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

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 23


Hello Chums

We are about to move from the firebox to the boiler and, before we do, a word or two about 'steaming' is in order.  And, no it is not a cautionary story about hard-working journalists leaving a Press Reception.

It's a term used by enginemen but I can't recall having seen a formal definition.

Let's suggest good steaming is the locomotive's boiler being able to maintain maximum working pressure, as and when required, with ease.  Even with an injector on and steam heat being provided to the train.

The basics of good steaming are airflow through the fire, efficient combustion, good draughting and efficient heat exchange from the consequences of combustion to the water in the boiler.

Poor steaming can result when one or more of these basics are not met.

This can be due to poor design (the LMS '5XP' 'Jubilee' class were bad steamers at first and there are many other examples), poor locomotive condition either due to ineffective maintenance or something going wrong when the locomotive is at work, poor quality coal, and inferior enginemanship, whether due to ignorance, tiredness, carelessness or laziness.

And one last reason for poor steaming - the locomotive was sulking that day.  As living things, they have their moods!

For the purposes of this series, we can discount most of these and focus on design.  Because this is the one that affects the appearance of our toy trains.

*

Thank you for your helpful posts and for your help regarding ^oF or ^oC. I now have a plan.

And please don't be concerned about remembering any of this - the threadingham will, hopefully, be here for ages although it might get 'buried' as this is a busy area of our FabulousForum.

Perhaps one thing to remember - George Jackson Churchward was probably the second most gifted locomotive engineer our country has produced.  I am enjoying quoting his words and am grateful to those who recorded and preserved them.

Oops-a-daisy; no picturingham yet.  I'll soon attend to that.





No. 46115 Scots Guardsman at Carlisle in the rain.  A 'Converted Royal Scot', now with features derived from Churchwardian practice thanks to Sir William Stanier and HG Ivatt.  This class was one of the stars of the 1948 Locomotive Exchanges but had no effect on the design of the BR 'Standard' classes. 

She was in fine form on the down journey back to Lancaster over the Settle & Carlisle.  At Mallerstang, that three-cylinder 'fliffle-wuffle-flaffle' beat changed into something close to the famous 'Royal Scot roar'.  I was invited onto the footplate at Carlisle and the enginemen were impressed with her.  She was steaming well that day.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Pip-pip

John

[Bealman]

Wonderful.

[PennineWagons]

After reading through this thread I can honestly say that I am no wiser than I was before.
I am, however, far better informed.
PW

[martyn]

I've posted on the Forum before somewhere about this, but I have a report somewhere reviewing the results of the 1948 loco interchanges.

I think it's by Cecil J Allen, and he says that the rebuilt 'Royal Scots' generally performed above their nominal power rating.

If I can find the report, I'll post a bit more (maybe?).

Martyn 

[Train Waiting]

I've posted on the Forum before somewhere about this, but I have a report somewhere reviewing the results of the 1948 loco interchanges.

I think it's by Cecil J Allen, and he says that the rebuilt 'Royal Scots' generally performed above their nominal power rating.

If I can find the report, I'll post a bit more (maybe?).

Martyn

Many thanks to @martyn for this and please do.  It would certainly be of interest.

I have CJ Allen's book, The Locomotive Exchanges (Ian Allan, London, 1949) and here's a couple of quotes:

About the driver:

'[...] the 'Royal Scot' driver achieved feats of brilliance that I should barely have conceived possible with an engine of such dimensions [...]

About the engine and driver:

'Relatively to the moderate dimensions and weight and the simplicity of design of these 4-6-0s, in the most capable hands of Driver Brooker, I should be inclined to rate their best performances above anything else that I witnessed during the test weeks and, like those of the Southern engines, these were a a tonic indeed.  Moreover, the drawbar h.p. outputs of 1,750 to 1,800 exerted by the "Scots" on some of the climbs must surely constitute a record for any British 4-6-0 design of no more than 83 tons in weight.'

