Tom Mallard’s Workbench L&B in 7mm scale and clockwork CR 828, 4mm Saints

Tom Mallard

Western Thunderer
Blimey! (puts thinking cap on)

I will try to do something soon then, but the easy thing would have been to photograph them as I went along even if the resulting image is tiny. Sadly I didn't do that this time.

If you don't mind having to use your imagination this time, then I can list how I put them together? I also expect that this is a rough draught of reality, omitting any aspects of profane language or despair.

In all cases I have a dimensioned drawing which comes from my CAD file for the model I am making. Of course a pencil sketch works fine.

I always keep the part held as part of the bar stock for as long as possible and keep the part as simple as possible in the sense that I will avoid adding parts unnecessarily if I am able to incorporate them as details turned or machined into the surface. That is not to say I am compromising on the detail level I choose, just reducing the chance of error or the number of processes or the possibility of the pattern disintegrating at some future time.

I make a 'blank' of the pattern which is the main body or simplest part upon which to attach the rest of the details and plan everything else around this.

For the valve guide, this is a cylindrical form which has the bolt detail holes and location for the valve slides drilled into the end using an indexing head. This is done on my Stevens 8mm milling machine, and the drills are shanked ones by Sphinx.

For these 4mm scale patterns, the bolt detail is 0.4mm wire soldered in with 188 solder paint. The bolt detail is then cut back with a file before putting back in my lathe for a few passes with a lathe tool to tidy them up. It is left oversized before the drilling so that the tiny drill is not given any opportunity to wander, after which the more or less final profile is done back in my lathe. I round the edges of the bolt detail off with a little cup shaped burr that jewellers use and this improves their appearance somewhat.

The main body was then cut from the bar stock.

The slides for the valve guide are an egg box construction from small etched parts. I could just as well have cut them from sheet, but etching seemed the obvious choice as much of the rest of the engine took advantage of this process. A tiny turning is also included for the gland. Small strips of material have been overlaid to thicken the pattern where the crossheads would run in real life, and are left oversized before dressing the ends of the slides to the final length

After assembly I ran the pattern in my lathe on it's mounting spigot and cut a miniscule groove where the steamchest front and cover meet, then carefully turned any build up of unwanted solder off the pattern and sharpened up any edges as I went. I am currently using a small abrasive mop type wheel and a fine automotive refinishing mat as a means to finish the surface prior to casting as casters always like to see shiney smooth patterns.

The whole pattern is 3% oversized, which on a CAD drawing is a very simple thing to do.

Well that's a start.

As a disclaimer, I am self taught which I hope can give others the sense that if you put your mind to things, then most things are possible.

Best regards

Tom
 

Tom Mallard

Western Thunderer
After checking my drawings and a few photographs, I have re-made the ashpan detail. It was a bit more fiddly than the first attempt as the outlet pipe had to be a separate part, and the front cover plate needed a groove behind it of only 0.3mm width.

I almost remembered to take some pictures as I went, so there's one just before the stock material is removed and the pattern is polished up.

It is clear from the photos that I have exceeded the limit of resolution for my camera! But it is only little after all...

Best regards

Tom
 

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Tom Mallard

Western Thunderer
Some lathework this time. I have taken the trouble to take pictures...

Based on the information I supplied on pattern making I have this time started on the main boiler fittings.

The fly cutting of the blanks takes place with the blank screwed to a bar mounted in my toolpost. The fly cutter is home-made from 1/4" mild steel with a piece of tool steel mounted at 45 degrees and held in place with a set screw. Both these attachments show how even very simple and/or crude devices can be used effectively to give a satisfactory result.

The skirt of the dome is started with a simple form tool, then blended in with a burr followed by a lot of supplementary dressing with files. The top profile is all done by hand gravers as illustrated. Using a graver is simple in theory but care must be exercised with spindle speed to avoid unnecessary chatter of the work, or taking unwanted gouges. Taking unnecessary gouges is extremely easy with the burr and I often worry myself at this stage. I nearly always leave extra material left around the piece to take into account mistakes and also to allow me to sharpen the work up at the end.

I will review the dome again later on once all the fittings are done and finesse it if I feel the need.

Best regards

Tom
 

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Tom Mallard

Western Thunderer
Just a small update now the frames are up and the castings for the valve guides have turned up...

I have attached the boiler/firebox to the cab front and put in the floor and half round beading for the back edge of the cab. The coupling rods have come out completely spot on, but I am now worried that Gresley high strength steel doesn't scale down to slim nickel silver etchings in terms of strength... I finally got the smokebox saddle together and it sits quite nicely against the smokebox itself plus the height is now properly set relative to the centre line of the boiler

The chimney, dome and door blank are done, too. I might return to photograph these more clearly as low artificial light and bad technique/lousy camera combine to give no depth of field.

Best regards

Tom
 

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Tom Mallard

Western Thunderer
More B2 this time, and I'm finally able to be happy that it is nearly done.

Lots of bit and pieces went onto the bodywork and the chassis, and now there's just a few details to put in and under the cab. The chassis has been configured to allow for a block of lead within the firebox space instead of the usual (lightweight) motor or gearbox. The centre of gravity is just ahead of the middle coupled axle so fingers crossed it performs as required...

The nameplates are from what must have been one of the few commissions undertaken by Diane Carney over the last year or two as she now edits Model Engineer, and although she drew the artwork it was up to me to have them etched. They're a cosmetic splasher face with the nameplate on top, as the original B17 to which they were fitted had a lower footplate with bigger splashers and hence a larger space to fit nice names onto.

I've just been running the gearbox a bit to check it and now look forward to finally giving the whole thing a proper test run (I usually leave this sort of thing until far too near the end of construction) in the near future.

Best regards

Tom
 

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Tom Mallard

Western Thunderer
I've added another K3 update of some key parts. With the firebox/boiler/smokebox permanently attached to the footplate, the strength of the bodywork is now set. I could remove the jig now to see it sat on the frames, but I think I must exercise some patience and use the valence jig to help mark the level of the handrails for example.

The keeper plate was a little bit awkward and all the Dave Bradwell spring dampers had their spigots turned down to suit my etched parts. Ultimately the pickups will also be attached to this, too.

The pony truck is something I am quite pleased with, though it still needs guard irons adding. The castings will likely be more or less invisible once the wheels are on.

The B2 made a visit to the Bristol Gauge O show where I discussed with Ian Rathbone what to leave off or add before he paints it. I also met the esteemed Dikitriki of this parish...

Best regards
 

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Tom Mallard

Western Thunderer
The B2 61632 is now ready for its paint.

Poor old Thompson got really hammered for interfering with Gresley designs, but I have gradually taken the view that the B2 is a handsome engine and in this form with the modified ex-P1 tender is very unusual.

Just to help it with the job it must do, I will likely put some extra lead in the roof of the boiler/firebox area as all the existing lead is siutated in or above the chassis frames.

Best regards

Tom
 

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