A Coarse Guide to the Steam Locomotive for ‘N’ Gauge Modellers

[martyn]

A short addendum about snifter/snifting valves.

By no means all superheated locos had them. Some had them for only part of their life.

The LNER used them extensively; the SR used them but were later removed.

See

https://en.wikipedia.org/wiki/Snifting_valve

for a better explanation than I gave!

Martyn

[joe cassidy]

 I'm surprised that our friend John@trainfish has not commented on this as he has been known to enjoy a snifter from time to time ?

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 42


Apology and a Feeble Attempt at an Explanation

Hello Chums

For ages now, I have been acutely aware that I abandoned this mini-series in a rather abrupt manner. I'm very sorry for this. My last postingtons were when I had contracted Covid which, incidentally, was worse than when I had it in 2021.  Much worse.

I had the next part drafted and the one after that saved in note form.  But I lost both due to the 'seven days for drafts rule' that came in with the last Forum upgrade.  Bother!

Then the disagreeable series of treatments I was receiving for my recalcitrant legs was suspended, followed by an appointment where a charming lady hit me with a hammer for half-an-hour and then stated, "It's getting worse." I'm now on a waiting list to get onto another waiting list for the nice people to decide what they want to do next.

All of this rather put me on the wrong side of the drag curve as regards motivation.  A sort of engine ennui.  But, up with this I cannot put.  No wimpish sniffling self-indulgence allowed. I decided to recommence the mini-series before the end of the year.  Our FabulousForum cautioned me against returning with this SuperStern massage:-

'The message has the following error or errors that must be corrected before continuing:
Warning: this topic has not been posted in for at least 120 days.
Unless you're sure you want to reply, please consider starting a new topic.'

Yes, bossy old thing, I'm sure I want to reply. 

*

On with the mini-series...


We sort of left off with my rhetorical question:

Why did Mr Churchward stick to the two row superheater giving an approximately 30/70 flues to boiler tubes ratio?

Many thanks to @chrism and @martyn who kindly replied.

I think the answer is clear - Mr Churchward's locomotives were head and shoulders (at least) above anything else in this country.  And this would remain the case until he retired in 1922.  I think there was an exception, Mr Maunsell's 'N' class 2-6-0 on the South Eastern & Chatham Railway.  We'll likely return to these locomotives later.

For just over twenty years, from his standardisation proposals of 1901 until his retirement, Mr Churchward led British steam locomotive development. Then Mr Collett took over as Chief Mechanical Engineer and remained glued to the 'Churchward Principles'.  And, he almost got away with it. In my view, the disruption came with the Second World War.  No longer could the world's best steam coal, expert enginemen and fastidious maintenance be depended upon.

Mr Collett retired in 1941 and it fell to his successor, Frederick Hawksworth, to try to find a way to adapt GWR locomotive policy into a railway world which had changed forever. Mr Hawksworth tried outside valve gear on the '15xx' 0-6-0PT locomotives and high boiler pressure (280 psi) with his 'County' 4-6-0 class.  But, to my mind, his most important contribution to Great Western locomotive development was his introduction of higher superheat.

And, nowhere was this more obvious than with his developments of Mr Collett's 'Castle' class 4-6-0s.  Since Mr Churchward's day, the pretty much standard arrangement for superheating on GWR 4-6-0 locomotives was 14 flues, arranged horizontally across the boiler, towards the top, in two rows of seven.  Hence the term, 'two-row superheater'.  This gave around 260 sq ft of superheater surface area.  In other words, over the 260 sq ft, the steam in the superheater elements was exposed to the heat of the gasses from combustion passing through the flues.

Meanwhile, on the Southern Railway, Mr Maunsell's 'N15' 'King Arthur' 4-6-0 class of 1924 featured 337 sq ft of superheating surface and his larger 'LN' 'Lord Nelson' 4-6-0 class of 1926 featured 376 sq ft.

Over on the LMS, not generally considered to be at the forefront of locomotive development in Sir Henry Fowler's time, the 'Royal Scot' 4-6-0 class of 1927 had a superheater surface of 399 sq ft.

But such was the excellence of Mr Churchward's legacy in other areas that the low superheat did not prevent GWR locomotives demonstrating their superiority over those of other railways. The tests of a 'Castle' on the LNER in 1925 and the LMS in 1926 gave conclusive proof of this and led to interesting developments in locomotive design on both these railways.

However, steam locomotive operating conditions in the nineteen-forties were significantly more difficult than in 1926 and Mr Hawksworth set out to improve the performance of the 'Castles'. He had already introduced a higher degree of superheating with his '6959' 'Modified Hall' class of 1944 and '1000' 'County' class of 1945.  Both of these featured three-row superheaters with 21 flues.