Praise indeed from 'CJA', an ex-GER and LNER man.

I'm fortunate +++ for this to have been Dr Tuplin's copy of the book.  'CJA' comes in for a barrage of pencilled annotations.  His 'no more than' in the quote ante gets circled and marked with a 'X'.

Even worse, earlier in the book, 'CJA's' use of 'extremely moderate' comes in for particular disapprobation with Dr Tuplin's use of a '?'.

If you are unfamiliar with the writings of the late Dr Tuplin, please ignore the last couple of paragraphs.  If you are familiar; you'll understand.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Cheerie-B

John

[Newportnobby]

The 'Scots' don't hang about even now........

46100 Royal Scot races through Leyland 15.8.20 by Mick Hollyoake, on Flickr

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 24


Hello Chums





At last... boilers!

Let's think about the 'kettle' analogy.  Much used and some railway enthusiasts appear to call steam locomotives 'kettles'.  I put water my kettle, boil it and then make coffee for Dame Joanna Lumley's morning visit to see my train set.

It then sits almost empty for a few hours until I refill it with fresh water, boil it and make a pot of tea for Jenny Agutter's visit in the afternoon.  That's a kettle for you: fill-boil-empty-repeat.  Sort of stop-start-stop.

It is better to think of a steam locomotive's boiler as a flow system with a variable throughput, unlike the fairly constant throughput in industrial or marine applications.  It's no use if the boiler goes 'off the boil' when it is being refilled with water and even less use if runs for a while until the boiler is empty and then needs to be refilled and boiled again - 'Mamod' steam traction engine, anyone?

The boiler must be able to produce steam, at its working pressure, whilst coping with the inflow of cold water, from the injector, to compensate for the steam that is, eventually, going up the chimney (unless the locomotive is one of these rarities, a condensing engine).

Nothing like my kettle, then, and those who use the analogy deserve our sympathy.

Possibly, the closest analogy in many houses is the 'combi' boiler which provides water at a (hopefully) steady temperature for the shower.  It's an imperfect analogy, but still a type of  flow system with a throughput.

My kettle is round with an empty space in the middle for the water, which is heated by a plate sort of contraption at the bottom.  Better than the old-style element which could get 'furry'. (But not here m'dear - between the Forth and the Tweed.  We have soft water.) Very limited 'heating surface'.

A locomotive's boiler is round, normally horizontal, unlike my kettle unless I have couped it again, and is anything but empty inside.  Since Rocket's time, it is packed with tubes, through which hot gasses from the fire pass, until about three-quarters of the way up.  Lots 'N' lots of tubes. The number varied with the boiler diameter - a North British 'Atlantic' of 1906 with a 5' 6" diameter boiler had 253.  A lorra, lorra tubes. Much better 'heating surface'.

Diameter - about that of the cardboard tube from a roll of lavatory paper - please see above.  My generation was 'Blue Peter' trained.  The picturingham below shows them 'in the metal'.





We'll look into this in some more detail next time.  Might even have a formula - eek!

*

I hope you'll excuse the many liberties I have taken with simplification (over-simplification?).  Any experts wondering about tube numbers please note I have chosen a typical (if large) example from 1906.  We'll get to t'other stuff later.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Toodle-pip

John

[Newportnobby]

I wondered why Joanna never answered my morning calls. At least I know to call in the afternoon now
 

[Bealman]

Yeah, I've had a furry kettle in the NE, and even in Australia.

I've had many furry tongues, though. 

Another great post in an amazing thread.   

[martyn]

For John's (and anyone else who is still interested) benefit, concerning the Royal Scots, some extracts from;

'New Light on the locomotive exchanges' by CJ Allen, published by Ian Allen in 1950. It is a supplement to 'The locomotive exchanges ' by the same author. It is a small (60 page) A5 size booklet.

