Nature's Gyroscopes

Entomologists and mechanical engineers ordinarily have little to do with one another. The first study bugs; the second design machinery. But last week the Sperry Gyroscope Co., designers of highbrow airplane instruments, told of a fruitful side trip into entomology.

The flight instruments which Sperry produces contain small, rapidly spinning flywheels called gyroscopes. Their useful characteristic is the obstinate way they keep steady while the airplane twists and turns around them. Most valuable service: they provide an artificial horizon; when a pilot cannot see the real horizon, he looks at the gyroscopic one, to see if he is on an even keel.

A small metal ball vibrating rapidly at the end of a stiff, springy rod is just as obstinate as a rotating gyroscope. It tries to keep vibrating in the same direction, no matter what its support may do. Sperry engineers wondered if a "vibrating gyroscope" might not be more efficient than the more conventional rotating type. There would be no bearings to worry about, and the ball could be kept in motion by the modern magic of electronics. So they dove deep into physics and mathematics.

Asking the Flies. They had hardly warmed up to the job when they discovered that Nature had done it 50,000,000 years ago: flies and other "dipterous insects" were actually equipped with vibrating gyroscopic flight instruments (see cut). Just behind the trailing edge of each wing they had "halteres": small rods with round balls on their ends. When the insect is airborne, or even walking, these vibrate 160 to 210 times per second. The plane of vibration is fixed in relation to the insect's fuselage. When the insect banks, turns climbs or dives, the gyroscope tries to keep vibrating in the same plane. Its struggles register upon a knot of nerves at the base of the haltere, and tell the insect how it is doing in space. If both halteres are removed, the insect loses its sense of equilibrium, goes into a spin, crashes.

The Sperry Co.'s engineers are keeping their eyes on the bugs, in hope that they will teach them the secret of bugless gyroscopes.

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