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

[Nbodger]

Is it just me or does the SuperSmelly diesel behind the marvellous 'Mogul' look as if has been crying?
 

Maybe sulking, well wouldn't you if you had failed on the overnight Condor two nights earlier then again on the return journey from Manchester Victoria to Leeds. She will soon be visiting Mable's Barrow.

apologies John for for bringing some frivolity to your wonderful thread, will delete if you wish.

[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

@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 in which the standard 16 element superheater had been replaced by a 24 element one...changing effectively a steam dryer to a high temperature superheat' and notes that this was the first significant change at Swindon from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

Martyn

as I am abroad and cannot acces my usual bibles I have taken this text from wikipedia

"The class proved to be capable and reliable when using the high-calorific South Wales steam coal, on which the GWR had always relied for its good locomotive performance. However, during the 1948 locomotive exchanges, King Henry VI performed disappointingly using Yorkshire coal, despite demonstrating the 4-6-0 type's unique sure-footedness when climbing out of Kings Cross, where pacific types were apt to slip alarmingly.

As originally built the class had a Swindon superheater with an area of 313 square feet (29.1 m2). However, in 1947 experiments were undertaken with a four-row high-degree superheater in No. 6022 King Edward III. As a result, the four-row superheaters were fitted to the whole class, and modifications were also made to the draughting arrangement, using No. 6001 King Edward VII as a test-bed. From September 1955, double blast-pipes and chimneys were fitted, initially to No. 6015 King Richard III. Following successful testing the whole of the class was subsequently modified and, as a result, their final years in British Railways ownership saw the very best of their performance, particularly on the steep South Devon Banks at Dainton, Rattery, and Hemerdon."

Regards,

Alex

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 27


Hello Chums

In Part 26 we saw that many locomotive engineers of the Edwardian era were reluctant to increase boiler pressures above 200 psi, with most glad to remain in the 150 psi to 180 psi range.  This was due to higher pressure boilers being heavier and, seemingly, much more costly to maintain.

Due to another development we will mention later, some locomotive engineers actually decreased boiler pressures during this decade or so.  A good example is the Glasgow & South Western Railway's '381' class of 17 engines, introduced in 1903, with 180 psi working pressure.  The two engines of the '128' class, of 1911, had a working pressure of only 160 psi.  This demonstrates the reluctance of most locomotive engineers of the time to accept higher boiler pressures.

There were two notable exceptions, one of whom made a lasting contribution to locomotive design and the other was more of a footnote who will receive an honourable mention.

It can be difficult for us now to imagine the impression George Jackson Churchward made on the  locomotive engineering establishment in the first decade of the 20th Century.  He took the best of American practice, added some French features, and created, in the heart of Wiltshire, a series of locomotives which represented a step-change in design and performance.  Not that they were universally popular when introduced - their austere American appearance came as a shock to people used to the 'gilded lilies' that were British locomotives of the time.

The four years from Mr Churchward's appointment as Chief Assistant to William Dean, the GWR's Chief Mechanical Engineer, in 1898, to his own appointment to the post in June 1902, following Mr Dean's retirement, gave Mr Churchward a useful opportunity to experiment.  By the time of his appointment as Chief Mechanical Engineer, he had a good understanding of what he intended to achieve.  An important part of this was concerned with boiler design and construction.

He looked to the USA for the latest developments in boiler design.  Brooks Locomotive Works was an exponent of taper boilers and the Illinois Central Railroad had been using a firebox with with curved rather than flat surfaces, direct staying and a generous space between the inner and outer firebox crowns.  It used a working pressure of 210 psi.  Swindon Drawing office had drawings of this boiler by 1902.¹.

Mr Churchward designed a range of standard, tapered boilers for most new construction, with working pressures of 200 psi for the smaller locomotives and 225 psi for the large engines.  He read his paper, Large Locomotive Boilers to the Institution of Mechanical Engeneers in 1906.  This paper described the important features of his approach to boilers:

Higher working pressures up to 225 psi;
Ample tube spacing;
Effective tube proportions;
Free circulation of water especially in front of the firebox tubeplate;
Ample space for steam inside the boiler above the normal water level - greatly helped by the use of a Belpaire firebox and a taper barrel.

