7mm On Heather's Workbench - a baby Small Prairie

Discussion in 'WR Action' started by Heather Kay, 2 August 2017.

  1. Heather Kay

    Heather Kay Western Thunderer

    This build will prove interesting, on a couple of counts. First, it's my first ScaleSeven loco commission. Second, it's a "Small Prairie", but not quite as we know it.

    Back in the early 1900s, George Jackson Churchward, chief mechanical engineer of the Great Western Railway, was looking to modernise the company's locomotive fleet. He had designed and had built prototypes of a 4-6-0 express passenger type, a 2-8-0 heavy goods type, and a 2-6-2 tank type as a "maid of all work". All three were a somewhat radical departure from the fussy Victorian period designs, and were to set the pattern for the Great Western "look" for the next half century or so. While these locos were under test - it was usual to build one new design and test it extensively over a couple of years - Churchward decided there was a need for a smaller 2-6-2T to replace the venerable and various species of 0-4-2 and 0-6-0 tank engines that were plying their trade in the further reaches of the West of England.

    Number 115 appeared from Swindon Works at the end of 1904. Within a year a further ten examples were built - among the last locomotives to be built by the GWR Wolverhampton works. Initially numbered in the 3100 series, the locos had a new standard coned boiler, outside cylinders and 4ft 1-1/2in coupled wheels. Although the tank and bunker capacities were somewhat limited, these little branch engines proved their worth. Eventually, they would be modified with larger bunkers and extended smokeboxes and assumed the more familiar GWR family outline. They ended their days renumbered as the 4400 class.

    So successful was this class, a slightly larger variant, the 4500 class, was developed from it, but that's another story.

    This commission build is to create the earliest form of the 3100 class, using the Malcolm Mitchell kit as a starting point. The kit does actually provide the parts for the early type, so it ought not be that difficult. Where there is a difficulty is the small class of eleven spent their entire lives in the darkest corners of the West of England, and consequently didn't find themselves in front of photographers very often. I've managed, with some assistance for which I am very grateful, to gather some photos and drawings of these machines, sufficient I hope to be able to build a fairly accurate representation. I've been helped by the client, who had acquired the kit some years ago, before the Mitchell range was acquired by Just Like The Real Thing. Over the years, detail parts, replacement parts, sets of wheels (reprofiled to S7), were all acquired and squirrelled away in the box. I am having a bit of a job deciding on the best parts, where there are multiple versions available to me!


    Research material. Most of the 4400 class were rebuilt to their final form by the mid-1920s, so finding good clear photos of them in their original form is quite the challenge. Across various publications, and not counting duplicates, I think I have six fair images that show enough detail to be useful. Happily, Les Golledge (@Les Golledge) was kind enough to let me copy various useful drawings he has in his possession. Most of these are of the slightly bigger 4500 class, but there are enough similarities to help build the smaller loco. I will spend a happy hour or so later with coloured pencils identifying various components and shading them in to make it easier for me to follow the drawing. I also find it a helpful way to familiarise myself with the shape and relative size of various components.


    Lots of bits that have been added to the box over the years. I had a custom numberplate for 3107, the chosen loco, by Narrow Planet. Others have said it, but I will say here anyway, what a helpful bunch of people they are. I'm sourcing plates for another build already on the bench, and Stephen at NP has been immensely helpful. I appear to have alternative sets of tank fillers, castings for boiler fittings that are really for later versions, and generally plenty to choose from.


    Premier Components milled rods - and a baggy with what looks like more - cast hornguides, detail packs from the original kit, plus extra detail parts from the JLTRT range. The latter includes cast parts for the pony trucks, cylinder details and frames.


