Bicycle crank arm and insert therefore
A crank arm for a bicycle may include a body extending along a body axis and having a first body end and a second body end axially spaced apart from the first body end. The crank arm may also include an insert provided toward the first body end. The insert may include a base portion having a radially outer surface. At least one extension may extend outwardly from the radially outer surface and may be encased within a corresponding recess in the body whereby relative planar movement between the body and the at least one extension in a first plane orthogonal to the radial direction is restrained. The retaining portion may have a retaining portion width measured in a first direction and the retaining width may be greater than a throat width thereby inhibiting relative radial movement between the at least one extension and the recess and preventing radial extraction of the extension from the corresponding recess.
1. A bicycle crank arm comprising:
a bicycle crank arm body extending along a body axis and having a first body end and a second body end, said second body end axially spaced apart from said first body end; and
a bicycle crank arm insert mounted within said bicycle crank arm body at said first body end, said bicycle crank arm insert extending along an insert axis, said insert axis substantially orthogonal to said body axis of said bicycle crank arm body, said bicycle crank arm insert further comprising:
a base portion, the base portion having a radially outer surface surrounding an aperture extending along said insert axis and through said base portion, said aperture configured to receive a fastener for coupling said bicycle crank arm body with another component of a bicycle; and
at least one extension disposed in a first ring of extensions, said at least one extension extending outwardly from said radially outer surface, said at least one extension configured to be at least partially encased within a said bicycle crank arm body to restrain relative movement between the bicycle crank arm body and said bicycle crank arm insert about a direction along said insert axis, said at least one extension comprising:
a neck adjacent said radially outer surface; and
a retaining portion spaced radially outward from said neck, said neck configured to extend through a throat region of said bicycle crank arm body, said neck having a neck width measured in a first direction, said throat region having a throat width measured in said first direction, the retaining portion having a retaining width measured in said first direction and said retaining width being greater than said throat width such that said at least one extension comprises a sidewall extending between said throat region and said retaining portion, said sidewall inclined, with respect to a radial direction of said aperture, from approximately 2-30 degrees, said retaining width being greater than said throat width inhibiting relative radial movement between said at least one extension of said bicycle crank arm insert and said bicycle crank arm body, and inhibiting radial extraction of said at least one extension from a corresponding recess in said bicycle crank arm body.
2. The bicycle crank arm of claim 1 , wherein said bicycle crank arm insert further comprises:
a second ring comprised of at least one extension extending outwardly from said radially outer surface, said second ring disposed proximate said first ring of extensions.
3. The bicycle crank arm of claim 1 , wherein said bicycle crank arm body is formed from material having a first coefficient of thermal expansion, and said bicycle crank arm insert is formed from material having a second coefficient of thermal expansion, said second coefficient of thermal expansion being greater than said first coefficient of thermal expansion, and wherein shrinkage of said bicycle crank arm insert relative to said bicycle crank arm body does not result in said radial extraction of said bicycle crank arm insert from said bicycle crank arm body.
4. The bicycle crank arm of claim 3 , wherein said bicycle crank arm insert further comprises:
a second ring comprised of at least one extension extending outwardly from said radially outer surface, said second ring disposed proximate said first ring of extensions.