LMS Black 5 5025

An austerity o-6-0ST has a nominal tractive effort of 23,870 lbs (almost as much as a Black 5). I probably wouldn't want one of those with 12 on over the Settle & Carlisle.

Andy

 

Or an 08 shunter is similar in TE to an A4, but probably about 1/6 of the sustained power output!

Tom

 

For high speed, you need power. So something in the boiler dimensions is a good starting point - for example, your ability to generate power is fundamentally limited by how much coal you can burn, and that in turn is related to grate area. Whether your cylinders can use all the steam you generate is another question, but if the boiler can't produce steam in the first place, you can have the biggest cylinders in the world to no avail. (Equally, if you put a Big Boy boiler on a Midland 2P, you can't use all the steam you have). So you need to consider both sides of the equation: the boiler fundamentally limits how much power you could produce, if the cylinders can efficiently use all the steam, being produced.

Tom

 

Actual (measured) Tractive Effort, stating also the speed at which it was delivered. T.E. declines exponentially with speed, which is why Nominal T.E. is valueless at all but zero mph.

Tom beat me to it regarding power output.

 

You can't make the comparison like that because your are not taking into account the driving wheel size. If you make the driving wheels small for a goods loco, it increases the pulling power but at the expense of maximum speed. If you make the driving wheels bigger it reduces the power but means it can run at higher express speeds. It is why goods locos have smaller driving wheels and express passenger big wheels, with a mixed traffic loco like a V2 or Black 5 something in between.

So the Jubilee is effectively much more powerful because it has bigger wheels 6'9" verses 6' than the Black 5 so can in theory run at higher speeds more easily. If they both had say 6 foot wheels then a more direct comparison could be made, but they are clearly designed for different roles hence the different wheel diameters.

 

Theoretically having grunt and the ability to apply said grunt in practise are two very different kettles of fish. Leaving aside known truly outstanding designs, compare Drummond's sorry F13s with the (TE-wise) broadly comparable Highland/Caley 'River'/938 class, or the less powerful Holden (Russell) GER S69 (LNE B12/1) with the 2nd (futile) attempt at turning Mr Macintosh's less than sparkling "Cardeans" into something useful.

Neither does TE take account of real world issues, such as how much fuel is needed to produce that grunt, as (the then) Mr Gresley learned from observation of Mr Chrchward's, sorry, Mr Collett's locomotive No.4079.

If anyone's twigged my fondness for a certain HR 4-6-0 design over several posts, have a gold star, you'd be right.

 

It is somehow the other way round.
A two cylindered non- USA locomotive gets unpleasant and difficult to fire at 5 revolutions per second.
A threecylinder locomotive can still be pleasant at seven revolutions per second and much kinder to track.
A railway with a satisfactory six feet driver,- two cylinder locomotive,that needs something faster can either make a six feet nine monster like King Arthur or a three cylinder 19 inch goods with five feet drivers.
A six feet driver set is 5 tons unsprung mass, and a six feet nine aroun 6.5 tons and a lot of hammerblow being two cylindered.
A five feet driver set with one crank is 3.5 tons unsprung and no hammerblow.
The civil engineers did not know what was important before bridge stress commision report 1927

 

I accept that loco designs can be a bit hit or miss, even with a great designer like Stanier. The only one of his which was a bit of a dud was the 2-6-2 tank. The others turned out to be excellent, and his final design, the Duchesses, were THE best loco ever built (imo!)

 

Duchesses used around 10% more steam for same work as a BR class 7 and 14% more than a class 8.

 

But they could also make that steam. They had the highest steam rate of any engine in Britain, so high it couldn't be measured as the boiler produced more steam than the wheels could supply power to the rails without slipping, but estimated at 42,000lb/hr.

 

So, was the 10% difference between the Coronation and the Britannia due to there being 2 extra cylinders? The boilers of the Brits were derived from that of the Coronation.

Richard.

 

They also had the highest ever power output, Duchess of Abercorn, 6234.