Much of it is tabular results from the trials, broken down by loco type and route. Not all results summaries seem to be tabulated. It does have some background about when the trial trains were delayed by signals, heavy traffic, or whatever, which adversely affected coal and water consumption.

One really needs to study the tables to get a picture of the full results, but talking about the Royal Scots, CJA says 'the more one studies these figures, so much more astounding does the Performance on the rebuilt 'Royal Scot' seem.

' ...nowhere in the trials....did the Western Region 'Kings' approach such horsepower outputs'.

'The peerless effort of the 'Royal Scot ' when Lavington bank was climbed ....the engine exerting 1630hp at the drawbar'.

However, the highest power output during the entire trials was by the Duchess (for a very brief period), and then the West Country.

In another book I have, 'Essays in steam' compiled by John Clay from articles written for the Stephenson Locomotive Society house magazine, his own essay on the Royal Scots, before and after rebuilding, includes '[unrebuilt] size for size, their work was not exceeded by contemporary British 4-6-0s or pacifics'. 'It may well be that the average Royal Scot worked more 500T trains than the average King, and, size for size, worked harder than the average Pacific'. It was in the 1948 loco exchanges that the Royal Scots scored their greatest triumph. It was rumored that the LMR authorities were more interested in the RS results rather than the Duchess'. 'It is suggested that continous horse power was just less than a Britannia, (around 2000hp)'. 'The best records of converted RS in sustained high speed haulage of heavy loads has not been surpassed by a King, nor has the highest maximum edhp....' (Note from me-the last statement of equivalent drawbar horsepower is a bit technical, but includes the effect of gravity when climbing gradients). 'they were equal to the best performing 4-6-0s in the world, the partly Chapelonised Est 2.3.0.K'.
'The converted Scots  have a strong claim to be the most thermodynamically efficient 4-6-0s, but the Kings were better riding vehicles'.

Whew, more than enough. If you've kept interest in this fairly technical post, well done!

Martyn

[EllieJae]

Ok John I give up.  " that three-cylinder 'fliffle-wuffle-flaffle' beat "   Tried all the functions on my dcc controller with my sound fitted 3 cylinder Jubilee, but I just cannot find the 'fliffle-wuffle-flaffle'  function key.       
What a great thread, thank you    Alan

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 25


Hello Chums





Part 25!  How did that happen?  When Poppy and I thought it might be a jolly jape to start this threadingham, we envisaged a pawful of postingtons.  And here we are at No. 25 and we're just thinking about boilers.

Thank you so much for your recent contributions, chums.  The 'Converted Royal Scots' were certainly excellent engines, if troubled by rough riding. 46104 Scottish Borderer was the worst.  A Polmadie engine - all this shed's 'Royal Scots' were rough.  46104 was also known to be a poor steamer.

Let's have a think about locomotive boilers - typical ones, mind, none of the fancy stuff.  If you can cast your mind back to Part 24, I commenced it with a picturingham of a roll of lavatory paper in order to give an idea of the diameter of a boiler tube.  Imagine, if you will, the paper has been used and we are left with the cardboard tube.  Before it goes in the green recycling bin, it can be another visual aid - virtual, this time.  Sit it lengthways and we have a passable scale model of a locomotive boiler.

That's right - a tube.  Not made of cardboard but, in the early days of iron (Low Moor iron from near Bradford was considered tip-top) and, from around 1880, of steel.  The LNWR led the way in Britain with steel boilers.  The various sections which made up the boiler were rivetted together - even on the Bulleid 'Pacifics'.  The description of 'welded boiler' often applied to them only is relevent to the firebox.

Imagine making a boiler from sheets of wrought iron.  A couple of sheets of paper will do.  Roll a sheet into a tube, with one end overlapping t'other by, say, half-an-inch and stick the ends together with your choice of glue.  Maybe make another one a tad bigger diameter and stick them together 'telescope' style.  Your 'two-ring' boiler shell.  Now over to Peter Purves with the Blue Peter layout.

