Neat – I like the finishing touch, the blacking to match the rest of the set.
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Trying to make my steam wagon's ash-pan, which is cylindrical, not rectangular.
The top component is an angle ring that will also form additional support , via supension-rods from brackets on the chassis, for the boiler.
I thought the rest would be a handy exercise in sheet-metal forming, using steel from an old central-heating boiler panel given me by a friend in the trade. I verified its 0.8mm thickness is just within the capacity of my forming machines, which are:
– a rotary-shear of unknown make,
– a Warco 12" 3-in-one rolls/bender/shear press, and
– a manual "Rotary Machine" (a swaging-machine, or jenny) from WNS.
Rolling the basic cylinder was easy enough, from a strip two feet long, for a diameter slightly over 7" plus joint overlap. Rolling a flange on it though, to hold the base, even with what looked the right jenny rollers, proved impossible and I had to roll the mangled strip back flat.
Forming the base with the flange on that was worse still, despite carefully following the information in an old, industrial training-manual that makes it look simple. In reality, guiding the revolving disc through the jenny rollers while also bending it upwards with one hand while the other hand rotates the jenny, merely crunches the steel into distorted crumples and wrinkles nothing like the desired diameter and profile.
Thinking perhaps the steel was too thick I tried a far thinner disc, cut from an old 5-litre can, but that was even worse. The training-manual shows some very fancy over-locked joints possible with these tools… Errr, how?
Defeated, wondering if this is why we model-engineers tend to machine from solid instead unless absolutely unavoidable as in locomotive superstructures, I took Bernard Cribben's advice. I stopped and "had another cuppa tea" .
Welding? Out of the question. Machine from solid? From a great chunk of half-inch plate – hmmm. Sacrifice a stainless-steel saucepan? Tempting….
Then inspiration. The WNS instruction-booklet shows the jenny's "Turning" rollers produce a semi-circular embossing – or groove from the other side. This is often done for rigidity.
I jenny-rolled such an embossing right along the strip, leaving a very narrow land between it and the edge; then used the slip-roll to reform the ring, with the embossing travelling through one of the roll's edge-wiring grooves. This gives an internal groove all round the shell in which to trap the base, which needs now be only a simple flat disc, cut from 1mm zinc-plated sheet (ex-server panel). A bit like a loose-based cake-baking tin, though those rest the wire-edged base on an internal wired edge whereas the ash-pan's base will be locked into place. Anyway, I cannot wire-edge circular work.
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I've concluded metal-forming beyond the very simplest cylinder-rolling, straight-line folding and bashing-it-over-a-block-of-wood, is of the Hermetic Arts. Although such sheet-metalwork is very long-established professionally, I have never seen any examples of, instructive literature on, or tools for, it beyond those basics, in model-engineering.