Flying Scotsman and the A4 Boiler

[70014IronDuke]

There was a group of senior managers involved in the decisions including Gerry Fiennes. They were determined to keep on improving speed and performance throughout the 1950s and not to let main line standards slip during the run up to diesel changeover, a policy that would also ensure they had a capable backup in place during the phase-in of the new traction.

That was a conscious decision at the time? Very interesting. I suspect much management just said; let's do minimum repairs and wait for the diesels/electrics.

And, of course, today I read quite often "XYZ TOC trains are in awful condition - they lose the franchise in 2 months."

(Mind you, I don't know if this is just idle speculation, rather than fact.)

The Kylchap conversion was a known quantity with drawings ready and heaps of positive evidence from prewar testing that it improved power output, steaming and fuel economy.
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Although diagrams were specifically allocated to A3s or A4s, in practice they were interchangeable, as A3s once modified were found to be able to keep up with the A4 timings easily.

AND they had not previously been able to achieve this?

After the first few A3s were modified it soon became obvious smoke deflectors would be required with the softer exhaust.
...
Dad suggested the German style deflector and Doncaster very quickly produced a design. I think rather to his surprise the Eastern Region Board immediately sanctioned their application to all modified locos. The drawing office had done a good job and, love or loathe their appearance, the deflectors performed very well maintaining crews' forward visibility of track and signals.

Why did your father think of German style deflectors? Had the A1 type not worked on Humourist?

So it was only the Kylchap locos that were fitted with these deflectors?

Somewhat ironically at the time (I mean, how could one be interested in 'foreign' locomotives with all their pipes an funny shapes - I always skipped those pages in TI/MR) I actually liked the German deflectors - added another element to the scene. Of course, as a then 10-11 year old, I understood next to nothing about why they were so fitted.

 

[MarkyT]

Why did your father think of German style deflectors? Had the A1 type not worked on Humourist?

It was the distinct inward fold at their bottom edge, sloping upwards towards the rear that provided the 'scooping' action making them particularly effective in creating the air currents that lifted the exhaust successfully. Non of the straight sided full deflectors had that detail and the high level 'mini wings' also tried in the 1930s on Humourist were not successful either, probably because they simply didn't channel sufficient air. Dad had taken a number of trips to Germany in the 1950s, including an organised professional tour with his engineering institution, and had ridden in cabs and taken many photographs of steam in action there. He had observed how effective the design was and noted that DB had standardised on the type for very good reasons. I think the Peppercorn A1 style must have been at least partially successful on those locomotives however as I'm not aware of any strong history of poor visibilty. It's interesting to note that the LNER originally wanted to apply a streamlined casing to the A1's but, by the time BR sanctioned their construction, that 'frivolous' feature had been discarded despite it being proven to be the best kind of smoke lifter of all. See my attached impression of a streamlined A1 based on a contemporary drawing - note it really is a A1 not an A4; the dashed hidden detail from the drawing reveals a middle cylinder set forward and driving on the front axle, and the side skirts over the wheels of the original A4s were omitted for ease of maintenance.

So it was only the Kylchap locos that were fitted with these deflectors?

Correct. I think the entire fleet of A3s eventually got Kylchaps though, didn't they?.

Generally, single chimney A4s had always beaten A3s in performance simply through the brute force of their higher spec design. The Kylchap system, like a racing exhaust on a performance car, freed up both designs to meet their true potential, as Gresley had known prewar, but the company could not justify the license fees of the patented design for widespread application. The 'Achilles heal' of the big Gresley designs, rod and axle bearing failures on the central driving wheelset (whatever the underlying reasons for that), were managed very effectively by the more frequent replacement of those components instituted post war, combined with the better alignment processes introduced at Doncaster. Those measures all but eliminated in-service failures due to that set of causes. Rather than any fundamental issue with the conjugated valve gear as many suspect, the problem may have simply been insufficient strength in the frames around the central driving axle, a single 'crankshaft' to which all three cylinders were connected and which is subject to extraordinary oscillating forces at full output. The A4 design had addressed that to an extent compared to the A3, as befitted it's higher designed power, but any further measures to increase the frame stiffness were probably impossible at the time due to overall and individual axle weight limits. Practically, given those constraints, dividing the drive as per the Thompson modifications was probably the only way forward for new designs, although post-war experience proved for existing engines the issues could be managed and there was no need for widespread extensive rebuilds as Thompson had proposed originally. The divided drive approach matured into the new-build Peppercorn A1s and A2s, and those designs proved in service to be among the most reliable and efficient large locomotives ever to operate in the UK, with the lowest maintenance costs by far.