No. 5097 was the last pre-War 'Castle', entering service in September 1939.  Passage of time and the difficult wartime conditions meant that, by 1945, the remaining 'Star' class locomotives were becoming worn out.  Mr Hawksworth obtained authorisation for the last 40 'Castles', Nos 5098 - 7037, which entered service between May 1946 and August 1950.

[Fun Fact.  Not all 171 members of the 'Castle' class were in service at the same time.  And, thankfully, it's not due to one being destroyed in an accident or by enemy action. No. 100A1 Lloyds, one of the 16 'Stars' rebuilt as 'Castles', was withdrawn in March 1950. The final batch of ten 'Castles', Nos 7028 - 7037, entered service between May and August 1950. And, one would have had to be quick off the mark to see the maximum of 170 locomotives in service as the next two, again, rebuilt 'Stars', were withdrawn in September 1951. ]

Back to No. 5098 Clifford Castle - she, like the other post-War 'Castles', was outshopped by Swindon with a three-row superheater.  She was regarded by many enginemen, at the time she entered service, as the best 'Castle' built.

Mr Hawksworth retained the Great Western concerns about the lubrication of locomotives with higher superheat and lubrication arrangements were changed with effect from No. 7000, which also entered service later in May 1946.  Nos 5098 and 5099 later had their lubrication arrangements changed to the new type.

Right at the end of the Great Western's existence as a company, in 1947, Mr Hawksworth had No. 5049 Earl of Plymouth fitted with an experimental four-row superheater.  In BR days, commencing in 1957, four-row superheaters were fitted to more of the class, finally reaching a total of 65 locomotives by the end of 1961.

Finally, following Mr Hawksworth's trial of a four-row superheater on No. 6022 King Edward III in 1947, the remainder of the 'King' class were fitted with four-row superheaters during the period 1949-1951.

*

I have mentioned before the difficulty of discussing parts of a steam locomotive in isolation.  I touched upon lubrication in this postington but ignored double chimneys.  These subjects are for consideration later.

Just one part more on boilers, specifically superheating, where a famous engineer was slightly caught out by the Churchward legacy, and then we'll get onto to the section about the engine itself.  Or, if you prefer, engines themselves.  I'll attempt to explain later.

*

Coda

The final development of the 'Castle' class was truly a magnificent locomotive and well adapted to post-War conditions.  In Portraits of 'Castles'* by Bryan Holden and Kenneth Leech, there is, on page 12, this interesting snippet.  It refers to No. 4090 Dorchester Castle, the first of the class fitted with both a four-row superheater and a double chimney.  The authors refer to her as being a 'remarkable engine'.  Then they add:

'Qualification of her performance is necessary because enginemen who had worked the 1932** 'Castles' which had made history on the 'Cheltenham Flyer' held firm to their opinion that the engines in those days were every bit as good as No. 4090.'

Allowing for a nice mixture of rose-tinted glasses and nostalgia, the enginemen made, in my view, a valid point.  A Churchward-style locomotive was, in its day, a magnificent machine.  However, post-War performance of the 'Castle' class was, due to the factors mentioned above, diminished and the modifications commenced by Mr Hawksworth and continued by KJ Cook and RA Smeddle restored them to well deserved excellence.


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

** Ten of the class were built in 1932, Nos 5013 - 5022.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Cheerie-bye

John

[Moonglum]

A very welcome return of this excellent and informative thread, thank you John.

All the very best,

Tim (back from the mists of Agincourt!)

[Firstone18]

Good to see your wonderful series returning.
I wish you all the best for 2025.
Cheers

[Papyrus]

Welcome back, John, to your highly entertaining dissertation. So sorry to hear you have been bothering the NHS. I hope it all gets sorted soon.

I had the next part drafted and the one after that saved in note form.  But I lost both due to the 'seven days for drafts rule' that came in with the last Forum upgrade.  Bother!

For what it's worth, I have devised a solution to this problem. Whenever I want to commit something to the Forum which requires a bit more thought than I am accustomed to, I draft it in MS Word first. Then, when I am satisfied with the Beauty and Lucidity of my prose I copy and paste it to the appropriate section of the Forum. That way you can work on it over a period of time without worrying whether it will disappear into the ether.

Anyway, your latest work was worth the wait as always, even though the GWR holds no interest for me whatsoever. That is obviously a severe character flaw on my part which I shall make no attempt to rectify.

Looking forward to the next chapter.

All the best,

Chris

[martyn]

I think that there will soon be posts which are more deeply connected to the LNER, Chris.

But it was the Castle trials against an A1 which directly led to the improvements in the latter, (led by Spencer and with Gresley seemingly not fully convinced), and then development into the A3, which was, performance wise, much better than the A1 and which the Castle could, possibly, not match, though the last development of the Castles might have been very close. We'll never know the latter, though...

Martyn

[Train Waiting]

Many thanks, Chums.

