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

[Newportnobby]

I travelled behind 'Scots Guardsman in 2012 from Preston to York and his performance was exemplary.

Preston


York

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 98


Hello Chums

The Final, Exhausting Section of Our Gloriously Brief Mini-Series

'Doubling Up - 2'

Although, as far as I'm aware, there was no especially scientific analysis involved - this was before Rugby Testing Station opened - the LMS locomotive engineers hit the 'sweet spot' the the draughting arrangements for the 'Princess Coronation' 'Pacifics' and the rebuilt 4-6-0s fitted with the magnificent 2A boiler. This instilled an enthusiasm for double chimneys amongst the LMS locomotive Engineers, including the Chief Mechanical Engineer, HG Ivatt (Mr Ivatt the Younger).

Let's start with the success. A pretty much guaranteed success at that. In 1946 they commenced rebuilding the 'Patriot' class 4-6-0s with the 2A boiler. Unlike the 'Converted Royal Scots' they were given Stanier-style side-window cabs and they were almost identical with the two rebuilt 'Jubilees' mentioned earlier. A bit less powerful than the 'Scots' - they had smaller cylinders - they were excellent performers on the road with lots 'N' lots of reserve in the boiler. However, the 'Royal Scots' were the priority and only 18 of the 52 'Patriots' were rebuilt.

In 1947, Mr Ivatt introduced a replacement for the venerable 'Fowler' '4F', beloved of JE Anderson and all the Midland Mafia who dominated locomotive matters for so long on the LMS. They had even talked Sir William Stanier into building 45 more for them between 1937 and 1941 (yes, they were still building '4Fs' in 1941!). Mr Ivatt put his foot down with a firm hand and a thoroughly modern 2-6-0 of power class '4F' was the result. They had the potential to be really good engines and 162 were built from 1947-1952. The BR 'Standard' '4' 2-6-0 was essentially the same design modified to look like the rest of the 'Standards'. One hundred and fifteen of these were built between 1952 and 1957.



[The first of the Ivatt '4F' 2-6-0s, No. 3000. An LMS Official photograph.]


Looking at the picturingham, it's difficult not to notice the massive double chimney. There were two blastpipes arranged in line but angled slightly to the front and rear respectively. Hence the massive casing. A wonderful idea in theory. In practice, the blighters would not steam. As mentioned earlier, use of this contraption was abandoned for new construction at the end of 1949. All the class built from 1950 had single chimneys, designed on SO Ell's principles. The first fifty all received single chimneys by 1956. Here's No. 34106 at Bridgnorth, contentedly minding her own business:





At the end of the LMS' life, Mr Ivatt embarked upon an extraordinary programme of modifications to the excellent Stanier 'Black Fives'. Construction of these engines continued into BR days. A few of these variants were given double chimneys. These fell into four groups:

44686/44687 Built 1951. The final Caprotti variant. Exceeding good engines.

44755-44757 Built 1948. The first Caprotti variant, three had double chimneys as well. Reputed to be little different from the single-chimney engines.

44765/44766 Built Crewe 1947. Two of the batch with Timkin roller bearings throughout and Walschaerts valve gear also had double chimneys. They performed well enough, although not hugely better than the similar single-chimney variants. The double chimney did appear to cause a problem with drifting smoke obscuring the driver's vision on occasion. I have seen a photograph of No. 44765 hard at work on Shap Bank in August 1966. This suggests these two engines reatained their double chimneys until withdrawal.

44767 Built 1947. The one-off! Timkin roller bearings throughout, outside Stephenson link motion and a double chimney. The double chimney didn't seem to suit this engine and was replaced by a single chimney in 1953. After that the locomotive acquired a great reputation for power and reliability, and achieved some of the highest annual mileages run by any of the class. Unusually for a one-off she was long-lived, being withdrawn in December 1967 and is, happily, preserved.

The 'Black Fives', essentially a design based on GWR practice, had been good steamers from their introduction and the double chimney experiments did not provide any great benefit, with the possible exception of the Caprotti-fitted examples.

I think it is fair to say, based on LMS experience, that double blastpipes and chimneys were not necessary on locomotives up to and including BR power class '5'. At the higher steaming rates likely to be required above BR power class '5', they provided a definite advantage as, hopefully, I have shown.

In the next part of this gloriously brief mini-series we'll discuss the use of double chimneys for the BR 'Standards'.

Once again, many thanks to @martyn for reviewing and kindly commenting on the draft.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Cheerio!

John

[port perran]

So that's what the original Bulleid Light Pacifics looked like with their boiler casing removed.
34106 was, of course, named Lydford 

Sorry John, @Train Waiting , I couldn't resist.

Sorry to interjest (sic) on your most excellent postingham.

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 99


Hello Chums

The Final, Exhausting Section of Our Gloriously Brief Mini-Series

'Doubling Up - 3'

Nationalisation of the railways occurred in 1948 and RA Riddles, formerly of the LMS, was appointed Railway Executive Member for Mechanical and Electrical Engineering. Once Mr Ivatt the Younger's deputy on the LMS, Mr Riddles had 'leapfrogged' him on return from Government service during the War. Mr Riddles appeared to have friends in high places on the LMS. In my view, Mr Ivatt would have been a better choice. Mr Riddles' Locomotive Engineering team had a distinct LMS bias and ES Cox was in charge of design. It was intended to produce a range of BR 'Standard' steam locomotives.

