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National Advisory Committee for Aeronautics, Technical Notes - Wind Tunnel Tests of a Cyclogiro Rotor

A cyclogiro rotor having a span and diameter of 8
feet was tested in the N.A.C.A. 20—foot wind tunnel. The
tests showed that the cyclogiro would be able to ascend
vertically, fly horizontally, and glide without power.
The power required for normal flight would, however, be
excessive. A comparison of calculated and experimental
results showed that the analytical expressions used gave
the correct variation of the power required with the rotor
forces but that the values calculated for zero rotor
forces were in error. 'It was also shown that the blade
profile—drag coefficient was incorrectly assumed and that
the error in the calculated power required arose from
that assumption. The effect of oscillating an airfoil is
considered a primary reason for the discrepancy between
the assumed and experimental drag coefficients and re-
search on an oscillating airfoil is believed to be neces—
sary.

During an extensive study of all types of rotating
wings, the National Advisory Committee for Aeronautics ex—
amined the cyclogiro rotor and made an aerodynamic analy—
sis of that system (reference 1). The examination dis—
closed that such a machine had suffici.ent promise to jus—
tify an experimental investigation; a model with a diame~
ter and span of 8 feet was therefore constructed and test—
ed in the 20~foot wind tunnel during 1934.

The experimental work included tests of the effect
of the blade motion upon the rotor forces during the
staticélift and forward—flight conditions at several rotor
Speeds and the determination of the relations between the
forces generated by the rotor and the power required by it.

The 20-foot wind tunnel, in which these tests were
conducted, is described in reference 2; the only altera—
tion required-for the cyclogino.tests was the installation
of two lateral—force balances. These balances were re—
quired because the rotor axis was mounted vertically and
the resultant rotor force was measured on the drag and
lateral~force balances.