    The nickel silver etches cover the frames and motion parts. I can identify some cosmetic parts for the inside valve motion. Although most of it is hidden behind the tanks, the front end can be seen. There's some nice complicated jiggery-pokery that gets the valve operation from inside to outside the frames. That'll be fun, as will the possibility of making a working vacuum pump…


    The brass etches cover the bodywork. You will note the upper etch has the more familiar bunker outline, with the bustle. The lower etch has alternative parts covering the earlier variants. I shall be aiming to build the earliest one, with only a flared top.

    When I first took delivery of the box, and peeped inside, it looked scary. So many parts, so many tubs and boxes! Looking at the parts laid out like this in broad daylight, it doesn't seem such a daunting prospect. I might actually enjoy this build - for a time, at least! ;)

    My first job will be to go over the etches and the instructions, and mark on the former part numbers if they're not already clear. Then a spot of colouring in! Kettle's on, time for a strong coffee!
    Last edited: 21 August 2017
  2. daifly

    daifly Western Thunderer

    For the uninitiated, it's one of these:
    3102 at unknown loc PC.jpeg
  3. Heather Kay

    Heather Kay Western Thunderer

    That's the baby. It's right at the transition between the Victorian fussiness and what would become the GWR house style. Nearly there, but not quite.

    I still can't get over the tiny driving wheels!
    Lightman likes this.
  4. Temeraire

    Temeraire Western Thunderer

    Although I'm generally a diesel man at heart I shall watch this one with interest. Handsome looking beastie!
  5. King John

    King John Active Member

    There is a photo of 3104 at Brent station on page 5 of The Prairie Papers No3 which might help with your research.
  6. Heather Kay

    Heather Kay Western Thunderer

    I have a copy of that. It's also in the Locomotive Portfolios book, as well as the GWRJ I have here. It's lucky the 4500 is very similar in overall look and feel, being essentially the same thing with larger driving wheels.

    I'm currently busy with the crayons, and have uncovered a conundrum I may share later.
  7. Ressaldar

    Ressaldar Western Thunderer

    Hi Heather,

    coincidently, I have just taken delivery of a white box from JLTRT with a 44xx within. However, it has been placed straight on the shelf, behind the Park NLR 0-6-0t which is behind three Inspection Saloons - all of which are quite close to the paint shop and must be completed first, then the Park then the 44xx.

    So I will be following you deliberations with great interest, but staying within the 7Finescale boundaries.

    Good luck with the build.

    kind regards

  8. John Rich

    John Rich Active Member

    Hello Heather, a tiny aside but I would be interested to know what you think of the Pen and Sword publication for reference, I haven't yet seen one in the flesh so to speak.

  9. Heather Kay

    Heather Kay Western Thunderer

    John, the production values are high, as is the price! Quality paper, thick board covers and dust jacket, good reproduction of photos and text. I'll be honest and say I've only flicked through the volume I have, as I purchased it specifically for the prairie sections (there's another one due next year from this workbench!), and the fact it had a handful of useful photos of the original designs. I can't say how much crossover or repetition there might be with other publications - photographs, particularly, often appear in other books and periodicals.

    I have a favourite saying that as modellers we can never have enough books. I have, in the past, bought books purely on the basis of a single photo of a specific loco that I hadn't seen elsewhere before. If you think the Pen & Sword range might suit, seek them out at exhibitions or book shops and see what you think in the flesh, as it were.

    Meanwhile, I have spent the day familiarising myself with the box contents and the drawings. I think I know what the loco ought to look like, and I think most of the parts to do that are there. My last act of the day was to go through the hordes of components to winnow out the parts not needed for this build.

    Tomorrow, I may well make a start on the frames.
  10. John Rich

    John Rich Active Member

    Many thanks Heather, shall only invest when I have seen one. Looking forward to following this build.

  11. Heather Kay

    Heather Kay Western Thunderer

    After the research and colouring-in, I felt I had a fair handle on what this loco is supposed to look like. One final tiny hurdle had to be crossed before serious metalwork could begin.


