Imaginary Locomotives

[6990WitherslackHall]

14 hours ago, john new said:

 

Agree. Shame those across the pond see the USA one running (if that's the word) in the getting filthy, uncleaned, state late BR period locos got into; Hogwarts Railways would never tolerate that!

Did you see the state of the two A4s when they were repatriated from the USA and Canada for the Great Gathering? They didn't look as good before Locomotion did them up. 

[62613]

On 15/03/2022 at 17:15, rodent279 said:

I *think* I follow.

So if I understand correctly, the relative positioning of piston valves & the associated cylinders, which by the nature of the fact that a piston valve steam chest will be a larger diameter than a slide valve steam chest, means that the cylinder centre line & valve spindle centre line are further apart in a piston valve arrangement that in a slide valve arrangement. This in turn leads to angular irregularities, which are not easily corrected in Stephenson's valve gear, but are in Walschaerts & its derivatives?

Remember that  slide valves are actually flat; in sectionthey would resemble the letter "C" or "D" on it's side, slideing backwards and forwards between the steam ports. Quite often, the valve itself will be contained in a "Bridle" attached to the valve rod, and the valve chest cover. The valve was pressed to the face by the steam pressure.

 

I suppose that, in the earliest engines, it was quite possible because of the smaller - diameter cylinders, to place the valvechests between them, but as cylinders became fatter, the space disappeared,so they had to go somewhere else. Having two big ends and four eccentrics on your crank axle is getting fairly crowded anyway!

 

[JimC]

27 minutes ago, 62613 said:

but as cylinders became fatter, the space disappeared,so they had to go somewhere else. Having two big ends and four eccentrics on your crank axle is getting fairly crowded anyway!

And even worse, as the larger valves move away from the centreline the best location for the eccentrics start to impinge on the space for the big ends. *If* I read the less than ideal drawing I have correctly, the GWR dealt with this on 4-4-0s by having a solid arm on the end of the valve rod, which would put a lateral load on it which I should have thought wasn't ideal. Piston valves could go above the cylinders, in which case they impinged on boiler/smokebox, below the cylinders as per above, in which case the steam passages were long and convoluted, or perhaps weirdest of all, on some 2721 pannier tanks, both on the centreline one above the other which must have made for steam passages like a nest of snakes!

[JimC]

9 hours ago, The Johnster said:

An idea might be to investigate the possibility of developments of the GW 56xx class.  Collett was not averse to messing about with driving wheel sizes or boiler pressure, and a 5'2" driving wheel version (76xx?) might have been a better replacement for pre-grouping South Wales passenger 0-6-2T locos

I just had a quick look. Its tricky. The piston valves on the 56 are as close to the bottom of the smoke box as they can be and still have a drumhead smokebox. So the boiler has to go up higher (or revert to slide valves). There is room for that,  but there's also weight to consider, and the bigger driving wheels seem to make a surprising (to me) difference.  So I suspect the tanks need to be appreciably smaller to keep the weight within limits. The water has to go somewhere though, so perhaps that forces you towards an 0-6-4T. But then you have to ask why this is a better solution than the Std 4 boiler Large Prairies. 

[62613]

40 minutes ago, JimC said:

I just had a quick look. Its tricky. The piston valves on the 56 are as close to the bottom of the smoke box as they can be and still have a drumhead smokebox. So the boiler has to go up higher (or revert to slide valves). There is room for that,  but there's also weight to consider, and the bigger driving wheels seem to make a surprising (to me) difference.  So I suspect the tanks need to be appreciably smaller to keep the weight within limits. The water has to go somewhere though, so perhaps that forces you towards an 0-6-4T. But then you have to ask why this is a better solution than the Std 4 boiler Large Prairies. 

0-6-4 classes; how many were there on UK railways? The only "large" class I can think of are the Deeley Flatirons. I know the Met. had some, but why so few overall? Was there something wrong with that particular wheel arrangement?