Now, I made a slightly controversial point earlier about there being a sting in the tail related to Sam Ell's brilliant work at Swindon on draughting. He achieved extraordinary improvements in steam production for several classes. This, rightly, attracted a great deal of attention.

Here is the quote that, hopefully, proves my point:

'Prior to Ell's work, it had been proposed to fit the larger standard engines with double chimneys as Plate 24 portrays, but this was based upon previous LMS experience where this arrangement had shown marginally more favourable results on the 'Duchess' Pacifics and the Class 5 mixed traffics. However, Ell was able to show the way to better results with correctly proportioned single chimneys than had been obtained formerly with some of the double arrangements, and it was decided to initiate the new series with the simple single arrangement leaving future development work any trend to multiple nozzles at a later date.'¹

Plate 24, from a BR illustration, mentioned in the quote is interesting - a double chimney 'Britannia' with bar frames:





I think the late Mr Cox's quote is fascinating. That use of 'marginally' might have been fair enough for the 'Black Fives', but surely the results of the 1939 trials showed more than a marginal improvement for the 'Princess Coronations' ('Duchesses'). And the quote completely ignores the magnificent '2A' boiler, with double blastpipe and chimney, which transformed any LMS 4-6-0 to which it was fitted. Yes, the 'Princess Coronations' performance in the 1948 Locomotive Exchanges was less than could have been expected but the 'Converted Royal Scots' set the rails on fire (metaphorically!).

Anyway, the BR 'Standards' were to be built with single chimneys. The exception was the sole '8P' Duke of Gloucester. Then, in September 1958, '9F' No. 92178 was turned out from Swindon Works with a double chimney. Her performance was such an immediate success that all new engines from No. 92183 were similarly equipped. Double-chimney '9Fs' were especially popular on passenger work. Some enginemen preferred them to a 'Britannia', finding them both freer steamers and better riding at speed. What a shame no 'Britannias' were fitted with a double chimney.

Then, in 1961, five earlier members of the class were rebuilt with double chimneys (Nos. 92000/1/2/6/79). Some of these saw much use on the Somerset & Dorset (S&D). The years 1960-62 were glorious ones on the S&D with double-chimney '9Fs' in charge of much of the summer traffic. No. 92220 Evening Star worked the last 'Pines Express' over the S&D on 8 September 1962. Nos 92220/4 were at Bath Green Park briefly in 1963 and that was that - the line was left wither away and its '9F' era was over. Such a shame.

I have found a good quote about the wonders of the double-chimney '9Fs':

'For a friend, then working at King's Cross, and his Driver - well used to working on New England's '9F's - the change was dramatic, and initially, puzzling. Given an almost new No. 92183 to find and prepare in the dark ready for a fish working, they noticed nothing unusual until they got out on the road. Then they found that they had something special and altogether different from the '9Fs' they had experienced before. They reckoned that the effortless power and much freer steaming produced something that was truly brilliant. Once on shed at the end of the journey, they found to their surprise that the locomotive had a double blastpipe and chimney and all was explained.² 

There's no doubt the double-chimney 'Nine' was an exceeding good engine and, I'd argue, the best of the 'Standards'. Yet, ES Cox devotes a single sentence [partly!] to them in his British Railways Standard Steam Locomotives:

'Apart from the above, a number of locomotives were fitted with straight forward double chimneys and blastpipes - No. 71000 as already mentioned, 80 of the Class 9 2-10-0s [...]'

As for the fiasco of the Franco-Crosti locomotives - five pages, with more in a later chapter. And there was a mystery amongst the 'Standards'. Mr Cox's sentence continues:

'[...] and, at a later stage, all of the Class 4 4-6-0s allocated to the Southern Region and some of these on the Western Region were altered to take the double arrangement.'

Mr Cox went on to bemoan the fact that Swindon and Eastleigh Works produced different-shaped castings for the double chimneys. He didn't like the Swindon version.




[The Swindon double chimney as fitted to No. 75029. [British Railways photograph]
Please forgive the missing rear of the tender. Whilst this would be typical of my coarse photography, it's actually from the original print. By the way, No. 75029 is, happily, still with us, complete with double chimney. She's on the NYMR and requiring a major overhaul - there's a public appeal open. She was purchased from BR by the late David Shepherd and given the name The Green Knight.]


One wonders why, with all of Sam Ell's know-how, a double chimney was fitted to locomotives of only BR power class '4'. It was found, in single-chimney form, these engines could evaporate 19,600 lb. of water per hour. The double chimney increased this to 22,400 lb. of water per hour. This is an interesting contradiction of the results of Mr Ell's earlier work which implied a properly designed single blastpipe and chimney was the equal of a double arrangement. 

This concludes our discussion of conventional double blastpipes and chimneys. I intend to conclude our ambitiously brief mini-series with a discussion of three of the more exotic arrangements. We'll commence, in the next part, by looking at a New Zealander's adaptation of a Belgian engineer's system. Sounds like such fun!

Once again, SuperSpecial thanks to @martyn for reviewing and commenting on the draft.
 

¹ ES Cox, British Railways Standard Steam Locomotives, Ian Allan. London, 1966, Page 80. Plate 24 is between pages 64 and 65.

² Mike Romans, writing in the Introduction to Locomotives Illustrated, No. 75, Ian Allan, Shepperton, 1991, Page 4.

³ ES Cox, British Railways Standard Steam Locomotives, Ian Allan. London, 1966, Page 119.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Tickety-tonk

John