Atlantic's works: Portable layout - Ground Signals Again

[Atlantic 3279]

This may get partially repeated if I describe the method in full soon, but so as to answer your question neatly and quickly:
Hornby B17 boiler, plus spare Hornby B17 dome and Ross pops, from East Kent Models.
Dave Alexander K4 smokebox door (he does the chimney too, but I had another, which was....)
Spare plant-pot chimney from Little Engines D10 kit.
Whistle from Bachmann O4, made spare by changing O4 to cab roof whistle.
K3 handrails, knobs, snifting valve, ejector pipe and modified backhead re-used.
Main outside cylinder steam pipes sawn off K3 boiler moulding, patched and re-used.
Lamp iron from oddments box.
Smokebox handles are two shortened Gibson shoulderless handrail knobs on a stub of wire
B17 washout plugs and mudholes carefully left untouched on cleaned-up firebox.
As far as I can think all the rest is care, patience, plastikard, plastic tube, glue, filler and PVC tape boiler bands.

[will5210]

Thats most helpful, thank you!

Will

[Atlantic 3279]

I must get on with the promised description of my K3 to K4 conversion method tomorrow if possible, as I am now able to make it a full story by including a successful conversion of a 4200 gallon tender to 3500 gallon version, scale length with right coping shapes and right wheelbase. Not actually that difficult if you don't tell yourself that it's difficult!

[Atlantic 3279]

If anybody can bear it, here's the detailed account of the K3 to K4 conversion:

1. My first job was to spend half an hour or so solvent-laminating strips of plastikard, leaf-spring style, into the splasher recesses of the B17 boiler moulding, so that when the splashers were trimmed away solid boiler barrel and firebox would remain. Lamination done, I set the boiler aside for 24 hours for the plastic layers to harden up.

2. The next evening, after stripping off the paint in a few minutes in Phoenix plastic-safe model stripper, I trimmed away the bulk of the splashers using a piercing saw, and then tried to get the dome off. It is a separate, glued-on fitting, but even after I had drilled through the bottom of the boiler and up through the boiler top into the interior space of the dome, no amount of persuasion or sheer violence using rods and punches from below would pop the thing off. I couldn’t pry at the edges without ruining the thing, so the only option was to cut the bulk of it off, file down the stump, and fit a new replacement. Luckily I’d bought some more B17 domes from EKM too! Dome off, I then spent a couple of hours or more carefully relieving the boiler of ejector pipe and all boiler bands, as well as filling holes and blending in the former splasher areas. Side cutters took off the bulk of the ejector pipe, then a coarse flat file, followed by finer files (including half round ones to deal with firebox lower curves) and ultimately wet 600 grit abrasive paper did the job. I had to go VERY carefully around the washout plugs, and whilst I “decapitated” the mudhole mouldings the recessed remainder left in situ still looks effective.

A rough start:

Underside

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Holes filled and final smoothing done:

Saved details on firebox:

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3. A couple of hours on my third evening included rummaging around for suitable parts, then proceeding as follows: I added a wrapper of pre-curved 20 thou plastikard to the smokebox end of the boiler, after deciding exactly where this should be by comparison with drawings and chassis-donor model. It has to be slight compromise as the cab is going to be a millimetre or two too far forward unless the running plate is cut, extended and rejoined, and I had no intention of doing that extra work.
Within the front of the smokebox wrapper I added three more rings of 20 thou plastikard, making these protrude forward of the outer wrapper. These would later be filed smooth to create the ring of the smokebox front, but I took care not to file them back flush with the front edge of the outer wrapper, as I wanted to leave a stepped edge looking just like the visible lap joint in the plating around the front of a typical Gresley smokebox. The hole within the three plastikard layers was just the right size to accept a Dave Alexander K4 smokebox door, originally bought with a view to making a Thompson L1 but ideal for this job after Hornby sank the L1 project. After plotting positions for new boiler bands (not adding these until later on, using black PVC tape), I then drilled the smokebox top to take the stem of a whitemetal chimney casting. This was a spare Doncaster plant-pot from a Little Engines D10 kit. A spare Hornby B17 dome was then temporarily blu-tacked on, and a pair of Ross pops fitted in the pre-drilled firebox holes – more Hornby spares obtained via EKM as useful “stock”, probably listed as B17 or D49 items if I remember with any accuracy.

