PURPOSE: To give the propulsive force to an object at any place in the water and air, by meshing two external gears, fixing one of them and giving the rolling motion to the other with mounted weights.

CONSTITUTION: Externally toothed gears 1, 2 are meshed then one externally toothed gear 2 of them is fixed to a fixed shaft 5 while weights 3 are mounted to the other externally toothed gear 1. In this way, if a rolling motion is given to the externally toothed gear 1, the weight 3 is approximated to and separated from the center of the fixed externally toothed gear 2, and the gear 1, when it is in motion to the separating direction, gives large propulsive force to an object, thus capable of propelling the object at any place in the water and air.