Loco musings ex the 71000 thread

As with 2-3-2U1 of course.
P.H.

 

Although somewhat off-topic, I put a large article along similar lines to the above on the withdrawal of 6202 on the LMS Forum and it has since appeared in Black Eight of the Stanier 8F Locomotive Society:

http://lmsforum.forumup.co.uk/viewtopic.php?t=64&start=0&mforum=lmsforum Part 1

http://lmsforum.forumup.co.uk/viewtopic.php?t=73&mforum=lmsforum Part 2

http://lmsforum.forumup.co.uk/viewtopic.php?t=74&start=0&mforum=lmsforum Part 3

http://lmsforum.forumup.co.uk/viewtopic.php?t=78&mforum=lmsforum- Bibliography

I believe you can access this without being members. Comments welcome!

 

Fascinating stuff, I have long been interested in the history of 6202 since reading the Official Accident Report in Liverpool's Central Library in the 60's ( now available on the excellent Railways Archive website for anyone interested http://www.railwaysarchive.co.uk/eventsummary.php?eventID=108 ). I had always thought it odd that 46242 had been repaired when 46202 had not when from the photographs 46242 looked at least as bad as 46202. Your additional information and very reasonable conclusions in the absence of actual evidence is compelling.
As for the link with 71000, who knows. In my spotting days around Crewe and Chester in the early sixties we were always disappointed when it showed up on trains we were expecting to be hauled by a Duchess or Britannia - which it seemed to do a lot!, invariably looking unkempt.
However as others have said, in preservation it is a magnificent machine and I hope to see it back on the mainline as soon as possible.

 

With regard to stoker firing. The Chapelon Pacifics were hand fired as were the first batch of 4-8-0s the 240p on the other hand was stoker fired. Up to 3500 h.p. or so you can probably get away with hand firing - the improvement in s.s.c. would help here. If you wanted to aim higher, and I see no reason why not, then some assistance would be welcome. Even with GPCS it would be worth the effort to ensure that maximum power was always available and the firemen are never going to be at their very best every single day so beyond a certain output a good mechanical stoker fitment would be advised, to make doubly sure.

 

I have my doubts that a loco of 3000 plus hp is feasible in this country for two reasons:-

1) It would mean 'crossing the rubicon' by having a mechanical stoker, thus accepting a 10 or more percentage increased fuel consumption due to (a) steam being used to drive the stoker mechanism, and, (b) coal ground by the mechanism into dust and being ejected from the chimney unburnt.

2) Secondly, the restricted UK load gauge profile has to be taken into account which limits the width over cylinders in this particular case. The article on the P2s in The Railway Magazine in the December 2013 issue states that the 'new' P2 will have to have this width reduced in order to increase platform clearances. "Cock O' The North" as built was 8' - 11-1/4" wide with 21" bore cylinders, and according to the article these will have to be reduced to 19-3/4" but this would be compensated by increasing the boiler pressure. By comparison, an A3 with 19" bore cylinders is only 8' - 9-7/8", a difference of only 1-3/8" maybe, but enough of a problem. When one also takes into account that ideally the outside cylinder centres really could do with being increased (to allow for bearing length and possible more side play of the leading coupled axle), well, it is going to be an interesting design exercise!

Readers may also recall another article in RM a couple of years back about the Chapelon 242A1 where a follow-up letter pointed out that a version of this loco trimmed and scaled down to fit the UK load gauge profile could only have a maximum of (say) 20" bore outside cylinders with a proportionately smaller inside high-pressure cylinder which altogether could only produce about 55% of the horsepower of its French sister, this being less that a Peppercorn A1 Pacific could produce.

As an aside, while in the UK we are limited to a height and width of about 8' - 10" and 13' over the chimney, it should not be forgotten that in Germany, for instance, they have 3150 mm (10' - 4-1/2") and 4550 mm (almost 15') respectively for these dimensions to play with, so I fear that Continental practice is of little help to us in the respect of gaining more horsepower.

 

Au contraire, "Duchess of Abercorn" achieved an equivalent indicated horsepower output of 3350 whilst on test in February 1939, the highest figure ever recorded by a British steam locomotive. You will probably find that most of the other British 8P locomotives would achieve over 3000 IHP as well. As 242A1 questions, could such an output be maintained.

Was it possible to have achieved even greater outputs? We know that the technology was available; as a demonstration of what was possible, the South African Railways modified class 25NC - No.3450, achieved an output of 4490 IHP on test and this on 3'-6" gauge with a similar width/height as the British locomoitves.

There was plenty more to be had from the steam locomotive in the 1950's, it is such a pity that by then, it was too late.

Cheers

Alan

 

If such high HP was achieved, what was the challenge turning it into Speed that meant we celebrate A4's today, not Duchesses ?

Could I guess that Stanier needed fast, but also more powerful due to the WCMLs higher gradients in the north, which the LNE didn't have , so he traded speed for power ? ... If that were the case wouldn't a Duchess on the LNE out pace an A4 ?

 

Perhaps I should have said "a continuous output much over 3000 hp". It really all depends on the fireman. BR reckoned on one being able to fire at the maximum rate of 1-1/2 tons an hour continuously and 2 tons an hour for one hour. Some of our high power locos (e.g. "Duchess", A1, etc.) were right on the borderline of requiring mechanical stokers, but would it have been financially acceptable under BR? I rather doubt it.

