To attain more highly efficient driving force by sharing rectilinear motion force among four gears in a manner of providing a rack on the whole surface of a columnar and supporting the rack with four faces and rotating a drive shaft engaged with the gears by causing a pair of columnar racks to make alternate rectilinear motion.

Columnar racks 1, 1' connected to an engine cylinder is contrived to make alternate rectilinear motion by coupling with a line 21 and gears 10, 10' of a free-wheel provided with a bevel gear on both ends are engaged with and bonded to a drive shaft 3, while other gears 9, 9' are engaged with a limited shaft 4 and universal gears 13, 13' and 16, 16' have all gears connected together respectively by bevel gears. The drive shaft 3 and the limited shaft 4 being connected together at a plural number of places by a spur gear, the columnar rack 1 is lifted up when the columnar rack 1' is pushed down and rectilinear motion is alternately converted into rotary motion by using the columnar rack.