Steam speed records including City of Truro and Mallard

I can only assume that this started from a very low base if that level of improvement was even possible. I doubt it would have been achievable with an A4, Stanier Pacific or the even the older GWR Kings.

 

The last large Pacifics built by the LMS, LNER and Southern were as big as could be squeezed into the British loading gauge, but it has been reported that the LMS contemplated a 4-8-2, presumably with the idea that even more power would be useful. It couldn't have been made any fatter, so the tube and flue heating surfaces could have been increased only by making the tubes longer, which wouldn't have been ideal. If a Chapelon-inspired loco the size of a Duchess or a bit smaller could have delivered more power than a Duchess, A1 or MN, would that have been useful?

 

I dunno, Ell managed some pretty dramatic improvements with even smaller changes.
Maximum steam rate on King from 25,000 to 30,000 lbs per hour, on Jubilee from 21,000 to 25,000 and Ivatt Class 4 2-6-0 from 9,000 to 17,000.

 

When the German class 01 pacifics were introduced in 1925 the tube length was 5.8 metres (around 19' so the same as Gresley's A1 and A3). It was only after the long tube idea came in during the 1930's that the later members of the class had 6.8 metre boilers with fewer but larger tubes. The total heating surface of the long tube boilers was actually slightly less than the originals, made up of a small increase in evaporative surface counterbalanced by a greater drop in the superheating surface.
As I understand the story of the alloy steel boilers in Germany the problem was that the steel became brittle in use leading to firebox cracks and this was the main cause of the locomotives being rebuilt after the war with new boilers having combustion chambers. It seems that boilers built with 284 psi were the worst affected and the pressure was reduced to the normal 225, reducing the capacity of the locomotives concerned.
Following the success of the Muenchen to Stuttgart electrification of 1933 the Germans decided to electrify all their main lines. In 1940 they introduced four prototype E19 1-Do-1 electric locomotives as the high speed power of the future, designed for a service speed of 180 Km/h and the ability to reach 225 (around 140 mph). Sadly the war intervened, though one did achieve 200 Km/h on test.

 

The NCB ordered 50 sets of the Hunslet gas producer system purely as a means of complying weith the 1956 Clean Air Act. It had nothing to do with efficiency. The fact was that they were pretty much a failure in service and soon fell into disuse, primarily due to problems with the underfeed stoker. When Hunslet re-visited this at Wheldale Colliery in 1980, I was involved. The system did work. The only problem was that it required a Hunslet fitter riding with the loco every day and, when he wasn't available, it soon fell out of use because it required too much 'mothering'.
Perhaps more successful was the Geisl ejector in terms of reliability but it didn't really contribute much to its intended purpose or reducing smoke.

 

Starting from a low base, probably in all Chapelon's earlier rebuilds, agreed.

But that was a a time before the A4s and the like were designed. The early rebuilds were of various old and inefficient engines from the 1920s.

What about the post-war Chapelon designs? 242.A.1, a rebuild of a poor 1930s engine completed in 1946, was so successful on test - producing very high power as well as economy - that it is alleged to have galvanised (yes, I know ..) French electrical engineers into redesigning some new locomotives intended for the Paris-Lyon line. The redesign increased their horsepower by 1,000 to 4,900, in order to head off the argument that the expense of electrification was unnecessary when new-tech steam was capable of equally good performances.

 

one of my (many) unwritten rules learned over many years is that you never achieve any such claimed in the real life of day to day operation. At best it will be 50% of the claim and more probably nearer 25%. On occasion it may even be a negative figure.

Responding to a lot of the posts without quoting them all, the main advantage of the Kylchap is that it will drag more air through the boiler and more air will allow more coal to be burned without having to have such a strong blast that most of the coal goes up the chimney. That is largely where the increase in power comes from, nothing to do with efficiency. Admitedly, it does reduce back pressure in the cylinders at the same time so there is a slight gain there.

I'm not disputing that the Chapelon improvements were not beneficial but I'm with Tom in saying that, in the hustle and bustle of everyday operations those advantages were minimised. Steam locos on the railways of old spent much of their time doing very little and it was only very few turns where the advantages could be realised. How often was a steam loco worked to its limit? I'm sure that the likes of Bulleid, Gresley, Collet, Cox, etc were well aware of the claims and weren't that stupid to simply ignore them without due consideration.

 

Its complicated though isn't it. If an upgrade is sufficiently compelling then it can be rolled round the fleet fairly quickly as heavy generals come round. Churchward decided on his optimum superheater configuration in mid 1910, and by the end of 1913 pretty much every express locomotive on the GWR was superheated and plenty more besides. although secondary types like the Dukes were still being converted in the 20s. No doubt the boiler shop was flat out building new boilers and rebuilding old ones. Yet AIUI some other lines didn't retrofit superheaters to their existing stock. And then extra power is going to be something of a forked sword, because if you upgrade the locomotive to produce 20% more power then how many other components are going to be inadequate and your availability goes through the floor.

