Atlantic's works: A needlessly complicated D7?

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Atlantic 3279
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

Certainly worth considering, if necessary. It would have to be a very neat, close joint in the boiler barrel to satisfy all inspections. Fortunately, the motor slots in to the fully round boiler as it is, and runs quietly on tests so far. In order to adopt the boiler cut-out / motor cradle idea, I'd probably have to put the very basic suggestion of inside motion onto the rocking chassis unit rather than having it, as now, as part of the running plate module. That might not suit potential resin casting plans quite so well.
Of course, if this project ever goes so far as to generate resin duplicate parts (for items other than the four coupled loco drive unit as I'm sure that other builders would want to do that in their own preferred way) then any builder will be free to cut out the boiler bottom if desired, along with the dummy motion between the frame tops on the running plate, re-using those pieces as he sees fit.
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Pebbles
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Re: Atlantic's works: A needlessly complicated D7?

Post by Pebbles »

Just as a matter of interest, and knowing that your are a member of the GCRS, can you give a pointer as to where loco and tender details/drawings can be obtained?
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

The drawings I've obtained so far are not at all ideal. I'm not sure whether I could have obtained better during the pandemic restrictions. I've been referring to:
1. A part of a works drawing that appears (or appeared) on the 567 loco group website (not the latter-day CAD rendition which is or was also there).
2. A basic line drawing from a book called "Locomotives worth modelling" - thanks due to John Quick for pointing that one out.
3. With due care to note the differences, a drawing for the later Class 11A (D6) at https://www.railwayarchive.org.uk/engin ... 56762_8238
Tony Gee reminded me about that third one.
The rest of the information has come from published dimensions such as in RCTS 3B, from photographs, and from comparison with the related J10 class.

John Quick also kindly lent me a large drawing for a Parker-era "3000 gallon" tender a couple of years ago. That allowed me to work out the ways in which it matched up to, or differed from, the later Robinson 4000 gallon versions.
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Re: Atlantic's works: A needlessly complicated D7?

Post by Pebbles »

Thanks for that. From what I have found the D7 Belpaire boiler is common to a few other types. I had also previously found the 567 group site and that part drawing. Additionally, for what its worth, I have Skinley Drawings for both the J10 and the D6.
Skinley Drawings are often much maligned, but many are quite sufficient for modelling purposes. I believe they can now be obtained from the HMRS.
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Re: Atlantic's works: A needlessly complicated D7?

Post by Chas Levin »

That's an interesting suspension mechanism (hope that's the right way to descibe it?), very keen to see how it performs. You mention avoiding doing up the mounting screws too tight, so I'm assuming that means you leave them a little proud to allow rocking? If so, how do you maintain them at the correct level - threadlocker?
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

The screws, with tight, self-cut threads in the plastic blocks, so far show no inclination to un-wind without the use of a screwdriver.

The "suspension system" is a slightly simplified version of the one that has proven successful for years in my mostly Little Engines D10 so I don't anticipate any problems. The D10 has the added sophistication of one rocking axle in the drive unit and one in the bogie too, effectively creating full compensation, but that was only ever intended to run on finescale track. With a view to possible guest appearances on layouts with universal track, I thought a simpler system (albeit one that keeps only six, rather than all eight of the wheels, on the track and bearing a load at any given instant) would be more sensible as the rigidity of each group of four wheels helps to reduce the likelihood of narrow wheels dropping into wide crossing gaps. It is akin to a vehicle on two four-wheeled bogies, although the rear bogie cannot turn so the leading one has lateral freedom as well as a pivot.

Another point about drawings, or actually photographs that are almost as good as drawings for model making: as well as a good "square on" side-view on the 567 website (a loco with extended cab roof but still with round-top, low-slung boiler) there are a couple of "square on" side views in E.M. Johnson's book on GC locos (vol 1), one of these having the higher-pitched Belpaire boiler. Reprinted carefully to scale they are a very good match to the key features of the official drawing.
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Re: Atlantic's works: A needlessly complicated D7?

Post by Chas Levin »

Atlantic 3279 wrote: Thu Apr 15, 2021 9:26 am The screws, with tight, self-cut threads in the plastic blocks, so far show no inclination to un-wind without the use of a screwdriver.
Oh - of course, I'd forgotten that the screws are going into plastic! :oops:
Atlantic 3279 wrote: Thu Apr 15, 2021 9:26 am The "suspension system" is a slightly simplified version of the one that has proven successful for years in my mostly Little Engines D10 so I don't anticipate any problems. The D10 has the added sophistication of one rocking axle in the drive unit and one in the bogie too, effectively creating full compensation, but that was only ever intended to run on finescale track. With a view to possible guest appearances on layouts with universal track, I thought a simpler system (albeit one that keeps only six, rather than all eight of the wheels, on the track and bearing a load at any given instant) would be more sensible as the rigidity of each group of four wheels helps to reduce the likelihood of narrow wheels dropping into wide crossing gaps. It is akin to a vehicle on two four-wheeled bogies, although the rear bogie cannot turn so the leading one has lateral freedom as well as a pivot.
Ah, interesting. And yes, I am growing more familiar with the mixed blessing of full compensation on non-finescale track... :roll:
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

Thinking that they looked suitable, I copied and fitted to the shoulders of my D7 firebox the same kind of hole covers that I'd used on B3 / B7 boilers. Once in place, I thought they looked a bit too big, but that the impression of excess size might be due to them being a contrasting colour, so I gave the whole assembly a quick blow over with grey primer. They still looked too big!
In between other things, I've therefore had a go at making from scratch a one-off plasticene mould for some smaller versions and have cast a strip of these ready for another try, after suitable cleaning up and trimming. I've also produced potentially suitable rough castings for a chimney and dome. By now, you might imagine I'd have had these fitted and much more besides. That's certainly what I expected, but an unmissable "limited opportunity" arose to carry out some work that may well stand me in good stead for another intended project, so I shifted the focus of my efforts for a while...
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

