Continuing the story, time to look under some sixwheelers, first off a pair of my old ones, scratchbuilt for an Irish Line. Contrasting them with a sixcoupled loco, the wheelbase for a loco is around 4.3”/108mm, and for a coach is 5.8”/ 148mm. Generally I build my locos with an uncompensated chassis for the drivers, just some float allowed for the carrying wheels. As long as the driver flanges are all touching down to start, they can run quite well on my track. With a coach the extra length does allow track irregularity to become more of a problem if the wheels are mounted rigidly. If the centre wheels sit on a hump, the leading wheels can rise off the rails, and then it’s only how deep the flanges are that can save the situation, which is where coarse scale modellers score over finescale. Because of this I like to have the centre pair capable of deflecting, with some springing.  Then in plan view having the outer wheel sets sitting on a curve, the centre pair have to have plenty of sideways displacement allowed for, much more than a loco needs. 

These two underframes meet these needs in two different ways. The one chassis, at the bottom, has the outer wheel sets mounted using Slaters components, one fixed to the coach floor, the other on a rocking mounting, common to a lot of their wagons. Then the centre set has inside bearings, with plenty of side movement, and springy brass strips to keep the wheels in contact with the rails.

The other chassis has a fixed wheelset mounting at one end, and the other two wheel sets mounted as a “bogie”, allowing plenty of movement. Both these work well, I think I prefer the non bogie one of the two, just because it’s easier to put the coach on the rails when the wheelsets are hidden behind footboards.

I finally have an update on brass etching of windows, and the good news for Mikkel is that it involves a Silhouette portrait cutter.  As Valerie Singleton used to say, you will also need... a Chinese Takeaway, a washing-up bowl, Ferric Chloride, Lemon Juice, hot water, garden wire and... some sticky backed plastic (vinyl).  And of course some brass sheet, I've used 5 thou Albion Alloys from Antics.

Degrease with Acetone (nail varnish remover) and sand the brass with a medium/fine grit paper circa 600 grit.  Cover the brass with the vinyl and send it through the Silhouette to cut out those parts of the vinyl where you want the sheet to be etched, carefully weed out the panes and a border around the part.  You don't need to leave tabs connecting the part to the sheet, this is single sided etching and you need to cover the back of the brass with a complete piece of vinyl, I would recommend this is transparent.  You must make sure you thoroughly burnish the vinyl mask on to the brass, I used the glossy backing from the vinyl to protect the mask, but don't rub too hard or the brass will distort

Eat the Chinese takeaway and wash out the plastic container.  Put about two inches of warm water in the washing-up bowl - ideally it wants to be between 18 and 30 degrees C - one of those electronic aquarium thermometers is useful.  Put the take-away container in the bottom and pour in about an inch of Ferric Chloride (diluted as necessary) and Citric Acid (Edinburgh Etch https://www.nontoxicprint.com/etchcopperandbrass.htm).  With a piece of thick garden wire (plastic coated) bend a shape I can only describe as a Crank Shaft, this will be a handle to tape on the back of the brass sheet with transparent parcel tape.  It should suspend the brass face down in the Ferric Chloride but not letting it touch the bottom.

Agitate the brass in the solution by rocking it gently, lift it out occasionally to monitor progress.

YOU MUST TAKE APPROPRIATE PRECAUTIONS USING FERRIC CHLORIDE, EYE PROTECTION IS A MUST, RUBBER GLOVES ARE STRONGLY ADVISED.  Work where a splash on your work surface is not a problem and likewise wear your gardening/decorating clothes - once Ferric Chloride gets on something it tends to stain it... forever.

Ideally the solution would be agitated with a stream of air bubbles, but occasional rocking will also do, but be careful not to slosh the solution about YOU DO NOT WANT THIS STUFF IN YOUR EYE! 

BTW: You must not dispose of Ferric Chloride down the drain, it can be reused time and time again before it is exhausted.  When that time comes it can usually be disposed at the local waste site that accepts used engine oil etc.  Call your Council for details.

Try to keep the water temperature (and therefore the solution) above 20 degrees C.  Don't put too much water in the bowl, you don't want the container with the Ferric to float and possibly tip over.

After about ten or fifteen minutes you should see that the Ferric is biting and the bare brass is indented and looks a deeper brown.  After 30 minutes or so you might start to see the pattern coming through on the back of the sheet - this is why I recommend using transparent vinyl and sticking tape for the back.  Keep gently agitating and watch the back, you don't want to over cook the brass or you might start to lose detail. 

When it appears fully 'cooked', remove from the solution and wash in clean water. As mentioned, you don't need tabs because the backing sheet will hold the pieces until you get to this next stage.  Pop the sheet into a bath of Acetone and give the vinyl and tape a few moments to come free, then wash in water and carefully rub with a paper towel, hey-presto, your very own etched brass windows to your own design and dimensions.

Cover the brass sheet with stencil vinyl and cut out the areas where you want the brass etched away.  You could also cut out the stencil with a scalpel.  Alternatively you can paint/draw the design onto the brass with a permanent marker (Sharpie) or Spirit Ink (StazOn).  In fact there are many ways of getting the design onto the brass, check out YouTube for various options. 

There's an existing RMWEB article on this subject and CWJ makes reference to an excellent document by The Hollywood Foundry of Adelaide, South Australia who, sadly, are no longer on the web.  I have  a copy of at least part of that document and I'll see if there's some legal way I can get it put into RMWEB or Scalefour Society  archives.

Just located (11:00 04/10/2020) a link to the Hollywood Foundry documents - also note there's a thread/heading(?) opened 'Etching in 2mm - 2mm Finescale'.  If something works at 2mm/foot it should certainly work at 4x the size in 4mm. 

The end result, a Silhouette cut pattern in brass.  It may be possible to make the glazing bars thinner using other techniques, they're just a little under 0.5mm, but I daren't measure them in case the vernier jaws snipped through - it's only 5 thou brass after all.

And finally, that all too revealing close-up after a quick coat of Tamiya Fine Surface Primer

I hope folks have found this useful, interesting even.  Remember, the chemicals involved can be harmful, but then so is a bottle of MekPak.  Use common sense, keep this stuff away from pets and children, use eye protection and a pair of rubber gloves.  Have fun.