Here's a picture of attempt #1 (hereafter v1). This is an overview, I'll address each section in separate posts.
The base is made from uni-strut. Coming vertically up from the unistrut is a 2' piece of 1/2"-13 threaded rod. There's a coupling nut which steps the 1/2" rod to 1/4"-20 rod.
The motor and gears are this, which is a servo and gearbox by servocity.com. I'm using the 8.6:1 ratio which has metal gears. This threads over the 1/4" rod and is held in place by bolts on the rod itself.
The pivoting mechanism (daily and seasonal) is a door hinge. The hinge is bolted to a piece of perforated steel angle, and the steel is screwed to the gear. The steel also attaches to the mirror frame. Movement of the gear moves the hinge for daily (azimuth) movement. For seasonal (altitude) movement, the other portion of the hinge can pivot.
The mirror is mounted to a frame made of aluminum angle. The mirror itself is a 4' x 2' piece of acrylic fixed to the frame.
Movement is controlled by an Arduino board with a motor shield.
OK, now will try to do breakouts of each component.