 

By definition, Power is Force (Tractive Effort, at that point) times Velocity (Speed), so the higher to power output in a given set of circumstances, the higher the speed. Truth is that the LMS did not have a suitable length of track sufficiently long to allow the ultra high speeds available to the LNER - amply demonstrated by 6220's near disastrous entry into Crewe station after reaching 114mph down Madeley Bank! The point of the 6234 trials was to see if timetable improvements could be made with heavier loads, and 6234's trailing load was 607 tons with twenty vehicles.

I feel that the 3,348 ihp produced by 6234 has been exceeded, and possibly in preservation. Andrew Roden in "The Duchesses" claims over 3,600 ihp calculated from performance logs and train resistance formulae. However, this video shows 6233 climbing to Shap with a trailing load of 632 tons (not the 610 claimed on the introduction). Speeds were similar to 6234 at Tebay but about 7 mph higher at the summit. 6234's output in 1939 was 2,963 ihp on that section.

 

A fair question. As you say, the LMS needed fast and in reality they got it with the "Duchesses". I suppose that we celebrate the A4s as high speed machines because they had the opportunity on a daily basis to post high speeds due to the nature of the railway route on which they were operated. Also, on that same railway, the speed record for steam was achieved by an A4, a feat which perhaps, enhances the celebratory nature of the A4s.

As for a "Duchess", this was - if you will allow me - an A4 with more, that is, more grate, more heating area, more cylinder and more Horse Power. Given the operating opportunities of the A4s, there is a good chance that the "Duchesses" would have posted similar high speeds with possibly heavier trains, heaven knows what would have been achieved if they too had been fitted with Kylchap exhausts..........

All conjecture of course, again, such a pity that steam didn't last another 10 years or so.

Cheers

Alan

 

What were the conditions? (For example, was that out on the line, or in a test centre)? How long did the effort last? And most crucially, how many firemen were involved?

Can't remember the exact figures, but I think for a sustained period, something like 50hp per square foot of grate is about the limit that can be sustained, and only by a very good fireman. That probably gives a continuous upper limit of about 2,500hp for a British loco. More could be achieved over a short period (for example, 5 - 10 minutes) but the state of the fire and / or water would be worse at the end, i.e. it is not a steady-state output. (For example, starting a climb with a deep fire and ending up with a thin one, and / or water lower than you started etc). That's probably enough to get you over a 3 - 5 mile incline at prodigious power output if desired, but that's not the same as running at greater than 2,500hp for an hour or more on end.

Tom

 

Indeed, mechanical stoking would probably have been a essential requirement for such high outputs. As you say, It all comes down to finances in the end. If the revenue from operating locomotives at a given cost for a given return is viable, developments would have happened, but as mentioned before, time ran out for steam and the railway operators in this country had other priorities during the 1940s/50s.

Cheers

Alan

 

Good morning Tom,

As mentioned by LMS2698 above, "Duchess of Abercorn" was tested out on line during 1939. The record power output was achieved over a 5 minute period during a test run from Glasgow to Crewe. As has been discussed in this thread, such an output could not be sustained by hand firing alone - although Bert hooker might have disagreed!! As you mention, the many variables of steam in Britain really precluded very high continuous power outputs.

Cheers

Alan

 

So which locos have exceeded 3000 ihp since 1968? I believe Tornado did this last year? on Beattock, or another of the Scottish banks - though I can't find a reference?

(Needless to say I'm not advocating this a regular way of operating!!)

 

The relatively poor sustainable power output achieveable by British locomotives is to say the least unfortunate.

40ihp per ton of locomotive weight is the benchmark. Achieved elsewhere, but not here. So the question is why that should be the case. There are those who believe that this figure was never achieved. The "not done here and therefore fiction" subset. These overlap the "it's my favourite, hence the best, and quite incapable of improvement" group. Further you have the "steam incapable of improvement" body. I could add more but you get the general idea.

As preservationists we should change as little as possible. Preferably nothing. Sometimes this is possible. Run engines and you have to renew things. Run on the mainline and things have to be changed. Worse, the lack of development carried out on steam traction in the UK leaves those with mainline certification functioning with a woeful power to weight ratio. There is a difference between steam preservation and preserving steam on the mainline. Some might be perfectly happy with the engines that we have. Others lean more to "if only" and "what if?". Take a little time and think about it. What if we had a locomotive capable of sustaining 4000ihp?

 

If the 5AT ever gets off the drawing board, that could well be it...........................................

 

Not quite. The 5AT would be the size of a Class 5 with about the power output of a Class 8. Sustained 4000 ihp would need at least the size of a Class 7.

 

Sir, I'll believe you, as I don't know too much about the project - t'was just a thought given the "advancements" involved for steam traction!

Maybe Sheff could enlighten us?

 

Very briefly the 5AT was designed for oil-firing, so comparisons can't readily be made. No issues about grate limit, fireman's back etc.

 

Excuse my ignorance, but how can oil fired not be comparable to coal fired? At the end of the day, the result is the same - to produce steam to power the loco...................................

And just what was the projected TE & ihp?