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.

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.

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.

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

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.

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!

The expansion link rocks to and from, its not set at a given angle. There are various videos on youtube which show how it all works, but I didn't immediately spot one I liked. I probably should do an animation of the actual GWR gear, but I haven't the best tools for that. I'm actually struggling to work out how best to explain how I see the design factors. I'm not sure this is the best place either. Perhaps some of you folk who work at 305mm to the foot could post links to your Mutual improvement Class material or something of the sort?

Lets see if I can clarify this a bit better... Mind you I am by no means a valve gear expert and I hope for those who are to correct me... I'm not sure angular irregularities is the best phrase. In the case of valve gear discussions that's probably best reserved for discussing the peculiarity that means that 50% of the piston stroke is not 50% of a wheel revolution. What I was talking about was just the relative alignment of piston rods, valve rods and cylinders. Piston rods pretty much must be pointing at the wheel axle no matter what everything else is doing or the relationship between piston stroke and wheel movement gets extremely odd. In Stephensons in its simplest form you have the valve rod pointing straight at the wheel axle which has the eccentrics on. So with slide valves between the cylinders the piston and valve rods would all be in the same plane viewed from the side. If with Stephensons you can't have the slide valve between the cylinders and all the rods in the same plane (usually lack of space) there are two commonly seen arrangements. The Stroudley arrangement, which normally has the valves below the cylinders, has the valves level, and the cylinders inclined by (say) 6 degrees, so valve and piston rods are not parallel. But both are still pointing directly at the axle centre. The indirect arrangement, as used on the Churchward standards, has the valves above the cylinders and valve and piston rods all parallel and level, but although the piston rods are pointing straight at the axle the valve rods are pointing at a point a good bit above. So in order to have the valve gear working properly the link and eccentrics are effectively inclined (lets say 10 degrees for sake of argument), and drive a lever on a shaft, and the lever at the other end of the shaft can be rotated by 10 degrees to drive the valve rod. With Walschaerts there's not the inherent symmetry from two eccentrics. And because there's just one eccentric driving the bottom of the link, the valve rod doesn't need to be aligned to the axle centre, and the way its normally laid out the valve and piston rods cannot be in the same plane. Does that help? Maybe this sketch will help too. Most of them are drawn from GW locomotives, but I altered the 15xx Walschaerts for clarity, and the slide valve between cylinders drawing is made up, especially the top view!

Which in turn got be thinking about 0-6-0Ts and 0-6-0s on the GWR. The 57xx and the 2251s had slide valves with this layout when built in the 30s, but piston valves had been tried on the 2796 and some of the 2779 lots of 2721 class pannier tank before about 1920. According to RCTS they had exactly the same valve gear as the Stephenson's fitted locomotives, but had the valves on the centre line, one above and one below the cylinders. The steam passages must have looked like a nest of snakes! RCTS says that the valve rods carried arms which provided the offset to the valve spindles. I'm not sure I altogether understand that, whether they were jointed or rigid, but it must have looked rather peculiar. Bet you never realised your Hornby model might have had something so unconventional hidden inside! And this in turn got me thinking about inside cylinders and 0-6-0s and why they survived so long. If you have inside cylinders for the lack of rocking couple and its presumed effect on the track, (I wonder if outside cylinders tended to make already dodgy track worse - that could be a consideration for industrials perhaps?). Why not put valve gear outside to make things easier. But then I wondered, if you did that might some drivers be a bit lazy about big end oil boxes? Dean tried external Stephensons valve gear, internal cylinders on one of his more outre experiments, but it would look bizarre on an inside cylinder locomotive. Do I feel another sketch coming on? [Later] - looked at external valves and gear on a 94 and it doesn't work. Wheels just as much in the way as they would be for outside cylinders.

