Exterior shear shoulder assembly for outboard motors and outdrives

摘要

An exterior progressive shear shoulder assembly which is adapted for connecting a marine propeller to a propeller drive shaft in such a manner that a selected torsional resistance of the propeller with respect to the drive shaft is achieved. In one embodiment a driver engaging the propeller drive shaft also receives a driver adaptor that fits inside the propeller hub and drivingly engages the propeller through interfacing torsion members such as torsion ribs and/or selected sets of shear rods, each having a selected length, composition and resilience. In another embodiment the drive shaft directly engages the driver adaptor. In the event that the rotating propeller inadvertently strikes or is entangled in an underwater object, the fixed or replaceable torsion ribs and/or shear rods deform and may shear between the propeller hub and driver adaptor to allow rotation of the driver adaptor in the propeller hub and absorb the torque shock. The torque load deformation and shearing actions are optimized in a preferred embodiment by the provision of air gaps defined on each side of the torsion members between the driver adaptor and a driver adaptor hub fixed inside the propeller hub and by resilient sheaths provided on the torsion members.