    Frame spacers. The kit spacers cover the gamut from 00 through EM to P4, dutifully enlarged to 7mm scale. Even the P4 spacers seem a bit thin. The drawing in my possession claims a gap of 4ft 1in between the frames, which I made out to be about 28.3mm at scale. The kit spacers measure 24.3mm. That would leave some hefty gaps between the backs of the wheels and the frames in S7. Helpfully, some time ago, the client had had made a set of nickel silver spacers which measure up at 25.9mm - still narrower than the prototype, but better than the kit parts. To add further measurement confusion, the reprofiled wheels haven't been thinned, remaining more or less the width of a standard finescale tyre (nearly two inches over width, or thereabouts).

    Now, all of that is by way of explaining what I did next! You see, in order to work out which spacers would be best for the job, it sort of made sense to temporarily assemble the frames, bung in the wheels and see how the land lies for clearances round the cylinders. If the new spacers didn't work, plan B was to use the kit ones.


    The the kit spacers are designed with folds, holes and tabs to make this job easy. If the replacement spacers are to be used, I will need to transfer a lot of those folds and holes. For now, I used three of the spacers, tacked in as square as I could make them (thank goodness for engineering squares and magnets!). By some miracle, the frames were within a gnat's crotchet of being bob on square, and I spent an enjoyable few minutes whizzing them up and down my test plank. I then quickly knocked together the cylinder framework so I could have an attempt at seeing how much space might be available around the slide bars and crossheads. On first blush, it looks like there'll be a fair amount, which is encouraging.

    My thinking is the frames will have all axles sprung. The client's layout is to S7 standards but limited to 1:6 crossings and 6ft radius curves. The relatively short wheelbase of this loco shouldn't be a problem, but I hope to be able to engineer sideplay in the rear drivers by mounting the gearbox on the centre axle. The leading and centre axles will essentially have little or no sideplay.

    With all that in mind, then, the plan is as follows:

    • Make the new spacers up to match the form of the kit spacers, with suitable holes and folds.
    • Cut out the hornblocks and remove the etched springs from the frames.
    • Work out whether the brake hanger holes need to be moved slightly to cater for the small wheels.
    • Assemble the frames, fit the overlays, and make up the etched sprung hornblocks.

    With a fair wind, I might just manage that tomorrow.
  12. daifly

    daifly Western Thunderer

    As I've said elsewhere, it is surely the dimension over the outside of the frames that really matters! I understand and agree entirely with the issue though!
    Stumpytrain, adrian and Dog Star like this.
  13. Dog Star

    Dog Star Western Thunderer

    Correct Dave.

    Distance between frames of 4'1" is common for those GWR engines which are in the baby / small / light brigade and such engines often have frame plates of 3/4" thickness. Larger GWR engines can run to 1 1/8" frames and hence either the distance between is less or the distance over is greater. This reads like a topic worthy of further study and may be just the thing to while away the nights in hotels on the continent ;) .
  14. Neill

    Neill Active Member

    I'm looking forward to following progress on this build. It is a kit that is high up on my list to build, and this is taking it to a higher plane!
  15. Heather Kay

    Heather Kay Western Thunderer


    Not quite as far as I'd hoped. My excuse is we had some mild disruption of a kitchen-related nature this morning (new sink, tap and associated plumbing installed).

    The first job, after disassembling the temporarily-assembled frames, was to make the replacement spacers match the patterns of holes and folds of the kit parts. Once that was done, I could sweat the overlays onto the basic frames, and then spend ages tidying the cusps. Once more relying on small squares and magnets, I spent a while attaching the spacers in more or less the right places on one side of the frames. Things were tacked at this stage, to make it a bit easier for tweaks and adjustments if required. The other frame side was attached without too much swearing, the only awkward moment being the front end spacer which means the frames have to be gently bent inwards. I had to take the spacer out to rearrange things, but it worked out in the end.

    A check on my bit of old mirror tile showed once again Lady Luck was smiling on me - things were pretty straight and square!

