| 摘要 |
A crank arm for a bicycle includes a crank arm body (1) having a pedal attachment hole (6) on a first end (4) thereof and a spindle attachment hole (5) on a second end (2) thereof. The crank arm body (1) defines an elongated interior cavity (7), wherein the interior cavity (7) is open to an exterior of the crank arm body. The opening (15) can be used to access the cavity (7) during and after manufacturing. In the method used to form the crank arm body (1) according to the present invention, a sand mold core (24) is positioned into a casting mold (20,21) so that a melt space (22) is formed around the sand mold core (24), molten metal is poured into the casting mold (20,21), and the molten metal is solidified to form a crank billet (29). Sand is preferably removed through an opening in the crank billet (29). This may be accomplished by drilling the crank billet (29) to form the pedal attachment hole (6) in a location that communicates with the sand mold (24) and then removing sand through the pedal attachment hole (6). <IMAGE> |
