The more I read these excellent articles the more fascinating the steam engine  becomes !

TY

Addendum to my post #374; TW Worsdell did use Joy valve gear on other classes he designed for the GER, but I don't know about the NER.

Martyn

Quote from: martyn on February 21, 2025, 02:20:51 PMAddendum to my post #374; TW Worsdell did use Joy valve gear on other classes he designed for the GER, but I don't know about the NER.

Martyn

Many thanks, Martyn.

Yes, TWW used Joy valve gear on the NER. The 'J21' class (LNER designation) had it. He was also keen on compounding.  WW had no time for either of these things and the NER soon became a conventional railway for locomotive design - with some absolutely excellent  engines as well.

Although their personalities were very different, TWW shared some of Mr Webb's attachment to 'gadgetry'.

I know I'll have to write a part of this incredibly brief mini-series on compounding - it's hanging over me like the Sword of Damocles. With a bit of luck someone will volunteer to write it instead.

Thanks again and all good wishes.

John

Quote from: fisherman on February 21, 2025, 02:00:00 PMThe more I read these excellent articles the more fascinating the steam engine  becomes !

TY

Thank you very much indeed for your kind and encouraging comment.

I think the steam locomotive is the nearest to a living thing that people have created, with the possible exception of a sailing ship.

I'm glad you are enjoying the mini-series and wish to acknowledge the fascinating contributions made in the discussion - these are much more interesting than my efforts.

There are some unusual things coming up - a racehorse that finished last and Dolgoch's strange valve gear.

Thanks again and all good wishes.

John

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 67


Hello Chums

The 'Tishies'

We mentioned earlier the death of CJ Bowen Cooke, Chief Mechanical Engineer of the LNWR, aged 61 in 1920. HPM Beames was appointed as successor. In anticipation of the 1923 Grouping, the LNWR and the LYR amalgamated on 1 January 1922. George Hughes had been appointed Chief Mechanical Engineer of the LYR in 1904 and was appointed Chief Mechanical Engineer of the enlarged LNWR.

At the Grouping, Mr Hughes was appointed Chief Mechanical Engineer of the LMS, a position he held until his retirement at the end of 1925. Sir Henry Fowler of the Midland was appointed Deputy Chief Mechanical Engineer to Mr Hughes and succeeded him after his retirement.

It's difficult not to feel a tad sorry for Mr Beames who went from Chief Mechanical Engineer of the mighty pre-amalgamation LNWR to Mechanical Engineer for the LMS Western Division, based at Crewe. This role had no design responsibilities.

*

We discussed earlier the Achilles' heal of Joy valve gear - the hole in the connecting rods for the pin for the jack link - and the connecting rod failures that occurred, especially as locomotives became more powerful in the era of the Big Engine. We mentioned a 'Prince of Wales' 4-6-0 suffered a catastrophic failure of a connecting rod which resulted in the death of both engineman.

Mr Bowen Cooke's new 'Claughton' 4-6-0 design of 1913 was equipped with Walschaerts valve gear.

But what of the 244 'Prince of Wales' class locomotives, construction of which commenced in 1911 and continued until 1922? These were powerful superheated locomotives capable of sustained hard work, particularly over the steeply-graded parts of the railway north of Crewe.

Mr Beames set his mind and Crewe Drawing Office to solve the problem. The solution was interesting - replace the inside Joy valve gear with outside Walschaerts valve gear.

Four locomotives were converted between March 1923 and April 1924 and then the programme petered out. Apart from an extraordinary occurrence.

The LMS ordered from Beardmore in Glasgow, which had already built 90 of the class during 1921/1922, another example. She was built with outside Walschaerts valve gear and had a Belpaire firebox. Built in March 1924 and given LMS crimson lake livery with number 5845, Beardmore exhibited this oddity at the British Empire Exhibition between April and November of that year. She was even given Prince of Wales nameplates when on exhibition. To avoid potential embarrassment, the first engine in the class, former LNWR No. 819, had her rightful Prince of Wales nameplates removed for the duration.





And, with other locomotives becoming available, that was the end of the conversion programme. Sir William Stanier's great restocking of the LMS was not kind to the 'Prince of Wales' class, with the four conversions being withdrawn between 1933 and 1936. No. 5845, then renumbered 25845, was withdrawn at the end of 1947.

Incidentally, the final member of the class, unconverted of course, survived until 1949.