 

[2392]

Speaking of the Kylchap chimney somewhat ironically the patent expired not long after the great man himself in 1941, or so I seem to recall. As you say MarkyT it was the cost of the licenses that put pay to the LNER fitting them, along with the War being at it's height and the UK being alone. Bearing in mind when Gresley died in April of '41 the Russians, Japanese and Americans were yet to join. The Russians joined the UK after Hitler invaded in June and the Americans after the Japanese attack on Pearl Harbour in December.

 

[MarkyT]

the patent expired not long after the great man himself in 1941, or so I seem to recall. . .along with the War being at it's height

That makes sense. The Thompson and Peppercorn pacifics, including Thompson's wartime rebuilds all had or retained the double Kylchap exhaust, apart from the A2s, seemingly an odd decision, but due to space conflict in the smokebox with a new 'self cleaning' contraption. Nevertheless a number of that small class were modified later to include the Kylchap, which in itself reduced the build up of soot anyway due to the greater induced draft.

 

[70014IronDuke]

Speaking of the Kylchap chimney somewhat ironically the patent expired not long after the great man himself in 1941, or so I seem to recall.

Which great man, please? Were there not two involved (ie Kyala and Chapelon)?

As you say MarkyT it was the cost of the licenses that put pay to the LNER fitting them, along with the War being at it's height and the UK being alone. Bearing in mind when Gresley died in April of '41 the Russians, Japanese and Americans were yet to join. The Russians joined the UK after Hitler invaded in June and the Americans after the Japanese attack on Pearl Harbour in December.

Can quite believe the money bit.

OT
Erm, a) the "UK" was not exactly alone - it had the entire Commonwealth/Empire fighting with it - no mean set of resources, when you think of it - although, of course, defending such vast swathes of territory had its own problems

b) The Soviet Union joined the allies in 1941, not "Russia".

I would agree that the USSR carried on with Imperial Russia's general policies under the banner of international socialism (eg Russifying wherever it went) , but many nationalities were involved, often against their will, and suffered in the Soviet forces.

Some may regard this as pedantry - no apologies from me - I regard it as important to differentiate.
--- old post above --- --- new post below ---

It was the distinct inward fold at their bottom edge, sloping upwards towards the rear that provided the 'scooping' action making them particularly effective in creating the air currents that lifted the exhaust successfully.
... Dad had taken a number of trips to Germany in the 1950s, including an organised professional tour with his engineering institution, and had ridden in cabs and taken many photographs of steam in action there. He had observed how effective the design was and noted that DB had standardised on the type for very good reasons.

V interesting. going to Germany in the 1950s must have been an experience in itself - I wonder if you father was alone in pondering and concluding such lessons. Probably quite a bit of prejudice against Germany around still then.

I also had no idea the Peppercorn A1s were originally to be streamlined - funny, some good friends were involved with the Tornado project - but they never mentioned this.

I think the entire fleet of A3s eventually got Kylchaps though, didn't they?.

Well, I thought so too - but there were plenty of locos with no deflectors running around in 1962-3, when withdrawals began in earnest.

....
The 'Achilles heal' of the big Gresley designs, rod and axle bearing failures on the central driving wheelset (whatever the underlying reasons for that), were managed very effectively by the more frequent replacement of those components instituted post war, combined with the better alignment processes introduced at Doncaster.

Sounds like a precursor to the Deltic maintenance programme! All very interesting stuff - thank you.

 

[MarkyT]

Which great man, please? Were there not two involved (ie Kyala and Chapelon)?

I think he meant Sir Nigel Gresley.

V interesting. going to Germany in the 1950s must have been an experience in itself . . . Probably quite a bit of prejudice against Germany around still then.

And vice versa. He said most people he met there were very pleasant and welcoming although a small minority were quite hostile towards a group of British engineers. I guess a lot depended on their personal experiences during and before the war.

I also had no idea the Peppercorn A1s were originally to be streamlined - funny, some good friends were involved with the Tornado project - but they never mentioned this.

Well it was certainly an option they considered, but we'll never know how serious the proposal was as the LNER never placed the order. All I know is my Dad was working in the locomotive drawing office in the late 1940s when the A1s were being designed. He recalls Peppercorn, unlike Thompson or indeed Gresley, concerned himself very little with the engineering details, leaving the drawing office to get on with the A1 and A2 design largely unhindered and only rubber stamping the result when it was ready for production.

Well, I thought so too - but there were plenty of locos with no deflectors running around in 1962-3, when withdrawals began in earnest.

I think some A3s had slipped into 'enemy hands' (i.e. under LM control) at Carlisle, so were never covered by the Eastern Region modification programme. Were there others in Scotland perhaps?

Sounds like a precursor to the Deltic maintenance programme! All very interesting stuff - thank you.

After steam ended, Dad moved on to the Divisional Traction & Rolling Stock Engineer post at Kings Cross where he became responsible for the Deltics and other locos at Finsbury Park.