Abstract: In a ships drive transmission, contra rotating propeller shafts are driven by powered means comprising concentric contra rotating drive elements, one of the shafts being connected thereto via epicyclic gearing. The propeller shafts are also coupled to each other through a part of the epicyclic gearing, to ensure equal loading.

Abstract: A drive transmission which is particularly suitable for ship propulsion, comprises nested, contra rotating propeller shafts which in one example are driven by a single input shaft and which transmits contra rotating drives to the shafts via respective planet carriers. Particular advantages are the equal division of torque between the shafts and the enabling of location of thrust bearings and in positions which are easy of access.

Abstract: A gear system has two ring gears engaging a coupling member directly instead of through an intermediate coupling ring. For example, the ring gears are mounted adjacent to one another on a common axis and have respective helical running teeth which engage oppositely-handed arrays of helical teeth on planet gear wheels which, in turn, mesh with a sun gear wheel. The ring gears also have arrays of external spur coupling teeth offset towards one another from the centers of the running teeth, respectively. The arrays of external teeth mesh with internal spur coupling teeth on the annular coupling member. The ring gears have mutually opposed lubricated abutment surfaces whereby respective transverse forces arising effectively at the centers of the running teeth and acting parallel to the common axis are countered by oppositely acting respective reactions exerted by the ring gears mutually one upon the other.