Panamarenko
In order to improve the vibration-mechanism, Panamarenko started from the proposition that insects must have an elastic property in order to continue flying with just a few muscular impulses.
But then each time at precisely the correct instant. It took a long time for me to figure out how to build-in the right sort of timing... - Panamarenko
By utilizing a torsion spring, Panamarenko was able to optimize the frequency of the wing-beat. He calls this the double trampoline effect. He is of the opinion that if a person jumps on a rubber table with the right rhythm he can easily reach a height of 3 meters, something ruled out under different conditions. In 1976, Panamarenko first incorporates the improved, elastic vibrating mechanism in his design Umbilly Detail. The wings are affixed to long steel rods, and run by virtue of a system of cogwheels. They function as elastic torsion springs, and effectuate the wings' return beat.
'Because the wings are connected to a spring, they maintain each other in balance. The wings spring open, air enters and is then expelled by the spring-driven return-beat.' - Panamarenko
(source: Hans Willemse and Paul Morrens, in: 'Copyright Panamarenko', 2005)