| 摘要 |
The wheel, designed to permit rotation in one direction only, consists of a hub (2) or rim with a series of curved or angled radial spokes (4), fitted with a friction coupling inside a rim (9) or to a hub. The inner surface of the rim is of slightly smaller diameter than the spokes or, where the spokes are fixed to the rim, the hub is of slightly greater diameter than the circle formed by the spokes' tips and can be grooved. The hub, which can be of metal or plastic, can carry a cog (8) or have a non-circular hole to engage with a matching shaft journal.
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