Govertical- I have been following this project from its infancy and it certainly has been interesting and educational to see how many pully, timing belt, and gear systems you can put together. I believe the key to the difficulty you may be having can be found in one of your quotes from about a month back stating the turbine spun at 130 RPM in 40 MPH without gearing. This suggests you have serious aerodynamic issues to deal with before even the best transmission system will aid your performance.
I don't recall off-hand the radius of your turbine but I remember a picture you posted and it looked around 15 or 16 inches. With that value you had a TSR of 0.304 at a speed rarely realized in real life situations.
There are two possible explainations to this. First being that this wind speed is well beyond the peak of your TSR curve - this is assuming that your aerodynamics for one reason or another lend themselves to peaky TSR curves. Does the slope of your RPM vs. windspeed curve drop or change sign throughout the considered wind speed range? You could calculate this by graphing the RPM vs. Windspeed - use a spreadsheet program to calculate a second degree polynomial trendline - then calculate the first deriviative of the trendline equation using matlab, similar or by hand if you like calculus. Graph the trendline derivative - where this line crosses zero is the wind speed for your optimal TSR. If this is the case and you have a curve with a peak (as oppossed to one that levels out) I would focus my efforts testing within a range of this peak. In any case I would focus my road tests on a range between 0 and 14 m/s and save the high speed runs to test the turbine survival speed.
If your tsr curve is not a peak and levels off at a max TSR of 0.3 unloaded (or even loaded for that matter) you have aerodynamic issues to deal with. Conventional theory states that the max tsr of a standard savonious is about 1 at a Cp of about 0.2 (ofcourse all these figures are debatable). In reality I dont imagine many diy-ers able to approach these theoretical limits but above 0.6 should be acheiveable. I realize you are trying some inner-cups/outter-cups type design but perhaps you should consider a more conventional savonious drag turbine. A google scholar search for Savonious rotor should yeild plenty of material to help with the aerodynamics of your turbine. I recall a paper from a researcher named Manet from some university in France. The paper presents dimensions for an optimized s rotor based on a vast amount of research around the world including sandia and all those guys.
Anyways, after some basic work on the aerodynamic assembly you may be able to increase your operating RPM by nearly double and this will put you in a much more reasonable range for generating electricity. Clearly, you enjoy what you are doing and your cnc/fabircation techniques are impressive so a little time on aero now can save a lot of drivetrain alternator time in the future. I realize I should have posted this five transmissions ago. Keep up the good work, we are all learning something!
-KBwind
