Imaginary Locomotives

[melmerby]

3 hours ago, The Johnster said:

It very probably was, and exceeded.  Had City of Truro achieved whatever it was that it actually, it did without an inspector on the footplate and a railway journalist with a stopwatch, would anyone have taken any notice of the Postal Inspector's timings?  And this was, and still is, disputed because it wan't official.  A timing of 140mph (!) based on signalbox passing times and timed on the footplate by some people who would not be described as amateurs including Collett and IIRC Stanier, was made for 2904 Lady of Lyon on a running in turn on the Badminton cut-off 2 years later, but the circumstances were such that those involved did not particularly want to draw attention to themselves and had in fact very nearly got themselves all killed.  It was apparently done for a bet that a new loco could achieve more than 100mph running light.  The actual speed is not known, but they were going very fast indeed and had trouble pulling up for the junction at Wooton Bassett.

 

A lot of very fast running went unrecorded by drivers who regarded it as all in a day's work.  Many steam loco did not have speedometers, and those that did would not have had them properly calibrated, especially as they took the speed from the wheel rotation which increases as the tyres wear without actually increasing the speed of the loco.  Speed was mostly estimated from passing times, and it was more important to maintain schedule than worry about how fast you were going, and average speeds were what were referred to rather than temporary peaks at the bottom of banks

"A lot of very fast running went unrecorded by drivers who regarded it as all in a day's work."

 

As most trains weren't timed with much in the way of more than just moderately fast running, the need or ability to do wondrous things must have been few and far between.

One of the problems with high speed running, more especially on much of the LMR was the track generally wasn't suitable with numerous bends, junctions, restrictions etc. making really high speed practically impossible, if not downright dangerous.

 

Look at the what happened when the LMS tried a high speed run (112+mph) with a Coronation, it ran out of track whilst still accelerating and ended up on emergency stop to get into Crewe station without a pile up, running through pointwork at way over speed with a resultant mess in the dining car. That, apart from all the smashed crockery, it came out unscathed is testament to the surefootedness of the ensemble.

Also to be noted that the whole lot then returned to London with speeds over 100mph without any damage to the loco (Unlike Mallard's feat)

 

[melmerby]

14 minutes ago, rodent279 said:

I suppose the County 4-6-0 was intended to provide the boiler power of a Castle with the punch and hill climbing abilities of the Saints/Halls.

It would also have been cheaper with only 2 cylinders but interestingly more Castles were built afterwards!

[The Johnster]

40 minutes ago, melmerby said:

It would also have been cheaper with only 2 cylinders but interestingly more Castles were built afterwards!

The Hawksworth Counties were rated at 6MT by BR.  They were the result of Hawksworth’s exploiting the availability of toolings at Swindon from the wartime build of Stanier 8Fs there, a plate frame 4-6-0 with King wheels and a domeless version of the 8F’s boiler, completed with Swindon cylinders and motion.  They did good work on the North to West main line and in Cornwall where a loco that could slog up a hill at a decent pace with a heavy train was very useful.  

 

They never really realised their potential as mixed traffic engines, though; big twin cylinders and the high pressure led to a surging motion under load that was not ideal with loose coupled goods traffic.  They are the equivalent of the BR Clan or the Gresley V2. 

 

Castles continued to be built to replace withdrawn Saints and Stars for general fast passenger work, as these were kinder to the track and, with lower boiler pressure, needed less boiler maintenance, giving better availability.  

[Northmoor]

1 hour ago, melmerby said:

Also to be noted that the whole lot then returned to London with speeds over 100mph without any damage to the loco (Unlike Mallard's feat)

 

Always used as an example of the perceived superiority of one company over the other, but simple physics says the reciprocating forces on Mallard's run were 25% higher.

[melmoth]

16 minutes ago, The Johnster said:

...a plate frame 4-6-0 with King wheels...

