query regarding Flying Scotsman and the use of an A4 boiler

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Nova
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query regarding Flying Scotsman and the use of an A4 boiler

Post by Nova » Sat Sep 09, 2017 6:52 pm

For those that know where to look it's easy to see that in the years leading up to 2005 Flying Scotsman carried an A4 boiler.

However a discussion on an online chatroom on this matter has lead to a bit of butting heads with some claiming that part of the reason for the advanced state of wear on 4472/60103's frames was due to being fitted with a supposedly heavier A4 boiler whilst under the ownership of William Mcalpine without the frames being strengthened. Whilst I've argued that she would have been fitted with an A4 boiler in BR days and that IF it is indeed heavier she would have had the frames strengthened then.

so to avoid the discussion being dragged on needlessly I've come here to ask members to help answer a number of questions on the matter.

1. Are the A4 boilers of a different weight to the A3 boilers, specifically heavier, and if so are the frames of the A3s that were so fitted strengthened to accommodate them?

2. was 60103 fitted with an A4 boiler in BR days?

3. if the weight or lack thereof of the boiler isn't to blame then what was it that caused the damage to 60103 during Mcalpines ownership of her
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greenglade
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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by greenglade » Sat Sep 09, 2017 8:46 pm

I don't have the tome to hand to answer your specific questions but I do have an opinion re what was done to 4472 under not McAlpine's but March's ownership when modified by Rowland. Also, I do not believe that the weight of the boiler was to blame, the A1/3's had issues with their frames from a very early date and these problems were dealt with a number of times but never really cured. I am going from memory here so forgive me if I have something wrong or have forgotten something. These were like thoroughbred racers with fairly light frames to run that power on, the frames did show weaknesses from very early on, usually around the front lightening holes. This was caused by a number of things, the most noted being the extra working of the middle cylinder with end covers being damaged due to impact from the piston. Things were changed to reduce this, holes were first made smaller and then later left off altogether, in comparison the rear was pretty strong. LNER used to keep spare frames to repair the Pacific's during heavy overhauls, most if not all required replacement frames at some point during their career. So things were rough going for the class long before Rowland got his hands on her, now add to this mix, larger bored cylinders, larger steam pipes, a much higher working pressure and tractive effort risen from around 30,000 to over 40,000, it's no wonder that 4472 required a completely new front end, (this happened to other Pacific's too) There has also been much written about the quality of the work carried out under Rowland's stewardship... To conclude, even if the boiler of an A4 is substantially heavier I wouldn't say that this was the cause of the damage alone, it wouldn't help but there were many other problems which are well recorded now, iirc the reports on 4472's condition are out there somewhere for those interested, I recall reading them at the time, they were very much public information..

Pete

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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by Hatfield Shed » Sun Sep 10, 2017 6:37 pm

On a more general note the A4 boiler fitted within the same 'exterior envelope' as the A3 types. It was heavier, mainly because thicker plates were used to obtain the required margin of safety for 250 psi, as compared to 220. But applied to an A3 it didn't have to be operated at 250 psi, it's the setting of the safety valves that determine what pressure is carried. UK railway practise was somewhat backward compared with the best elsewhere in the world: the A4 frame was superior to the A3 design, an American operation would likely have ceased production of the A3 type, and have used the A4 type thereafter when frame renewals were required.

It was a long standing complaint of M. Chapelon that potential European steam loco power development was hampered by reluctance of the railways to increase the load bearing of the track and structures. All the UK pacific designs were pushing at the limits of frame design technique of the time in making best use of the weight of metal available. Frame failure was relatively common, and this was not a Doncaster problem solely. Among various examples it may be recalled that an attempt to generate cylinder indicator diagrams on a Bulleid pacific on the Rugby test plant could not be achieved. The engines were flexing the frame to the extent that there was no sufficiantly stable datum on which to mount the measuring equipment. Crewe's pacifics not only broke their frames requiring regular welding in of replacement sections but worked their cylinders loose. The one BR pacific design that got a real work out began to show its collection of structure failures as steam was wound down.

