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

[cmason]

Many thanks John for this marvelous postington - I have been wondering about what a Giesel ejector is and how it works as only last week I purchased on Yahoo auctions one of Mr Kato's models of a Giesel fitted D51 Hokkaido cold weather spec loco as used up until 1975. Train Trax has a description here.

I am now educated in the mystery!

Colin.

[chrism]

Many thanks John for this marvelous postington - I have been wondering about what a Giesel ejector is and how it works as only last week I purchased on Yahoo auctions one of Mr Kato's models of a Giesel fitted D51 Hokkaido cold weather spec loco as used up until 1975. Train Trax has a description here.
I am now educated in the mystery!

There's nothing particularly fancy about it, it's just a more refined form of blastpipe.

Instead of the exhaust steam being simply blown up a big hole (the chimney) with a broad petticoat pipe to make sure it does go up the hole, the Giesl ejector is a more finely tuned combination of a converging coned blastpipe, a converging combining cone to add the smokebox gases and a diverging cone to exhaust the combined exhaust steam and smokebox gases out of the chimney - all multiplied by the required number of these to both allow the cylinder contents to be properly exhausted and to give the required "draw" through the fire and boiler tubes.

It works on exactly the same principle as a brake ejector, water feed injector or, even, a car carburettor.

[Train Waiting]

A Coarse Guide to the Steam Locomotive for 'N' Gauge Modellers - Part 102


Hello Chums

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

'Multiple Jets - Kylchap'

Let's begin with a questioningham. How many of the 'Big Four' grouped railways used the Kylchap exhaust?

Now, to France. Mr, later Sir Nigel, Gresley [for simplicity, let's abandon chronological exactitude and refer to him as Sir Nigel from now on] of the LNER took a great interest in locomotive developments in France. He was on good terms with M. Lancrenon of the Nord and M. Chapelon of the Paris-Orleans. 

The latter caused something of a sensation in 1929 when he rebuilt one of the Paris-Orleans' compound 'Pacifics'. In original form the locomotive was competent but less than efficient. After rebuilding on Chapelon principles, its performance was SimplyStunning. Sir Nigel, like many other locomotive engineers, made the journey to Paris to see the wonderful locomotive and discuss it with M. Chapelon.

Economic conditions meant it wasn't until 1934 the Sir Nigel was able to introduce a new class of locomotive incorporating Chapelon principles. This was the 'P2' 2-8-2 class for the difficult Edinburgh-Aberdeen road. Two engines entered service in 1934, with four more following in 1936.

The first of the class, No. 2001 'male chicken' (changed by forum) o' the North (I fear our Fabulous Forum will have made me look rather foolish) was taken to France for testing, both at the testing plant at Vitry-sur-Seine and on the track between Orleans and Tours. She performed well and Sir Nigel stated publicly that any further members of the class would be modified in the light of what had been learnt from the tests in France.

The Chapelon principle that interests us here is the Kylchap double blastpipe and chimney, fitted to all but one of the 'P2' class. And, yes, the 'chap' refers to M. Chapelon who had modified and developed earlier ideas. And patented his system. This is a sophisticated system, using two blastpipes [M Chapelon's one-off 242A-1 had three blastpipes¹] and precisely-located cowls or nozzles which direct the gasses from the boiler flues out of the chimney. Here's a diagramington, based on the LNER Kylchap arrangement:-




[The Kylchap exhaust seen here consists of a pair of four stacked nozzles, the first is the blastpipe 'A', known as the primary nozzle, which, in the Chapelon design has four triangular jets. That exhausts into the second stage, the 'Kylälä spreader' 'B', which ejects the gasses from the lowest boiler tubes. That then exhausts into the third stage, designed by Chapelon, which ejects the gasses from the middle rows of tubes. Finally, this exhausts into the fourth stage, the chimney cowl. We'll hear a little more about the Kylälä spreader right at the end of this surprisingly brief mini-series.]


The benefit of the Kylchap exhaust is a strong draught, which gives good steaming, and very low back-pressure in the cylinders, giving enhanced power and efficiency. The disadvantage is the need for the precise location of the various components in the smokebox.