With regard to No. (2)5845, Mr Beames had developed a programme of replacing the round-top boilers on as many LNWR locomotives as possible with Belpaire boilers. The LMS-liveried 'Cauliflower' shown in a picturingham in Part 65 is a good example of this. That explains the Belpaire boiler. The outside Walschaerts valve gear was the same as the four recent conversions, so that is understandable.

But why on earth order a single 'Prince of Wales' two years after the last member of the class had been delivered? What were the LMS authorities thinking about? (2)5845 was the last locomotive to be built to an LNWR design.

This is purely speculation (all right, a guess), but I wonder if Beardmore, keen to diversify its munitions factories into locomotive construction, and wanting a locomotive to display at the British Empire Exhibition, made the LMS an offer it couldn't refuse.

*

Why was this part entitled, The 'Tishies'?

Please look at the outside valve gear in the picturingham of No. 5845 and imagine what it looked like when the engine was running.

At the time there was a well-known racehorse called Tishy and she had the strange characteristic of changing her stride during a race, giving the appearance of her crossing her legs. Notwithstanding this trait, she had been successful and was the favourite to win 1921's Cesarewitch Handicap. She came in last! A feat which I understand she repeated in 1922.

She became something of a national institution and even featured in a cartoon strip in a newspaper for many years.

Seeing the first conversion running, with her valve gear seemingly moving in all directions, when Tishy was so much in the public mind, made the name inevitable.

So there you are - a strange tale about locomotive valve gears. Tishy died in 1923 but her memory lives on amongst steam engine people with an interest in the odder branch lines of locomotive history.

In the next part, we'll consider the peculiar case of Dolgoch and then have a brief discussion of poppet valves.

After that, it will be on to locomotives with more than two cylinders and then, if we can stand the excitement, compounding. If anyone fancies writing a part or two of this remarkably brief mini-series about compound locomotives, I'd be especially glad to hear from you. A bribe with chocolate can be arranged. 


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Cheerie-bye

John

Go Tishy!!!

Another excellent instalment, thank you John.
I am learning so much about steam engines (locomotives?) from your series; I am now even beginning to understand some of the conversations at club evenings now!! I have a vague idea what compounding is based on my encounters with steam powered model boats when I was in my pre-married condition some 45 years ago, so hoping to understand your description by the third read through.
Cheers 

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 68


Hello Chums

Other Valve Gears Continued

Before we get into the main subject of this part, let's take an agreeable diversion to the Talyllyn Railway and consider its locomotive No. 2, Dolgoch, an 0-4-0WT built by Fletcher, Jennings & Co at Lowca Locomotive Works, Whitehaven in 1866. Her works plates proudly proclaim her to be 'Fletcher's Patent'. Undoubtedly, she is a much-loved locomotive and her place in history is assured. If she had failed during the first couple of seasons of operation of the Talyllyn Railway, the world's first preserved railway, it is unlikely that the project would have succeeded.





But Dolgoch is an oddity.  You see, she has a long wheelbase and the firebox sits between the two axles. Her outside cylinders drive the rear coupled wheels. The proximity of the firebox to the driven axle means there is no room for the eccentrics for her valve gear on that axle.

Mr Fletcher didn't worry about that, instead, he placed the eccentrics on her leading coupled axle. Lets think about this for a moment.

Locomotive valve gears derive their necessary movement from the strokes if the piston. Pretty much universal practice is to take the drive for the valve gear from the driven axle, although we noted Joy valve gear which took the drive from the connecting rods. In the case of Dolgoch, the drive for the valve gear was taken from the coupled axle, not the driven axle.

It's always good to hear from LTC Rolt - here he is on this peculiarity of Dolgoch:

'[...] while to incorporate the inside valve motion, which was almost universally favoured at that time, a devious and not altogether satisfactory expedient had to be adopted. Because the rear driving axle was behind the firebox, the eccentrics must needs be mounted on the leading axle whence they drove the Allan straight link motion, while the valve rods, of banjo form to clear the axle, passed between these eccentrics. This means that the valves were driven via the coupling rods, and the more technically minded will appreciate that this added source of lost motion gravely prejudiced the maintenance of an accurate valve setting. Moreover, sandwiched between such narrow frames, the lay-out was necessarily cramped and inaccessible.' ¹

Therefore, if we are going to design a steam locomotive, I suggest we take the drive for the valves off of the driven axle. However, that supremely practical and confident engineer, Mr Ivatt the Younger, chose to take the drive for the valves of this LMS '5MT' 4-6-0 from the leading coupled axle, rather than the driving axle:-





Poppet Valve Gears

I know, I know! I'm a cheeky chappie including that picturingham purporting to show the drive for the valve gear.  But it does - it's just a different type of valve gear and the drive is by means of a single rotating shaft driven from the leading axle.