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Smokebox front filed back to required degree, leaving subtly stepped edge:

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4. The rear end of the firebox is too long compared to the intended cab front, but arrangements have to be made to fill the gap in the cab front left by the original, larger, plug-in firebox rear. Oddly enough, there’s a small inner corner of lower cab front on each side that has to be removed to accommodate trial fitting of the smaller boiler (as yet un-trimmed at the rear), as this otherwise interferes with the wide part of the curve that leads down into the waisted-in firebox bottom.

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5. Fitting the smaller boiler to the running plate at the right height, and making sure that it will fit over the motor and DCC socket involves the cutting out of a lot of material from the bottom of the boiler. Also, as the smaller boiler has no added covers along the lower edges of the firebox, these are not wide enough to fit outside the two ledges on the inboard edges of the running plate. Those ledges must therefore be removed. I taped over the adjoining running plate to protect it as much as possible whilst running a coarse file across to remove most of the ledges. The hard cast metal of the running plate does not file down quickly! Trial of the boiler in place appeared to show that even the tape-thickness remnants of the ledges kept the boiler sitting a little too high, so I had to take the ledges down absolutely flush using great care to avoid scarring the unprotected running plate excessively with the file. Even then the boiler wouldn’t sit down as nicely as it should, and I discovered that the inner edges of the bottom of the firebox were catching on the wide, lower part of the motor cradle. Having already opened out the firebox bottom to the full internal width of the firebox moulding, I therefore had to file a taper on the inner bottom edges to clear the motor cradle. All this done, the boiler sat down nicely on the running plate at almost the perfect height, controlled by the depth of the B17 firebox sides, although after some further scrutiny I decided that a half-millimetre trim from the bottom of the firebox sides gave a further improvement in the boiler pitch.

[Atlantic 3279]

6. I considered various ways to fill the void left in the cab front, along with backhead options. I could have butchered a spare Hornby B17 cab for its backhead, or made a cast resin copy of it and fitted that. I suspect that Markits may offer a suitable cast brass backhead too, but I decided that the larger K3 backhead would still be acceptable because it is so well hidden in the depths of the cab, especially when the crew are in the way. A cast metal backhead helps with weight at the rear of the loco too. The simplest overall solution seemed to be to fit a horseshoe shaped patch of 0.040” plastikard into the cab front, cut off the rear part of the firebox that projects back into the cab, and take off the raised lip on the front of the backhead where it previously plugged in to the rear of the larger firebox – the latter involving more heavy going with a saw and file. This approach does involve aligning and making butt-joints between the patch and the rest of the cab front, which are not the strongest things in the world, but I hope they are in relatively invulnerable positions. I actually made the cab patch by scribing around the inside edges of the cab front whilst holding it steady on my sheet of plastikard. I then very quickly and cleanly cut out the approximate shape using a few taps with a wood chisel before filing it to a good fit. The cut off line at the rear of the firebox was through holes for the original rear handrail knobs.

[Atlantic 3279]

7. As the original large boiler moulding incorporates the main steam pipes to the outside cylinders, and the sand fillers, these had to be replaced by new items, either scratch built or from the parts trade. I tried some SE Finecast K3 steampipes that I had but these are a bit slim and their bases do not fill the gaps between the representations of the lagged exhaust steam ducts on the cast running plate. I decided that rather than put up with these gaps, or try to fill them, I would split the Bachmann steam pipes from the K3 boiler using a razor saw and then fit these. All that was needed was to clean up the sawn top edges with a half round file, add a little pad of 20 thou plastikard, file this to match the shape of the rest of the pipe, and then stick the steam pipes to the somekbox, thus keeping the boiler and running plate separable. A new reversing rod also had to be made up, and larger balance weights should be fitted to the wheels to aid the illusion that they are the 5’ 2” type. Strips of plastic were also added around the cut-out in the smokebox base to represent the top edges of the cast saddle, and some new boiler bands, in tape, were applied. The conversion was more or less completed by an ejector pipe, boiler handrails, smokebox door handrail (height to suit chosen period for the loco in question), and snifting valve (all taken from the K3 boiler) plus a whistle stolen from my Bachmann O4 which gained a spare Hornby whistle let into its cab roof in LNER period style instead.