His fellow Chief Mechanical Engineers were not all convinced by this Churchwardian logic and Mr Hughes, whom we met in Part 26 spoke during the discussion about the maintenance difficulties and costs associated with higher boiler pressures.  Mr Hughes was an enthusiast for moderate boiler pressures of not more than 180 psi.

HC King, Swindon Works Manager and without doubt speaking with Mr Churchward's approval, shot this fox by making the point that a boiler properly designed and carefully built to withstand higher pressures would not require increased maintenance, but a boiler designed and built in the traditional way and pressed to higher pressures undoubtably would.

As far as I'm aware, the only other British locomotive engineer to take advantage of higher working pressures at this time was Richard Deeley on the Midland, whose celebrated 'Compound' 4-4-0 locomotives had a working pressure of 220 psi.  Later reduced, under Sir Henry Fowler, to 200 psi.  More of that later.





At the time of the Grouping in 1923, apart from on the Great Western, boiler pressures were in the 180 psi to 200 psi range.  Even the first Gresley 'Pacifics' were only 180 psi.²

Post-Grouping developments came quickly.  Mr Maunsell on the Southern went to 220 psi for his 'Lord Nelson' and 'Schools' classes but otherwise stuck to a 200 psi maximum.  The 'Royal Scot' class, built by the North British Locomotive Company for the LMS used 250 psi. Subsequent locomotive classes, designed by Mr (later, Sir William) Stanier, for the LMS were in the 200 psi to 250 psi range according to the power of the engine, with 225 psi being commonly used.

Mr Churchward's successor on the Great Western, CB Collett, stuck firmly to established practice with the exception of his 'King' class 4-6-0 which had a boiler pressure of 250 psi.

Mr (later, Sir Nigel) Gresley on the LNER took the same approach with a range from 180 psi to 250 psi for the most powerful locomotives.  Interestingly his final design, the two 'V4' engines of 1941 for secondary work also used 250 psi.

There was a slight trend to higher boiler pressures at the end of the Grouping era.  OVS Bulleid used 280 psi for his three Southern 'Pacific' classes and FW Hawksworth also used 280 psi for his 'County' class 4-6-0.  All of these were subsequently reduced to 250 psi.

The BR 'Standard' classes used boiler pressures of 200 psi, 225 psi and 250 psi according to their power classification and it is reasonable to say that this represented the final consensus for British locomotive practice. 


¹ ES Cox, Speaking of Steam, Ian Allan, London, 1971, SBN 7110 0236 3 p45

² Sir Vincent Raven's North Eastern Railway 'Pacifics' were built with a working pressure of 200 psi.


'N' Gauge is Such Fun - even when the pressure's tremendous!

Many thanks for looking and all best wishes.

Pip-pip

John

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 28


Hello Chums

In Part 27, we mentioned tapered boilers, which Mr Churchward adopted after initially using parallel Belpaire boilers.  A tapered boiler is an obvious feature of a model locomotive and it is worth spending a moment considering the advantages claimed for this type of boiler.

The main one is that the volume of water in the boiler is more concentrated at the firebox end, which is where the heat resulting from combustion is most intense.  As we have seen, Mr Churchward took great care to allow for free circulation of water, especially in front of the firebox tubeplate, and ample space for steam, especially above the firebox.

A taper boiler is lighter at the front which helps with weight distribution as certain heavy components, such as the cylinders, are located at the front of a locomotive.

A taper boiler provides a slightly better forward view for enginemen.

Under braking, when reaching the top of an up gradient or heading down a gradient, the water in the boiler runs towards the front which can risk uncovering the firebox crown.  A taper boiler provides less water capacity at the front and can help to reduce this risk.

A GWR standard tapered boiler was normally  6 in or 7 in less in diameter at the front than the rear.