 

 

[JimC]

5 minutes ago, 62613 said:

0-6-4 classes ... Was there something wrong with that particular wheel arrangement?

Perhaps just that 2-6-2T, with guiding wheels at both ends, was usually better .

[PhilJ W]

15 minutes ago, 62613 said:

0-6-4 classes; how many were there on UK railways? The only "large" class I can think of are the Deeley Flatirons. I know the Met. had some, but why so few overall? Was there something wrong with that particular wheel arrangement?

 

6 minutes ago, JimC said:

Perhaps just that 2-6-2T, with guiding wheels at both ends, was usually better .

The Metropolitan 0-6-4T's were primarily freight engines based on the Metropolitan 4-4-4T's a passenger engine also with a rare wheel arrangement. Neither 0-6-4T was very successful largely because a lot of weight that could have been useful for traction was over the trailing bogie. The Metropolitan 4-4-4T's were relatively successful as passenger engines but even then a 2-6-2T would have done just as well and being more versatile. Both being 'balanced' could run just as well bunker first as smokebox first.

[Nick Holliday]

1 hour ago, 62613 said:

0-6-4 classes; how many were there on UK railways? The only "large" class I can think of are the Deeley Flatirons. I know the Met. had some, but why so few overall? Was there something wrong with that particular wheel arrangement?

 

 

 

36 minutes ago, PhilJ W said:

 

The Metropolitan 0-6-4T's were primarily freight engines based on the Metropolitan 4-4-4T's a passenger engine also with a rare wheel arrangement. Neither 0-6-4T was very successful largely because a lot of weight that could have been useful for traction was over the trailing bogie. The Metropolitan 4-4-4T's were relatively successful as passenger engines but even then a 2-6-2T would have done just as well and being more versatile. Both being 'balanced' could run just as well bunker first as smokebox first.

There were several classes of 0-6-4 tanks that ran on the standard gauge in Britain.

The Midland ones numbered around 40, and were primarily for passenger use, at least at first. The SECR had about 15 J Class tanks that were for passenger services, and the Mersey Railway had nine outside framed passenger locos, though many of them ended up on freight when sold off after electrification. The Barry Railway had ten rather elegant tanks, probably for goods, and the Lancashire, Derbyshire and East Coast Railway had nine goods tanks. The Highland had eight intended for banking duties, and the Metropolitan lagged behind with only four. As all these tanks were inside cylindered, it seems unlikely that the Met tanks inherited much from the elegant 4-4-4 tanks, apart from, perhaps, the boiler; of all these designs the Met tanks were, in my view, the ugliest, making the MR Flatirons quite pretty, at least before the extended smokeboxes arrived.

I wonder if it was the extended ‘fixed’ wheelbase that was their downfall?  The Met tanks developed a reputation for spreading the rails in some goods yards, and a 2-6-2 with more flexible pony trucks at each end might have been a better proposition. As for weight distribution, most of it would have been forward of the cab, and the consumption of coal would have progressively reduced the adhesion weight during the journey, so the 0-6-4 design would have had a theoretical advantage.

[62613]

28 minutes ago, Nick Holliday said:

 

There were several classes of 0-6-4 tanks that ran on the standard gauge in Britain.

The Midland ones numbered around 40, and were primarily for passenger use, at least at first. The SECR had about 15 J Class tanks that were for passenger services, and the Mersey Railway had nine outside framed passenger locos, though many of them ended up on freight when sold off after electrification. The Barry Railway had ten rather elegant tanks, probably for goods, and the Lancashire, Derbyshire and East Coast Railway had nine goods tanks. The Highland had eight intended for banking duties, and the Metropolitan lagged behind with only four. As all these tanks were inside cylindered, it seems unlikely that the Met tanks inherited much from the elegant 4-4-4 tanks, apart from, perhaps, the boiler; of all these designs the Met tanks were, in my view, the ugliest, making the MR Flatirons quite pretty, at least before the extended smokeboxes arrived.

