An Anniversary Parallel Boiler Royal Scot with CSB

Discussion in 'Workbenches, including workshop techniques.' started by andrewb, 29 October 2017.

  1. andrewb

    andrewb Western Thunderer

    In 2018, the RAF celebrates its 100th anniversary - on 1st April to be precise and, although the comedy value of that precise date has always amused me, I mention it primarily as it is the deadline I've set myself to produce a model of this magnificent beast:


    Yep - 6159 The Royal Air Force in near original condition - its smoke deflectors just added scarcely 2 years after it rolled out. One of the batch of the final 20 to be built at Derby in 1930, complete with bogie brakes, slide bar vacuum pump (t'other side) and (unusually for Royal Scots in general but some references state common with the Derby lot), a fully vermillion front buffer beam. I have a very blurred photo of it prior to getting its smoke deflectors and I haven't completely ruled out building it exactly as it rolled off the production line. That rather depends on what modelling shortcomings I may need to hide with those very useful 'screens'..!

    I'm using David Andrew's lovely kit, although have already decided not only to pair it with a Ragstone Models Fowler 3500g 'Old Standard' tender, but also to incorporate CSB in the loco (it's already in the tender kit) - something I think adds a considerable degree of realism to the way the model moves, from my experience with P4.

    It's my first attempt at CSB in 7mm scale.
    Last edited: 5 November 2017
  2. andrewb

    andrewb Western Thunderer

    I'm planning to blog it, not only to elicit helpful comments from fellow WT'ers, but also to try and fly the flag for CSB, which seems to be something of a niche area in 7mm. I've a few busy days ahead so won't start immediately, but hope to post within the next fortnight.
  3. adrian

    adrian Flying Squad

    What scale would that be? [edit - spotted you mentioned 7mm before I could reply!!]

    A really nice choice for prototype. I spent two weeks work experience working for Bob Moore ( one of the finest engineers I have ever had the chance to meet). At the time he was rebuilding a 10 1/4" gauge parallel boilered Scot that eventually ended up at Great Yarmouth. So I have done a bit of work on these locos and will watch with interest. It is a class of loco that I would like to build at some point.
    andrewb likes this.
  4. Dikitriki

    Dikitriki Flying Squad

    I must admit I like the parallel-boilered LMS locos - I have a couple of Patriots in various stages of build and I fancy doing a p-b Scot with a Stanier tender sometime. I shall follow the build with interest.

    andrewb likes this.
  5. warren haywood

    warren haywood Western Thunderer

    Just to whet the appetite, built by Andrew Childs painted by yours truly

    Peter Cross, 3 LINK, daifly and 11 others like this.
  6. Heather Kay

    Heather Kay Western Thunderer

    Think you need a longer bit of track there, Warren! :thumbs:
  7. Cliff Williams

    Cliff Williams Western Thunderer

    Stunning Scot - was it based on a kit?
  8. andrewb

    andrewb Western Thunderer

    @warren haywood, whetting the appetite indeed although also setting the bar nicely high! ;) I’ve admired your work elsewhere on the site Warren, and wonder if you’d please keep an eye on progress to advise from the painter’s perspective?
  9. warren haywood

    warren haywood Western Thunderer

    Will do Andrew
    andrewb likes this.
  10. warren haywood

    warren haywood Western Thunderer

    David Andrews with extras Cliff
    Cliff Williams likes this.
  11. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Parallel boiler Scots... Mmm.... aren't they just baby Nelsons? :)

    No 6159 with the Fowler tender piled high as in the first photo would be interesting.
  12. andrewb

    andrewb Western Thunderer

    The late great Squadron Leader David Jenkinson would probably have held a different opinion! ;):D
    Last edited: 31 October 2017
  13. Steph Dale

    Steph Dale Western Thunderer

    Hurrah!!! Well done, Dave; somebody had to say it, and for once it wasn't me... :D

  14. Lancastrian

    Lancastrian Western Thunderer

    No they weren't. Although the LMS did receive drawings from the Southern they only used them for the firebox. The boiler was a version of that used on Big Bertha, the motion was derived from the Fowler 2-6-4T's and it was 3 cylinders instead of 4 so the front end was completely different. If it wasn't for the dead hand of Anderson and other ex Midland LMS management types, we could have had a compound Pacific instead !

  15. John K

    John K Western Thunderer

    Meet me outside the school gates Steph.
    Lancastrian likes this.
  16. andrewb

    andrewb Western Thunderer

    This is the only photo I’ve been able to find on t’internet of 6159 prior to fitting the smoke deflectors, and it’s of only marginal usefulness - looks like a very low-res scan of a small photo: does anyone have anything better, or know of a source that would be worth tapping? I’d particularly love to see whether there are any of a military parade-style naming ceremony, as happened with the Army regiments’ locos
    Last edited: 4 November 2017
    Tim Watson likes this.
  17. andrewb

    andrewb Western Thunderer

    Aargh! With the wretched day job getting in the way, spoiling all my fun, it feels like I'll never be able to start this project!

