The Salter RD-7000 Wind Turbine Design

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PHOTO: MOTHER EARTH NEWS STAFF
We've eliminated the weather vane tail, expensive gearboxes and complicated feathering mechanisms needed by most windplants," says Edmund L. Salter. "That makes our unit simpler, quieter, and less expensive than other wind-driven generators."

“We’ve eliminated the weather vane tail, expensive
gearboxes and complicated feathering mechanisms needed by
most windplants,” says Edmund L. Salter. “That makes our
unit simpler, quieter, and less expensive than other
wind-driven generators.”

Mr. Salter — a mechanical engineer and President of San
Diego-based Wind Power Systems, Inc. — is talking about his
firm’s new development, the RD-7000 Wind Turbine. And, as
his remarks indicate, the working prototype of the turbine
is radically different from most wind-driven generators of
the past and present.

The basic Salter unit (without tower) is 20 feet tall and
consists of a central alternator driven by three three
bladed propellers. The rotor blades are constructed of poly
urethane foam over alloy steel spar tubes and weigh less
than two pounds apiece. A circular steel rim around each
tri-fanned rotor, it is claimed, “Improves efficiency as
much as 20% by preventing air spillage at the blades’ tips,
adds strength and rigidity to the propeller, and — by
pressing against a motorcycle wheel attached to the
alternator’s drive shaft — automatically spins the generator
five times as fast as the rotor turns.”

The RD-7000 can produce 7,000 watts of 120-volt direct
current in a 25 to 28 mph wind and a maximum of 10,000
watts when driven by an air mass moving 32 mph. Salter
figures that one of the units, mounted on a tower at least
40 feet tall, will supply enough electricity to run a
single family home in any location with a minimum average
yearly wind velocity of eight miles per hour. Several of
the generating units can be grouped on one or more larger
towers to produce power for factories, subdivisions, and
small towns.

“The real secret of this design,” says Salter, “is its
simplicity. The rotors run downwind of the machine’s pivot
point. That eliminates the need for a tail vane and cuts
thirty to forty bucks off the cost of the windplant.

Our rim drive turns the generator 1,250 to 1,375 rpm in a
25 mph wind without costly gears. And the RD-7000’s damping
device — which is no more complicated than a door closer — just
kind of lets the whole rig lay over further and further
whenever the speed of the wind increases to a more and more
dangerous level. This decreases the area of the rotors
exposed to the gale in a very straight forward and
inexpensive manner. It’s ideas like these that should allow
us to install our wind turbine — less batteries — at a price of
about $450 per kilowatt.”

Patents are pending on the RD-7000 and the prototype unit
is still being tested. Which is to say that the Salter
windplant probably won’t be on the market for at least
another two years. But that doesn’t stop it from being a
very interesting concept right now!.