Very Happy Jan
Finally had a chance to test the system out in daylight. Simply fantastic - just want I wanted.
Photos of the finished result are attached. From the outside all that is seen are eight nice stainless steel countersunk hex drive bolt heads on the side of the mirror box and two plastic caps on top. From the mirror cell end, the chain drives can be seen but are inside the mirror cell. Everything inside the mirror box above the mirror surface has a layer of chalkboard paint on it and none seems to have got into the bearings.
Operation is just as I wanted it. Not much backlash, though that didn't matter and I can adjust that by pulling on or releasing the bottom rod support against the two springs it sits on. (The purpose of the springs was to allow the chain to be slackened off so it can be removed without having to remove the "breakable link".) The primary tilts smoothly in the two controlled directions. I had no idea how sensitive the control would be - too much or too little. However it is just right. about half a turn on the flexible drives gives me the range of tilt I wanted - fantastic. I can insert and remove the two flexible drives and the mirror doesn't flinch at all.
Only slight downside is a bit of misalignment on one side, between the access hole and the top of the drive rod, but nothing I cannot cope with. I guess I shouldn't have expected a piece of Bunnings rod to be perfectly straight!
If all else fails (or I forget to bring the flexible drives - duh!) I can still operate from the mirror cell end as before. There is a little more force required to drive the chain and rod as the bolt is turned, but not much.
Big thanks to my helpful machinists - Alan in Melbourne and John in Sydney - who says Melbourne and Sydney don't get along!
Next post shows more photos of the setup and the remote primary collimation in action.