I'm thinking whether my construction of three struts will have repeatable results. Two of the struts (A/B) can change, and the third (C) is rigid.

There are 6 axis of freedom in general: up/down, left/right, forward/backward, and 3 rotations.

By having one strut rigid, but with a pivot point, I'm putting in constraints;

- C: forward/backward, left/right, up/down

- A/B: forward/backward, left/right, rotation around

All rotations are still possible; rotation around the C axis (vertical), rotation in up/down plane, and rotation in left/right plane.

Currently the stiffness of each strut is dependent on the length of the strut, and the mirror position is a function of the stiffness of each strut and friction (?) in the frame.

The rotation around the central axis of the mirror (defined by the point not supported by the strut and the point attached to strut C) is now depending on the stiffness of the flexible coupling and the length of the two struts.

Hmm.. I'm not sure about this design yet, because the next phase could be to replace all couplings by universal joints, which remove the spring action that the struts currently have.

However, by using rotating platforms etc this system becomes more defined but harder to set and control.

(to be continued)