Imaginary Locomotives

[pH]

On 28/07/2021 at 11:31, ScottishRailFanatic said:

“Night of the Living Bread”

A joke Q1 0-8-0T, just to make it look even more like a bread loaf on wheels!

If anyone can find a use for it you’ll get a proverbial medal

The actual Q1 0-8-0T did bear a vague resemblance:

 

https://thetransportlibrary.co.uk/index.php?route=product/product&product_id=91721

 

 

[Gibbo675]

6 hours ago, The Johnster said:

 This meant that there was in fact very little room for a chimney any taller than provided.

 

The double chimney King versus rebuilt Royal Scot argument is a long standing one, and probably too highly partisan for any useful conclusions to be drawn from it.  Both locos were very powerful for 4-6-0s, but the Scots should have had the edge for speed, because of the larger diameter driving wheels.  The Scots had a reputation for rough riding which seems to have been to do with the load transferred from the rear of the locomotive by the tender.  Both locos suffered stress failures in the frames due to power being increased beyond what the frames were designed for.  Neither class lasted to the end of steam, which suggests that there were deep rooted problems with both of them.

 

Hi Johnster,

 

No. no . no. no. no !!!!!!!!

 

It is all to do with the capacity of the steam circuit to both fill and empty the cylinders when the time period for doing so is shortened due to road speed, period.

 

Try filling a tender tank with a four inch fire hose and see how long it takes you compared with a six inch water main as fitted to water columns. It is all to do with flow rate.

 

Gibbo.

 

 

[Corbs]

Is that what Chapelon concentrated on in his rebuilds, increasing the diameter of pipework and the volume of steam chests?

[ScottishRailFanatic]

“Sir, I think Mr Bulleid has gone mad.”

”You say that as if he hadn’t lost his marbles beforehand. The bleeding thing doesn’t even have front buffers.”

Edited July 30, 2021 by ScottishRailFanatic

[ScottishRailFanatic]

“I fear no man. But that… thing…”

 

“It scares me.”

[Compound2632]

8 hours ago, The Johnster said:

The double chimney King versus rebuilt Royal Scot argument is a long standing one, and probably too highly partisan for any useful conclusions to be drawn from it.  [...] Neither class lasted to the end of steam, which suggests that there were deep rooted problems with both of them.

 

But both were express passenger engines and therefore candidates for early replacement by diesels - surely that explains why they didn't last to the end, rather than any defect?

[Northmoor]

56 minutes ago, Compound2632 said:

 

But both were express passenger engines and therefore candidates for early replacement by diesels - surely that explains why they didn't last to the end, rather than any defect?

There is no escaping the availability benefit of a diesel loco compared to steam.  I recently read of some loco nameplates for a GWR Castle and a "Western" which referred to their histories.  The diesel was withdrawn at 12 years old having averaged roughly 100,000 miles/year.  The Castle was withdrawn at roughly 20 years old, but had averaged just under 50,000 miles/year.

 

Consider also that big steam locos working at high speeds (and hence high wheel RPM) will wear themselves out quickly in a way diesels won't.  The only reciprocating forces in diesel locos are in the engine itself, which when coasting or working on part load, is reducing those forces and the number of load cycles.  Much of the reciprocating forces in a steam loco at speed remain even when the driver shuts the regulator, while the cycles/second remain the same.   The impression I get is that freight steam locos, even with smaller wheels, were generally operating much slower so the wheel RPM was also slower (wheels typically 75% of the diameter but only operating up to 50% of the speed).  They also probably spent a higher proportion of their operating day standing still, stuck in a loop waiting for a path (which an express passenger engine would not).  Therefore the frames of freight locos were much less likely to reach their fatigue life, which is a function of the forces and number of load cycles.

