Shaft Passer

A shaft passer is a hypothetical device that allows a spoked wheel to rotate despite having a shaft (such as the axle of another wheel) passing between its spokes. The device is usually mentioned as a joke between engineers, in the manner of a fool's errand, since there is no evidence of one ever having been constructed.

A similar, unnamed and also unattested, mechanism allows one cable to pass through another without breaking either. The device works by using a spoked, rimless wheel that allows cables to pass through as it rotates. The ends of the spokes are widened, and the cable is held together by a short curved sleeve through which these spoke ends slide.

One of the earliest printed references to these devices was made by Richard Feynman, who was told by a colleague at Frankford Arsenal in Philadelphia that the cable-passing version of the device had been used during both world wars on German naval mine mooring cables, to prevent the mines from being caught by British cables swept along the sea bottom.

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Famous quotes containing the word shaft:

    Why should not our whole life and its scenery be actually thus fair and distinct? All our lives want a suitable background. They should at least, like the life of the anchorite, be as impressive to behold as objects in a desert, a broken shaft or crumbling mound against a limitless horizon.
    Henry David Thoreau (1817–1862)