 

Not quite right, the Kings had 6' 6" driving wheels and the Counties had 6' 3" ones 

[rodent279]

2 hours ago, The Johnster said:

The Hawksworth Counties were rated at 6MT by BR.  They were the result of Hawksworth’s exploiting the availability of toolings at Swindon from the wartime build of Stanier 8Fs there, a plate frame 4-6-0 with King wheels and a domeless version of the 8F’s boiler, completed with Swindon cylinders and motion.  They did good work on the North to West main line and in Cornwall where a loco that could slog up a hill at a decent pace with a heavy train was very useful.  

 

They never really realised their potential as mixed traffic engines, though; big twin cylinders and the high pressure led to a surging motion under load that was not ideal with loose coupled goods traffic.  They are the equivalent of the BR Clan or the Gresley V2. 

 

Castles continued to be built to replace withdrawn Saints and Stars for general fast passenger work, as these were kinder to the track and, with lower boiler pressure, needed less boiler maintenance, giving better availability.  

I'm looking forward to seeing the rebuilt/replica County on the mainline. Of all GWR classes, I think I like the Counties most. Hopefully it'll live up to the performance of its predecessors after they were modified with double chimneys.

[melmerby]

2 hours ago, Northmoor said:

Always used as an example of the perceived superiority of one company over the other, but simple physics says the reciprocating forces on Mallard's run were 25% higher.

But the Coronation sustained it's forces for much, much, longer hence the Coronation was superior................

Seriously though, the middle engine on Gresley's locos was always a weak link and had far more hot bearings than Coronations in everyday traffic where they would be running at similar speeds.

Peppercorn seemed to have cracked it as his 6' 8" pacific rarely had a problem.

 

[Corbs]

I have a question; why did compounding never really take off in Britain?

[PhilJ W]

3 minutes ago, Corbs said:

I have a question; why did compounding never really take off in Britain?

Good question, many steam road vehicles were compounded. Possibly because the restricted British loading gauge limited the size of the lp cylinders?

[Corbs]

On the outside, maybe, but LP inside cylinders were not unknown. I know I keep banging on about Chapelon but I've been reading a bit about him recently because he's pretty cool. The 231 Nord's specs:

HP

15.52 in x 25.59 in (420 x 650 mm) (outside)

LP

25.19 in x 25.59 in (640 x 650 mm) (inside)

 

LP cylinder is 152.38% the size of the HP cylinder (? - my maths is sketchy at best)

 

For comparison a 9F with two outside cylinders:

20 in × 28 in (508 mm × 711 mm)

 

LNER P2 (3 cylinders)

21 in × 26 in (530 mm × 660 mm)

 

LMS Princess Coronation (4 cylinders)

16.5 in × 28 in (419 mm × 711 mm)

 

Was it a question of maintenance burden, or ease of construction, maybe?

[rodent279]

23 minutes ago, Corbs said:

I have a question; why did compounding never really take off in Britain?

I think it was reticence at the increased cost and complexity, and British footplate men were not (allegedly) trained as well as their Continental counterparts-they picked it up on the job, rather than being trained to understand the complexities.

In short, I think over here we preferred the simplicity of single stage expansion.

[brack]

55 minutes ago, Corbs said:

I have a question; why did compounding never really take off in Britain?

Compounding gives better thermal and thus fuel efficiency, but requires better training of drivers, usually higher boiler pressures and correspondingly higher maintenance costs. The NER did comparisons which suggested the advantages of compounding was reduced on shorter runs. Given that we had loads of decent quality coal available in the uk and distances between stops were generally short, the extra maintenance costs weren't thought to be worth it.

[RLBH]

8 hours ago, rodent279 said:

I think it was reticence at the increased cost and complexity, and British footplate men were not (allegedly) trained as well as their Continental counterparts-they picked it up on the job, rather than being trained to understand the complexities.

In short, I think over here we preferred the simplicity of single stage expansion.

Worth noting that the North American railways generally reached a similar conclusion to the British ones - when first tried, compounding increased efficiency but was more complex. Superheating offered similar gains in efficiency without the increase in complexity. Compounds did continue to be built into the late 1940s for some really big, slow mineral locomotives to haul immense trains, but was generally felt not to be worthwhile.