    Here are some initial thoughts:

    I've a very nice looking kit to start when time allows.


    S'cuse the smartphone photos, but this is just a quickie post. No real surprises (aside from the scale that I'm not used to!).

    Nice clean castings too -


    I think I'm going to enjoy this. I'm re-thinking some of the white metal components, as nice as they are, simply because I hate white metal! I'll give them a go though. Some neatly detailed components - there are nicely featured Brake Crossmember brackets, for example, shown on the sprue lower left. On the other hand, I was a little disappointed with the absence of half-etched rivet marks around the horn block area on the frames - something I think is much more clearly visible on the prototype. I'm still making up my mind whether to mark them up and go ahead anyway, although I'm mindful that David Andrews is scaling back and I'd hate if it went wrong and I needed a replacement! Might let that one go. Minor point really!
    Last edited: 17 November 2017
  18. andrewb

    andrewb Western Thunderer

    Choosing horn blocks, however, has been tricky. In the short spells I've had available for modelling I've tested a few concepts for CSB, none of which I'm all that happy with. The photo below shows, from left to right, examples from Comet Models, Slaters, Laurie Griffin and Finney 7, all - the latter 2 especially - being great for the purpose they were designed for. But...


    Pros and cons: Comet comes close: no horn guide detail across the top of the slot to worry about, only a small lug to remove and quite a nice close fit. In addition, their axle blocks had plenty of room to drill for a CSB 'peg'. But their overall depth was too much to fit the motor gearbox on the powered axle. I explored the Slater option as a space-saving alternative. There was a bit more material to remove before it would work, but the inherently thinner axle block meant I had to cut off the 'collar', reverse the bearing and cobble together a soldered-to-the-outside option on the wider segment in order to align with the Comet 'peg' holes. It looked a bit vulnerable and I don't trust it to be strong enough. Laurie Griffin's separate Horn Cheeks look absolutely brilliant and, with Comet axle blocks being exactly the right size, are probably as close to prototype as it's possible to get. Unfortunately, like the Comet ones, they're too deep for the motor. Finally, some Finney 7 Stanier Horn Guides intended I think primarily for their amazing Princess Coronation were the nicest fitting of them all, but with the smaller axle block (o/d of axle sleeve being 6mm) and a generally less deep square section with little or no place to fix the pegs I ruled them out. Besides which, it ain't a Stanier!: I'll put them back in the Duchess box until I come to make that kit!

    So - options. Do I seek a narrower gearbox/motor combo and run with the Laurie Griffin? The frame spacers are 24mm and the ABC gearbox takes up 16 of those. I'd rather not, as the motor/gearbox was a bit expensive just to take 'into stock'! Current thoughts are gravitating towards using the Slaters, particularly bearing in mind its axle stays, essential for the front axle fitted on the prototype with coil spring suspension. Horn guides filed back only a little (not nearly as much as in the concept trial one), the collar remaining on the axle block (as shown in photo) and resting the CSB wire on that rounded surface rather than struggling with a peg. It feels like a bit more of a compromise than I hoped would be the case, but would probably work absolutely fine. Plus, with the CSB wire being a bit lower, I can probably hide it even more than originally thought. Decisions decisions!
    Last edited: 18 November 2017
  19. andrewb

    andrewb Western Thunderer

    I've also been busy with the sums. Positioning the CSB pivots on the frames so they avoid me having to drill through surface detail, looking for a consistent deflection of 1.5mm for a range of sprung masses from 850g to 2250g, in increments of approx 200g per thou using piano wire that'll fit in a Markits WD handrail post, I've managed to achieve a theoretical chassis gradient of 1 in 567545. Close enough for jazz. I'm reasoning that the 'as made' weight of the kit will be around the former figure and the maximum I'd ever want to bulk up to is around the latter. C of G is within 1.5mm of the intermediate coupled axle, which is biased 4% 'softer' than the front and rear axles, thus avoiding the risk of porpoising while still having near equal traction. I've a similar set of figures available for a 2mm deflection, and am still researching which would be best. In P4 the target deflection is only 0.5mm so in either case it's way above prototype. This is all theory, of course, and I wonder if I went for the non-peg Slater option suggested above whether it would slew the figures too much. Probably not.
    Last edited: 16 November 2017
  20. andrewb

    andrewb Western Thunderer

    Just to put numbers on the hornblock issue:

    Spacer width 24mm
    Griffin horn cheeks depth inside frame 4.3mm each
    Remaining space for gearbox (not including some space either side) 15.4mm
    Space required by ABC gearbox itself 15.6mm
    Last edited: 17 November 2017