 

Cox locomotive panorama vol2 Steam in retrospect:

MaxEvap --- IHP -- Coal rate ---Mass--- engine

31410 ----- 2200 --- 5066 --- 96--- BR class7
36000 --- 2550--- 6000--- 107-- Duchess
31000---- 1990---5670---95--V2

 

Cylinder size matters and design of BR clas 7 was 20 years after Chapelon
Duchess ca10.

 

Cox tends to be a bit on the unreliable side.

From BR Report R13, July 1958 from the tests of 6225, as quoted by John Powell in 'Stanier Pacifics at Work' (1986) Ian Allan, Shepperton ISBN 0 7110 1534 1:

'Steaming rates, using the live steam injector, range from 14,640 up to 41,5001b/hr on the test plant and from 15,000 to 40,0001b/hr on the line, the upper limits being set by the liability to slipping, but also, on the line, by the limited water capacity of the tender, which was designed for ... a route exceptionally well equipped with water troughs, and by the difficulty of handling bagged coal at a sufficient rate in the confined space of a coal bunker'.

and

'. . . an actual steaming rate of 36,000lb/hr is very close to the limit with Blidworth coal. For the South Kirkby coal the limit is less clear: it is certainly appreciably above the maximum rate at which a test was completed without being prematurely ended by slipping, namely 41,500lb/hr. . .'

 

If we were doing the ridiculous dick measuring contest that is tractive effort, the Gresley W1 was the most powerful express passenger locomotive in the British Isles in its rebuilt form. 41,437lb versus the Duchess at 40,000lb.

Had it ever been comparatively tested, including its ability to raise steam, it probably would have come out not far off the Duchess. We will never know though and that's kind of the fruitlessness of the discussion around Top Trumps statistics in railways.

Ultimately the railways concerned only cared about whether the locomotives did more than enough work for the railway, at minimal cost. So the comparison of Duchess to A4, just as an example, is the wrong one: ultimately everything else has to concede to the brilliance of the Peppercorn A1 and the rebuilt Merchant Navies.

 

So where does the 3 cylinder 71000 sit in these comparisons...in its restored form!

 

We somehow left the normal track.
36000 or 40000 lbs steam needs two firemen working flat out.
A more interesting comparison is I think at 3000 lbs/h blidworth coal from a unionized fireman.
Class 7 makes 1240 Drawbar horsepower at 35mph,
Duchess is 1290/35
Class 5 is 1200/37
and the best:
Class 9 makes 1360/30.
A 4-8-0 based on 9 f boiler and two Duke cylinders would have beaten everything.
Idle losses will be highest for Duchess.
Big grate and boiler outher surface.

 

If you shovel the same coal at the same rate into different fireboxes, it should hardly be surprising that by and large you get the same power output.

That doesn't mean a Black 5 is the equivalent of a Duchess though, since it overlooks two crucial factors. The first is that on a loco with a large grate area, it can work for longer at the same rate before degradation of the fire (and associated power loss) becomes significant. Therefore such a loco can work longer duties between needing to go on shed for fire cleaning. The second point is that such a loco can - for short periods, work at a maximum power output that is far in advance of what is sustainable at a firing rate of 3,000lbs/hr.

Tom

 

These posts saying "why bother with the Jubilee, the Black 5 was nearly as powerful and simpler" are missing the point that the Jubilee was the earlier design...
The Jubilee was just the Stanier version of the Patriot - a type which the LMS had found to be extremely useful and wanted lots more of!
That's why they built them: they did the work they wanted done...
The introduction of the Black 5 was a masterstroke by Stanier, filling a niche the LMS had been missing since its formation. Of course Stanier had the Hall as inspiration.
I love a Jubilee as much as anyone, but the Black 5 is, all in all, the superlative British steam locomotive.
If you were a railway operator of the period, and could only have one mainline British steam locomotive (silly question I know but bear with me) you'd pick a Five.

Sent from my Pixel 3a using Tapatalk