LMS2968

Probably, judging from the brake's carrying side lamps.

Yes, both of the two 5Xs!

And limits wheel size. This was the problem encountered when designing the later Stanier Pacifics: The biggest boiler possible was specified along with 6' 9" coupled wheels, and the top front corners of the firebox had to be drastically cut back to achieve it.

I don't think there is any suggestion of similarity below the running plate, and the boilers were very different also. Attention was mostly on the firebox, and as I said, there is a similarity in profile but not cross-section.

The LN and Scot fireboxes show similarities in profile but are very different in end view. Eric Langridge, a draughtsman at Derby, a was equally adamant that the Scot owed nothing to the LN design.

The original distance between the Liverpool & Manchester Railways Up and Down lines was 4' 8 1.2", reportedly to allow wide loads to run along the centre. What happened when the came to pointwork isn't explained, but wide loads were envisaged in the 1820s.

We have to deal with the practical, not the theoretical!

As engineers, we use indicator diagrams a lot, including for internal combustion engines. But you can also measure the TE on a rolling road or at the drawbar with a dynamometer car.

Hmm, you're a physicist while I'm an engineer; basically, engineering can be considered as applied physics and we both work to the same formulae. There has been a lot of talk in this thread about tractive effort (a force) when the poster is actually talking about power, which as you intimate is Force (T.E.) x Velocity (say speed for simplicity). With a steam engine, maximum tractive effort occurs at zero m.p.h., while by definition power output is none (Tractive effort x 0 m.p.h. = zero h.p.). At zero m.p.h. full boiler pressure is available in the cylinder as at least one valve will be permanently open to admission so the boiler's ability to generate steam doesn't come into it; once moving - and at speed - the boiler's steam-raising ability then becomes the major factor to keep up the demand from the cylinders. If it can't, pressure falls and power output falls with it. By the way, Compound, that wasn't aimed at you: I know that you already know all this!

The snag here is that the independent loco builders had obtained an injunction preventing one railway company from building engines for another. This was obtained after Crewe built several engines for the Lancashire & Yorkshire Railway in the Nineteenth Century; to the best of my knowledge, it was still in force in the mid-1920s, and wasn't broken until the Southern built LMS 8Fs for the LNER (confusing, I know, but that's what happened!).

The formula for Nominal Tractive Effort was Bore (squared) x stroke x number of cylinders x boiler pressure x 0.85 all divided by 2 x driving wheel diameter, all in inches. There is no reference to speed and is, by definition, an approximation of the T.E. at starting. Once moving, the time available for steam to flow to and from the cylinders reduces so the Mean Effective Pressure within the cylinder reduces. The shorter cut-offs used as speed rises also reduces the M.E.P. so Actual Tractive Effort falls exponentially as speed rises. For the most part, power output is dependent on the boiler's ability to generate steam, never a reliable quality of the 5XPs right to the end. If all the parameters were good, they could be excellent, but if there was any problems they were mediocre to poor.

The 5Xs ran the Euston - Birminghams - the fastest scheduled expresses except the Coronation Scot on the LMS - for many years. But each was on its home railway, built to suit those conditions: coal type signal sighting (from which side of the footplate), familiarity to similar types of engine, etc. They were happier were they were.

A clean WD! Wow!

I think the weathering is a bit excessive on that thing to the right!

Note that the Garratt has been turned so that the the smokebox end is trailing; originally it ran the other way around but its length made buffering up a challenge, with a few fairly heavy bumps to the train.

True, but previously in the LNWR list, Camden had been 1 and Willesden 2. Camden became 1B to Willesden's 1A, and as there had always been some rivalry, this more than stirred things up a little!

It was the number plates which tended to be absent from ex-LNWR locos rather than the shed plates, which they did get. The LNWR and L&YR used enamel plates, black or dark blue figures and border on a white background. The plates were on a peg which fitted into a slot on the rear of the cab roof. Post Grouping, these plates, which were still oval but more rounded than the Midland cast plates, were moved to the smokebox door. New build, including Stanier classes, engines received them up to 1934 when they were replaced by the cast iron type. Until then, the LNWR and L&YR shed numbers were retained on the plates, although L&YR sheds were prefixed C for Central Division. There were no alpha suffixes to any of the plates, including the cast Midland ones. From 1935, the entire system was replaced and all engines received cast plates in a new numbering sequence with no duplication across divisions, which there had been before. All got an Alpha suffix, A being the Concentration shed responsible for most loco repairs while its sub-sheds were lettered from B onwards.