From being a GWR feature in the Edwardian era, the taper boiler gradually gained general acceptance.  I believe the really important example of that was REL Maunsell's 'K' class 2-6-4T and 'N' class 2-6-0 locomotives for the South Eastern & Chatham Railway, both introduced in 1917.  The designs were prepared in 1914 but construction was delayed by the outbreak of the Great War. The classes used the same type of boiler which tapered from 5 ft. 3 in. at the firebox end to 4 ft 7 1/4 in at the smokebox.

Mr (later, Sir William) Stanier took the GWR-style tapered boiler to the LMS as can be seen in this picturingham of his Class 5 4-6-0:





Even on the Great Northern and, later, the LNER, where Sir Nigel Gresley had made it clear he did not favour the Belpaire firebox, the boilers on the wide-firebox locomotives had a distinct taper.  I understand Sir Nigel used the term 'coned boiler' to describe these.  For narrow-firebox classes he and his successors preferred the traditional parallel boiler.  This 'B17' 4-6-0 is an example:





'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Cheerie-Bye

John

[martyn]

Thanks again, John.

Popping back a post to boiler pressures, the 280lb/sq in of the Bulleid Pacifics and the GWR 'Counties' was the highest pressure used in the UK for normal locos.

But there were at least two examples of higher pressure locos, albeit one-offs for special testing. There may have been more, I don't know.

The LNER W1 'Baltic' 4.6.4, # 10000 alias the 'Hush Hush' had a pressure of 450 psi as built, and this pressure was used for the high pressure cylinders of the compound design. The boiler was also not the normal 'firetube' (or 'locomotive') boiler, but a water tube one. Let's not go there, Google water tube boiler if you want more details. There were many variations of this type of boiler.....

When rebuilt as a conventional three cylinder loco, the new boiler was 250 psi.

But even exceeding this was the LMS 'Fury' # 6399. Nominally responsible was Fowler, though the boiler was designed by The Superheater Company. The boiler raised steam in three stages, and the first stage used a closed loop recirculating pressure of between 1400-1800 psi. This water heated a second steam source which worked at 900 psi, and this steam was used in the first stage of the compound cylinder arrangement. A third system raised steam at 250 psi for the second stage of the compound arrangement. The loco wasn't successful; a high pressure tube burst on an early trial, killing one of the test staff; and though repaired and run on further tests for four years, it was (nominally) rebuilt as 'Royal Scot' #6107 British Legion. Wiki says that it was economics rather than technical failures which doomed the loco; unlike the original W1, 'Fury' never hauled a revenue-earning train

For further details of these locos, Google has quite a few leads, and the W1 is extensively covered in the RCTS History of the LNER locos, vol. 6C; the latter is now available online.

Martyn

[Bealman]

Is that LNER one Dapol or Farish, John? I have a feeling I may own one!

[Papyrus]

Thank you, John, this is all so interesting. I thought I knew a bit about steam locos, but all I know now is the depth of my ignorance!

Have you thought about editing it into a series for the N Gauge Journal? Or even a small book-ette for the general public to buy? Seems a shame that the fruits of your labours should only be seen by we favoured few.

Thanks also to Martyn and others for their valuable addenda.

Cheers,

Chris

[Bealman]

Wot Chris said.

[Ed]

This 'B17' 4-6-0 is an example:

Not to be confused with ....

https://en.wikipedia.org/wiki/Boeing_B-17_Flying_Fortress#/media/File:B17_-_Chino_Airshow_2014_(framed).jpg

 

Ed

[martyn]

One further thing to remember about boiler pressure.

As the pressure on the water surface increases, so the temperate required to make it boil (and hence produce steam) increases as well.

By the time steam pressure is 225 psi, then it is boiling at 200C/392F (according to a set of tables I found online).

Superheating can take temperatures to 500F or above. The original A1 boilers had superheat steam temperatures of about 575F; trials were arranged to try and make this higher, to about 700F, with a new design of superheater. However, the new design did not have the results hoped for,  with average results only about 30F higher than previously, though a max of about 650F was recorded.

Martyn

[Train Waiting]

Is that LNER one Dapol or Farish, John? I have a feeling I may own one!