Yeah, grafting the 4-4-0 layout of the leading wheels being driven onto a 4-6-0 chassis is problematic. However laying things out to drive the middle wheels requires more design expertise than I possess. I'm not uncomfortable with having plenty of smokebox behind the saddle - think 4700 in Std 1 boiler form or the Bulldogs with Std 3 boilers, but a forward extension of the smokebox might well have been necessary, it's a good thought. Valves on the City/Aberdare/Duke series are *under* the cylinders, in what's called the Stroudley arrangement, which leads to rather convoluted and long steam passages but does help with space. It also gives direct drive to both valves and cylinders, rather than indirect via rocker as in the Churchward Standards. The cylinders and valves are not on the same axis, the valves are level in line with driving axle, the cylinders inclined 6 degrees. Now I think of it, I idly wonder if this inspired Holcroft when he pointed out to Gresley that valve and cylinder didn't need to be on the same axis with the centre cylinder of his conjugated gear. Another thought from writing this is that Stephenson valve gear layout is best with direct drive - valve rod aligned with wheel axle, but Walschaerts doesn't require this. Hence it seems to me that slide valves between cylinders is an ideal layout for Stephensons, but with large piston valves and cylinders I guess it's easier to get a good layout with Walschaerts. The Churchward outside cylinder classes have the complication of rockers to align everything correctly, whilst the 4 cylinders take advantage of the intrinsic properties of Walschaerts (and the scissors gear on 40 was really a Modified Walschaerts) to fit everything in. Cylinders saddle and chimney are typically vertically aligned on GW 2 cylinder classes and I wanted to follow that pattern, thus cylinders between bogie wheels. On reflection I probably should have paid more attention to the layout of the cylinders on the Stars, rather than looking solely at the City for the workings, but the inspiration was the Dapol kitbash. Also the further I go from the Swindon draughtsmen's work the more likely it is that my lack of knowledge and training will result in something ludicrous that could not work, which is a problem for me if not for the topic! Very good thought provoking post, I fear I've just edited it into a long essay, got me thinking about a number of design issues I hadn't considered before. I hope my guessing/interpretation is reasonable, and I'm not coming up with false speculation.

I had a bit more of a play with the inside cylinder Saint, and drew up the valve gear and cylinders. That was all very well, but that made me realise the front bogie was in the wrong place re the cylinders, so I had to extend at the front (and move the chimney on the smoke box) . Then I realised the brake cylinder was all tangled up in the motion and I had to change the brake setup round , and it started getting difficult. Still not sure that will work. I also gave it a short cone boiler and removed the top feed to make it look more Edwardian. I'm really surprised by how much that changed the appearance. Just for a bit more amusement, here's a wire frame of the drawing. Basically the cylinders, motion and (steam) reversing gear are from the City Class, so the valves are under the cylinders, Stroudley style. The drawing I had seems to be for the as built condition with slide valves. Presumably piston valves would have come later. The performance would doubtless have been rather second rate compared to a real Saint.

Perhaps get the first two driving wheels as close together as possible and aim for something like an inside cylinder Saint?

In RCTS (pC24) they mention No 245 having had at different times a Swindon boiler put on at Wolverhampton, and a Wolverhampton boiler put on at Swindon. I suppose one might imagine a Swindon boiler swapped off a locomotive at Wolverhampton, repaired, and put on the next repair, but I get the impression that in the 19thC boilers were not swapped regularly in the way they were after Churchward. A train of various boilers being taken from one factory to the other would be something different for modellers! More likely, I suppose, that they would go one at a time on normal service trains, but its a fun thought.