Over the pond, North American practise had moved to integrally cast frames and cylinders as maximum cylinder horsepower rose above 3,000, and this despite starting with a heavier built up frame construction. The 2,000+ hp from UK pacific cylinders on a significantly lighter built up frame construction had inevitable consequences, from which our steam technique never significantly moved on.

It will be interesting to see how the improvements in metallurgy, analysis, design, construction and maintenance techniques since large scale steam traction construction ceased in the UK, will benefit 'Tornado' . Hopefully it will confer real gains in operational longevity free from structure failures.

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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by JJC » Mon Sep 11, 2017 12:35 am

These reports might answer your question
https://group.sciencemuseum.org.uk/wp-c ... r_2012.pdf
Section 8.1 para 2 looks to be relevant to your question
Also
http://www.nrm.org.uk/AboutUs/~/media/C ... 279915.pdf
Executive Summary para 11 and Section 4 - Findings para 4.5 also Appendix 4 para 3 & 4

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Fairway 2746
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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by Fairway 2746 » Thu Nov 09, 2017 10:20 am

Hi All,

I have read with some amazement as to the limited knowledge shown by many commentators of Gresley Pacific build details (this includes A1 - A3 - A4) on this forum & others especially when a very great documentation base is available. Every LNER fan should endeavor to obtain or at least read RCTS part 2A covering all Pacific types & OS Nock's two volume treatise on Gresley Pacifics. The NRM also has, obviously, considerable technical resources. A review of the readily available literature would answer most of the questions posed.

However, very briefly, there is very little actual weight difference between A3 & A4 boilers as the extra thickness required for 250lb operation is only 3/32" (with that on only a portion of the boiler). Frame material thickness is also mostly the same but, arranged more efficiently. Peppercorn A1's appear to show how later Pacific frames were improved, although the finished engines do not ride anywhere near as nicely as Gresley's versions. This may be due to having divided drive with the resulting weight distributions being inferior to A-3 - A4 machines.

Plate frame construction is not inherently inferior to bar or cast engine beds especially in Britain. As in any engineering problem, many factors must be weighed in deciding how to design & fabricate a locomotive plate frame. Throwing metal at the issue by use of bar or cast frames is not the answer. Commentary by the various British designers of the day in 1948 editions of the Journal Institution of Locomotive Engineers show that frame problems (cracking, horn guide / horn block fractures, racking etc) were not at all completely understood. With that in mind, note how the 9F frame is an outstanding example of plate frame construction.

Previous comments on the limited loading gauge variations in Britain certainly hilite how performance improvements could only be obtained by incremental upgrades. Huge differences were effectively impossible. For example, adopting Beyer-Garretts en masse for freight would have been a waste as siding lengths would have to have been greatly increased, a huge undertaking (effectively illustrated by Gresley's P1 2-8-2's). The only real improvement would come later with faster BR 9F's & they had to deal with the bottleneck at Potters Bar (upgraded only in the late 1950's).

British railway engineers have been trying to squeeze a quart into a pint bottle since the end of the 19th century. Frankly, given the persistent lack of funds, the LNER probably did a better job than their rivals & one of the reasons I admire this railway so much.

Finally, everyone should get their hands on Andrew Dow's "The Railway - British Track Since 1804". A must read

Best regards to all LNER enthusiasts,
Papyrus 2750

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Fairway 2746
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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by Fairway 2746 » Fri Nov 10, 2017 5:03 am

Hi All,

I wanted to address some of the other comments yesterday but, it was 2:00AM & I was out of steam (how droll, I know. ha ha ha anyway).

greenglade's observations regarding Rowland's modifications are partly correct. While employing full 7" piping & smoothing of the steam passages allow the engine to breath better, she was never really correctly restored in other very important details. The higher 250psi boiler pressure & 20" cylinders combined with drivers flogging her & firemen over firing to compensate for the 41.25sq ft grate really hurt her (Peppercorn A1's have 50sq ft & LNER staff reduced the cylinders on A3's to 19" obtain a better balance with the power of 220psi boilers - BR never used the full 250psi available from the A4 type). Her cylinder installation error & her abuse combined to leave her in very poor condition as outlined in the reports to the Science Museum & the NRM (thanks JJC for posting the links for others - I had reviewed both some time back). If she had been restored accurately in all other respects, even the performance improvement allowed for by the higher pressure & larger cylinders would not have been enough by themselves to hurt her as long as she was driven properly & not overloaded. Keep in mind that tractive effort is a calculated figure & essentially meaningless except for starting. A3's are approx 2200hp engines, give or take. I believe Rowland & Marchington thought they could get 2700hp out of her without ill effect. The higher power available was certainly over-used which exacerbated her uncorrected problems. An improper rebuilding combined with unmerciful flogging of the poor girl were the real crimes.