 

[rodent279]

13 hours ago, Gibbo675 said:

Hi Stephen,

 

The Scots had three cylinders of a shorter stroke than the Kings which allow for more power at elevated speeds in the same way that Gresley and Bullied Pacifics were both fast and powerful, this allows for a different torque characteristic and better cylinder filling at speed. Another factor that is not always appreciated is that the steam circuits of the Scots, and the Gresley and Bullied pacifics is considerably better designed in that the steam pipes are not only of much larger diameter but also much straighter giving a greater manifold effect at speed and reduced boundary layer friction, also better exhaust passage design, both again assisting the cylinder filling and exhaust back pressures at speed. Bullied went one step further with the manifold effect within the steam chest by way of outside admission rather than inside admission, this also assisted the exhaust by better mixing the exhaust steam further from the blast pipe tip thus reducing the pulse effect that can lift a fire bed under conditions of high speed and power.

 

Stroke to wheel diameter ratios:

• Scots 26:81 = .32 
• A3/A4 26:80 = .325
• MN/WC/BB 24:74 = .324
• King 28:78 = .358
• Star 26:80.5 = .323

It would seem that the King class was a somewhat backward step from the Star class of twenty one years earlier.

 

That a King class can start a very heavy train is not disputed, however hauling that train at high speed is beyond them compared to a Scot as most of the power they produce works against itself by way of the arrangement of the steam circuit. The LMS Princess Royal class were just as powerful and just a sluggish as the Kings for the very same reason.

 

Gibbo.

 

Hi John,

 

As described above, it is what you can't see from the outside that makes all the difference. The full arrangement of the chimney extends down into the smoke box to about the level of the top hinge door strap. The full height of the chimney would have been about 36" as measured from the top of what is seen atop the smoke box.

 

Gibbo.

I guess what that highlights is that the King was designed with the objective of getting a 4 as the first digit of the tractive effort figure.

Would I be right in inferring that a shorter stroke and/or larger wheel diameter might have made the King a freer running machine, albeit with a lower nominal tractive effort?

[JimC]

1 hour ago, rodent279 said:

a freer running machine, albeit with a lower nominal tractive effort?

But the Castle was already in existence as a freer running machine with a lower nominal tractive effort. Surely the extra brute power was the business need?

 

Edited July 30, 2021 by JimC

[AlfaZagato]

1 hour ago, JimC said:

But the Castle was already in existence as a freer running machine with a lower nominal tractive effort. Surely the extra brute power was the business need?

 

Not entirely a need, but a desire.   The top GWR brass were unhappy at not having the 'most powerful in the UK' after, I believe, the introduction of the Lord Nelson.

[The Johnster]

5 hours ago, Compound2632 said:

 

But both were express passenger engines and therefore candidates for early replacement by diesels - surely that explains why they didn't last to the end, rather than any defect?

The Kings' frames were destroyed by the power output needed to run the 2 hour Paddington-Snow Hill trains, one can regard them as sacrificed to maintain the traffic while the Euston-New St. route was compromised by electrification work.  BR got away with it, just, the 25kv work being completed to New St. and the Westerns were coming into service just as the Kings were dropping like flies.  The class was more or less wiped out over 1962/3.

 

I would contend that there was still work for rebuilt Scots after 1965 on the LMR, but it was actually done by Britannias, and Jubilees on the S & C.  They were withdrawn early because of frame stress issues.  As to the 7P versu 8P, my view is that a rebuilt Scot could do any work that a King or Lord Nelson could, and equally effectively. 

 

We had a guard at Canton in the 70s who had been a fireman at Patricroft; he reckoned a rebuilt Scot would beat anything on flanged wheels anywhere anytime, and that they were easier to fire than a King, if you could keep your feet; he considered them frankly dangerous at 90 or over.  The Kings were at Canton for such a short period that few of our native drivers who had fired hem considered themselves experienced enough to counter argue, not that that stopped the partisans.  The Kings were undoubtedly better riders and arguably better sloggers on the banks, due to smaller driving wheels and, I am told, the setting of the Stephenson valve gear.  Bad riding is a bad trait in a loco; it is not just a matter of crew comfort and fatigue, but of loco maintenance as bits are continually shaken loose or cracked by the unabsorbed shocks, and wear damage to the per. way.  This is a shame, as the rebuilt Scots were certainly capable of very fast running.