I think a desire to standardise parts was widespread. Gooch rejecting locomotives that didn't come up to specification is a often noted early example, and there are lots of examples of 19thC Locomotive Superintendants attempting to standardise parts across two or three new classes. I think the credit due to Churchward is not that he founded the concept, but that he was the best at it, and by commitment and vision did a far better job than anyone else. Another part that we perhaps tend to overlook is how important competent management was. Railway workshops - perhaps all workshops - had a definite tendency to revert to doing one job at a time with little regard to the big picture when it seemed convenient. Perhaps Churchward's biggest achievement was not that he introduced a number of classes with standardised parts, but that the (G)WR was still operating to those principles thirty years after he retired. I don't have too many non GWR books - only so many bookshelves even in a house where we have thousands of books, but one is Cox' 'Chronicles of Steam'. Around p48 Cox is talking about standard boilers, and reading between the lines some of us may judge that the LMS draughtsmen pushed back mightily on Stanier's ideas to refit LMS locomotives with a range of standard boilers by claiming it was just too difficult and not worth it. We might note their contemporaries at Swindon managed, but doubtless Stanier judged which battles were worth winning. ----------------- Incidentally, am now going through RCTS trying to produce a rational list of pre Armstrong 0-6-0s. Damn its going to be a struggle. Did I mention management - locomotive policy in the early days was (predictably I suppose - it was early days) chaotic and loans, rebuilds, renewals, reconstructions, make it a very challenging task. Makes me recall why I tended to fight shy of that era in the book, and also increases my admiration for the RCTS author(s) who had to try and make some kind of order out of what must have been a spectacular mess of source documents from all over the place. In the past I've wished the author of RCTS Part three had used a more tabular and less narrative style describing classes, but I'm starting to realise that, especially in a pre word processing age, doing so would have been an almost insufferable burden. What a filing system he must have had to create!

Something that's struck me today, looking at these and trying to find pictures of them in their later careers - can anyone help - is what an incredible rag-bag of 0-6-0 freight engines the early GWR possessed. I haven't looked at numbers, but there seem to be many more than I imagines, quite outnumbering the GWR constructed early 0-6-0s. They were pretty much all rebuilt or renewed at Wolverhampton, tending too merge towards a common style, especially with GWR boilers fitted, but all different, all different. No wonder that Armstrong's class were called Standard Goods: there was so many that were anything but. I imagine the same is true of 2-4-0s and 2-2-2s, although I haven't really explored, but the 0-6-0s really struck me today.

This seems OK now. Have you changed something (if so well done) or is it a side effect of the site running in basic mode?

I've been trying to sketch out an express Atlantic based on the GWRs notorious Krugers, but I just couldn't make it work. The grate on the Kruger is quite long even though its a wide box, and the whole thing was out of balance. I got this far before I gave it up as a bad loss... You'll notice that various vital components are missing which I hadn't got to before I gave up. Thought I'd post the part complete anyway to provide, hopefully, a smile in times that need them... One thing for sure, if anything its got even uglier!

Found an illustration of the 2-4-0 :-). This is from the same article in the Engineer as the image I linked to earlier. There's also some discussion and more images on this thread:

I've had a first stab at the locomotives in original condition, which I've added at the top. For the vexed question of livery, I've seen mention of dark reddish-brown, and that's my idea of a dark reddish brown. As is my convention I've left off lining. I'm being naughty by giving it the number 1 - it seems that four of the locomotives carried names, but probably not their numbers, while those that were nameless displayed the numbers. No 1in the stock list was the mis-spelt Treffrey. Coal - well maybe @MarcD can tell us from the GA drawing. I note, however the diagonal line of rivets towards the back of the tanks, which looks like a watertight partition. I'll speculate, on no more evidence than those rivets, that possibly there might have been a coal supply there. The eventual Lynne & Fakenham/Eastern & Midland/M&GNJR version of the locomotives as 2-4-0s with larger driving wheels would be an interesting addition to the page, but rather off my theme. But does anyone have a photo they could upload? There's a photo of one as an 0-6-0 tender locomotive here. https://rogerfarnworth.com/2019/11/16/the-lynn-and-fakenham-railway-part-1/ Interesting to note that at this stage it still retains the side tanks, complete with the original CMR number plate, but has acquired a reasonable cab.

