U.S. Centennial of Flight Commission home page
Launoy and Bienvenu designed a version of the Chinese top that consisted of two sets of rotors made of turkey feathers that ro

Launoy and Bienvenu designed a version of the Chinese top that consisted of two sets of rotors made of turkey feathers that rotated in opposite directions, which solved the problem of torque.

Credits - Gary Bradshaw; To Fly Is Everything