A totally tickety-boo boiler shell?  Sadly, no.  Remember Pte Baldrick's Great War poem - 'Boom, boom, boom'.  Well, in mid-Victorian Britain, locomotive boilers staged a grand recital of this poem.  And one of the leading causes was these joints.  What you made earlier is called a lap joint.  A boiler ring with a lap joint was not truly circular and steam pressure tended to distend a boiler made this way into a precisely cylindrical shape.  Once higher steam pressures over 100 psi were used, this became a particular problem.

Each time the boiler pressure varied and, especially, as the boiler was warmed up or cooled down, small stress cracks appeared in the inside of the barrel, along the lap joint.  The cracks rusted, then became a groove and, if the plates were not renewed in time, the boiler split open.  William Kirtley, later Locomotive Superintendent of the London, Chatham & Dover Railway, described the problem, in a paper to the Institution of Mechanical Engineers, in 1866. 

He made it clear lap joints were not suitable for horizontal seems in boiler plates but were suitable for the annular seems that connect one ring to another.  Also, to minimise corrosion, the horizontal joints should be placed above the water line.

As Mr Kirtley had said, the introduction of double-strip butt joints solved the problem, but (sorry) they were adopted slowly.  The last boiler explosion attributable to lap joints and grooving was at Seaton (Cumberland) in 1890. [Furness Railway 0-6-0 ST No. 107 - 27 November.]

If we cut a couple of strips from our sheet of paper, then roll the sheet into a tube, with the ends butting together this time, rather than overlapping, and glue a strip along the join on both the inside and outside of the tube, we've made our own.




[A locomotive boiler showing safe riveted joints.]


Boiler diameters of around 4 ft. were commonplace by the Eighteen-Fifties and diameters increased so slowly that, prior to 1896, no locomotive boiler in Britain exceeded 4ft. 6 in.  John McIntosh on the Caledonian caused a right old fuss that year with his famous Dunalastair 4-4-0 with a 4 ft. 9 in. diameter boiler. Diameters soon exceeded 5 ft.





As seen in the picturingham, the NER introduced a 5 ft. 6 in. boiler for 0-6-0 locomotives in 1904 which gave locomotive people something to talk about.


The next stir was caused by Mr (later, Sir Nigel) Gresley's 'K3' 2-6-0 of 1920 for the Great Northern with a 6 ft. diameter boiler.  He exceeded this with the 6 ft. 5 in. boiler fitted to his 'A1' 4-6-2 class of 1922 and that diameter became an LNER standard.  It was slightly beaten for British conventional locomotives by the LMS 'Princess Coronation' 4-6-2 of 1937 with a maximum boiler diameter of 6 ft. 5 1/2 in. 

Next time, I'll write some more about boiler-ish matters.  So much to do; the pressure's tremendous!


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Toodle-oo

John

[Hailstone]

It would not surprise me to find out that as a result of the locomotive exchanges the Kings were trialled with a four row superheater and double chimney with which all of the class were subequently fitted

Regards,

Alex

[martyn]

It would not surprise me to find out that as a result of the locomotive exchanges the Kings were trialled with a four row superheater and double chimney with which all of the class were subequently fitted

Regards,

Alex

@Hailstone

Correct, Alex.

CJ Allen in the booklet mentioned in my last post says that there was a separate set of trials for all the (G)WR locos but using Welsh coking coal from Abergorki, which had a higher calorific value than the other coal used in the trials across all the regions for all locos.

But, quote, 'by far the most interesting feature of the additional WR tests ...were those made with King 6022... in which the standard 16 element superheater had been replaced by a 24 element one...changing effectively a steam dryer to a high temperature superheat' and notes that this was the first significant change at Swindon from Churchward's principles.  The new superheater brought coal consumption (and water?) down noticeably. I'm not a student of the GWR, but I think all Kings subsequently had the new superheater, and many had double chimneys.