I wonder if it was the extended ‘fixed’ wheelbase that was their downfall?  The Met tanks developed a reputation for spreading the rails in some goods yards, and a 2-6-2 with more flexible pony trucks at each end might have been a better proposition. As for weight distribution, most of it would have been forward of the cab, and the consumption of coal would have progressively reduced the adhesion weight during the journey, so the 0-6-4 design would have had a theoretical advantage.

So that looks like about 100 out of around 40,000 standard gauge mainline locos ever, then. One of the faults of the flatirons seemingly, was the configuration of the passages between the valve chest and the cylinders; with the short travel slide valves and narrow passages with two right - angled bends in each, they can't have been very free - running or economical.

[The Johnster]

All of which seems a cromulent explanation of why the 56xx was never given 5'2" driving wheels.  I was thinking of something like a Swindon version of the Rhymney P class, in much the same way as a 56xx can be regarded as a Rhymney R class built out of Swindon standard parts.  'Swindonised' Rhymney Ps were handsome beasts, and used Swindon standard no.2 boilers which were not pitched ridiculously high.  Finding space for the valve chests is the limiting factor in this line of putative development, and it is interesting to note that, AFAIK in all cases in which Collett altered the driving wheel size of previous designs, Saint to Hall, 54xx to 64xx/74xx, 61xx to 81xx, 3150 to 1938 31xx, it was to reduce it in order to increase T.E.  Hawksworth effectively reduced the driving wheel diameter of the 2251 to achieve the 94xx, and it is I think fair to say that the 2251's boiler is pitched about as high as you'd like to go for comfort in regard to centre of gravity.

 

What seemed to me to be a natural Collett progression from the original 56xx to a passenger version is, as you have all proved, not as simple as it looks.  A loco with 5'2" driving wheels does not feel like a passenger engine in many places outside the South Wales Valleys of course, but several of the local independent pre-grouping companies had come up with 'passenger' 0-6-2Ts of this sort.  The accepted wisdom was that you had 0-6-2Ts with 5'+ drivers for passenger work, 4'6" or so ballpark for mixed traffic and general goods, and 4'+ for the heavy mineral jobs, and there were plenty of those...  The Taff Vale only had one section, between Radyr and Crockherbtown Jc, that could sustain 70mph running, and the fastest speed anywhere on the Barry was 50mph.  The Rhymney had fast sections south of Ystrad Mynach to Crockherbtown, restricted to 50mph between Aber Jc and Wernddu. 

 

Not that particularly high speeds were achieved with passenger trains even where they were permitted; uphill was a slog and the frequent station stops prevented much in the way of blowing out the cobwebs on the downhill runs; in any case the timings did not require much more than 50mph or so, and the 56xx were easily capable of that.  So my 76xx is not so much a neverwazza as a neverevenlikely! 

 

Canton might have found a few useful for the short haul main line Pontypool Road runs with Manchester or Liverpool trains, which changed engines there; large prairies and 56xx did this work in reality.  The other possibility is the daily Porthcawl-Cardiff and Swansea commuter services, the 'residentials'; Tondu had 3100, a Collett 1938 large prairie with a no.4 boiler and 5'3" drivers that could accellerate the 5-coach train away from the main line stops to keep out of the way of faster traffic.  This loco was invovled in a 'heavy impact' with the stop block at Porthcawl in 1958 and, after a few weeks of potching about as an Ogmore Junction yard pilot while the damage was assessed, was withdrawn at Swindon despite being only 20 years old. 

 

Hardly enough work to justify a separate class, but, having said that, there were only 5 of the Collett 1938 31xx.  More were intended and this class was to be the standard for all new large prairies, but the war intervened and Hawksworth built 5101s instead.  These proposed 31xx would have done the work of my 76xx, and the 41xx series did in reality.

[AlfaZagato]

I'd suggest spinning the wheel arrangement, to 2-6-0, but then you may as well build a prairie of some sort.

 

I know a couple of Welsh lines built 0-8-2s.   Would that have been the next stage from a 56XX?

