My ‘Geeetech E180’ printer seems to be performing exceptionally well at present, so I have been cracking on with some items from my ‘to do’ list.
After the poor results I was getting last year, I made a point of going through the long list of adjustable parameters in the ‘Cura’ slicing software. I suspect that the most significant change I made was to the ‘line width’ setting. The default setting matched the print-head diameter of 0.4 mm but I reduced the setting to 0.3mm. Since the print-head has a circular aperture, only a small part of the filament cross-section is as wide as 0.4mm. The closer spacing of successive paths does appear to result in a much smoother surface. Most of the model photos I have shown recently have been ‘straight off the printer’ and very little ‘fettling’ has been needed.
The original design of GWR Horse Box was another Broad Gauge oddity, in that the wheelbase of 6 feet was shorter than the track gauge! The length of the box was apparently determined by measuring the girth of a ‘typical’ horse and then allowing sufficient room for 4 horses to stand side-by-side, standing across the vehicle. A loading ramp and doors were provided on only one side of the vehicle. There are drawings in Whishaw’s book ‘The Railways of Great Britain and Ireland’ and examples can also be seen in some of J.C.Bourne’s lithographs. I have also made much use of the invaluable information provided in the Broad Gauge Society Data Sheets.
Creating the Body
My model was constructed by my now usual method. I created the two ends together with the floor. I used the ‘push/pull’ tool in ‘Fusion 360’ to emboss lines of planking into the end panels and then drew the outside frames and extruded them to stand proud of the planking.
I created the two sides as separate ‘bodies', with the detailing of the drop-down loading ramp applied to only one side. This method allowed me to print the sides lying flat on the print bed, so each side only took a few minutes to print.
I made each louvred panel in the upper doors by drawing a ‘toothed’ side profile and then extruding this drawing along the width of the door panel. Previously, I have used the ‘chamfer’ tools to create the sloping slats but my more recent method is much quicker and easier to implement. I often look back at some of my earlier designs and realise that some of my methods were unnecessarily ‘long winded’ but that’s all part of the learning curve. I have always described my models as ‘experimental’.
Creating a Louvred Opening
I now had a set of components from which to construct the body of my Horse Box, as shown below, exactly as they emerged from the printer.
3D-printed Components of Horse Box
Creating the Chassis
I was able to create the chassis fairly quickly, by adapting chassis components from earlier models. Thus, I did not have to spend time creating springs and axle-box details. I simply adjusted the wheelbase and overall length of the solebars to suit the current model.
Unusually, however, for the early period on the Broad Gauge, this Horse Box ran on wheels of 3’ diameter, rather than the 4’ wheels preferred by Brunel. I used my existing models of 4’ diameter Losh-type wheels and reduced the diameter to 75% while keeping the same tread-width and separation.
This size reduction led to some problems with printing the spokes since, when I checked the ‘printability’ of the new version on the ‘Cura’ print preview screen, the spokes turned out to be too narrow to print correctly. Once again, I used the ‘push-pull’ tool in ‘Fusion 360’ to move the side faces of the spokes, to ensure that there was sufficient width for my printer to resolve the outlines correctly.
3D-printed wheels on printer bed
Note the use of a ‘brim’, which can be applied automatically by the ‘Cura’ slicing software, that helps to ensure adhesion of small components to the printer bed. The half-axle sleeves are designed to fit around a standard 2 mm diameter steel pin-point axle, to provide automatic alignment of a pair of wheels.
Assembling the Components
I fitted the two panelled sides between the fixed end panels and added the roof. All the components had printed cleanly and fitted together easily, with no ‘fettling’ being necessary. The body is currently just resting on the chassis for the following photographs.
my assembled Horse Box
The small diameter of the wheels is very noticeable and, when combined with the extremely short wheelbase must have contributed to a rough ride for the unfortunate inhabitants of these vehicles. The comment by @Michael Hodgson on my previous post that they’d be OK for rocking horses seems very apt
The three vehicles that I have produced over the last few weeks vividly illustrate the ‘primitive’ nature of railway design at this early period, around 1840. With the benefit of hindsight, it is hard to understand how anyone could have thought these designs were appropriate for vehicles intended to operate at the high speeds that Brunel expected to achieve with his railway. To set these thoughts in context, however, it was only a few years earlier that many people thought that a locomotive could not operate at all, by rotating metal wheels over a metal rail!
my three recent GWR Broad Gauge models
Following my recent rush of activity, I expect there will now be a pause while I contemplate the rather larger task of building a model of one of the early Broad gauge locomotives.
My best wishes to those looking forward to the Easter holiday.
The header picture is of sketches from J.C.Bourne’s notebook
Edited by MikeOxon