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Scrap Tank - shaping the chassis


antyeates1983

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Having drilled the holes in the frames, I stuck on a template again and cut around it in time honoured fashion with a piercing saw:

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Files were then used to finish the shape. As you can see, these include crude representations of the springs (just shadows behind the wheels, really). Shaping (and thinning) of the guard irons will be left until later. The extra material at either end was to facilitate clamping during the drilling operations but shouldn't be needed any longer.

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The next task was to shape the chassis block from 6mm square brass stock. I took advantage of the Proxxon mill for this - here the slots are for the axles, and the holes will be for the screws that hold on the frames. At this stage, the slots are slightly undersized - I opened them out fully a bit later. The brass is shaped following another paper template (on the underside in this view). I tried to make it as large as I could get away with, without (hopefully) being too obvious in the finished model.IMG_1341.JPG.d6151f155b3e69dcc4055d2e35524f84.JPG

 

In the next shot, I have plugged the fixing holes with 3mm acetal rod (from eBay). These were subsequently drilled and tapped for 12BA screws.

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Next it was back to the Proxxon to mill out slots for the various gears, while leaving as much brass in place as possible. I'm using a 1mm cutter here to get the corners quite sharp. Again, I opened this out to final size with a file once I had the gears to hand later. You can also see the drilled and tapped screw holes, for which I used one of the frames as a jig.

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Here are the results in component form. The bottom two layers are the 5 thou styrene insulating layers. In this view I've also soldered in the brass bushes for the gear shaft.

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And finally, this is what it looks like attached together. One one side I had to cut the plasticard layer into two separate pieces to clear the gears, so I will probably glue them in later to keep them in alignment. I don't want to do this yet as there will still be soldering to do (I'm thinking of the cylinders, for example).

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  • Like 9
  • Craftsmanship/clever 3

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Did you rule out fixing the insulating layers to the central block? I'm assuming there's limited soldering there, if any.

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