| 摘要 |
A hub includes an inner surface that defines a noncircular, and preferably airfoil-shaped, aperture. The aperture is sufficiently sized and shaped for the inner surface to circumscribe a member having a noncircular cross section for retaining the hub to the member. A wheel is rotatable around the periphery of the hub. The hub thus functions as an adapter to enable a wheel to rotate about the noncircular member.
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