Yeah, we got a bit carried away!

Ah, sorry. My mistake. As far as I know - and I don't claim any expertise - they were all the same. They're the figures Arthur Cook gives for the G7S and I've never read of any changes in the layouts. I doubt there would be many changes to the G7 as it was already a successful type. But the art of correct ratios wasn't known, even into the mid-1930s (witness the Stanier 5XP debacle) so there might have been some experimentation. The G7 was fitted to several different classes over a long period so who knows what went on previously.

Not in tubes, no. They were the same boiler and firebox shell but with different tubeplates. Some of the G7's small tubes were sacrificed to make room for the flues of the G7S. The G7S had 21 flues 5 1/8" diameter and 146 small tubes 1 3/4" diameter, the elements being 1 1/2". Unfortunately, Mr Cook does not give the information for the G7 but there would have been more small tubes with no flues.

. . . as per G.J. Churchward's theories about low degree superheat.

No, the gases had given up their heat to the elements en-route from the firebox end and were then below the temperature of the elements further back, but at or above the temperature of the water in the boiler. I believe this was substantiated on the Rugby Test Plant.

I certainly agree with the last bit! The gas temperature at the smokebox could vary a lot depending on the A/S ratio (cross-sectional Area of the tubes / Surface area of tubes in contact with the water), easily worked out for the small tubes but less so with the flues as the A/S of the elements has to be calculated and subtracted from that of the flues. It was rare and undesirable to get ambient temperature at the smokebox; it was usually high as witnessed by the burnt and crinkled paint. Realistically, you didn't want it lower than the water temperature as this would mean the last few feet of tubes would be extracting heat from the water and therefore reducing the steaming. But the gas exiting the flues was sometime less than the superheated steam temperature, the Stanier Pacifics were a case in point. Attempts to lag these last few feet came undone when the tubes needed rodding out.

To move this on a bit and also to justify my comments, I'd like to look in more detail about the two boilers. G7S: This was a superheated development of the saturated G7 boiler as fitted to the 3Fs and was regarded as a prolific steam raiser. All that was done to make the G7S was to add the superheater: it used the same firebox and grate area so both had the same fire producing the same amount of heat. In the G7, all this heat was used to generate steam, but in the G7S some was diverted to raise the temperature of steam already generated, so less heat was available to produce steam in the first place. The steam raising capacity therefor fell, but the superheating made the 4F a stronger engine than the 3F, justifying the higher power class. G9AS: This boiler's problems go back to the design stage, where an emphasis on free water and steam circulation was a priority. Hot water and steam bubbles rise, and if blocked by an excess of tubes, steam generation is compromised. In this boiler the tubes were widely spaced to allow free circulation, but this reduced the number which could be fitted within the tubeplates, decreasing the tube surface area in contact with the water and so the ability to generate steam. This was less of a problem with the Compounds which, as designed, ran with full regulator opening and short cut-offs, but in any case used the steam twice, once in the high pressure cylinder then again the low pressure cylinders. The S&DJR 7Fs were a different story. Their short-travel gear demanded long cut-offs, especially when climbing that line's steep banks with heavy trains. When five new examples were built in 1925, they were given bigger boilers to aid steaming. Admittedly, when these boilers wore out no new ones were build but the engines converted to the G9AS boiler like their sisters. A lot is revealed in 'Raising Steam on the LMS' by Arthur Cook (1999) RCTS Huntingdon ISBN 0 901115 85 1

More steam than a 2P could use, because its valve chests were below the cylinders requiring very tight passages for the live steam and exhaust steam to and from them. This restricted the amount of steam which could reach the cylinders to below what the boiler could generate, so the boiler was never really pushed. The 4F was different. I probably overstated the case here. The 4Fs were reasonable steamers and generally coped well enough; they did a lot of good work over many years, but it has become fashionable to denigrate the. I didn't intend to join the anti-4F Club!