 

And that last point is where I think lots of people are failing to engage. It’s one thing to show an efficiency gain for a loco when working at high output. But I’ve never seen a cost / benefit analysis of the cost of rebuilding; nor what the real -world cost savings were (including all the times where the loco was static or working lighter trains); nor what the availability impact was, nor whether there were any changes in maintenance required etc.

The point about being an engineer is not to optimise one parameter, it is to give the best balance across many parameters. Those pursuing the cult of Chapelon seem to go very quiet whenever you try to steer the conversation away from “look, 60% more power”.

Tom

 

If only! There are many, many 'upgrades' instructions that I have in the 8F Society Archive, some of them safety critical, dated in the 1930s and signed off as complete in the 1950s. Many were reissued to catch those which had escaped the net and sometimes jobs were closed when the total modified was still unknown. Bear in mind that the LMS could do these at Crewe, Derby, Horwich and St Rollox. And the engines which were late in compliance might have been given several Heavy General repairs in the meantime along with any number of Light and Intermediates.

This is another point missed by the 'let's increase the power output' brigade. Steam engines, like other machinery, is designed for a normal long-term power output with a short-period maximum, above - and perhaps substantially above - this figure. They will be designed to accept these loadings and probably something above this, but the more failsafe you build in, the heavier your engine and the fewer routes it can be used over. So there is a limit on how big an increase in power output you can add unless reliability, availability and maintenance costs are going to suffer. The classic example is probably the Gresley A1, designed for short travel valves, single chimney and 180 p.s.i. pressure. It finished up with long travel valves, 220 p.s.i. and a Kylchap exhaust, and the not too substantial frames suffered. Later, someone decided it would be a great idea to run the preserved example at 250 p.s.i., so Riley's finished up welding on replacement front frames.

Engines are designed in their entirety so all parts are adequate for the required work and the output needed to meet it.

 

I beg to differ! The Kylchap trick is to draw the same amount of air and have a larger exhaust orifice area at the same time
kind regards,
Jos

 

Yes of course, the first requirement of an operating locomotive is that it is available !

That does not relegate everything else to comparative insignificance.

Thermodynamics; if you can get more without significantly increasing weight
and you carry out any alterations concomitant with a general/major overhaul.
Similarly if you can obtain more HP per weight of coal / water consumed.
( whether by higher superheat temperature, lower pressure drops twixt
boiler and steam chest etc. ). On the Southern water savings were operationally
significant in the absence of water troughs as an example.

(similarly improving water treatment, both internal and external, to extend
periods between wash outs )

Some random thoughts.

I am not aware of Bulleid dismissing either mechanical or thermal efficiency ?

Pre WWII when Stanier was considering something larger than a Duchess
(600 ton express trains over Shap ) as some have observed he would have
been constrained by loading gauge and boiler geometry. A Chapelon type
approach would surely have come to the fore. ( Not that the
Duchess were thermodynamicslly bad ). From 12% to 15% front end efficiency
increase , perhaps aligned with boiler efficiencies > 80%.

Post WWII any idea that coal costs were incidental seems unlikely.
Coal was important, not just the cost, but because it could be exported
( foreign currencies in support of an ailing pound The rush to oil firing and
equally rapid retreat with hindsight, recognising the macro economic
situation, appears strange. )

Whilst savings on shunting engines are unlikely ( indeed there is a mindset
that says even superheating is financially counterproductive ) thermal efficiency
improvements to steam motive power were very much in the minds of
post WWII designers, ( eg Cox’s justifiable excitement at the high front end
efficiency of the Duke of Gloucester, even if his 86% of Rankine is perhaps
arguable, the Cook/Ell work at Swindon, Eastleigh improving Class 4 locos.
etc.)

I do feel this discussion has ventured into Chapelon good, Chapelon irrelevant -
loco availability premier division, other issues relegated to league two, etc.

The irony of steam locomotive development may well be that as technology
allowed for a more sophisticated design that was; thermodynamically more
efficient, mechanically more reliable, more user friendly eg prep time and
required less intermittent attention the limitations encapsulated within
the Second Law and the superiority of both electric motors and diesel
engines rendered such developments irrelevant.

Michael Rowe

 

I still find it interesting if the three rows of numbers under the final and important miles are the LNER evaluation on the Roll?

Mallard by Hermod posted Dec 5, 2023 at 10:03 AM

 

I’ll send you a PM.

 

And Manors after 14 years went from 10,000 to 19,600.
It will be possible to better Chapelon after plus 90 years by putting a big low pressure cylinder between frames and line up the existing outside ones.
Webb was best and rigth all the time.
And there are Manors enough.

 

Thank You.
Look forward to start my slide rule

 

Havig trouble making table

 

I'm not sure that many folk under 50 will recognize a slide rule!

Now where did I put my 4-figure logarithm tables?

 

I believe the Manors were fitted with a standard although not very well thought out British exhaust system and Sam Ell replaced it with a standard but well thought out British exhaust system. I don't remember anything about widely applied Chapelon theories being involved.