Epicyclical gearing

consists of two gears mounted so that the center of one gear revolves around the center of the other

thumb|right|Bookwheel, from Agostino Ramelli's Le diverse et artificiose machine, 1588 The bookwheel (also written book wheel and sometimes called a reading wheel) is a type of rotating bookcase that allows one person to read multiple books in one location with ease. The books are rotated vertically similar to the motion of a water wheel, as opposed to rotating on a flat table surface. The design for the bookwheel originally appeared in a 16th-century illustration by Agostino Ramelli at a time when large books posed practical problems for readers. Ramelli's design influenced other engineers an

thumb|Internal Schematic of a Rohloff Speedhub 500/14 Rohloff AG is a German company from Fuldatal near Kassel that manufactures hub gears, bicycle chains and tools that are known for their durability and high performance. The company's logo is a black silhouette of a raven on a yellow background.

internal hub gear for bicycles