[Niels]

8 hours ago, Corbs said:

On the outside, maybe, but LP inside cylinders were not unknown. I know I keep banging on about Chapelon but I've been reading a bit about him recently because he's pretty cool. The 231 Nord's specs:

HP

15.52 in x 25.59 in (420 x 650 mm) (outside)

LP

25.19 in x 25.59 in (640 x 650 mm) (inside)

 

LP cylinder is 152.38% the size of the HP cylinder (? - my maths is sketchy at best)

 

For comparison a 9F with two outside cylinders:

20 in × 28 in (508 mm × 711 mm)

 

LNER P2 (3 cylinders)

21 in × 26 in (530 mm × 660 mm)

 

LMS Princess Coronation (4 cylinders)

16.5 in × 28 in (419 mm × 711 mm)

 

Was it a question of maintenance burden, or ease of construction, maybe?

 

Mr Cox explains it in World Steam 20 century.

If Low pressure cylinders of a four cylinder compound has to be inside for loading gauge consideration,crankshaft design is difficult.

This  left only three or two cylinder compounds as realistic candidates in UK after WW1.

Three cylinder compounds died of neglect.

A front drive three cylinder  compound Royal Scott  size was proposed by Fowler.

There was more glamour in making streamlined pacifics .

Streamlining a 55 mph train like Elizabethanian sounds expensive.

The two cylinder compound was never considered but is interesting.

A two cylinder compound has same cylinder volume in high presure cylinder as one in the corresponding simple and the low pressure cylinder can be 2.25 times bigger in volume.

Lets try it on an alternative A2/2 rebuild of  LNER P2 .

The A2/2 was wildly overcylindered and slipping prone and if rebuilt with two cylinders they could be sized from lets say a B1.

Dog wants airing.

Se You later

 

[melmerby]

9 hours ago, Corbs said:

I have a question; why did compounding never really take off in Britain?

Ships frequently had triple expansion engines but then again they would be running at constant speed for long periods.

[Clive Mortimore]

14 minutes ago, Niels said:

 

Mr Cox explains it in World Steam 20 century.

If Low pressure cylinders of a four cylinder compound has to be inside for loading gauge consideration,crankshaft design is difficult.

This  left only three or two cylinder compounds as realistic candidates in UK after WW1.

Three cylinder compounds died of neglect.

A front drive three cylinder  compound Royal Scott  size was proposed by Fowler.

There was more glamour in making streamlined pacifics .

Streamlining a 55 mph train like Elizabethanian sounds expensive.

The two cylinder compound was never considered but is interesting.

A two cylinder compound has same cylinder volume in high presure cylinder as one in the corresponding simple and the low pressure cylinder can be 2.25 times bigger in volume.

Lets try it on an alternative A2/2 rebuild of  LNER P2 .

The A2/2 was wildly overcylindered and slipping prone and if rebuilt with two cylinders they could be sized from lets say a B1.

Dog wants airing.

Se You later

 

Is that why the LMS built 195 3 cylinder compounds after WW1?

[RLBH]

36 minutes ago, melmerby said:

Ships frequently had triple expansion engines but then again they would be running at constant speed for long periods.

And plenty of space for large low-pressure cylinders! The Liberty ships (to take a convenient example) had LP cylinders of 70" bore x 48" stroke; even the HP cylinder was 24.5" bore. While the boiler ran at 220psi, marine engines can also easily use a condenser - which isn't practical for railway applications - which gained another 12.75psi at the bottom end.

 

Having lots of space, practically no weight constraint, and an ample supply of cooling water makes the engine design problem a very different one.

 

In hopes of relating this to railways, the railway steamers would certainly have been fitted with machinery of such a design! I know that Swindon turned the shafts for the GWR's steamers, presumably the railway works must have done a lot of the steam engineering for their own ships as well.

Edited July 9, 2019 by RLBH

[Niels]

Lets play the game of rebuilding P2 into a two cylinder simple Pacific for wartime austerity.