[tythatguy1312]

On 17/03/2022 at 17:58, AlfaZagato said:

Would that have been the next stage from a 56XX?

I honestly suspect that  2-6-2 makes more sense as an evolution, as a 56xx was adequately powerful but suffered rough riding and smokebox door clearance issues. Of course, the GWR had hundreds, but I do see why.

[The Johnster]

Which returns one's thoughts to the Churchward 31xx and it's derivates.  The GW in pre-grouping days used small and large prairies for it's South Wales work, with a backing cast of various saddle/pannier tanks, and even loaned them, 45xx to the Rhondda & Swansea Bay and turned out in that company's very smart red livery, and 31xx to the Barry for the Cardiff commuter services on the Cogan branch.  The 42xx and it's derivates handled the heavy jobs.  All the indepenent South Wales companies had come to the same conclusion with regard to 0-6-2Ts, for a good reason; this layout provides a compact and powerful loco with tankage and bunker capacity well suited to the work.  Usually they came in 3 wheel sizes, for passenger, 'goods' (mixed traffic in the parlance of the day) and mineral jobs, the mineral locos usually not having vacuum or air (Rhymney) brakes.  A side benefit was often stated to be that the radial axle beneath the bunker, leading on the downhill runs, assisted the ride when the speeds were higher.  I've never set much store by this personally; speeds were not that high anyway and 'incline working', the practice of pinning down enough brakes on loaded mineral trains for the loco to have to pull the train down inclines against the drag of the brakes (most of the time, but the inclines all had piles of wrecked wagons at the bottoms...).

 

So, the GW at the time of the grouping, with a CME new in the big chair, was suddenly and through no fault of their own presented with a large fleet of South Wales 0-6-2Ts and 0-6-0Ts, which was variable to say the least in regard to it's further use to the railway.  Boiler inspectors from Swindon examined this group of locos within the first few months of the grouping, and many Barry locos were stopped forthwith, while the Rhymney fleet were well regarded; this is to show the variability in the quality of these constituent and absorbed locos. 

 

The grouping must have been regarded as xmas come early by the GW's shareholders, as the railway was gifted the golden ticket, the South Wales coal trade!  Within a decade it had all gone sour and the downward trend began only 3 years after the grouping with the damage done by the General Strike and the long coal strike that engendered it, with the Great Depression being another major nail in the coffin.  Collett signed off on 200 56xx, based on the Rhymney R class to some extent, to replace the older constituent/absorbed 0-6-2Ts, and embarked on the task of overseeing a program of rebuilding the new ones with GW boilers and fittings.  This was a not inconsiderable job, and is often overlooked as one of his achievements by those who focus on the glamour end, the Castles and Kings.  New boilers were designed and constructed amongst many other details. 

 

But I sometimes get the impression that the 200 56xx were really only built because it was the recieved wisdom that 0-6-2Ts were the norm for South Wales Valley work and it was therefore necessary and expected to build a standard Swindon solution.  We accept this nowadays without demur, and it was probably accepted in the same way in 1924, but I would pose the question 'did the GW really need 200 56xx?'.  Perhaps not; 57xx might have done much of the work, more 5202s the heaviest mineral jobs, and small or large prairies everything else.  There might then have been a need for a heavy mineral 0-6-2t for such jobs as the 8-coupled tanks were too heavy or too long in the wheelbase for, and it could have had 4'1" standard driving wheels, though I can't see tne need for more than about 50 of them.

 

South Wales came back to haunt Collett in the 30s with the need to design a 4'7" driving wheel variant of the 54xx for auto work in the area, as the 54xx couldn't manage 2 trailers on the banks, and again in the 50s when the need for 3- or 4-trailer autos in the area led to the fitting of 4575s with auto gear.  Might it have been simpler to fit some 57xx/8750s with auto gear instead, bearing in mind that these locos were doing 4-coach work on Neath-Treherbert trains and 3-coach slogs from Newport-Brecon?  I'd argue that an auto-fitted 57xx is a lot more use in 'non auto' mode to a shed foreman than a 4575 or a 64xx. 

