i would love to see someone on the board build a tracker with the copper tubes connected to a hydraulic ram and filled with oiled freon-12. much like
http://www.motherearthnews.com/Do-It-Yourself/1977-11-01/Mothers-Super-Simple-Solar-Tracker.aspx
then they could work out all the kinks, so i could follow in their footsteps!
i've always wanted to make one like that. takes zero electricity, auto returns to east in the am, and should run flawlessly for a very long time.
build it, and i will follow! 
adam
For Freon/Thermal tracking . . .
We put 4 of these on a site about 5 years ago, and are still working fine, afaik.
http://zomeworks.com/products/pv-trackersUses HUGE shock absorbers to keep it smooth and dampen wind loads. Took (2) 200 pound guys hanging on the shocks to get them to extend.
The overall post(s) 20 foot long, 8 inch pipe, with 8 feet buried in concrete.
Seems to handle the wind pretty well.
