chapter on batteries details how to choose, charge and test batteries.It specifically applies to
American conditions, and would be of little use to someone in a developing country. Likewise,
the chapter on "Using Electricity" applies to American conditions.
The authors provide information on what I believe to be rather costly and complicated control
Detail construction is described for three alternative designs. The end plates are made of
plywood (use marine quality if you use plywood!).
The method of locating center points and marking circles is described in detail.Cutting oil drums
in half with a gas torch, as suggested, would be impractical in a developing country; it can be
done easily enough with a hammer and cold-chisel. L-brackets are used to attach half-drums to
discs instead of the lips of the drums.
The "skeletal" assembly which is the alternative to the basic design seems unnecessarily
complicated and expensive. As the author suggests, its only merit might be for experimental
Recommended bearings do not have to be both flange mounted and eccentric-locking.
The bottom bearing should be preferably flange-mounted and self-aligning, but the top bearing
need not be.
The authors do not recommend using a water pipe for the shaft of the rotor.In both of my S-
rotors I have used ordinary water pipe and have experienced no problems. The suggested method
of using flanges and threaded nipples is unnecessarily expensive, particularly in a developing
Two basic types of supporting structure are suggested: one is a vertical shaft on a pivot, which
enables the rotor to be brought to the horizontal position on the ground for maintenance, etc.; and
another is an external structure.I believe both to be somewhat impractical.
A simpler framework is shown, whose ends can be dug into the ground and which can be
supported by four or six anchored guy wires with turnbuckles.
Spoilers are suggested to slow the rotor in very high wind speeds.
I believe it would be very difficult to come up with an arrangement where both spoilers move
and open up by exact amounts. Small errors in the design and construction of the mechanism
could cause very serious imbalance and vibrations at higher speeds.
It would help the reader to emphasize that steady wind speeds above 12 mph (at which only a
fraction of one watt is generated per one square foot of the S-rotor's surface) are very rare in
most parts of the world. And surely a cautionary statement about the suitability of an S-rotor for
wind speeds below 10 mph should be included at the beginning of the book.
SAVONIUS ROTOR CONSTRUCTION
Vertical Axis Wind Machines From Oil Drums
by Jozef A. Kozlowski
1600 Wilson Boulevard,
Suite 500 Arlington,
Virginia 22209 USA