The limitations of the NRM staff & Britain's reduced industrial abilities, especially in heavy railway engineering made it difficult at best to undertake her restoration with any real ability to accurately advise the public of the final price tag or completion date. Quite the learning curve & I'm sure everyone received something of value besides Flying Scotsman. Future projects will no doubt, benefit from this program's trials & tribulations.

Regards,
Fairway 2746

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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by Blink Bonny » Mon Nov 13, 2017 11:15 pm

Ay up!

A reason for the frame weaknesses caused by A4 boilers on A3s I heard was due to the combustion chamber at the front of the firebox affecting the weight distribution and putting odd stresses on the frames.

Certainly Scotsman's frames showed all the problems caused by A4 boilers in BR days,
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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by Hatfield Shed » Wed Nov 15, 2017 11:05 am

Fairway 2746 wrote:
Thu Nov 09, 2017 10:20 am
...British railway engineers have been trying to squeeze a quart into a pint bottle since the end of the 19th century. Frankly, given the persistent lack of funds, the LNER probably did a better job than their rivals & one of the reasons I admire this railway so much...
The Doncaster team still do not get the proper credit for solving 'the problem' of a maximum power steam express locomotive format that could fit within UK network constraints and had great future development potential, and all done under significant financial pressure. The 1948 comparative trials by BR revealed that the A4 alone was suitable to operate - as built - anywhere on UK principal express routes, on less coal and water while doing equivalent work, and with greater range thanks to both the efficiency and large tender capacity. No account was taken of it being the cheapest of the pacifics in first construction and maintenance costs as well. (There was nothing freakish in this either, as the two other LNER classes tested revealed very clearly the falsity of the cult of the expensive Belpaire firebox' supposed advantages.)

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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by Tina19 » Wed Nov 15, 2017 9:46 pm

JJC wrote:
Mon Sep 11, 2017 12:35 am
These reports might answer your question
https://group.sciencemuseum.org.uk/wp-c ... r_2012.pdf
Section 8.1 para 2 looks to be relevant to your question
Also
http://www.nrm.org.uk/AboutUs/~/media/C ... 279915.pdftransfers CDG
Executive Summary para 11 and Section 4 - Findings para 4.5 also Appendix 4 para 3 & 4
thanks for that

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Re: query regarding Flying Scotsman and the use of an A4 boiler

Post by Fairway 2746 » Thu Nov 16, 2017 9:11 am

Hi All,

I agree with Hatfield Shed on how little credit is given the LNER on its effective use of the moneys available, with emphasis on "effective". Later improvements in quality control by former GWR shed man KJ Cook can be seen in better frame assembly due to the use of optical alignment tools & slightly revised center cylinder connecting rod big end but, should not distract anyone as to the qualities of Doncaster's design staff & their products. Bert Spencer's revised valve motion which permitted longer lap & travel should be noted. These details improved the A3's & were applied to both the A4's & V2's (probably on all LNER 3-cylinders locomotive as well) resulting much improved performance.

The "reports" of A4 boilers causing frame problems due to the combustion chamber moving weights around is likely without merit. The diagram 107 boiler was only marginally heavier than either the 1927 diagram 94HP or 1934 diagram 94A boilers plus the difference is concentrated aft where A1 / A3 frames usually have no problems. Their frames are weakest forward where the bulk of problems occurred.

Another detail to the LNER's credit was noted in Andrew Dow's "The Railway" where they purchased a Morris tracklayer which significantly increased the rate of track installation. The machine was also overhauled & employed after the war. Yet another area where the LNER lead all other UK railways.

Regards,
Fairway 2746

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