As modellers, the contents of the smokebox are of little concern (unless we have a Tri-ang Hornby 'M7' 0-4-4T in H0/00 gauge), but the large double chimney is a distinctive feature of the locomotive's external appearance.

Worth noting in passing is, in 1935, Sir Nigel arranged for the experimental high-pressure 'W1' 4-6-4 No. 10000 to have the same Kylchap arrangement as 'male chicken' (changed by forum) o' the North fitted. No. 10000 retained the Kylchap exhaust after rebuilding as a conventional locomotive in 1937.

In 1935, Sir Nigel's masterpiece, the 'A4' 'Pacific' class, was introduced. With a single blastpipe and chimney. Why the seemingly backward backward step?

In service, the 'P2s' gained a reputation for being heavy on coal, although No. 2001 was not an extravagant engine [OVS Bulleid's terminology] when on test in France. What was going on?

We can blame the Scottish Area operating people. Instead of having the'P2' class working through from Edinburgh to Aberdeen, they stuck to good old North British Railway practices and changed engines at Dundee. This meant they achieved lower daily mileages and spent far too much time hanging around at Edinburgh, Dundee or Aberdeen. Steam engines also burn coal when hanging around doing nothing and the 'P2' class had a 50 sq./ft. grate area.

Unfortunately, there were fears the Kylchap exhaust was contributing to the high coal consumption. So, the 'A4s' had single blastpipes with jumper tops.

Then, in 1937, Sir Nigel arranged for an 'A3' 'Pacific', No.2751 Humorist, to be fitted with a Kylchap exhaust. She performed brilliantly, although the consequent softer blast led to drifting exhaust when working at short cut-offs. She was given small smoke deflectors in 1938, similar to those she had experimentally carried in 1932. These were replaced in 1947 by large deflectors plates like those used on the post-War 'Pacifics'.




[No. 2751 Humorist (what a delightful name for a locomotive) poses for the LNER's photographer after fitting of the Kylchap exhaust but before the addition of smoke deflectors.]


In 1938, four of the final batch of 'A4s' were built with Kylchap exhausts. The Bugatti-inspired wedge front, with a small indentation behind the chimney, meant these had no problems with drifting exhaust. It's always nice to have a list of locomotives, so here they are:

No. 4901 Capercaillie (Sir Charles Newton from 4/6/1943)
No. 4902 Seagull
No. 4903 Peregrine (Lord Faringdon from 24/3/1948 )
and, of course,
No. 4468 Mallard

These four engines were responsible for some wonderful feats of haulage at speed, the most famous of which occurred down Stoke Bank on 3 July 1938. 126 m.p.h downhill with a 40% cut-off! Driver J Duddington, Fireman T Bray and Inspector J Jenkins. A world record - beating a German 4-6-4's 124.5 m.p.h, achieved on 30 May 1936.

It seems that Sir Nigel decided to use the Kylchap exhaust for any future 'Pacifics' to be built but did not commence equipping existing engines with it. PN Townend, of whom we'll hear a lot in the next part, conjectured this was because Sir Nigel was waiting for the patent to expire in 1941.

We'll catch up with post-Gresley LNER 'Pacific' developments in the next part. Let's return to our opening questioningham - 'How many of the 'Big Four' grouped railways used the Kylchap exhaust?'

We know all about the LNER - Mallard's exploits make sure of that, but what about the others?

It's probably safe to rule out the Great Western, but what about the LMS or Southern - did either use the Kylchap system?

The answer is, both did!

We have already noticed the Southern's 'Lord Nelson' class never, at least until after Mr Bulleid's modifications, seemed to live up to expectations. Mr Maunsell arranged for a series of modifications to be made to individual engines in an attempt to improve the breed.  Here's SC Townroe:

'The first really noticeable improvement in performance was observed in 1934 when No. 862 Lord Collingwood was fitted with a Kylchap blastpipe and chimney [...] The device improved draught significantly, at the same time reducing the back-pressure on the exhaust steam. Despite favourable reports from the Locomotive Running Department, this improvement was not followed up immediately.'²

It appears at least two other 'Lord Nelsons' had Kylchap exhausts; one was No. 865 Sir John Hawkins in 1938, seen here in a photograph by the late Rev AC Cawston:-





CJ Allen logged many examples of locomotive performance, including three runs between Surbiton and Basingstoke in the 1937-1939 period. One was behind No. 860 Lord Hawke which he described as being Kylchap-fitted. I have not been able to ascertain if there was more than one Kylchap exhaust, or this is simply due to the boiler and smokebox with this arrangement being exchanged between locomotives during overhaul.

