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Tuesday, 15 October 2019

0 Gauge Class 33 Scratch Build - Part 3

Bodywork Commences

Like any diesel locomotive the body is just a rectangular box - right? - wrong! There are complex curves and angles going on here that are a real challenge to model in 3D CAD.

The first decision was where to make the split line since the entire body length is too long to fit on my 3D printer bed. The best place is either side of the central door as the split lines mostly fall in the gap between the door and its frame. Thus, the body is in three parts with the roof being a separate entity also.

The three sides of the body shell shown in the photo is one piece printed from the base up (except for the curved base explained below)

The design must take into account printing limitations with respect to overhangs and bridges. For example, the ends of the body have overhangs that curve below the buffer beams. Clearly, they cannot be printed below the print bed. I could have configured 'infills' that fill the gap beneath the body sides and the overhanging end, these being cut away after printing but, the complex curve of the overhang and the curved bottom edge of the sides just compounds the problem. I chose to split the body again just above its base and print the base upside down. This printed part is seen on the right in the photo above.

Most of the apertures in the sides needed infills configured to support their top frames, otherwise they would droop.

I was unsure whether it would print satisfactorily at all.  Thankfully, it did. Sanding needs to be done to eradicate the stratification of the print layers and there is a lot of added detail yet to be designed, including the radiators that fit in the biggest apertures.

The roof has even more complex curves. It had to be designed along with the sides so that a convenient split line could be identified.

To Part 4.

To Part 1 of this series.


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