And this takes us nicely on to the matter of poppet valves for steam locomotives. These were already well-established for internal-combustion engines and steam engineers began to wonder if they could be used to give more accurate valve events for locomotives.

A couple of types were tried in Britain, over a period of about quarter-of-a-century - the Lentz and the Caprotti.

Both used cams to operate the poppet valves, as in a petrol or diesel engine. They differed in their arrangement but that's not really of much relevance to us 'N' gauge modellers.

The LNER was the largest user of poppet valve locomotives, followed by the LMS, particularly late in its life as an independent company. I'm not aware of the Southern Railway having any poppet valve locomotives - Mr Bulleid contenting himself with a miniature version of Walschaerts valve gear, driven by a chain and enclosed in an oil bath.

The Great Western had one. A 'Saint' class 4-6-0, No 2935 Caynham Court, was converted to use rotary cam Lentz poppet valves in 1931. I understand she retained the Lentz valve gear until withdrawn from service in 1948.

In the next part we'll take a really quick look at some of the LNER, LMS and BR locomotives with poppet valve gear.


¹ LTC Rolt, Railway Adventure, Constable, London, 1953, Page 8. There have been a plethora of editions of this splendid book over the years, so you might find the quotation on a different page. It will be in Chapter One.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Toddle-oo

John

I love the first photo, obviously a postcard,which says "Tal-y-Llyn Toy railway" 

Awesome!

Quote from: Train Waiting on February 21, 2025, 07:35:53 PMI think the steam locomotive is the nearest to a living thing that people have created, with the possible exception of a sailing ship.

I would add the paper machine to your list.

Just caught up with this brief discourse again. I now know what a poppet valve is! However, you did miss out a Fun Fact - why is it called a poppet valve? I'd like to know why it has such a silly name.

Cheers,

Chris

Quote from: Papyrus on February 23, 2025, 12:57:53 PMJust caught up with this brief discourse again. I now know what a poppet valve is! However, you did miss out a Fun Fact - why is it called a poppet valve? I'd like to know why it has such a silly name.

According to Wikipedia;

QuoteThe word poppet shares etymology with "puppet": it is from the Middle English popet ("youth" or "doll"), from Middle French poupette, which is a diminutive of poupée. The use of the word poppet to describe a valve comes from the same word applied to marionettes, which, like the poppet valve, move bodily in response to remote motion transmitted linearly. In the past, "puppet valve" was a synonym for poppet valve; however, this usage of "puppet" is now obsolete.

John has casually thrown in the Allan straight link valve gear. He and I have punned on this valve gear a few posts ago.

It was a derivative of a derivative of the Stephenson gear. The first derivative was the Gooch valve gear, mainly used on his own locos on the GWR. But it was noted that in direct comparison with Stephenson gear, the latter generally performed better.

The Allan straight link gear was an improvement to the Gooch gear. Allan was amongst other things works manager at Crewe and locomotive superintendent of the Scottish Central Railway, and was credited with inventing the 'Crewe' type of locomotive front end, but this has been challenged.

Google him for more information.

I had added a bit about poppet valve use in the UK, but I've deleted it to let John make a better job than me.

Martyn

Quote from: martyn on February 23, 2025, 06:01:26 PMI had added a bit about poppet valve use in the UK, but I've deleted it to let John make a better job than me.

Martyn

Many thanks, Martyn.

a) I wish you hadn't!

2) No, I won't.

But a part on LNER poppet valve locomotives is imminent. Then, after that, LMS.

With all good wishes.

John

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 69


Hello Chums

Poppet Valve Gears - 1

By 1920, piston valves were the norm for new locomotive construction and Walschaerts valve gear had achieved widespread acceptance. Which meant, I suppose, that there would be interest in something different. At least in certain quarters.

The Lentz valve gear originated in Austria and the Caprotti in Italy.

As far as I can establish, the first locomotive fitted with poppet valves in Great Britain was also the country's first 2-8-2. Any ideas?