 

To summarise, I would give the overall honours to the Scots.  Kings were too restricted by route availability to be the general purpose top link locomotive they were originally intended to be, though the GW's publicity people made a lot of them.  The Scots, equally beloved of the publicity people on the LMS, were not a noted success initially, but were built in much larger numbers and were used across the main lines of that railway.  Ivatt's rebuild transformed them into very fast and powerful engines, easily capable of all but the pacific turns and much more widely distributed.  Backed up by the rebuilt Patriots, they gave the LMR a solid base of express passenger locos throughout the 50s and into the early 60s; I would back either loco against a class 40 diesel any day.

 

 

Edited July 30, 2021 by The Johnster

[rodent279]

8 minutes ago, AlfaZagato said:

Not entirely a need, but a desire.   The top GWR brass were unhappy at not having the 'most powerful in the UK' after, I believe, the introduction of the Lord Nelson.

Agree. The motivation for building the Kings was partly a need for a locomotive that could manage heavier trains unassisted over the south Devon banks, and partly scoring "prestige/publicity" points in having the locomotive with the highest TE on paper. Felix Pole requested Collet to get the TE figure over the 40,000lbf mark, and I believe this is where the non-standard 6'6" wheel diameter & 28" stroke came from.

What I was getting at is would a King with standard wheels & stroke be a "better" engine, in that it would still have had the same cyl dia. and boiler, but would not have consumed steam at such a high rate at speed, and would not have had such a high flow rate in the internal pipes?

The bigger boiler would give it the capacity to slog up hills without running short of steam, the larger wheels and shorter stroke would make it a freer running machine at speed.

Edited July 30, 2021 by rodent279

[JimC]

4 minutes ago, The Johnster said:

and, I am told, the setting of the Stephenson valve gear.  

It was Walschaerts, but the implementation, according to the late Don Ashton, who was something of an expert on these things, was far better than on any LMS locomotive. 

[JimC]

11 minutes ago, rodent279 said:

Felix Pole requested Collet to get the TE figure over the 40,000lbf mark, and I believe this is where the non-standard 6'6" whell diameter & 28" stroke came from.

The smaller wheel diameter was established early on in the design AIUI. It was something of a feature that driving wheels on express locomotives became smaller over the 20thC, and it can be argued the King started a trend that was followed by the Merchants and Britannias. The technical GWR sources state that the over 40K mark was achieved by taking the early Kings out to what was in IC terms first rebore on the cylinders, and there are hints that by no means all of them left the works with the cylinders taken out the extra quarter of an inch. 

Edited July 30, 2021 by JimC

[Miss Prism]

Was the 'Bristolian' the only London-Bristol non-stop?

[Compound2632]

23 minutes ago, The Johnster said:

The Scots, equally beloved of the publicity people on the LMS, were not a noted success initially, but were built in much larger numbers and were used across the main lines of that railway.  

 

Operationally, the Scots were a resounding success in 1927 that they were capable of handling the top WCML expresses that were really beyond the capabilities of the (more numerous) Hughes and Bowen-Cooke 4-cylinder 4-6-0s. They were and effective solution to the WCML express locomotive crisis of the preceding decade and held the fort until the arrival of the Pacifics. Of course from a design point of view, they did have defects.

 

As far as I'm aware, none were transferred to the Midland Division until BR days, and after rebuilding. But perhaps you're not counting the Midland Division routes among the LMS's main lines?

Edited July 30, 2021 by Compound2632

[Compound2632]

21 minutes ago, rodent279 said:

What I was getting at is would a King with standard wheels & stroke be a "better" engine, in that it would still have had the same cyl dia. and boiler, but would not have consumed steam at such a high rate at speed, and would not have had such a high flow rate in the internal pipes?

 

The Castles, as built, had boiler pressure of 225 psi, against the 250 psi of the Scots and Kings. Were they later fitted with higher pressure boilers? On paper, 250 psi would make an 11% increase in tractive effort - would that give a genuinely "Improved Castle"? As is well-known, the re-arrangement of the draughting under Cooke made a really significant difference, certainly in speediness - learning from the experience gained elsewhere.