It is a Dapol model, George.  I bought it when I ventured into 'N' gauge in 2007.  It is a nice looking model but a shocking runner.  It, and a few others, led me to abandon British 'N' gauge for US-outline, mostly Kato.  What a revelation!

Then, in 2014, I saw a Union Mills advertisement in the Railway Modeller and thought I'd try one.  The 'B12' was, and remains, a very fine model and I returned to British 'N' gauge with some fixed beliefs (hardened prejudices?), subsequently reinforced.

I once tried to give away the 'B17' on our FabulousForum and received no interest.  I'm glad to offer it again if anyone would like it.  At one point I thought about attempting to rebuild it with a Union Mills tender drive but concluded that would be a waste of the Union Mills parts.  One cannot polish a sow's ear.

With all good wishes.

John

[Newportnobby]

One cannot polish a sow's ear

How very polite, dear boy

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 29


Hello Chums


Moving to the inside of the boiler and, although not necessarily appearing to be of direct concern to 'N gauge modellers, there are a couple of matters I'd like to mention as these do influence the appearance of a locomotive.  They might also be of interest.

The first is free gas area through the boiler tubes.  It slowly became clear to locomotive engineers that the ratio of area through the tubes to grate area was important.  It wasn't until the 1920s that Herr Wagner in Germany established that the optimum value was 15%.

The second was tube length.  From around 1895, as the British 4-4-0 developed into the 4-6-0 and, occasionally the 4-4-2, the improvement in performance was often disappointing.  There were often problems with the steaming qualities of some of the new, larger locomotives.  Typically, the new engines had significantly longer boilers than the generally successful 4-4-0s, increasing in length from, say, 11 ft. to 17 ft.  Typical boiler tubes of the period were 1 1/2 in to 1 3/4 in diameter.

Research done by the Pennsylvania railroad at its Altoona test plant, and also by Herr Wagner, established that the optimum tube length to diameter ratio was 100 to 1.

This is, I believe, one of the reasons for the disappointing performance of so many 4-6-0s that were, effectively, extended 4-4-0s.  Put simply, their tubes were not of sufficient diameter for the length of the boiler.  At least part of the solution was the increasing use of tubes of up to 2 1/4 in in British practice.

However, an interesting irony concerns the North Eastern Railway's 'R1' 4-4-0s of 1908.  The 'R' class 4-4-0s of 1899 had been outstanding successful and the 'R1' was an enlargement of the earlier design.  They used a shortened version of the boiler from the 'V' class 'Atlantics' of 1903, 11 ft 3 in between the tubeplates rather than the 4-4-2's 16 ft 3 in.  The larger boiler's 2 in diameter tubes were retained - whilst almost perfectly proportioned in the original use, these were too large in diameter for the shorter boiler and the class was regarded as poor steamers.




[The NER 'R' class 4-4-0 - a splendid locomotive with excellent proportions.  Enlargement proved difficult.] 

*

Then along came the 4-6-2, or 'Pacific', even longer than the 4-6-0 or 4-4-2.  The first to run in Britain was Mr Churchward's The Great Bear in 1908.  She appears to have been a shy steamer.  Her boiler was 23 ft in length (I have seen 22 ft 6 in quoted as well but I don't think six inches make much difference here).  I have been unable to find out her tube diameter, but I assume, unless advised otherwise, that it was 2 in, which was used by the GWR on 4-6-0 classes at the time.  According to the formula, this is distinctly undersize and 2 1/4 in diameter might well have been better.

Rather like The Great Bear was, effectively, an elongated 'Star' 4-6-0, Sir Vincent Raven's NER 4-6-2 of 1922 was an enlarged NER 'Atlantic'.  The especially long external appearance of the boiler barrel with three large safety valves at the firebox end resulted in the class nickname being 'Skittle Alleys'.  The boiler barrel was 26 ft long, externally, but the distance between tubeplates was only (only!) 21 ft.  Which takes us on to a feature of some locomotive boilers we have not yet discussed.