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This second image shows the steam pipes, with top pads filed to matching shape, fitted to the K4 firebox. Having no suitable sand fillers to hand (though the SE Finecast K3 ones would have been perfect) I stuck a D-shape of plastic to each side of the the lower front of the boiler, addded a piece of tube behind it and then filed that to a taper to represent the funnel-top of the sand filler. This, and the previous image also show the large area cut out of the B17 boiler bottom, as mentioned earlier.

Here's the fitted appearance of the steampipes, sand fillers, and a lot else besides. The balance weights were extended firstly by sticking a strip of 20 thou plasikard over the wheel spokes adjoining to the straight edges of the weights, then adding an overall facing of 5 thou plastic.

A late change, just this morning, was the Ross Pops. I thought the B17 ones, while adequate, were a shade too tall and chunky, and they seemed to me to upset the "high cab roof compared to boiler line" look that is essential in making the loco look like a K4 rather than a K3. I susbstituted the finer valves from the K3 boiler. To do this I had to plug the larger holes in the B17 boiler top with 2mm plasic rod and drill this 0.9mm to take the valves, in the process making the correct raised bases / bottom flanges for the valves.

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And so to the tender. As well as a choice of Loch Long as loco identity being convenient in terms of allowing me to leave the livery black for the time being, to suit 1937 to 1941 existence, the supplied tender with the K3 was the low front 4200 gallon type which allowed me to leave the front end of the tender body untouched when converting to the 3500 gallon version initially coupled to Loch Long.

Starting point:

Body stripped for action:

First razor saw cut, 8.5mm from tank rear

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Further razor saw cuts, all from the inside of the detached rear piece, firstly to split the tank-piece from the soleplate/valance/rear buffer-beam, then through the tank rear to separate the sides from the rear:

More razor saw work to detach the rear portions of the side copings:

And then the rear coaplate and water chute dome, intact. Awkward work as the surviving sides of the tank are still higher than the top deck. Patient use of tip of knofe and tip of saw required, without force or slashed fingers!

Yet another cut, 8.5mm from rear edge of deck, the idea being that on reassembly I'd get a stronger and more easily aligned and reinforced joint here, rather than along an edge. This also preserves the socket into which the water filler was planted. Notice that I've damaged the lifting shackle mouldings in the rear corners of the tank top. Had I angled outwards the tops of cuts through the rear of the tank, I might have managed to save these.

Final preparatory cuts, removing rear 7mm of soleplate and valance

[Atlantic 3279]

Where the rear copings were cut away I filed the tank down to 21mm height, and arranged the rising curve to peak 21.5mm from the new rear edge of the tank. Tank rear next bonded back into place, using slabs of 40 thou plastikard inside to align and brace the joints;

On the outside, I pushed strips of 10 thou into the saw cut gaps and bonded this in with solvent, hoping to get better strength than filler would provide. Layers of 5 and 10 thou were also bonded to the area to which I wanted to re-attach the rear piece of soleplate / buffer beam, as experience shows that I cannot firmly stick Bachmann plastic to Bachmann plastic direct using any solvent I've tried. An intervening layer of soft styrene is essential. The refitted rear soleplate piece should project up to 1.5mm more than it did on the original 4200 gallon tender. Compared to those larger tenders, the 3500 gallon version had the tank shortened to a greater degree than the underframe.

More fillets of plastic bonded into odd corners, cleaning up of shape started, and strips of 15 thou black plastikard wider than tank-sides bonded to top edges to create the look of the beading. Sticking on a wide strip on the edge is much easier than attempting to add a genuine thin beading of plastic to the face of the tank!
Note that I also plated over the rear tank deck with a sheet of 15thou black plasic, leaving just the fitting hole for the water filler showing. This saves awkward filing and smoothing of the main joint, and gives that joint additional support.