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N Gauge Discussion / Re: A Coarse Guide to the Stea...
Last post by martyn - Yesterday at 02:28:07 PM
Interestingly, the RCTS green Bible is critical of the 50 sq ft fireboxes fitted to the Thompson and Peppercorn boilers, and adds that 'Doncaster's whole [later] policy with boilers was wrong'. Without getting too technical (some of which I don't understand anyway), was that the firebox was producing too much heat for the small evaporating tubes to handle, and the superheaters were having to heat the steam to the required temperatures.

it was also stated after road tests that the large grates were wasteful of coal, as locos fitted with smaller grates could handle the trains with adequate steaming rates. Interestingly, the A4s with a 42.25 sq ft grate were much more economical in general; it was said that at times, the large grates were being fired 'just to cover all the firebars'. But then the A4s came out best of all the locos trialed in the 1948 exchanges.......

I've also read comments alluded to already; the original A1 boiler was effectively a scaled down Pennsy K4 one to fit the UK loading gauge. Further boiler development at Doncaster gradually departed from the ratios first used for the A1 boilers, seemingly not always to advantage.

And of course there is a subject about which I know little; the 'boiler horsepower' and the 'cylinder horsepower'. 
It was no good having a huge boiler and firebox if the cylinders could not effectively use the steam generated.

The RCTS History of the BR Standard Pacifics has a table of test results for the BR Standard tender locos, and principal express locos of the four regions, plus the Black 5. It gives boiler efficiency of ~70% for all classes tested, but cylinder efficiency of ~14%. I think it is the latter which shows just how inefficient the steam loco was, though things like compounding and re-superheating could add a few percent to the overall ratio.

Thanks again for another fascinating postingham, John.

N Gauge Discussion / Re: A Coarse Guide to the Stea...
Last post by grumbeast - Yesterday at 02:22:35 PM
Another fine post John.

I am so glad you mentioned the LMS Princess Coronations.  While ostensibly a GW man given my place of birth I can't help but be in awe of the Duchesses and was able to recently procure one (in BR Maroon).  It is a testament to their effect on the local populace that I feel an affinity for the GWR even though I was born over 20 years after its demise!

Back to technical things, I think the grate area of UPs big boys is a bit like apples and oranges, one does have to remember that they did use automatic stokers, it would be simply impossible to fire such a monster by hand!

I was curious about the firebox size of other articulated locos of other companies and was surprised to discover that both the N&W y6bs and the DM&IR yellowstones have grates quite a bit smaller.  The y6b I get as it doesn't have the same tractive effort / HP as the Big Boy but the yellowstones are pretty much on par (slightly higher tractive effort at a whopping 140000lbs) but will a grate area of *only* 125sqft. I wonder why that is?

As for F or C, its fine, I have to endure those south of the border here insisting on using Fahrenheit all the time :)

N Gauge Discussion / Re: A Coarse Guide to the Stea...
Last post by Ali Smith - Yesterday at 01:02:17 PM
Farengrade or Centiheit, I don't mind. I am finding this series both interesting and informative and hope you will continue with it. There is a great deal of information out there about such matters as when no.1234 received the new type of safety valve, but not so much about how no.1234 worked or indeed how it went about its business.

Perhaps you could include the temperature conversion formula, which if I remember correctly isn't too complicated.
N Gauge Discussion / Re: A Coarse Guide to the Stea...
Last post by Newportnobby - Yesterday at 12:56:18 PM
Quote from: Train Waiting on Yesterday at 12:13:05 PMI soon will mention temperatures.  In steam days this was done in Fahrenheit and the sources use this.  Are you content for me to use oF, or would you find it easier to read if I use oC?

Either suits me, John, but your excellent thread will now be inundated with replies to that question. Once you've decided, I can remove them for you as I think that would be cleaner
N Gauge Discussion / Re: A Coarse Guide to the Stea...
Last post by Train Waiting - Yesterday at 12:13:05 PM
A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 22

Hello Chums

At the time of the Grouping, on 1 January 1923, the Belpaire firebox was used, to a greater or lesser extent, by most British railways apart from the London & South Western, North Eastern and Great Northern.  The wide firebox was much less common - its use being confined to the Great Northern, North Eastern and London, Brighton & South Coast.

After the Grouping, the Great Western carried on in the narrow Belpaire firebox tradition established Mr Mr Churchward.  The LMS under George Hughes and, later, Sir Henry Fowler, pretty much universally used narrow Belpaire fireboxes for new construction. The Southern, under Richard Maunsell, favoured Belpaire fireboxes (Mr Maunsell's technical team had carefully chosen men from Swindon and Derby), but as we have seen earlier continued with round-topped fireboxes for locomotives derived from London & South Western designs.

Which leaves the LNER as the odd one out.  Strange, that - the GWR is so often though of as being the oddity, but in the matter of boilers in 1923, it was pretty much in line with conventional thinking.

The LNER, under HN (later Sir Nigel) Gresley and his successors pretty much restricted new constrution to locomotives with round-top fireboxes, although Mr Gresley was open-minded enough to continue construction of good pre-Grouping types which had Belpaire fireboxes.  As time went on, certain pre-Grouping locomotives with Belpaire fireboxes were reboilered with round-top fireboxes.  And the wide firebox could only be seen, for nine-and-a-half years from  January 1924, on the LNER.1

LNER classes with wide fireboxes were -
4-6-2-2: 'W1' (as rebuilt) (Gresley)
4-6-2: 'A1' (Gresley), 'A2' (Sir Vincent Raven), 'A3' (Gresley), 'A4' (Gresley), 'A1' (Peppercorn), 'A2/1', 'A2/2', 'A2/3 (Thompson) and 'A2' Peppercorn
2-8-2: 'P1' and 'P2' (Gresley)
2-6-2: 'V2' and 'V4' (Gresley)

Quite a list - have I forgotten any?