The Ravenglass & Eskdale Railway had been converted from three foot gauge to fifteen inch gauge during the Great War. By 1920 it was apparent that a new and powerful locomotive would be required to work both the passenger and stone trains.

2-8-2 River Esk was designed by Henry Greenly and built in 1923 by Davey Paxman of Colchester. I understand this firm had the British rights to Lentz poppet valve gear and this might have been part of the reason for River Esk being fitted with it. Unfortunately, the valve gear wasn't successful in this application and she was rebuilt in 1928 by the Yorkshire Engine Co, when Walschaerts valve gear was fitted.

And here she is, waiting to leave Ravenglass with a train to Dalegarth.  What a railway this is. If you haven't been on it yet, I recommend you consider a visit. The people are lovely, the locomotives are fascinating and the scenery is exquisite.






*

Developments on the LNER

Meanwhile, over on the LNER Mr (later, Sir Nigel) Gresley was taking an interest in poppet valves.  As far as I'm aware, the first standard gauge British locomotive to be fitted with Lentz valves was an ex-GER 'J20' 0-6-0 goods locomotive, No. 8280. She was converted at Stratford Works in 1925.

No. 8280 was reported as giving satisfactory service in this form, although she was converted back to piston valves in September 1937.

In 1926, 'B12' 4-6-0 No. 8516 was converted to Lentz valves gear, followed by another five between 1928 and 1930.

In a 1929 paper to the Institution of Locomotive Engineers, OVS Bulleid noted that the Lentz valve gear on Nos 8280 and 8516, '[...]has been consistently good throughout their respective periods of service: allowance must of course be made for the fact that, being the first engines so fitted, they were well looked after and were worked by the same drivers as far as possible'.

Such was the LNER's enthusiasm that the 1928 batch of 10 'B12s', built by Beyer Peacock had Lentz valve gear from new.

After some time in the rough and tumble of everyday service, the Lenz-equipped 'B12s' began to have problems, firstly with their camshafts and then, more seriously, with cracked monoblock cylinder castings on the 1928 engines.

From November 1931, the LNER started converting some of the 1928 engines to piston valves. By 1934, all sixteen of the Lentz-fitted 'B12s', both conversions and the 1928 locomotives, had either been given the original type of piston valves or had been rebuilt as B12/3s with long-travel piston valves.

*

Class 'D49'

In September 1927, the first of a new class of 4-4-0 for intermediate passenger duties emerged from Darlington Works. This was the 'Shire' class - 'D49/1' in the LNER classification system. Six of the class were fitted with Lentz poppet valves and were designated 'D49/3'. Similar to the 'B12' 4-6-0 locomotives with Lentz valve gear, the 'D49/3's weren't as successful as hoped and, when these six engines required new cylinders in 1938 they were rebuilt as piston valve locomotives and became part of class 'D49/1'.

It is important for us to note that these early experiments with Lentz poppet valves were of the oscillating type, where the cams were driven by modified conventional valve gear, either Stephenson or Walschaerts. As we have seen, they were something of a disappointment.

*

Rotary Rather than Oscillating

However, Mr Gresley still thought poppet valves had potential, but a different operating system would be required to give a rotary motion. 'J20' No. 8280 was given an experimental rotary gear, driven from a coupled axle through a gearbox, in 1927.

The experiment was successful and, in 1929, 'D49/1s' No. 336 Buckinghamshire and No. 352 Leicestershire were fitted with Lentz poppet valves operated by rotating cams, driven by a bevel gear off the driving axle.

Although this gear had the disadvantage of initially only allowing five cut-off positions, a further series of these locomotives, built for the North Eastern Area, were fitted with rotating cam Lentz valve gear, which was modified to allow seven cut-off positions. This was the 'Hunt' class; No. 336 and No. 352 were renamed The Quorn and The Meynell in 1932 and became part of the class, designated 'D49/2'. The D49/2s retained their rotary cam Lentz gear until withdrawal.




['D49/2' No. 365 The Morpeth

*

Other LNER Locomotives with Poppet Valves

Several other locomotives were fitted with poppet valves, including two 'C7' 'Atlantics, formerly NER 'Z' class, Nos 732 and 2212, becoming 'C7/2'. It appears they performed well but no other locomotives in the class were converted.