My computer-thingy doesn't have MS 'Word', so, unfortunately, I'm not able to use it for for drafts.  But, it sure looks like a wizard wheeze for those with it at their fingertips.  I'm wondering if my drafting postingtons on locomotive draughting will finally cause our Fabulous Forum to blow up.  We'll see.  We'll even meet a Finnish chap, later on, which might be a fitting way to finish [Thank you!] the mini series.

Yes, indeedy, there will be lots 'N' lots of lovely LNER stuff to come.  But not yet.  Our attention in the next part is firmly on the LMS.  I know: I've just made it up written it following diligent and fastidious research.

With regard to GWR engines and any lack of interest thereof:-

Firstly, it's not compulsory.

Secondly, listen (with eyes firmly closed if necessary) to a GWR engine accelerate a train away from a station on a gradient - Keighley is a good example.  The purity of the exhaust sound is deeply moving.

Thirdly, Sir Nigel Gresley was unsparing in his praise of Mr Churchward.

Next part soon...

Thanks again and all good wishes.

John

[Firstone18]

Train Waiting: try Libre Office, it is freeware and the equivalent of MS Office.
It runs well on Linux too!
Cheers

[maridunian]

Train Waiting: try Libre Office, it is freeware and the equivalent of MS Office.
It runs well on Linux too!
Cheers

Alternatively, Google Docs. Free. Nothing to install. Wordy. Works on anything connected to the internet.

https://docs.google.com

Their 'Sheets' (Excelish) and 'Slides' (Powerpointy) are also very good.

Mike

[chrism]

Or, even, Notepad (or whatever similar Apple include)

[Bealman]

I don't do any of that myself, even though it makes infinite sense. I've lost many a post I've typed into the forum.

Anyway this is starting to look like a thread hijack of what is the most brilliant thread here!

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 43


A Little Difficulty on the LMS

Hello Chums

I expect you know the story - by 1931, eight years after the Grouping, locomotive affairs on the LMS were not wholly satisfactory.  There had been some in-fighting and the Motive Power Department, which was separate from the Chief Mechanical Engineer's Department, was heavily influenced by Midland Railway practice going back to the time before the Great War.  George Hughes, from the 'enlarged' LNWR and before that the LYR, was the first Chief Mechanical Engineer (CME) from 1923 until he retired in September 1925.  He was succeeded by Sir Henry Fowler, previously of the Midland, who had been Deputy CME of the LMS since the Grouping.

The 'Fowler Years' saw a lot of interference and less progress than would have been expected.  The LMS Board recognised this, shunted Sir Henry into a Research Department siding and appointed Mr EJH (later, Sir Ernest) Lemon as CME in January 1931.  This was an acknowledged interim measure as the Board had asked Sir Harold Hartley FRS, of Balliol College, Oxford and recently-appointed Vice-President and Director of Scientific Research of the LMS, to find a suitable person to be appointed as CME.

WA (later, Sir William) Stanier, Principal Assistant to the CME of the GWR, was the chosen individual and he commenced as CME of the LMS on New Year's Day 1932.

Amongst a generally lacklustre group of locomotive types introduced on the LMS from 1923 to Mr Stanier's appointment, four, in my view, shine out as rather good engines:

'Horwich Mogul' 2-6-0 of 1926 - essentially designed under Mr Hughes;
'4P' 2-6-4T of 1927;
'Royal Scot' 4-6-0 of 1927 and
'Patriot' or 'Baby Scot' 4-6-0 of 1930 - the first two were nominal rebuilds of ex-LNWR 'Claughtons', the remaining 50, under Mr Lemon's direction, were new engines.

*

The LMS Board had been eager for the LMS to have Swindon 'know-how' at its disposal and Mr Stanier's first four designs, introduced in 1933 and 1934, were much influenced by the Churchwardian design philosophy.  They were:

'Princess Royal' 4-6-2
'5MT' 2-6-0
'5XP' 4-6-0 - generally known as the 'Jubilee' class but, of course, King George V's Silver Jubilee was in 1935, after the class was introduced;
'5MT' 4-6-0 - the immortal 'Black Fives'.

The first examples of these classes featured typical Swindon two-row superheaters. This was a conscious decision, due to the superior GWR-style taper boilers which Mr Stanier intended to use. Let's quote ES Cox, who was in the CME's Department at the time:

'Stanier firmly believed that the arrangement of steam and water spaces gave, in combination, advantage in steam production.  He explained to us that these elements would counterbalance the effects of low degree superheat which was a feature of Swindon practice and which he now applied to all of his first designs for the LMS.'¹

In practice, the 2-6-0 and the 'Black Five' worked well, especially the latter.  Both were straightforward two-cylinder designs very much in the Churchward tradition.

Only two 'Princess Royal' locomotives were built at first and these prototypes struggled to live up to expectations, especially with regard to steaming.