B1 has 51 tons adhesive and 27000 lbsf tractive effort.

The P2Be will have 66 tons and therefore can use  a cylinder volume  1,3 times greater and still  be  as surefooted as the B1.

Cylinder  can either be placed as Thompson did ala de Glenh and driving second driver or be put between the bogie wheels like Claughtons,B16,Myriads of 4-4-0s etc.

On the  de Glehn scheme it will just be possible to have cylinder diameters like the P2 to go where P2 was supposed to rule.

That is 21 inch diameter and therefore needs 30 inch stroke.

Going the best Raven way will allow ca 22.5 inch  cylinder diameter as it can be placed closer to center.26 inch stroke.

My favourite is the Raven scheme with 21 inch and three driving wheels borrowed from Halls that is 30 inch stroke.

A two cylinder compound can be made by pairing one of these cylinders with a 2.5 times as big a lowpressure one that is 34 inch dia times 26 inch stroke so we can keep the crankshaft.

Between the frames has room for this monster cylinder like had  did for mr Webb.

Mr Corbs has already photographed one side of this animal.

 

de Corbs compound high pressure view

Edited July 14, 2019 by Niels

[Niels]

On 09/07/2019 at 10:18, Clive Mortimore said:

Is that why the LMS built 195 3 cylinder compounds after WW1?

 

it was the best they had and a mr Diamond said it was rather lousy in efficiency.

It was not so important this efficiency thing.

Edited July 10, 2019 by Niels

[Corbs]

One of Ivatt's Caprotti 8Fs with double chimney.

 

Edited July 10, 2019 by Corbs

[34theletterbetweenB&D]

22 hours ago, The Johnster said:

... A timing of 140mph (!) based on signalbox passing times and timed on the footplate by some people who would not be described as amateurs including Collett and IIRC Stanier, was made for 2904 Lady of Lyon on a running in turn on the Badminton cut-off 2 years later...

I shall at some point present my thesis that the claimed maximum speeds achieved by Swindon locomotives increases proportional to the passage of time, so that by 2100 at least two will have managed 200mph, and of the tender classes all but the 28xx will have 'done the ton'.

 

14 hours ago, melmerby said:

But the Coronation sustained it's forces for much, much, longer hence the Coronation was superior................

Seriously though, the middle engine on Gresley's locos was always a weak link and had far more hot bearings than Coronations in everyday traffic where they would be running at similar speeds.

Peppercorn seemed to have cracked it as his 6' 8" pacific rarely had a problem.

 

It wasn't the axle bearings, but a detail design fault on the middle big end that led to the overheating, (and another factor). The inside big end had an 'IC engine' rear strap with insufficient cross section; the fault of course being that an IC engine is single acting, whereas the steam locomotive engine is double acting. So the strap has to take the same power  load as the front of the bearing. This only showed up when working hard, the strap would deform and pinch the bearing and failure here we come. D.W 'Bill' Harvey eventually got to look at it and diagnosed the trouble and proposed the solution of putting a deep rib on the rear of the strap to increase its stiffness. This was implemented reasonably adequately - though not completely to DWH's liking - and the problem 'went away'.

 

The other factor was the overtravel of the centre valve which increased proportional to speed due to inertia and consequent deflections of the conjugated gear beams that derived the drive to the centre valve. What this lead to was the centre cylinder doing more work than the outside cylinders, and by the time the A4 was going 150mph (see, we can do it too when in irresponsible mode) the centre cylinder was doing as much work as the two outside cylinders combined. One solution, fit independent valve gear to all cylinders, alternatively find a drive method not dependent on oscillating rods flailing about. Sadly the poppet valve rotary drive systems came to maturity too late for Gresley. May also have been partly what subsequently led Bulleid to experiment with bike chain drive...

 

13 hours ago, Corbs said:

I have a question; why did compounding never really take off in Britain?