The 'combustion chamber' is an extension of the firebox into the boiler barrel, with the firebox tubeplate recessed into the barrel.  The theory is it allows more space for combustion to develop and increases the firebox heating surface.  The basic idea goes back to Mr Dewrance's Condor locomotive of 1845 for the Liverpool & Manchester Railway and was developed by Mr Beattie, Senior, on the London & South Western Railway of the eighteen-fifties.

The GWR had used a combustion chamber in the boilers of its 'Kruger' 4-6-0 and 2-6-0 locomotives of 1899-1903 and these had proved troublesome.  Perhaps that's why Mr Churchward did not use one on The Great Bear.

Sir Vincent Raven's 4-6-2 design had a combustion chamber, as did another 'Pacific' introduced slightly earlier in 1922 - Mr (later, Sir Nigel) Gresley's 'A1'.  The distance between tubeplates on the 'A1' was 19 ft., achieved by using a combustion chamber and setting the smokebox further back than normal, perhaps a contributing factor to the supremely elegant appearance of these engines.

Mr (later, Sir William) Stanier's second design for the LMS was his 'Princess Royal' class of 1933.  These had rather the appearance of an elongated GWR 'King' 4-6-0.  Fortunately, he built two prototypes to see how they would perform - unlike for his later '5XP' 'Jubilee' class, but that's a story for another time.  The Princess Royal and Princess Elizabeth had boilers 20 ft 9 in between the tubeplates.  It became clear that all was not right with the two prototypes and the production series of ten, and the 'Turbomotive', had, amongst other refinements, the distance between tubeplates reduced to 19 ft 3 in by the incorporation of a combustion chamber.

*

I think there is a general point of interest we can see from all of this.

It's that the British 0-6-0 and 4-4-0 locomotives of 1875 - 1900, give or take, were blessed by having intrinsically good proportions.  This was serendipity in action - their designers were unaware of the science behind the good proportions which they had achieved.  Unfortunately, simple enlargement could not be guaranteed to retain these useful proportions and the advantages they conferred.  Time for a digression.

*

Phil Irving, the designer behind much of the Vincent motorcycle, said that the single cylinder machine's many advantages were outweighed by vibration above 350cc.  From the late 1930s, 500cc vertical twin models became popular.  These were easier to start and smoother-running than the 500cc 'Big Singles'.  Then, after the War, partly due to pressure from the US market (you can't beat 'cubes'), the twins' capacities increased to 600cc, 700cc, 750cc and 850cc.  Many riders preferred the original 500cc machines.  Too late, unfortunately, came the British 750cc 'triples' - three in-line cylinders giving perfect balance - Sir Nigel Gresley would have approved!

The point of the digression is to show that enlargement only works so far; after that a redesign is preferrable.  Just like Mr Churchward did in 1902.

*

Back to the proper stuff.  Of the four 'Pacific' classes we discussed ante, I believe the most successful was the GNR/LNER 'A1'.  And it was the only one which was a fresh design, rather than basically an enlargement of a successful smaller locomotive.

I have made the point, several times, that innovation in steam locomotive design moved, to a great extent, away from Britain around the eighteen-sixties.  References, here, to the Pennsylvania Railroad and Herr Wagner reinforce this.  British locomotive engineers, by and large, were aware of these developments, and sometimes took advantage of them, but did not contribute to them to any great extent.

Here is a good example.

In the USA, in 1904, several locomotive builders amalgamated to form what became 'ALCO'.  In 1910, the new firm built an experimental 'Pacific', No. 50000, which it claimed to have 'rationalized proportions of boiler, firebox and cylinders'.  The Pennsylvania Railroad was impressed by No. 50000 and ordered a slightly heavier version of the new design which it tested exhaustively on its Altoona plant.  From this evolved the famous Pennsylvania 'K4' 'Pacific'.  A series of articles was published in Engineering during 1916 and it is understood that these had a profound influence on the design of the 'A1'.

Not only were the Churchward designs greatly influenced by American and French practice, so were the 'Gresley Pacifics'.  Quintessentially British locomotives, but with a great deal of overseas influence.  I don't want to labour the point, but I think it is unhelpful to restrict one's interest to British railways.  A fuller understanding benefits greatly from a wider field of interest.