 

The 76xx now becomes a 4'1" mineral loco, and might even  have been an 0-6-2T version of the 2251 with a no.10 boiler, the 2251 itself presumably influenced by the success of the rebuilt TVR A class.  This sort of happened eventually in the early 50s with the 94xx, the final chapter of the rebuild/replace South Wales loco program, and intended to take on the work of the likes of TVR 04s, so the 76xx could even have pannier tanks if you like.  How about a 2251-dervived passenger 0-6-2T, not unlike a rebuilt TVR A, for work on routes that were GW pre-grouping given that the As were fairly widely dispersed off the TV system to Barry, Dyffryn Yard, and East Dock? 

 

Would Cameron have turned out separate goods and a mineral versions of the A had not the grouping intervened?  All fertile ground for speculation and imaginary locos!  I'd suggest that, while expanding or devloping the 56xx into a prairie seems logical from the perpective of neary a century later, the zeitgeist of the time renders it unlikely; the mindset was very much that it was unquestioned and unquestionable that, 'obviously', South Wales needs 0-6-2Ts despite the GW not having built any for that area or anywhere else previously whilst having considerable route mileage and heavy traffic there (Vale of Neath, Pontypool-Aberdare, Gwent Eastern and Western Valleys, Tondu Valleys), because that's the standard answer to South Wales's problems.  It is also fertile 'imaginary loco' territory, though, a large prairie with a no.2 boiler, 4'7" wheels, and possibly inside cylinders, or a no.4 boiler version with outside cylinders looking like a prairie version of a 42xx. 

 

That's enough for my Saturday avo Wales lost to Italy therapy ramble, enjoy drawing up the suggestions, gentlemen!

 

 

[tythatguy1312]

Something that has intrigued me with the 56xx's is why they weren't tried on the China clay trains. They seem powerful enough, and they're certainly physically flexible enough to get past the monstrously tight curve at Saltash.

[JimC]

4 hours ago, tythatguy1312 said:

, as a 56xx was adequately powerful but suffered rough riding 

And indeed was probably about as powerful as was sensible for an inside cylinder locomotive, so the only advantage of going for 8 driving wheels would be axle load, which wasn't really an issue on the welsh valley lines.

It seems to be that an 0-6-2T configuration tends to be suited to inside cylinder locomotives, since the cylinders can be between the driving wheels to drive the centre axle, and a 2-6-2T is better for outside cylinders where the cylinders must perforce be in front of the wheels. The 2-6-2T can also go a bit heavier and longer in the boiler. There's also the problems we've noted above where the cylinder/piston arrangement impinges on the boiler and limits how large it can be.

 

Its one of the minor mysteries to me that the GWR almost never put autogear on the pre group 4'7.5 wheel tank engines. I think a few of the outside framed locomotives were used with it, but I don't recall ever seeing a record of fitment to the later more powerful inside frame types.  Which also meant that the autofitted fleet was 4'1 wheeled 2021s and relatives, plus Metro and 517 2-4-0s with 5'2 wheels. 

[JimC]

Here's johnster's 2251 based passenger 0-6-2T. I imagine it with screw reverse and autogear blasting up and down the valleys between two pairs of 70ft auto trailers. Very quick to draw for me, and probably for Swindon. 2251, extend frames, add 5101 trailing axle assembly, drop on a 5101 cab/tank assembly and modify it for the straight footplate.

[This image seems to have gone for ever, not on my PC, but see the modified version a couple of posts down]

 

 

Or if the access to the motion is too impossible, then perhaps a pannier tank. Its basically a 94 tank, but the water capacity would be greater than a 94 with a bigger tank under the coal space.

