Thanks Nathan! Despite all intentions to plan well ahead I run out of brass for the cylinders build and have to put it on hold for a while. But thanks to that I had time to prepare some pics from the circle build.
The basis is this 210 mm (over the tips) toothed wheel, which was laser cut from 6 mm (1/4") stainless. Here with an MDF fixture for centering the ring (see further down).
Here you see the shaping of said ring from a 4 mm x 19 mm bar in a simple bending device. If you wonder what the black dots at the edge are, here´s the story: As I milled away 1 mm along the edge from a 4x20 bar I must have released some surface tension having the effect of bending the whole bar in its main plane, the milled surface being convex by about 2 mm in the middle portion
. Trying to straight that out in the vice in a controlled way I imagined to be rather frustrating if not infeasible
, but I remembered that there´s always this problem with contraction with welding. So I made all these welding spots with the TIG, starting sparsely and adding more until the bar was back to straight. I´ll tell you it was a good feeling turning that problem to my advantage and watching the bar returning to straight almost effortlessly.
Due to the elasticity (you see the spring back two pics above) the bending core is this small and makes an overlap necessary. I reckoned a coiling overlap to be less detrimental to the end result than a layer on layer kind of winding. In any case, it allowed the forming wheel (the ball bearings) to be closer to the core.
The ends stay straight or become bent with the wrong radius, so have to be cut away.
Attaching the ring to the cog wheel.
Then the bearing surface was ground.
The resulting surface compared to the raw laser cut to the right.
The edge if the ring is internally reinforced by this narrower ring.
Thanks for looking.
Stefan