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and 1398 absent presumably date the diagram to between April 1883, when 1398 was sold, and November 1906, when 1392 was withdrawn.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).

Probably not long before withdrawal in 1933, 1397 has a lower, fatter chimney (which would be transferred to the 1361s when these 1392s were withdrawn), and is looking very 1361-ish, with a 2-segment 1361 tank. Note the wrap-around handrail.

What tiny bunkers these engines had!

(image re-instated)

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.

Looking at a CMR map, I'm not sure those engines ever encountered a high-level coaling stage (unless there was one at Newquay?). Probably done with buckets from low-level stages.

On 10/03/2022 at 15:50, Miss Prism said:

Looking at a CMR map, I'm not sure those engines ever encountered a high-level coaling stage (unless there was one at Newquay?). Probably done with buckets from low-level stages.

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!

40 minutes ago, JimC said:

According to RCTS a lot of them lived at Swindon.

Presumably to work the carriage and wagon shops. The CMR workings were rarely photographed, and I really don't know what locos the GWR used for the mineral workings - presumably small and medium-sized saddles. There was always a smattering of Buffalos at St Blazey.

40 minutes ago, JimC said:

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?

I'd certainly go along with the cab entrance being moved forward - the bodywork was a complete rebuild.

There's a strange phrase on the Wiki pages regarding the locos - "they were intended to be used in pairs, bunker to bunker". Are those rear buffers short ones?

 They might have been used on the Liskeard & Caradon after its acquisition by the GWR although more likely the 19xx or 20xx saddle tanks.  Doubtful if there were special buffers on the CMR!

  Interesting era and well documented.

       Brian.

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. 

I have a GA for the loco in its original form. There is a lot of info on these locos in the M&GN loco book. When they were used by their new owners they were paired with a Sharp Stewart 4 wheel tender, without having their tanks removed.

Marc

2 hours ago, MarcD said:

I have a GA for the loco in its original form.

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

I have read that St Blazey depot was built to house the entire fleet of eighteen CMR locomotives, two to a road hence nine roads. Nice planning.

One point that confuses me is that, if the locos were coupled back to back with two opposing fireboxes for the energetic fireman to feed, where was the coal carried......?

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.

3 hours ago, JimC said:

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

I will dig it out. I'm away at moment so it will be Monday before I get to it.

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: 

Some great stuff here guys 👍

Been trying to compile information on this fascinating little class and noticed there's fair amount of contradictory information on them but Their origins seems to hark to 1870 when Frövi - Ludvika Järnväg

ordered a batch of back-to-back saddle tanks.

They arrived in 71 and a follow up order was made in 73. The Cornish order, E643 was made just prior to the Swedish Central Railway's as theirs was designated E660. The saddle tanks had a capacity of a 1000gals over the 780 figure for the combined side tanks but while the wheelbase and drivers were equal the cylinders for the Cornish engines were larger 16.25"x20" over 14"x18. and likewise the heating surface was greater 823.5sq. ft. vs 741sq. ft.

Trevithick obviously had some influence on the design but as can be seen Sharp Stewart must of done a lot of the heavy lifting. William Richardson Roebuck ordered the 18 tanks in 73 but the 15 unnamed engines were completed in 74. They arrived as the roundhouse and other parts of the network were still under construction. Roebuck was caught out by the overproduction of China clay and the envisaged traffic on the CMR was never reached. As such it's believed a number of the 18 builds were never steamed while it's not clear if they ever worked back-to-back either. In 77 Roebuck opened negotiations with the GWR to work the line and this was signing was sanctioned on the 10th of August for them to do so on the 1st of October. The GWR kept on 9 to operate the traffic while 3 were sent back to Sharp Stewart to settle some of the outstanding £43200 they were bought for. The remaining six were stored at St Blazey and in the early part of 1880 W.J.Man inspected five of them officially for the Lynn & Fakenham but more so as a favour for John Crabtree, the Managing Director of the CV&HR, who was keen to curtail the renting of engines from the GER. Finances only allowed for one engine to be purchased and Works No.2358 was acquired on the 8th of May. It does not seem the engine returned to its maker and based on the fact that the CMR numberplates are still in place in this photo below it was not immediately repainted dark green, though a spectacle plate was soon added to make reverse running more tolerable for the crewmen. 

Mr W. Bailey Hawkins was both Chairman of the CV&HR and South Hetton Colliery which is no doubt how the engine was sold to the latter in 89, by which time it had already been renamed Haverhill.

It survived long enough for become NCB property but was cut up between the 18th of May & 2nd of July 1948. Prior to a photo taken on the 15th of April 1933 No.2 was already in its final form feating dumb buffers, a built up chimney, an iron and wooden cab and a rear bunker, the original coal space area having been cut back to make some room for this set up.

between books such as 'The Locomotives of the Great Western Railway Part Three Absorbed Engines' which states that the three sold back to Sharp Stewart were given bunkers, while the diagram featured in 'An illustrated History of M&GNJR Locomotives' shows the firm only extended the roof and added some kind of back sheet in place of the original 'walk through' design. Anyhoo I'm wondering if anyone can clear up whether the five sold to the Lynn & Fakenham were purchased and sent to Sharp Stewart & Co for their tender fitting in March 81, or if this is when they were delivered to the Lynn & Fakenham (Absorbed says they were sold at this point while 'The Midland & Great Northern Joint Railway and its Locomotives' states this is when the already delivered three were reunited with the five with their tenders already added).

Also a bit of long shot but does anyone reading this own 'The Colne Valley and Halstead Railway' by Peter Page? It looks a good modern book over previous softbacks on the line, but a bit reluctant to fork out £40+ without knowing if there's anything of note on the lone engine that found its way there and later South Hetton Colliery.

Regards

Steve