[The Johnster]

The 6'6" driving wheels of the King, a departure from the Churchward standard range, was to accommodate the larger diameter boiler within the loading gauge, so that the centre line of it could be set an inch lower; every dimension was squeezed to the limit on the Kings.  Smaller driving wheels were used with big boilers following this as it was realised that the cylinder and motion lubricants could withstand the higher operating speeds, and appeared on the Bullied pacifics, Hawksworth Counties, Thompson pacifics, all intended for express passenger work at high speed.  The Bullieds and Thompsons used 6'2", a dimension shared with the Britannias and Standard 5MTs, but those latter two designs had a mixed traffic element to them and were not intended for top link express work; the Brits were used in this role nonetheless on the GE and the South Wales trains, and the 5MTs put in some remarkable express performances on the North Kent route. 

 

One must remember that some of those locos were designed at a time when there was a blanket 75mph speed restriction on all British railways, and heavy loading was common.  It is to their credit and that of those who designed them, yes, even Thompson, that they were able to put in some very fast running in the 50s and 60s.

[PenrithBeacon]

The usual interpretation of the 6'-6" wheels is that their use pushed the tractive effort up to 40,000 lbs

[The Johnster]

13 minutes ago, Compound2632 said:

 

Operationally, the Scots were a resounding success in 1927 that they were capable of handling the top WCML expresses that were really beyond the capabilities of the (more numerous) Hughes and Bowen-Cooke 4-cylinder 4-6-0s. They were and effective solution to the WCML express locomotive crisis of the preceding decade and held the fort until the arrival of the Pacifics. Of course from a design point of view, they did have defects.

 

As far as I'm aware, none were transferred to the Midland Division until BR days, and after rebuilding. But perhaps you're not counting the Midland Division routes among the LMS's main lines?

No, I wasn't trying to infer that the Midland was not a main line railway or regarded as anything other than a main line railway by the LMS, and did not realise that the use of Scots on it was a BR development.  But there is a question mark over the Scots' work on the WCML, in that the LMS apparently considered Castles would have been better and that apparently North British suggested something like a Lord Nelson, which was then hobbled by the LMS' insistence on certain standard ex-Midland features, or so goes the usual story.  In the event as you correctly point out the Scots and Patriots held the fort over Shap and Beattock until the pacifics appeared, and for a long time after that on everything except pacific work and timings, and once they were rebuilt by Ivatt it is doubtful that a better 4-6-0 could have been provided.  A Lord Nelson might have equalled it but a King would probably have been to heavy even if it didn't smash it's frame to peices in the effort.

[JimC]

1 hour ago, The Johnster said:

The 6'6" driving wheels of the King, a departure from the Churchward standard range, was to accommodate the larger diameter boiler within the loading gauge, so that the centre line of it could be set an inch lower;

You've said this before, but I have trouble believing it. Its not something I've come across in any of my reading, and there are two items of evidence against it. I would be very interested in a source. 

The first is that the boiler barrel diameters of the King are the same as those of the Bear, which did have 6'8.5 in wheels,
and the second is that, admittedly at a cost of horribly squashed boiler furniture, preserved Kings have been cut down to well below the GWR loading gauge.  

Its also interesting that the boiler pitch of the Kings is identical to that of the 47s, which again had the same barrel diameters as the Bear, but with 5'8 wheels presumably had no clearance problems.

 

[later]

The surviving weight diagrams for the 1920 proposals for Star and Saint fitted with Std 7 boilers (ie the 47xx boiler) show a pitch of 9'0", 0.75" higher than the King. On the one hand that suggests that the drawing office may have taken advantage of the smaller wheels to drop the boiler a tad, but on the other it suggests that a higher pitch could have been fitted within the gauge. OTOH one must also be aware of the corners of the box. I've attached an extract from a GWR King cross section that does suggest that although tight, the boiler could have gone up to 9'0" pitch. (Note that the original c/s was right side only, I mirrored it, hence the extra ejector, lamp bracket etc.)