    I've made a start forming the etched hornblocks, but I will need to sort out the coupling rods and the assembly jig to ensure things are aligned properly.
    Last edited: 6 August 2017
  16. john lewsey

    john lewsey Western Thunderer

    Very nice Heather clearly I left toooo early today still sink plumbed in off to the next one
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  17. Heather Kay

    Heather Kay Western Thunderer

    After a lapse of reason, where I misread the drawing for assembling the etched hornguides and built a couple of them bass ackwards, I managed to get things back on track.

    I'm not a big fan of milled rods. While they are nicely made, do actually fit, and include a form of knuckle joint, they lack the scooped rear face that helps the real thing avoid clouting the wheel bosses each revolution. I was in several minds about whether to use the ones the client had squirrelled away into the box, or break out the soldering iron and assemble the etched ones. Laziness, in the end, won out. It was simply quicker to use the milled rods. I wanted this thing on its wheels by the end of the session.


    They still clout the wheel bosses, though. There's still lots of sideplay at present, and that doesn't help. I wanted to see if they were actually feasible with minimal fettling, and they may well be. Provided I fit enough washers behind the crankpin top hat bearing, clouting is minimised - but that may lead to issues with clearances elsewhere. I still have the option to build the etched ones, something I've done a few times now and feel comfortable with despite it being a long-winded process. The alternative would be to do some careful filing on the backs of the milled rods to thin them appropriately. If I felt brave enough, perhaps even actually mill the backs - it wouldn't be the first time. :eek:

    As it is, the chassis has ended up reasonably straight, the wheels spin freely, and despite no springs in the hornguides it rolls nicely along the test plank. Incidentally, I have got the rods the right way round. All the photos of the early 3100s show the joint leading.

    The Slater's wheels have what I think are older style fixing screws. No matter what I try, I can't get the screws to settle down flush with the face of the boss. I wonder if any WTers have a solution to this. It is also being considered whether the tyres need to be thinned a little as they appear to be over scale width. Anyway, I'm pleased to have got the frames rolling on coupled wheels. I can sleep well tonight!
  18. Steph Dale

    Steph Dale Western Thunderer


    I use a 5mm countersink to deepen the front of Slater's wheels as is occasionally needed. It came from RDG Tools, IIRC.

    Paul Cambridge and Heather Kay like this.
  19. Heather Kay

    Heather Kay Western Thunderer

    Thanks Steph. I feel a tools and bits spend coming on!
  20. Heather Kay

    Heather Kay Western Thunderer

    There are days when you know something isn't going to work out as you had hoped. Today was that day for me.

    I planned to fit the SDK brass spring castings. The problem was, they didn't fit. Something was awry with the hornguides, and after consulting the drawing I realised I had fitted them too low in the frames. That would explain the unsightly gap above them, then.


    Having achieved a reasonably free-running set of frames, it was painful pinging the bits off again so they could be fitted back in the right place. How did I make such an obvious error? Well, the kit designer had helpfully provided a half-etched dashed line along the inside of each frame. There were corresponding half-etched lines on the hornguides. There isn't anything explicit about the lines in the instructions, which are mainly written for 4mm scale, so I put two and two together and made several. I lined things up along the dotted line. It worked, albeit with the extra gap at the top. Only when I offered a spring casting up did I begin to realise my error.


    So, out with the chassis jig again, and luckily for me the designer had made things so careful alignment with the use of the Eyeball, Human, Mk1, would lead to axleboxes that still more or less fitted the rods.

    Big sigh of relief.


    The SDK spring castings are from JLTRT. Obviously, they aren't exactly right according to the drawing, particularly the mountings at the front and rear axles. Still, they fit with some fettling and a little removal of material so they are less likely to clobber bits of permanent way - they are very low slung with those teensy wheels!

    The next thing, I think, ought to be working out the brake rigging, followed by the pony trucks. Then I can work out the best way to get this thing powered up and trundling under its own electrickery.