OS Nock was less than impressed by a Kylchap-fitted 'Nelson':-

'In passing, it may be mentioned that a [Kylchap] double blastpipe and chimney had been tried by Maunsell on one of the 'Lord Nelsons', No. 862, Lord Collingwood, but it did not appear to make any difference to the steaming; in fact, that engine in its modified condition contributed to the rather large collection of indifferent runs I personally experienced with the 'Lord Nelson' class engines on the Southern Railway in the last years of the Maunsell regime.'³

More so even than the 'Nelsons', the '5X' or 'Jubilee' class three-cylinder 4-6-0s of the LMS were something of a disappointment at first. And that's a serious understatement. Much tinkering took place over the years, right up to the fitting of a double chimney to No.45596 Bahamas in 1961. This produced an excellent engine as she takes every opportunity to demonstrate out on the main line.

In 1937, the LMS fitted No. 5684 Jutland with a Kylchap exhaust. The result was a significant deterioration in performance. Here's the late ES Cox, who was getting quite senior in the LMS locomotive hierarchy by this time:-

'Improved draughting was one of these. Previous attempts at higher efficiency in this sector had often been unsuccessful, culminating in the volcanic display of a '5X' class 4-6-0 which, when fitted with a double Kylchap arrangement in 1937, had produced a continuous spray of incandescent fuel from the chimney top at anything above the lowest output, the smokebox at the same time filling up with ash to the level of the blastpipe cap during a journey. This was, of course, due to gross unsuitability of the tube proportions, and the lesson was quickly learned that the benefits from more powerful and efficient blast was only fully to be attained by use of a larger number of smaller tubes in the boiler, the end product being increase in evaporative capacity combined with low back pressure in the cylinders.'⁴

Quite!  The Klychap apparatus was swiftly removed.




[The picturingham is from an LMS Official photograph of Jutland after conversion to Klychap exhaust.]


Incidentally, the context in which Mr Cox was writing was last years of the LMS, when Mr Ivatt the Younger was working hard to develop steam locomotives suitable for post-War operating conditions. He was also much involved in the construction of Great Britain's first two main-line diesel locomotives. These were much better than some of the 'Modernisation Plan' efforts that appeared almost ten years later - but there was Government interference aplenty with these. 'Nuff said?

My point is Mr Cox singles out the unfortunate experience with the 'Jubilee', acknowledging it wasn't the fault of the Kylchap exhaust which was, effectively, too good for the engine. He doesn't mention the superb results obtained by the LMS from the '2A' double-chimney boiler retro-fitted to many 4-6-0s or the successful equipping of 'Princess Coronation' 4-6-2s with double chimneys. I have made a similar point before about Mr Cox's writing.

The next part will look at the use of the Kylchap exhaust in the final years of the LNER and under British Railways. It will also discuss another unfortunate consequence of SO Ell's brilliant work at Swindon on draughting.

Better still, it is my hope that the next part will carry this mini-series' tail lamp.

Many thanks to @martyn for reviewing and commenting on the draft text.


¹ 242A-1 entered service in 1946 and was a stunning performer. A three-cylinder compound 4-8-4, she remained a one-off as electrification was seen, in France, as the way ahead. Unforgivably, in my view, she was scrapped in 1960.

² SC Townroe, Arthurs, Nelsons and Schools of the Southern, Ian Allan. London, 1973, Page 54.

³ OS Nock, Sothern Steam, David & Charles, Newton Abbot, 1966, Page 153.

⁴ ES Cox, Chronicles of Steam, Ian Allan, London, 1967, Page 146.


'N' Gauge is Such Fun!

Many thanks for looking and all best wishes.

Toodle-oo

John