A Special Builder's Notes


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20 June 2020

Another 'Meet The Future' Moment.

This time from the Bronzecraft foundry.

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This is printed with sand! It's a single-use mould for a handle. The curved part on the left of the left-hand block is the main part of the handle and is mirrored in the right-hand block. The data is first collected from a 3-D scan of the original part, then the mould is printed from that. The funnel shape is where the metal is poured and there are channels for the escape of gases and air. I'm told that the best results in casting are obtained by a controlled and steady pour, directing the metal so the mould fills from the bottom upwards. This method prevents turbulence and allows time for air and gases to exhaust without entrapment. It's the way the reproduction of otherwise unobtainable replacement parts is going, and will in time, be at a fraction of the cost of traditional pattern-making.

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John at Blue Swallow Aircraft (link in the sidebar) uses the more traditional and lengthier process involving several delicate stages before pouring. I don't know if the FAA and the CAA require traditional methods of manufacture - they can be a bit funny about that sort of thing. I remember when the subject of new Hawker Hurricane wings was first mooted, the manufacturing and heat treatment of the centre section panels had to be exactly as was in the day, regardless of the advances in metallurgy. Still, I would imagine that there's always an element of 'we know this works, so that's the way we'll keep doing it'.

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These radial engine exhaust fittings were the result of the sand box method above - there was a certain amount of finishing to be done when they came out of the mould, as there would be with the sand-printed mould.

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This is a bellcrank for a Wright Flyer. John produced the pattern with his CNC milling facility after creating the files on the computer. It all gets a bit mind-boggling when you start to explore all the creative avenues nowadays available. My coupé model was dropped off at S-CAN who will re-scan the latest version and create the .dxf files for a CNC router to produce the components of the buck. I'll also get a hard copy of the actual measurements so I can let in the rear windows, boot lid and anything else that I decide to incorporate - the passenger's ejector seat exit panel for instance. One thing I have noticed about the results of all this highly convenient tech stuff, is that it can be jarringly perfect. Some things just don't look right, especially small details like the lettering on instrument faces which originally would have had some physical depth - a roundness if you like. It would be perfectly possible to print the faces with an expanding ink - we used to use it in textile printing - but nobody seems to bother and the flawless, though flat results, I think spoil the ship.

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And talking of ships; this is my future for the next couple of months.

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