Bookwheel
The bookwheel, an alternative version of the revolving bookstand, is a device designed to allow one person to read a variety of heavy books in one location with ease. The books are rotated vertically much like a Ferris wheel (as opposed to a flat, rotating table surface). This device was invented by Italian military engineer Agostino Ramelli in 1588. To ensure that the books remained at a constant angle, Ramelli incorporated an epicyclic gearing arrangement, a complex device that had only previously been used in astronomical clocks. Ramelli undoubtedly understood that gravity could have worked just as effectively (as it does with a Ferris wheel), but the gearing system allowed him to display his mathematical prowess.
As the engraving shows, the gearing employs three types of gears. The central gear is fixed to the stand, and thus immobile relative to the ground, while the intermediate and outermost gears are free to rotate around their axes. A simple calculation shows that if the outermost gears have the same shape as the central gear, then no matter the size of the intermediate gear, the outermost gears will not rotate relative to the ground, thus making the books remain at a constant angle.
Ramelli's design was copied by subsequent authors. It appears in Heinrich Zeising's "Theatrum machinarum" (1611), printed by Henning Gross and possibly engraved by a young Andreas Bretschneider. It also appears in a German copy of Ramelli's work appearing in 1620. It too was printed by Gross and engraved by Bretschneider although the plate clearly differs from Zeising's edition. The book wheel was copied once again in a Chinese work edited by the Jesuit missionary Terrence Schreck. This Chinese copy is notable because it misrepresents Ramelli's original epicyclic gearing arrangement, perhaps indicating a lack of mechanical competence on the part of the engraver. The book wheel makes a final appearance in 1719. Grollier de Serviere criticized Ramelli's overly complicated design and presented a much simpler gimballed design.
References
- Rybczynski, Witold. One Good Turn: A Natural History of the Screwdriver and the Screw. Scribner, 2000.