 

Edited July 30, 2021 by JimC

[The Johnster]

6 minutes ago, PenrithBeacon said:

The usual interpretation of the 6'-6" wheels is that their use pushed the tractive effort up to 40,000 lbs

True, but a King could not be built to conform to the loading gauge height had Castle wheels been used; the smaller drivers did increase the T.E. as well of course, which the publicity guys were appreciative of.  I would contend that the Lord Nelson was the most successful of these big 1920s 4-6-0s, but that the Southern's work was not as glamourous as the image of a Scot slogging over Shap or Beattock, 'shovelling white steam over her shoulder', or of a King timing to Plymouth with a fully loaded Cornish Riviera after leaving Paddington 10 minutes late.

 

Non stop long distance fast work of this sort was less of a feature on the Southern; Exeter is not as far away from London as Plymouth, or Glasgow, and the 'Cunarder' pullmans were almost outer suburban work in comparison, so while good work was being done on the Southern by the King Arthurs and Lord Nelsons, few were paying much attention to it.  The contest between the ECML and WCML big pacifics and the glamour of the streamliners took the lion's share of the headlines over the next decade, along with the Castle hauled Cheltenham Flyer, the Fastest Train in the World...

 

The Kings really made very little impact either on their own railway or to the national scene, but might have the route availability issue been resolved.  As things were, Collet pushed the Castle idea perhpas a little beyond what it was suitable for, at least on the GW.  The Lord Nelsons represent IMHO what could have been; they could at least run on most of the Southerns's trunk routes, which is not really true of the Kings, though new routes were brought into their remit by BR(W).  The heavy Swansea-Paddington trains in particular could have benefitted from the extra grunt; they did from Cardiff, very briefly, in the early 60s.

 

 

.

[Compound2632]

5 minutes ago, The Johnster said:

But there is a question mark over the Scots' work on the WCML, in that the LMS apparently considered Castles would have been better and that apparently North British suggested something like a Lord Nelson, which was then hobbled by the LMS' insistence on certain standard ex-Midland features, or so goes the usual story.  

 

The "usual story" contains a lot of folklore. I thoroughly recommend D. Hunt, J. Jennison and R.J. Essery, LMS Locomotive Profiles No. 15 The ‘Royal Scots’ (Wild Swan, 2019) for a corrective to some of the more fantastical elements that have made their way into the tale. For instance:

• Anderson's remark that he would not mind having twenty Castles was made before design work started on the Scots, so one can hardly say that the Castles were within the LMS management generally though to have been a better option after the Scots had entered service.
• Although the NBL drawing office had access to a set of Nelson drawings, very little from these was used directly. The NBL drawing office did most of the design work, under the direction of Derby drawing office staff, and using elements derived from existing LMS drawings. There was certainly informal influence from the Nelson design, Fowler and Maunsell being personal friends, and Chalmers meeting with Holcroft and Clayton, which resulted in the Nelson drawings being sent to NBL.

Clayton was ex-Derby and Derby influence was clear in much of his work at Ashford, so one could argue that as the Nelsons and the Scots were both designed in the Derby tradition against similar operating requirements, any similarities are those of siblings rather then parent and offspring!

[Michael Edge]

The Lord Nelson drawings were requested by NBL for the Belpaire firebox, something they were relatively unfamiliar with.

[Compound2632]

24 minutes ago, Michael Edge said:

The Lord Nelson drawings were requested by NBL for the Belpaire firebox, something they were relatively unfamiliar with.

 

That doesn't quite square (so to speak) with Hunt et al., op. cit., so I'm curious as to the evidence for this. The boiler design was very much in the Derby tradition, being based on the boiler for the Lickey banker. Obviously the Derby LDO would have been able to supply NBL with the relevant drawings.

 

Anyway, here's an NBL-built Belpaire-boilered outside-cylindered 4-6-0 of 1905.

Edited July 30, 2021 by Compound2632