Shock absorbing hub assemblies and methods of making shock absorbing hub assemblies for marine propulsion devices

A marine propulsion device comprising:

• an engine that drives a propeller shaft and propeller hub into rotation via a clutch and a transmission, the propeller hub having an inner diameter defined by a plurality of planar stop surfaces and an axially adjacent contiguous and coplanar plurality of engagement surfaces;
• a shock absorbing hub assembly that connects the propeller shaft to the propeller hub, the shock absorbing hub assembly comprising:
• an adapter component having an inner bore that mates with a splined outer surface of the propeller shaft, the adapter component comprising a body having opposite first and second end portions, wherein the first end portion has a plurality of axially extending engagement surfaces for engaging the plurality of planar stop surfaces on an inner diameter of the propeller hub;
• an elastic hub component over-molded onto only the second end portion of the body, the elastic hub component having a plurality of planar outer engagement surfaces that abut the plurality of engagement surfaces of the propeller hub;
• wherein upon initial rotation of the propeller shaft, the elastic hub component deflects so as to allow the adapter component to rotationally travel with respect to the stop surfaces on the inner diameter of the propeller hub such that said initial rotation of the propeller shaft does not cause corresponding rotation of the propeller hub;
• wherein upon further rotation of the propeller shaft, the plurality of axially extending engagement surfaces on the adapter component engages with the propeller hub such that said further rotation of the propeller shaft causes corresponding rotation of the propeller hub;
• and
• wherein the elastic hub component has a spring rate that is small enough to reduce rattle of the clutch and yet large enough to isolate shift clunk of the transmission.

A method of making a shock absorbing hub assembly for a marine propulsion device having a propeller shaft and a propeller, the method comprising:

• providing an adapter component having an inner bore that mates with a splined outer surface of the propeller shaft, the adapter component comprising a body having opposite first and second end portions, wherein the first end portion has an outer diameter with a plurality of axially extending engagement surfaces for engaging stop surfaces on an inner diameter of the propeller hub, and wherein the second end portion has an outer diameter with a continuously smooth surface such that the second end portion has a circular cross-section;
• over-molding an elastic hub component on only the continuously smooth surface of the outer diameter of the second end portion of the body, the elastic hub component having a plurality of planar outer engagement surfaces that abut a plurality of corresponding inner engagement surfaces on an inner bore of the propeller hub;
• wherein upon initial rotation of the propeller shaft, the elastic hub component deflects and allows the adapter component to rotationally travel with respect to the stop surfaces on the inner diameter of the propeller hub such that said initial rotation of the propeller shaft does not cause corresponding rotation of the propeller hub;
• wherein upon further rotation of the propeller shaft, the plurality of axially extending engagement surfaces on the adapter component engages with the propeller hub such that said further rotation of the propeller shaft causes corresponding rotation of the propeller hub;
• and
• selecting a material of the elastic hub component so that the elastic hub component has a spring rate that is small enough to reduce rattle of a clutch and yet large enough to isolate shift clunk of a transmission.