PURPOSE: To obtain the engine capable of generating a comparatively large output in accordance with the eccentricity of a fixed disk rail by connecting a rotary disk rail, integral with a main shaft, to the fixed disk rail, eccentric with respect to the main shaft, through a movable disk.

CONSTITUTION: The main shaft 1 is supported rotatably by a column frame work 5 through bearings 10 and a plurality of straight rails 3 are attached to the main shaft 1. A circular rail 2 is fixed to the frame work 5 at a location eccentric with respect to the main shaft 1 while the movable disks 4-2, whose number of sets is equal to the same of the straight rails 3, are fitted slidably into the circular rail 2. The movable disk 4-1, engaged slidably with each straight rails 3, is connected to the movable disk 4-2 rotatably with each other and the main shaft 1 is rotated by the movement of the movable disk 4-2 through the straight rails 3.