Good coal readily available, in addition to the more cheaply achieved gains of superheating, better steam circuit, valve design and exhaust systems, and relatively few long runs where the compound shows to advantage. (I also believe that rather than piston compound, the better way is turbine which eliminates both heat cycling losses and the energy consumed in oscillating large chunks of metal with very significant knock on benefits for frame life. Might have been interesting if all the experimental spend used on high pressure compounds in the UK had gone on improving turbine drive.)

 

It was the French school that made the most of compounding where high sustained power output was required: poor indigenous coal was an expensive problem in France. Though behold the wondrous Y6b of the Norfolk and Western, with its 4' LP cylinders up front. This despite the fact that it was designed for coal turns from a coal field, presumably the reduced coal consumption was worth it in some way.  From what relatively little I have read on the subject I gather that the power stoking machinery essential on the 'superpower' designs was maintenance intensive and thus expensive to keep operational: and the N&W was possibly the most scientific in the USA in terms of rational engineering management of its traction assets.

[The Johnster]

The 'Little Somerford incident' is a fairly well known and verified story, though the actual speed 'achieved' is moot.  Unfortunately for it's credibility, it is mentioned by Tuplin...

[RLBH]

 

28 minutes ago, 34theletterbetweenB&D said:

It was the French school that made the most of compounding where high sustained power output was required: poor indigenous coal was an expensive problem in France. Though behold the wondrous Y6b of the Norfolk and Western, with its 4' LP cylinders up front. This despite the fact that it was designed for coal turns from a coal field, presumably the reduced coal consumption was worth it in some way.  From what relatively little I have read on the subject I gather that the power stoking machinery essential on the 'superpower' designs was maintenance intensive and thus expensive to keep operational: and the N&W was possibly the most scientific in the USA in terms of rational engineering management of its traction assets.

The N&W was, in some ways, a very 'British' railway for America. It built its' own steam locomotives in its' own works, and was perhaps wedded too long to improving them rather than dieselising because of institutional inertia and a ready supply of cheap coal.

 

Though the Y6b merely had 3'3" LP cylinders. It was the Virginian's Class AE 2-10-10-2 that had 4' LP cylinders - although the Virginian was later acquired by the N&W.

 

As far as speed records go, enthusiasts of American steam in general, and the Pennsylvania Railroad (which reminds me of the GWR in some respects) in particular, claim that the T-1 duplex could do 140mph routinely. Skeptics claim that its' wheels were perfectly capable of slipping at 140mph whilst the rest of the train went nowhere. In order to resolve the dispute, they are attempting to build a new one, although quite where they're going to test it remains to be seen.

Edited July 9, 2019 by RLBH

[RedGemAlchemist]

24 minutes ago, The Johnster said:

The 'Little Somerford incident' is a fairly well known and verified story

Which I was totally unaware of. 

[34theletterbetweenB&D]

 

26 minutes ago, RLBH said:

...the Y6b merely had 3'3" LP cylinders. It was the Virginian's Class AE 2-10-10-2 that had 4' LP cylinders - although the Virginian was later acquired by the N&W...

Oh dear, brain fart there. I never had a memory problem until, I forget when exactly...

 

28 minutes ago, RLBH said:

... as speed records go, enthusiasts of American steam in general, and the Pennsylvania Railroad (which reminds me of the GWR in some respects) in particular, claim that the T-1 duplex could do 140mph routinely. Skeptics claim that its' wheels were perfectly capable of slipping at 140mph...

I am in no doubt at all, that in actual service the Milwaukee Road F7 4-6-4 for the Hiawatha services was the fastest steam loco. This because it regularly achieved a scheduled 81 mph end to end speed over a 73 mile route stage. To achieve this there is no avoiding sustained speeds well over the 100mph mark to allow sufficient time for acceleration and braking.

 

(And yet: the most fantastic part of this operation was the provision of an over track coaling station near the mid-point of the 400 mile Hiawatha route at New Lisbon. The fact that a 22 ton bunker had to be replenished after 200 miles gives a good idea of the power output these locos were required to deliver.)