On Apr 25, 4:47*pm, Morris Dovey wrote:
[snip]

The sun-tracker will, of course, need to make one (controlled) cycle per
day, and somehow (automagically) start out facing east in the morning.


That's an easy one. Expanding gas cylinder like the greenhouse people
use to open a vent. Hide it in the shadow of the collector itself, so
when the sun peeks around, it starts expanding till it creates its own
shadow again sortakinda like a wheatstone bridge but mechanical. When
the sun stops playing peek-a-boo with the cylinder at night, it is
brought home by its own collapse, perhaps helped by a counterweight/
spring.
The cylinder would sit lengthwise along the obvious edge. It could sit
in a slot in the collector itself for extra intensity. The mechanical
challenge is minimal.


Maybe something bi-metal?