G-Train Locomotive Works / Graeme King Joint Venture - GCR/LNER 4-6-0s - B3/1 & B7 available; B3/2 in progress

[Atlantic 3279]

Patterns or masters for further resin twiddly bits for the four-cylinders - you saw them here first:

Held in place temporarily on square of double-sided tape, and close-to-scale if the published works drawing was actually followed, a sand-box lid. A slice of 3/32" brass tube with a slice of plastic strip inserted.

Another.

No keys under this piano lid I'm afraid.

Sand box lids on other side.

Cylinder front cover, again to scale as far as I can tell from the drawing and from photographs. I've tried to capture my impression of the Robinson style of these, which appear to me to be slightly convex across the main face with a rounded edge. Discs of 1mm plasticard cut using a suitable size of brass tubing with a sharpened edge, then temporarily stuck to the flat end of something such as a pencil to facilitate shaping and smoothing with files and abrasives, turning the work piece constantly to get a uniform shape. The centre fixing is a stub of wire fitted into a tiny hole.

Front sandbox which will be all but hidden behind the motion bracket, slidebars, crosshead and con-rod.....

If I've read the very "busy" drawing of this area of the loco correctly, these front boxes had a partly tapered outer face as well as different tapers to front and rear. I've tried to include all of those tapers. The tops of these boxes will need a trim as I now realise that the etched stretcher for the motion brackets has to pass through what is currently the upper 1 to 1.5mm of these items.

Rear sandboxes.

Once I have the details on the boiler I should be ready to start some mould making!

[Hucknall Central]

Anything GCR is in my world; please put me on the waiting list, Graeme.
Thanks, Paul Greenwood.

[Atlantic 3279]

Noted. Thank you.

[Rustynuts]

Please put me on the waiting list too, looking forward to building any of the locos you produce.

regards

Paul

[Atlantic 3279]

Gladly!

[Horsetan]

Stunning. B3 was fascinating, even though none survived ultimately.

Looking forward to having a go at the production model in P4.

[S.A.C. Martin]

Just out of idle curiosity, is there much similarity between the D11 and B3 boiler wise? Just curious as to why the cheapo GBLK knock off D11 couldn't be used as a basis for resin casting (complete with tender).

The etching is exquisite there, really captures that high shouldered look.

[Horsetan]

Just out of idle curiosity, is there much similarity between the D11 and B3 boiler wise?...

Maybe not

[Atlantic 3279]

Depends on degree of pedantry. The Directors had boilers 3" fatter than the Atlantics, medium 4-6-0s and the O4s, and 3" slimmer than the big 4-6-0s, so if you can live with, or ignore a 1mm discrepancy in girth in 4mm scale the only real difference between say B3 and D11 is barrel length. The firebox and smokebox are remarkably similar.

[LNER4479]

Due to two days away on a work assignment, got a bit out of sync with postings on the dark side...

So, catching up slightly, some further details of the chassis build. Tonight, focussing on the valve gear.

Valve gear? But it is doesn't have any, does it ... well not as you can see on a model?

Well ... yes and no. There IS some valve gear visible on the outside and it does move - the real loco wouldn't move at all if it didn't!

So, the etch includes parts such as this which are purely an optional extra. The outside parts can of course be assembled in a fixed position. However, this is what is entailed to get it all to move. These are the parts for a simplified version of the inside eccentrics, sufficient to impart a prototypical movement to the outside valves.

Now assembled, the off-centre hole for the axle is clearly apparent from this view.

These are the outside parts in cruel close up. There are two pin joints to allow for the slight rise and fall of the valve rod, connecting the crank to the valve piston (although such a rise and fall is very slight). The bottom of the crank is fixed to a shaft that runs through the lateral tube (highlighted at the end of the last post) to link with the inside part of the gear.

This shows the complete assembly, showing more clearly how the inside motion is imparted to the outside via the cross shafts. The installation on the far side is a simplified version, just trying out the two types as part of the test build.

[LNER4479]

Meanwhile, this shows the now completed motion bracket with the connecting rod now linked to the piston/crosshead. There should be a vertical handrail as part of this, which is attached to the bottom of the slidebar strap.

Putting it all together, it all revolves around smoothly, with just a nice lazy back and forth movement of the valves.

I'll try and get some video of it all in motion for the next post as the chassis now has a motor in it and will power itself.

[kimballthurlow]

That valve gear excentric motion is exquisite.
Should we have excentric and exquisite in the same sentence?

Kimball

[Atlantic 3279]

Depends how you spell them....

[drmditch]

I think some of us are eccentric enough already!
(I certainly am.)

[Atlantic 3279]

Each in our own ways....

I have not been able to get back to the B3 boiler until this evening, but it now has what I regard as the most important three dimensional details plus some pencil guidelines only for bands while I think about those a bit more. I'm inclined slightly towards the belief that no matter how I choose to portray boiler bands on the resin casting, they will end up not suiting somebody's views on the matter. I may be persuaded to leave them off entirely, leaving the matter to builder's choice.
I still need to consider whether to include pop-marks for handrail knob positions, and possibly some faint scribed top-dead-centre lines where the chimney, snifting valve, dome and safety valves should sit.