 

 

 

Edited May 19, 2023 by JimC
replaced images

[tythatguy1312]

First concept has a flaw that I can also see on the "absurdly heavily modified Class E2" seen on Thomas the tank engine, in that you'd need to be smaller than a water main to access the motion. Mechanical lubricators could solve it, but I'd still be impressed if anyone could access it

[John Besley]

To oil up a 45xx you do need to access the front parts of the motion for the slide vales oil pots which can be done off the front part of the running plate,  as for a pannier everything has to be accessable from under the tank or between the frames, so agree that the first drawing while looking nice would be impractical

 

 

Edited March 20, 2022 by John Besley

[JimC]

Yes, as soon as I uploaded the first image and looked at it I worried about the access and went back and drew the pannier tank. A half and half like the 9700s or the 1101s might be a possibility too. One really needs to be a proper designer who can do a weights study to work out which would be best. There would also be the possibility of extending the bunker and back tank to juggle the weights. 

[JimC]

OK, a little bit more thought. 
The 2251 was lightest on the trailing wheels, so I've cut the tank back and given it a further cut out low down to give access to the motion. I rejected the pannier tank to lighten the front end. The trailing wheels have been moved back a few inches and the bunker lengthened to match which should bring back some of the water capacity. There's also a few other minor tweaks.

 

 

Edited May 19, 2023 by JimC
replaced image

[JimC]

18 hours ago, The Johnster said:

the mindset was very much that it was unquestioned and unquestionable that, 'obviously', South Wales needs 0-6-2Ts despite the GW not having built any for that area or anywhere else previously

Do you think there might have been an element of wanting to be seen to be adapting to welsh norms, bearing in mind that many of the staff of the Welsh lines were less than enthusiastic about being subsumed into the GWR?

[The Johnster]

That's a handsome looking engine as 0-6-2Ts go, sir, and the final version looks very much like what I had in mind.  No 70' auto trailers for it, though, not in South Wales where shorter trailers were used for some reason.  I have no difficulty picturing it blasting up the bank between Queen Street and Heath Jc under Monthermer Road bridge on a crowded 4 coach rush hour Coryton, one more than a 4575 was allowed!  It would have the 'range' for longer haul autos as well, and might have made hauled stock a rarity in the Valleys.  The Taff As, broadly similar, could manage Barry-Merthyr or Penarth-Rhymney.

[rodent279]

3 hours ago, JimC said:

OK, a little bit more thought. 
The 2251 was lightest on the trailing wheels, so I've cut the tank back and given it a further cut out low down to give access to the motion. I rejected the pannier tank to lighten the front end. The trailing wheels have been moved back a few inches and the bunker lengthened to match which should bring back some of the water capacity. There's also a few other minor tweaks.

 

Another option to provide valve gear access would be full length side tanks, with a J50 style cutout in the tank.

[john new]

32 minutes ago, rodent279 said:

Another option to provide valve gear access would be full length side tanks, with a J50 style cutout in the tank.

Given these are imaginary (experimental) ideas what would it look like with either an early adoption of outside valve gear like the later Hawksworth 15XX pannier tanks or the Stephenson gear outside a-la the LMS built Black V (4)4767? Would outside cylinders and outside v-gear even be an option on a GWR engine? Outside cylinders they used but I don't recall any other outside valve gear* other than on 102 La France and they bought that in.

 

*(Excluding anything inherited in 1923).

 

 

Edited March 20, 2022 by john new
Extra info added after spotting some typos.

[Nick Holliday]

37 minutes ago, john new said:

Given these are imaginary (experimental) ideas what would it look like with either an early adoption of outside valve gear like the later Hawksworth 15XX pannier tanks or the Stephenson gear outside a-la the LMS built Black V (4)4767? Would outside cylinders and outside v-gear even be an option on a GWR engine? Outside cylinders they used but I don't recall any other outside valve gear* other than on 102 La France and they bought that in.

 

*(Excluding anything inherited in 1923).

What about the 0-4-0 101 https://www.rmweb.co.uk/community/uploads/monthly_01_2013/post-7075-0-55831600-1359046609.jpg, the Class 1100 tanks and all the steam railmotors?