As for the French influence on LNER locomotives, that's for a later postington.




[Sir Nigel Gresley's masterpiece - the 'A4' 4-6-2 of 1935, seen in post-War condition.  This class was the last LNER-designed 'Pacific' to have the ALCO/Altoona/Gresley 'rationalized proportions'.  Later designs varied and we might consider this later.  The excellent 'A4' boiler featured a combustion chamber.]


The 'R' is by Union Mills and the 'A4' is from Minitrix.  Her eight-wheeled tender appears to have been over-demanding of this coarse modeller's dexterity.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Toodle-pip

John 

[martyn]

An excellent post again, John. Thank you.

Looking forward to further instalments.

Martyn

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 30


Hello Chums

'Something for Nothing?'

This diversion is so long that it has a postington of its own.  Viewer discretion is advised as it deals with infernal confusion engines and (clothes peg on nose time) SuperSmelly diesels.  It is intended to help make a point about the quest for efficiency but can be avoided happily if desired.

Not much about motor bicycles this time - we'll start with motor cars instead.  Hopefully, we'll get to trains later.  For a while the supercharger (or 'blower') was in vogue.  Driven off the crankshaft, this was a contraption that compressed the inlet charge for induction, resulting in more petrol/air mixture in the cylinder.  This cause a fiercer explosion and a stronger power stroke, allowing your 'Blower Bentley' to thrash the opposition.  A benefit indeed.  Incidentally, WO Bentley was not enthusiastic about supercharging and there was a lot of private development work done.

But the engineering cost (why is there always a cost?) for this benefit was a drain on crankshaft horsepower (hp) to drive the supercharger and, of course, the complexity, and financial cost, of the supercharger.  For racing, providing one had a wealthy sponsor, the latter was liveable with.  As for the former, providing the additional hp obtained exceeded the hp used, the supercharger was a benefit.

Motor bicycle moment; Georg Meir won the 1939 Senior TT with a supercharged BMW flat twin.  Dashed unsporting conduct and jolly bad form.  Post-War, blowers were banned.

Superchargers never really caught on for private motoring as the additional hp obtained was hardly worth the costs for road use.

But what if the benefits of the supercharger could be obtained without a drain on crankshaft hp by making use of the residual power in the hot exhaust gasses that were otherwise going to waste?  The costs would reduce to simply be the cost of the apparatus and the turbocharger arrived on the scene.  Some motor cars have these and the young-at-heart motorists that particularly enjoy them usually refer to them as 'turbos'.

A much, much more beneficial use of turbochargers is for diesel engines in commercial road vehicles. And, of course, the SuperSmelly diesels that run on rails. 




[This English Electric 'Type 21', probably the most successful of the 'Modernisation Plan' diesel classes, has an 8SVT engine developing 1,000 hp.  My late Father-in-Law was an engineman at Inverness and he was particularly impressed by this class, considering them powerful and reliable locomotives.  The model is by Wrenn and is based on Hornby-Dublo tooling.  Someone, not me, has done a magnificent re-numbering job.]


The English Electric designation - '8SVT' - can be explained easily. The number is the number of cylinders, 'S' means supercharged, although it's actually turbocharged, 'V' is the engine type (other types have different letters - 'K' is an example - and 'T' is for traction use.

It was discovered that compressing the inlet charge caused it to heat and a cooler, lower density charge is more efficient, so an 'intercooler' was added to some engines to cool the charge.  This is designated by a 'C' (for cooling) - 8CSVT. A turbocharger and intercooler can make a diesel engine more than half again as powerful than in a normally aspirated state.  This is considered to be well worth the cost associated with the apparatus.

Which takes us to the point.  'Something for nothing' is difficult to obtain in engineering.  Rather, it is all about the cost to benefit ratio.  We'll return to steam in the next part for a first look at an example of the quest for economical increased efficiency.


'N' Gauge is Such Fun - as is Hornby-Dublo and Wrenn!

Many thanks for looking and all best wishes.

Cheerie-B

John