However, the second book I quoted mentions that Kings never seemed to run as freely as other classes, and many theories were put forward for this; possibly restricted steam pipes between regulator and cylinders. I think it was never really sorted, as they could do the work required of them, but this internal resistance, whatever it was, is thought to have precluded regular really fast running.

The CJA booklet has many insights into the test results, and there's lots more I haven't mentioned, including freight and mixed traffic classes.

(Later- note you say they all later had 24 element superheaters and double chimneys; I had no idea).

HTH

Martyn

 

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 26


Hello Chums

Let's have a quick think about boiler pressure.  It doesn't normally have much of an effect on the external appearance of a locomotive, so probably isn't that relevant for 'N' gauge modellers.  Nevertheless, I think it is worth spending a little time on it.  Let's start with the Rainhill Trials of 1829.  The rules allowed a maximum boiler pressure of 50 pounds per square inch (psi) and the three entrants: Novelty, Rocket and Sans Pareil all used this pressure.

By the mid-1840s, pressures of 100 psi were in use and the celebrated 'Jenny Lind' 2-2-2 locomotives, designed by David Joy and built be EB Wilson & Co, of Leeds from 1847, used a boiler pressure of 120 psi.  These engines were especially successful and much of the credit for this has been attributed to their higher boiler pressure.

Boiler pressures of 120psi or 125 psi were common throughout the 1850s and early 1860s.  By 1865, the LNWR and Midland were using 150 psi for certain express passenger locomotives.  At the end of the century, boiler pressures of 175 or 180 psi were commonplace with 200 psi used on occasion..

Locomotive engineers were aware that higher pressures required heavier construction and, especially, resulted in increased maintenance costs.  Because of this, there was a desire to limit further increases in pressure, and, in some cases, reduce the boiler pressures in use. I'll return to this apparent retreat in a later postington.

An especially good example of a locomotive engineer taking a very cautious approach to boiler pressures is George Hughes, Chief Mechanical Engineer of the Lancashire & Yorkshire, 'Greater' LNWR and LMS.  Mr Hughes is on record as expressing serious reservations regarding high boiler pressures.  His only design for the LMS, the 'Horwich Mogul' 2-6-0 of 1926, is interesting in this regard.  It is usually attributed to 'Hughes/Fowler' as Mr Hughes had retired in 1925 and Sir Henry Fowler added a few of his beloved Midland features to the design.  Not for the better, I think.





Mr Hughes wanted a boiler pressure of 180 psi, only 5 psi greater than the Fowler Midland '4F' 0-6-0 of 14 years earlier.  In order to obtain the the required power, 21 in x 26 in outside cylinders¹ were decided upon.  To give sufficient platform clearance (that restricted British loading gauge - and especially on LMS routes in Scotland - again) the cylinders had to be high and sloping.  Just as well I qualified the point in my second sentence with 'normally'.  The picturingham, from a photograph kindly supplied by @Nbodger and taken on his SuperSpiffing Hillsden layout shows a locomotive of this class.

In 1933, Mr (later, Sir William) Stanier introduced his version of a 'Mogul', of the same power classification, to the LMS.  This class had completely horizontal outside cylinders, the only Stanier design to have this feature, of only 18 in. diameter.  This was permitted by a longer stroke, 28 in., and a boiler pressure of 225 psi.  We'll meet this class, of only 40 engines, again.

The next part will concentrate on the engines of the two British locomotive engineers who dared to use higher boiler pressures in the Edwardian era.  Any ideas who they were?


Many thanks to Mike for the photograph.  Is it just me or does the SuperSmelly diesel behind the marvellous 'Mogul' look as if has been crying?

¹ Outside cylinders of over 20 in. diameter were unusual in Britain.  Even the mighty '9F' had 20 in diameter, but I'm getting ahead of myself - this is a subject for a later postington.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Cheerie-bye

John