When the paint had dried on the arm and 'opaque glass' it was time for a trial assembly. The first of these I built I didn't make work, because it's sat about 40mm from a tunnel mouth and 70mm from the wall and there seemed little point so I just did the lamp conversion.  This is new territory now. It all went together nicely, except that the arm was jammed in between the 'glasses'.

At this point I remembered commenting in a way earlier post the strip seemed a bit thin and I'd try a wider bit next time. So, welcome to a slightly belated next time. Another rummage in the metallic bits and bobs box sourced a suitable bit of strip. Forming this was a bit of a trial, I don't know if brass comes in different flavours, but stuff was harder to bend smoothly so to speak. After quite a lot of faffing, and I confess a little Language, it was finally the right shape and soldered on.

Thence trial assembly 2.0.

This worked much better, the arm moves freely and doesn't rub on the 'glass' leaving scuff marks. The clamps are brilliant little things I got from a sewing shop, they are meant as a replacement for pins when hemming (so I am assured) and are right little limpets. At this point I got to wondering how the arm would be rotated, the drawing just shows a somewhat ethereal loop arrangement. All the photos I can find show, or appear to show, electric signals. Some sort of bearing and crank is going to be needed I think, probably requiring strengthening the pivot support by thickening or adding a strip to make it a T shape.  I've cut a bit of tube and painted the inside of the case (still missed a bit though!) and am now going to put the headphones on and have a ponder about how the thing is to be worked. It looks like its going to be a raid on the matallic bits and bobs box as the rod needs to come down from the signal, turn 90' to run under the platform, and then turn 90' again to go down the side of the post. Then should there be a balance arm? I guess there would have to have been pre-electricity  (did they exist then?) There will be a prototype somewhere...  that's my story.