A good deal of time on the information super highway has confirmed these signal were not available in mechanical flavour, so plastering it with cranks to make it work is no longer a plan. Neither is the rod going up the post, since with three ninety degree bends there would be way to much flexing going on.
So the plan is now to turn the drive through ninety degrees with a crank or similar. Having soldered the bearing tube to the pivot support and doing a trial assembly it seems the pivot support, when backed up by the 'glass', is sufficiently rigid to work ok without bending. However putting a crank on, even after cutting off the unused arm would obscure the lamp somewhat. And not look good. Apart it all came again. Looking at the instructions again I realised that bending the shaft ninety degrees at the pivot would not only provide the required direction change, but also act as a clamp to hold it in place. While the shaft was still straight I fitted the platform, the little bit that goes in from of the repeater on the platform and cut the new lamp support tube. The wires went down the post. I cleaned the white paint off the obscurred 'glass' because whatever I do it scratches off, so I'll paint it at the end.
With all that done, I bent the shaft and tarted up the paint that will be inaccessible later. Hopefully tomorrow the paint will be dry (it's not warm in the loft) and the thing can finally go together
Edited by Miserable