear. The difference was that new components had been made where necessary to give better performance at smaller cut-offs (ie at running speed), and not just re-use the old versions. This was a success, and finally Gresley agreed to altering locos to long travel.

it was thought by most that 'long travel' would result in more wear, but in fact, when the cut off was in running position, the lap was bigger that short travel, and hence the actual travel at the same speed for each type was less in the long travel. See John's post on 'lap'.

Finally, on most (not just LNER) locos at that time, the valves were made steam tight with broad rings right around the circumference. Change was made in the LNER locos to narrow split rings (labelled for different locos in the RCTS Guide as 'CPR, Knorr, or GER'), resulting in less friction, better lubrication, and better control of the valve events.

Improvements of lubrication methods also improved around this time, making the valves less prone to carbonization and wear.

Phew!

I think once again, I've gone a bit far far from 'A Coarse guide....'

Carry on the good work, John, you're getting through it very well.

Martyn

Quote from: Train Waiting on January 29, 2025, 09:55:19 AMThen we'll move on to something that was still a work in progress at the end of steam - getting the exhaust out of the chimney in the most useful way. We'll meet a clever French chap and, as mentioned before, finish with a Finn.

Don't forget about the Belgian 

Monsieur Chapelon
Kylala the Finn
Walschaerts

Quote from: crewearpley40 on January 29, 2025, 12:59:24 PMWalschaerts

I wasn't thinking of that Belgian in respect of exhaust designs.

Quote from: chrism on January 29, 2025, 01:38:13 PM

Quote from: crewearpley40 on January 29, 2025, 12:59:24 PMWalschaerts

I wasn't thinking of that Belgian in respect of exhaust
designs.

lemaitre

Quote from: crewearpley40 on January 29, 2025, 01:41:40 PM

Quote from: chrism on January 29, 2025, 01:38:13 PM

Quote from: crewearpley40 on January 29, 2025, 12:59:24 PMWalschaerts

lemaitre ?

Yep 

You continue to boggle my mind, John; honourable mention also to your co-author @martyn . 'The more you learn, the more you realise how little you know.', to quote that railway pioneer, Aristotle. (Well, I believe he would have been had he lived a little longer.) As for what you are going to do when it's finished, I should have thought a cup of tea and a bit of a lie-down might be in order.

In all seriousness, this has been so instructive and entertaining I shall be very sad when you write 'The End'. It has even given me an appreciation of Mr Churchward and his labours, though I doubt I shall ever learn to love the GWR!

All the best,

Chris