Making a change from Lentz valves, the LNER converted two 'B3' class 4-6-0 four cylinder express locomotives, Nos. 6166 and 6168, to Caprotti valve gear in 1929. These locomotives were from the former Great Central's 'Lord Faringdon' class which was known to have an especially high coal consumption.

The two converted locomotives had am average coal saving of 16%. Two further B3 class engines, Nos. 6167 and 6164, were fitted with a modified Caprotti valve gear in 1938/1939. The conversions were classified 'B3/2'.




[One of the first two Caprotti-fitted 'B3' 4-6-0s, No. 6167]

*

We Began with a 2-8-2...

... so it'll be a jolly jape to end with another 2-8-2. Mr Gresley's mighty 'P2' for the difficult Edinburgh to Aberdeen line.

The first locomotive of the class, No. 2001 'male chicken' (changed by forum) O' The North was completed in May 1934. She was to a striking design, with her front reminiscent of No. 10000, 'Hush-Hush'. She was fitted with Lentz rotary valve gear and had an ACFI feedwater heater.

In December 1934, Mr Bulleid took No. 2001 to the locomotive testing station at Vitry-sur-Seine near Paris for extensive tests. These were hampered by niggling matters like overheating bearings. On her return, No. 2001 entered service.





[No.2001 'male chicken' (changed by forum) O' The North

The second of the class, No. 2002 Earl Marischal was completed in October 1934. She was similar No. 2001 'male chicken' (changed by forum) o' the North but had piston valves and the ACFI feedwater heater, which had proved troublesome on No. 2001 was omitted.

The other four locomotives entered service in 1936. They were equipped with piston valves. Unlike the first two, they had wedge-shaped fronts, like the 'A4' class. In my view, they looked wonderful in this condition and the first two were altered to suit. Then, Mr Thompson rebuilt the class as ungainly 'Pacifics' designated 'A2/2'. The rebuilds returned to Scotland but were soon banished to the southern part of the East Coast Main Line.

As to why only No. 2001 had Lentz valve gear, it is difficult to be precise. Certainly, she appeared to have a higher coal consumption than No. 2002, but this might have been resolved by further development of the valve events. On test, her coal consumption per drawbar-horsepower hour was not excessive.  But, in service, she was what Mr Bulleid called 'an extravagent engine'.

He pointed out that this was due to the engine diagrams:

'Instead of working trains well up to her capacity over long runs, she was employed in a service such as Edinburgh to Dundee, went to Aberdeen and hung about there, and did a very poor mileage per day, with the result that she showed a heavy coal consumption, most of the coal being burnt through misuse rather than in working trains.'¹

What are we to make of the LNER's experience with poppet valves?

Sir Nigel Gresley's persistence was commendable. Even after mediocre results with the oscillating cam type, he effectively persuaded the British licence holder to produce, in conjunction with the LNER, the rotary cam development.

Whilst prototypes are a good thing, the true worth of a steam locomotive can only be assessed when in the rough and tumble of day-to-day service.

I am unaware that the rotary cam 'D49/2' 'Hunt' class engines were, as a whole, superior to the piston valve 'D49/1' 'Shire'. OS Nock's best run with a 'D49', substituting for a 'Pacific' from Newcastle to Edinburgh with the down 'Flying Scotsman', was with a piston valve engine, No. 249 Aberdeenshire. Thirteen on, 435 tons, unassisted. Minimum speed of 46 1/2 mph up the in 200 to Grantshouse, requiring about 1,230 drawbar-horsepower - exceptional for a 4-4-0.²

The Caprotti conversion for class 'B3' were successful. It improved an indifferent locomotive of an older design.

But the Lentz-fitted No. 2001 appears to have been inferior to the piston-valve fitted No. 2002. Both were right up-to-date designs. Was it a case of more  development required for the Lentz-fitted engine? Would she have been better with Caprotti valve gear?

In the end, I believe Mr Gresley rather lost interest with poppet valves as he set his mind to the development of fast streamlined trains and his masterpiece, the 'A4' 'Pacific'

In the next part, we'll have a quick look at what the LMS was doing with poppet valves.


¹ Sean Day-Lewis, Bulleid Last Giant of Steam, George Allen & Unwin Ltd, London, 1964, Page 90.

² OS Nock, LNER Steam, David & Charles, Newton Abbot, 1969, ISBN 0 330 02680 1, Page 101.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Pip-pip

John