That would be interesting and useful to see. Would you be able to share it with me or let me know the source?

https://www.vintagedition.com/1890-cornwall-mineral-railway-1873-locomotive-metamorphosis This is from an article in "The Engineer" about the other members of the class that were rebuilt as 2-4-0 tender engines somewhere well to the east of Swindon, but the drawing is very helpful. I tend to be suspicious of drawings (and models) as sources, on the grounds that the artist may well not have been any better informed than I am, but that one clarifies a number of smudges I was unsure of in the photo and seems well founded. I was also delighted to spot in the text a dimension for the footplate height, which is rarely documented on the weight diagrams but enormously helpful for getting proportions correct. The buffers appear to be conventional but short, which is also the case in some other small locomotives of the period I have sketched. Supposedly as pairs they were single manned, and you can see how the cab steps would make transfer between the cabs on the run possible, but surely rather perilous even for 19thC concepts of safety. You'd think a gate in the rear cab sheet would have been far more practical. Maybe though, if they were used in pairs, they tended to run with the driver in one cab and fireman in the other. Also one imagines that speeds on a 19thC mineral railway would have been very low, even compared to the conventional 25mph of unfitted freight on the main line.

According to RCTS a lot of them lived at Swindon. Here's a thing. I'm just looking at sketching up the as built configuration as per this very useful photo. RCTS states that the frames were lengthened at the back to fit in the bunker, but when I line up this photo with my drawing it seems as if in fact they didn't. Instead the cab entrance was moved forward. At least I'm finding that the cab spectacle plates and wheels only line up with the photo if you assume they didn't extend it. What does the panel think? And another curiosity- the locomotive is assumed to have been named after Joseph Treffry, a major local land owner and entrepreneur who had built several horse drawn tramways that became parts of the Cornwall Mineral Railway. But if so they spelt his name wrong!

I do wonder how much coal they spilled coaling these from a standard GWR stage. There were special carts for smaller bunkers as below at Didcot, but even so it must have required some precision. The glazing on that rear mounted spectacle plate must have been awfully vulnerable too.

For interest, these are the two images I made most use of for this sketch. The numbers shown with 1392 present and 1398 absent presumably date the diagram to between April 1883, when 1398 was sold, and November 1906, when 1392 was withdrawn. My best guess is that the weight diagram is the condition after they were converted to saddle tanks in 1883/4, and the photograph is possibly after the first boiler change which was Jan 1904 for 1396, but it could be any time up to March 1934, by which time it would presumably have had a 1361 boiler (RCTS doesn't mention dates for that change).

An interesting class, not least because they were significant as being the basis of the design of the 1361 and 1366 classes. In their original form the locomotives did not look much like this, being side tanks with no back to the cab and intended to be used in pairs operated by a single crew. They were built by Sharp Stewart for the Cornwall Minerals Railway. The designer is a little obscure. Its apparently credited to an F. Trevithick. Francis Trevithick, son of the great pioneer, had formerly been Locomotive superintendent of the Northern division of the LNWR and was resident in Cornwall at the time working as Factor for the Tehidy Estate, which had considerable mineral connections. One of his subordinates had been Alexander Allan, inventor of the eponymous valve gear, with which these locomotives were fitted. There were other F. Trevithicks, but he seems to be considered most likely. The GWR took over running the line in 1877, but only acquired nine of the line’s eighteen identical locomotives as the other nine were pledged as security against various debts and were sold separately. The GWR numbered their locos 1392-1400. In 1883/4 they were all converted to saddle tanks and given a rear frame extension to provide a conventional cab and bunker. They received a variety of cabs, tanks and bunkers over the years and were twice reboilered, the second time with 1361 class boilers, but were otherwise little altered. One was sold in 1883 and 1392 scrapped after a collision in 1906, but otherwise they survived into the 1930s. After 1392 was scrapped the class became known as the 1393 class! At the 1912 renumbering 1400 was renumbered 1398, being the number of the loco sold in 1883. In GWR history they were significant as being the basis of the design of the 1361 and 1366 classes. Harry Holcroft tells the story of "a roll of musty old drawings" being deposited at his drawing board, which were those of the 1392s, which he was instructed to use to design a complete new class. This sketch is partly based on a 19thC weight diagram which is minimal in the extreme, and partly on 20thC photographs. I think its hopefully reasonably representative of an 20thC configuration for the class, although I've had to rely a little more on the known similarity to the 1361 class as is perhaps advisable. Later weight diagrams exist and it would be interesting to see those to try and tie things down a little more.