Ballast Cleaning Train - Part 19 (SLA Resin 3d Print Version)

 This is the final part for this project.

Matisa 3B5 Ballast Cleaning Machine (late 50s early 60s BR era)

Aerial view of the machine and its electric generator wagon

How they were coupled for travelling.
In operation the generator was coupled to the other
end of the machine and an electrical cable connected between them.

To the beginning of this SLA Resin Printed 3D model series.

Read about the SLA (stereolithography) resin 3D printer here.

Read about the FDM 3D printed version and its train here.

Movie below features the FDM 3D printed model and its train.

Ballast Cleaning Train - Part 18 (SLA Resin 3d Print Version)

Photo shows the cabins for both wagons and two other bits for the generator wagon after a spraying with black gloss car paint.

Why black for wagons that are to be finished in 1960s departmental yellow? Black is a common base for figurine painting as it enhances shadows caused by creases in clothing when overpainted to let the black through in places. The same principal is applied here except there is so little relief in these parts that shadows are minimal. Furthermore, I found that it changed the hue of the final yellow coating requiring multiple layers to recover. I will not use black for the remaining parts of this build. However, it was useful in simulating the rubber surround of the window panes that were revealed when the masking tape was removed.

It was really difficult to emulate the yellow colour of the prototype. The Railmatch 2304 I chose was far too yellow. My first approach was to tone it down with a white wash.  This made it too pale so I followed up with a brown wash that brought it as close to prototype as I could achieve.

There are seven components that are resin printed, including the chassis with all its levers, rods, axle boxes, leaf springs etc. printed as one piece. The railings are galvanised wire, the couplings Hornby, the wheelsets proprietary, the lights are ends of a biro ink tube with polystyrene gell glue infilled and the vacumn pipes are wire with thinner wire wound around. These could have been integrated with the chassis print.

Here is a comparison between the FDM printed model (background) and resin printed model (foreground).  For the uninitiated there does not seem to be much difference. But there is!

First, we may notice the colour change. The FDM paint finish is completely wrong having a green tinge. Next is a difference in equipment. I believe the resin model is more representative of the picture in the book and an early period photo I used for reference. The equipment on the other is based on a later version that was photographed in a yard awaiting scrapping.

Other notable differences where the resin printed model wins over FDM:

• No visible print layers
• Finer details e.g. axle boxes and leaf springs fully formed - as good as injection moulded. (For the FDM model I butchered a proprietary wagon and implanted its injection moulded axle box and leaf springs to achieve detail.)
• Sharper corners and edges
• Fewer parts

All the parts for the ballast cleaning machine have been printed and painted. Assembly next, which will be featured in the next blog posting.

To Part 19.

To the beginning.

Read about the SLA (stereolithography) resin 3D printer that I used here.

Read about the FDM 3D printed model here.

Ballast Cleaning Train - Part 17 (SLA Resin 3d Print Version)

Spent some time viewing tutorials on weathering to learn a method for the two chassis.

First stage was grey primer even though one recommendation was not to bother because the plastic base will take acrylic paints and the more layers of paint that are applied the more the definition of fine details will be lost.

However, the next layer was not acrylic. It was gloss black car paint that I had to hand and this needs a primer. The finish gave the models an ex works pristine appearance.

Before applying weathering a spray of matt varnish is necessary to dull the gloss and give good adhesion for the weathering layers. The varnish I purchased was Pebeo Auxiliary Matt Varnish which, due to a mix up, was not the one I intended to buy. I intended to buy a rattle can but this one is for brush application and has a white appearance in the bottle. At first I was not at all sure if it would be suitable. Anyway I mixed 50:50 with water and sprayed a test piece. It quickly dried giving the required matt finish and also suppressed the black intensity to a dark grey which is also what I wanted.

The first weathering layer was a wet on wet application of watery mid grey paint. What this means is water is brushed over the model and then paint applied which runs into crevices for highlighting and gives a mottled effect on flat areas.

The light grey areas in the photo are where masking tape has been removed. Those areas are for gluing the superstructure in place. 

The next layer is various coloured, scraped pastel sticks (powders) brushed onto the chassis sides. This final effect was quite pleasing until I sprayed with an artists fixer compound to seal the powders. It glossed the surface and suppressed the powder colours! I remedied with more powder covering and left it like that. Not quite as good as the pre fixer coating.

The Generator Wagon has footboards painted the same colour as the superstructure. The closest match to that seen in prototype photographs that I found was Railmatch 2304 Early Warning Yellow. However, once applied it looked too bright so a wash of watered down white was brushed over. It is still not right. But, who is to say old photographs accurately portray colour anyway.

To Part 18.

To the beginning.

Read about the SLA (stereolithography) resin 3D printer here.

Read about the FDM model here.