Thermodynamics, DBHP and related technical matters

Difficult to directly compare the performances of wide shallow grates/ fireboxes with long deep ones
Purely in terms of grate area a Britannia murders a Castle or a Royal scot, but we know that this isn't so.

 

4 small cylinders use more steam than 2 big for same work.
Ridless idea for a world beater was a Clan /King mix with long narrow firebox and two Caprotti cylinders and 4-8-0 wheelbase.

 

Proof?

 

do we ?
70005 was tested at max rates on the S&C Around the same time as 46225 , but the figures were never made public . 71000 was also tested but nobody seemed to want to talk about that either. I imagine if the Brit had bettered the Duchess we would know
AFAIK no Scot has ever been tested at max rates altho' 46115 has produced some fine work . I would be surprised if the Scot did not beat the Castle for DBHP but the Castle would be faster . I have never seen any record of much over 90 mph from a Scot . -probably a bit too lively I imagine .
the fastest record for a Brit that I have seen is 105mph thro' Diss on the GE.
Scot v/s Brit DBHP ? probably a dead heat although a Brit should be able to maintain it longer .whether the fireman could is another matter

 

Searching

 

A few years ago seem to remember that 5043, 46115 and 70013 all did barnstorming runs over Shap in the same summer with very little between them.

Although cost may have had something to do with it, post 1951 the remaining Royal scots m,ay well have been scrapped and replaced with Brits rather than rebuilt if they hadn't been up there.

Having said that we don't know what a double chimney/ re draughted Britannia would be capable of ( other than racking itself to bits even faster...).

 

Wasn't part of the design philosophy of the larger Standards to give them generous grate areas in proportion to their other dimensions to cope with poorer quality coal than the Big Four's pre-war classes had been designed for? Tuplin is criticised for some of his claims, but one that surely was bang on was that the ability of a steam locomotive to deliver sustained power output depends on the ability of the fireman to shovel coal.

 

Re: 2 vs 4 cyls .... I'm assuming we're talking about the same swept cylinder volume when talking about 'the same work'? Is there any test data to support the view that 4 cyls use more steam than an equivalent 2cyl design? With a more complex steam circuit, I'd expect more by way of losses, but all else being the same, can't for the life of me see why there'd be higher steam consumption.

The only locos I can think of where 2 and 4 cyl versions existed were the GSR (Ireland) '400' class ... with their abysmal original steam circuit being the reason seven were rebuilt as 2cyl machines (resulting in two distinct flavours, though it's actually more convoluted than that) and the remaining three scrapped while still young.

Do we know when Riddles made his proposal? I ask, as a long, narrow firebox is something I associate with oil burning.

 

Let us play rebuilders.
A GWR King with two outside cylinders of 22 inch bore and 30 inch stroke have more or less same cylinder volume.
According to a mr Postupalsky of 1953 referred by dr Giesel this will save 9%steam and much more coal.
The german version of mr Cox, was mr Norman and he quotes ca 4.5 % extra steam going from two to three cylinders in german pacifics.
It reflects ,I think , the surface in contact with steam(doing ugly things) relative to volume(doing good things).
Leakage,condensations etc.
I am sure mr Ridless gave the Clan rebuilding advice as very old man to some madmen building steam locomotive models and competing on efficiency.
All my Model Engineer magazines were recycled some years ago.

 

Look left - George Evans. Model based on BR designed/not built Standard 2-8-2 believe this was a winner in several of the aforementioned efficiency tests, but we are digressing now.

I follow your argument that fewer larger cylinders may be more efficient, but surely its fractions and a nicely balanced multicylinder arrangement causes fewer stress / rotational mass related problems elsewhere.

 

If losses within the steam circuit increased all that much with the number of cylinders, I suspect we'd have not encountered the resistance to application of thermodynamic theory which seems to have occured everywhere Chapelon and Porta weren't involved. OVSB certainly didn't have a high opinion of concerns about surface losses within the steam circuit.

Remaining arguments re:multiple cylinders, devided drives etc. (pro and con) surely take us back to Churchward's work in the earliest years of the 20th century.

 

Sorry my ignorance, but what means OVSB?

 

Oliver Vaughan Snell Bulleid....

 

indeed they did , but that is not the same as bagged coal of known calorific value and constant steaming rates etc , so the only thing those runs show is what was achieved on a day . it is not scientific testing

I struggle to imagine a Castle going over Ais Gill at 50mph with 25 on as 70005 did . a Scot might well do it tho'. …….?


if WAS had not got the Scot chassis to play with , he may well have built the Compound Castle that Collett didn't like . now that could have been summat .
If the LMS had continued to 1951 we could well have got a fleet of Ivatts instead of Brits. although if Riddles was in charge ...who can tell ?. 30 sorted 71000 class?, probably not. a 3 cyl Caprotti Duchess maybe ?

 

Postupalsky based his data on cylinder volumes of 200 liters. If I am right a single cylinder of the King can contain 380 liters. I have severe doubts whether
Postupalsky is still applicable. In the publications of Cox the 4-cylinder King is so close in steam consumption to the BR 2-cylinder standards which were
20 years younger that the whole argument has little merit imho.
Kind regards
Jos

 

Considering that a Castle dates from 1923 (and is essentially an update/enlargement of a design from 1906) it would be rather surprising if a design from 1951 was not at least a little better.....

 

it was Class8Mikado's comparison - not mine

 

a further thought -- if Fowlers' Pacific had lived , Sir William could well have had them to rebuild instead of Royal Scots

 

GWR fourcylinder locomotives were not nicely balanced relative to rails and main bearings.

 

16 inch diameter and 26 inch stroke is not 380 litre.
British steam indicated consumptions are suspect but Kings have big valves relative to cylinders and that is good.
Britania valves were to small maybe and that can explain the enormeous difference between Standard class 7 and 8 pacifics.