Yesterday I filed the chimney and dome bases to the right shapes to seat properly on the boiler, then tacked them temporarily in place with little slices of double-sided tape. I also removed the large covers from the firebox shoulders, cut and filed my new smaller castings to the best shapes I could manage within the limits of my patience, stuck them in place with a touch of Liquid Poly (which only acts on the plasticard boiler, but is enough to goo the tiny resin blisters in place) and then gave the firebox another waft over with grey primer. Today, after working out dimensions from photographs last night, I've cobbled together a representation of the two-column cased safety valve, using four little pieces of plasticard and an offcut of very small section square brass bar. When I've created a suitable smokebox door I think the next items begging for attention are the roof and upper front of the cab...
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Re: Atlantic's works: A needlessly complicated D7?

Post by S.A.C. Martin »

The D7 is looking most excellent Graeme.
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

Nice of you to say so Simon.

Tediously long job making a smokebox door today. I knew of no available commercial example of the right type, and I did not imagine that it would be easy or particularly effective to take an impression of the door on my DJH J10 with a view to copying in resin. Cab roof likely tomorrow, as I gather we are expecting more cool, windy and possibly wet "better off indoors" weather.
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

I started with a 16mm dia disc of 1mm thick plasticard for the smokebox door, drilled centrally and screwed onto a mandrel meant to carry miniature abrasive discs. I couldn't be bothered to set up my rudimentary lathe (electric drill clamped in a Workmate), but I managed to turn the front face of the disc to approximately 40mm radius by rotating the mandrel by hand in a pin-chuck with the plastic rubbing against files and a Stanley knife blade at various stages, everything supported steadily of course. I then added another 16mm disc, 0.25 mm thick, solvent welded to the rear face and rounded the edge gently, before adding yet another 0.25mm layer of slightly larger diameter to represent the seating ring of a later type smokebox door. I also left a side tab on that final layer to help to support the hinge parts when I added those. The hinge plate was cut to shape from more 0.25mm plastic, and once well stuck to the door I formed the short straps to shape over the piece of 0.45mm brass wire that I had added, and superglued them down. Finally, I stuck a piece of 2mm plastic rod into the central hole I'd made for the mandrel, and filed this back leaving just enough proud of the door to represent the circular plate behind the door handles. The door is shown held in place only be little bits of double sided tape.
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The basic cab roof and upper front have now appeared too. The roof is of three layers of 0.015" plastic, pre-curved then bonded together to set the required final curvature. Only the top layer will project over the cab sides (too much so at present, allowing for final trimming), the smaller middle and lower layers forming a rebate at the edges to give a reasonable chance of a strong joint and helping to maintain correct width of the cab. The front edge is rebated too, allowing a small overhang of the top layer. The basics of the cross-ribs have gone on too, from 0.7 x 0.5mm microstrip, on its narrow edge. Once joints have hardened I'll thin the ribs down a little towards their top edges, and add the flats of the angle irons to the roof skin using 0.7 x 0.25 strip. I can then trim off the ends of the cross ribs and add the rain strips near to the roof edges.
I've left the cab front solid at this stage, and removable. I'll see if it is possible to drill and file out the spectacle shapes without breaking through the edges, otherwise I'll have to build the outer edges up from strip, working on a thin backing layer.
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Re: Atlantic's works: A needlessly complicated D7?

Post by James Harrison »

I must say looking very impressive indeed. I'm watching with particular interest as I'm a supporter of the 567 project.
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

Hello James. It's interesting that you mention 567, which is, I gather, to be re-created in original MS&L form. Although I'm not making it particularly easy to do a backdating job, if this model does end up becoming a set of resin castings I'm deliberately preserving some scope for conversion back to original class 2 / 2A condition. The firebox top is a half-cylinder internally, so the Belpaire shoulders could be filed off VERY carefully to match the 19mm external diameter of the boiler clothing. A millimetre or so could be filed off the smokebox base and the tops of the wheel cut-outs in the boiler to allow it sit lower. The front of the smokebox could be trimmed back to restore the original length, and the cab roof cut back to leave just the one rib 17mm from its leading edge. A new plate for the upper cab front with round spectacles might be easy enough for most modellers to make. The side coal plates shouldn't be enormously difficult to trim off the tender cornices. You'd need a different chimney and safety valve from somewhere of course.

If I'm feeling incredibly keen and well-off for time, eventually I might even consider an additional mould for a round-topped boiler.
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Re: Atlantic's works: A needlessly complicated D7?

Post by Atlantic 3279 »

When I offered up my upper cab front to my working drawing for the spectacles I realised how thin the outer edges would have to be prior to adding the frames, so I abandoned the idea of drilling and filing out the apertures. Instead, I cut the upper corners of the plate away completely, and reduced its width slightly too, then added various strips to re-create the outlines and to represent the raised framing around the glass. I'm not convinced that I've got exactly the desired profile to closely follow the shoulders of the Belpaire firebox, but I cannot persuade myself to attempt further refinement at this stage. That will not prevent tweaking of any resin copies, if the will is there, should they come into being.
I've completed the addition of strips to the roof too, although I now need to add an edging strip around each cut-out in the cab sides. It is beginning to look a lot more like a complete loco...
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