The '5XP' or 'Jubilee' was Mr Stanier's development of the 'Patriot' class and, with them, he ran into serious trouble.  The requirement for the locomotives was urgent and he did not build any prototypes, instead, 90 were built 'off the drawing board' in 1933 and 1934.  They turned out to be poor steamers and nowhere as good as the 'Patriots'.

To quote ES Cox again:

'A situation arose, therefore, which was very serious for a while, and there was considerable recrimination from the motive power and operating sides [Departments]'²

Quite.




[A '5XP' or 'Jubilee' 4-6-0.  This one is by Rivarossi for Peco and her performance has not resulted in 'considerable recrimination'.  Quite the opposite, in fact.}


But, what was wrong?

It's always nice to quote from David L Smith, who saw these engines at work in Scotland 1935:

'A Newton Heath fireman, leaving Glasgow Central with the 4.30 pm, told me to watch the exhaust as they pulled out.  Sure enough, in the centre of the column of white steam was the thin black column of water, like the lead in a pencil.'³

Being a good engineer, Mr Stanier did not forbid criticism of his designs and the problems were identified.  The 'Patriots' had 24 flue superheaters, but the new design had the traditional Swindon two-row, 14 flue superheater with a surface of 227 sq ft.  It was found that this resulted in a 100^oF (38^oC) reduction in steam temperature compared with the 'Patriots'.

After a series of experiments, and considerable development of other parts of the boiler, a 24 flue superheater became standard for these engines, increasing the surface to 307 sq ft. Still, in my view, on the low side for the time.

Incidentally, there were other important changes made, but these are outside the scope of this part.  I've a feeling we'll return to them later in this mini-series.

These lessons weren't lost on the 'Princess Royals' - the 10 'production series' locomotives were delivered in 1935 and had four-row, 32 flue superheaters.

For the 2-6-0 and the 'Black Five', larger, 21 and 28 flue superheaters, respectively, became standard.  These gave the mixed traffic 'Black Fives' a superheater surface of 359 sq ft - significantly more than the express passenger 'Jubilees'.

The lessons were not lost on Mr Stanier and his magnificent 'Princess Coronation' 4-6-2s of 1937 had five-row 40 flue superheaters, with a surface of 856 sq ft.  I understand this was the highest superheating surface area of any British locomotive.

*

I found an interesting epilogue to this part in JE Chacksfield's C.B. Collett A Competent Successor:

'In 1935, Collett received a note from Stanier, now well-established on the LMS. In the note was the revelation that the application of low-degree superheat on the LMS was not particularly successful and in investigations to try to overcome the short-comings, it had been noticed that the area for the passage of steam through the 14 flue superheater tubes was less than the area of the main steam pipe from the regulator. Stanier had been led to this by his attention being brought to continually low steam chest pressures. On changing to a 28 flue superheater a dramatic change in performance had ensued.'⁴

*

Thank you for your understanding regarding the delay in completing the 'boiler' section of this mini-series.  The next section will, hopefully, commence next year.


¹ ES Cox, Locomotive Panorama Volume 1, Ian Allan, London, 1965. Page 103.

² ibid. Page 106.

³ DL Smith, Legends of the Glasgow & South Western Railway in LMS days, David & Charles, Newton Abbot, 1980 ISBN 0 7153 7981 X. Page 87.

⁴ JE Chacksfield, CB Collett A Competent Successor, Oakwood Press, Usk, 2002 ISBN 0 85361 586 1. Page 85.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Toodle-oo

John 
 

   

[Bealman]

As usual, amazingly awesome. Thank you, John!!

  

[martyn]

Gresley was aware of restricted steam passage design, and when designing the A4s made sure that two right angle bends in the A1/A3 cylinder arrangement were eliminated and that the bore of the pipes was sufficient, even ensuring that pipe joins didn't have tiny internal 'flanges' or casting faults to restrict steam. This ensured that effectively 100% of boiler pressure was available in the steam chests at fully open regulator.

It was said that the 'Kings' had a reluctance to run really fast consistently, and it has been suggested that this could have been due to internal steam pipe clearances. They were a better riding loco than the 'Scots', though. The original 'Scots' seem to have been a mixture of Derby and North British Loco practice, with a bit of the Southern 'Lord Nelsons' thrown in.

I've seen it said that the 'Black Fives' were so named at the time to distinguish them from the 'Red Fives'-the 'Jubilees'.

I've also seen in print-jokingly, I think-that Swindon didn't really design any new engines from Churchward to the 'County' class; they just looked around and saw what Churchward had already designed for boilers, cylinders, and wheel sizes and just did 'mix and match'.

Not quite true, perhaps.......

But certainly Churchward and his team at Swindon were well ahead of contemporary loco practice and other designers followed some of his principles.

Thanks again for another wonderful lesson, John, and look forward to the next ones.

Martyn