If anyone is still interested, I posted a piece about this on:
No. This isn't spam.
Sorry for my double post earlier. The computer told me the first one did
not go through. Great to have people interested in the problem or
puzzle if you like. Especially good that David found the natural math
element of it!
While the arm thing does not sound that difficult to do, a "right now"
"this week" solution for making the first working prototype or working
model is to get or make a parabolic dish of dimensions close to what
David calculated and cut it in half down the middle.
Mount them on an equatorial mount like I show in the video.
2 half dishes with one focus up and one down.
For sterling engine or solar cooking or hot water collection, the hot
spot is right there on the axis at the focal point easy to access.
If you use an arm, hot water collection becomes more difficult because
more joints and bends come into play.
I am pretty sure (but not certain) that if you get it balanced at
equinox, the movement of one dish up and the other down will keep the
"Wheel" balanced throughout the seasons. I think that if it is set up to
be balanced at equinox, the movement required at each side is the exact
mirror of that required at the other. That certainly appears to be the
case when I move the 2 sides of my model!
Morris Dovey wrote: