Having been inspired by a recent post by @Annie, I’m having a go at creating a 3D-print of one of those ‘ugly-duckling’ 4-4-0STs, much liked in the West Country as very successful engines.

As usual, I’m applying ‘quick and dirty’ methods, to create as much as possible by extruding ‘bodies’ from existing drawings – in this case those by Ian Beattie, reproduced in the Broad Gauge Society magazine ‘Broadsheet No.73’

I imported the front-elevation drawing as a ‘canvas’ into ‘Fusion 360’ and used its drawing tools to trace around the outlines of the smokebox and the tanks. I extruded the area of the smokebox to form a 3-dimensional ‘body’ and repeated the same process for the tanks.  My intention was to fit these two parts around a brass tube, which will form the engine’s boiler.

Initial sketch drawn over imported ‘canvas’

Smokebox extruded from initial sketch - Tank also produced by the same method

My next step was to import the drawing of the side elevation and use it to extrude the frames and splashers, as shown below.

Frames extruded from sketch over imported ‘canvas’

Now I had three virtual components to pass to the 3D printer. I used ‘Cura’ software to generate the printer files and this software also creates any necessary support structures. The following screen shot shows the infill that reinforces the internal structure of the tanks:

Cross-section of Tank in ‘Cura’ print pre-view

Note the information, on the above screen-shot, that the Tank structure takes 1h 29m to print and has a filament cost of about £0.13. The other components took under 30 min each to print.  After printing the three components, I stacked them together, to show how the final assembly could look:

Loose assembly of 3D-printed components

The tank and smokebox printed well but the frames are a little too thin, with very fragile axlebox horns, so I shall strengthen these areas. Because the individual components print quickly, it is easy to make modification on the basis of the trial prints. The brass tube forming the boiler is just visible below the forward part of the tank in the above photo. This part of the assembly is shown more clearly below:

Tank and Smokebox slid over Brass Tube

I think these steps demonstrate the feasibility of designing a locomotive around parts which are simple extrusions from published drawings.

At present, I am trying out my ideas on various locomotive types that I find of interest. Many of my previous models have been based around the South Wales line from Gloucester and I note that four of these 4-4-0ST engines were operated by the short-lived Carmarthen and Cardigan Railway before being sold to the South Devon and Cornwall railways. This allocation to South Wales could be used to justify this type being found together with my other models.

Mike