The ones I've tested I found the torque is that of 1 tier for the entire machine. What it does is offset the torque pulse from 180 degrees to 90 degrees. You have lower torque but a more continuous torque.
I built a 4 tier unit with the blades offset by only 22.5 degrees, very similar to the "twisted" or "helix" savonius. This actually seemed to remove the torque pulse but still only carried the torque of one tier or slightly above.
Overall I never achieved much more than 20% efficiency with any of the units I built. They provide a very good torque at low rpm and would be well suited for pumping water, running an air compressor and such but for electric they present a number of challenges. It can be done...
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Have Fun!
Windstuff Ed
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