As is well-known, Sir Henry Fowler was promoted horizontally and WS (later, Sir William) Stanier was appointed Chief Mechanical Engineer of the LMS with effect from New Year's Day, 1932.  Barely eighteen months later, the first two of his 4-6-2 'Princess Royal' class appeared.  These prototype locomotives had a certain 'elongated Swindon' (with perhaps a hint of an updated The Great Bear?) look about them (Sir William had come from the Great Western), but with a wide Belpaire firebox above a rear Bissel truck.

A couple of years later, ten more were built and these benefitted from design modifications made in the light of experience with the two prototypes.  Also in 1935, a fascinating varient of the 'Princess Royal' class, No. 6202 - unnamed but usually called 'Turbomotive' appeared.

Then, in 1937, Sir William's masterpiece, the 'Princess Coronation' 4-6-2 class was introduced.  Essentially a much improved 'Princess Royal'.  Thirty-eight were built, including the final two in 1947/48 with clever detail modifications by that most practical engineer HG Ivatt.  These locomotives had an enormous wide Belpaire firebox with a 50 sq. ft. grate area (the 'Princess Royal' class was 45 sq. ft.) 

Although this was a massive grate area for British practice at the time, Sir Nigel Gresley's 'P2' 2-8-2 of 1934 also had a 50 sq. ft. grate area.2

Just look at that enormous firebox on No. 6233 Duchess of Sutherland.  Just the thing to produce the power for the banks on the West Coast Route.  I was born too late to appreciate main line steam (I can only just remember it) but my late father took me, in a work's van, to the road outside Butlin's holiday camp at Heads of Ayr to see this magnificent locomotive.  I like my Graham Farish model of her, but it's of 'Far East' manufacture.  I'd swap it in an instant for a ProperlyPoole one.  With an additional bribe of some cash in a wee broon envelope.

And so to the Southern, when its locomotive orthodoxy was turned on its head in 1937 with the appointment of OVS Bulleid as Chief Mechanical Engineer.  His 'Merchant Navy', 'West Country' and 'Battle of Britain' classes introduced the wide Belpaire firebox to the railway.  These had grate areas of 48.5 and 38.25 sq. ft. respectively.  Also, most unusually, these classes had welded steel fireboxes.  Welding technology was developing at the time and Mr Bulleid took it to its limit.  The first 10 'Merchant Navy' boilers were replaced after only seven years and a special X-ray inspection technique was used to monitor the state of the welding in the others.3

After nationalisation, the Belpaire firebox reigned supreme for new 'Standard' engines, narrow for most designs, but wide for the 'Britannia', 'Clan', 'Duke of Gloucester' and '9F' classes.  The latter was originally schemed as a wide firebox 2-8-2 with 5 ft. 3 in. coupled wheels by ES Cox, but Robin Riddles insisted that, by reducing the coupled wheels to 5 ft., a 2-10-0, with much better adhesion, could be (just) accommodated within the loading gauge.

1 GWR 4-6-2, No. 111 The Great Bear was withdrawn in January 1924 and rebuilt as a 'Castle' class 4-6-0, Viscount Churchill.  It is thought that little of the original survived the rebuilding.

2 As did the rebuilt 'W1' in 1937 and the later Thompson and Peppercorn 'Pacifics'.  Whilst this figure was not surpassed for conventional locomotives in Britain, the LNER 'W1' 2-8-0+0-8-2 Garratt had a 56.5 sq. ft. grate area.  She was later converted to oil firing but this wasn't a success.  A Union Pacific 'Big Boy' had a 153 sq. ft. grate!

3 Not really relevant to 'N' gauge, the fireboxes also were fitted with thermic syphons to improve heating and circulation of water in the boiler.  Effectively, the colder water at the bottom of the boiler was circulated upwards through the thermic syphons.


Help please!

I soon will mention temperatures.  In steam days this was done in Fahrenheit and the sources use this.  Are you content for me to use oF, or would you find it easier to read if I use oC?

'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.




General Discussion / Re: R.I.P. Donald Sutherland
Last post by Portpatrick - Yesterday at 11:55:23 AM
So versatile.  A serious role in Don't Look Now (loosely based on a Daphne du Maurier story from memory).  And a bordering wartime "comic" in Kelly's Heroes and Dirty Dozen.  His eyes were so expressive - a touch of John Laurie.
N Gauge Discussion / Re: Took some stock to the clu...
Last post by Trainfish - Yesterday at 11:47:10 AM
Mine are also very similar to each other. You have to look very carefully to spot the differences:

General Discussion / Re: R.I.P. Donald Sutherland
Last post by Bealman - Yesterday at 11:16:38 AM
Yep, that's the one. Scared the bejeebies out of me  :uneasy:
General Discussion / Re: R.I.P. Donald Sutherland
Last post by Newportnobby - Yesterday at 11:00:46 AM
Quote from: Bealman on June 20, 2024, 11:50:26 PMI always remember him in that one shot in Venice where the little guy in the red mac slashes him in the end.

'Twas "Don't look now" with Julie Christie
General Discussion / Re: R.I.P. Donald Sutherland
Last post by Mr Sprue - Yesterday at 08:23:41 AM
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