WAn epicyclic gear train consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates to carry one gear, called the planet gear or planet pinion, around the other, called the sun gear or sun wheel. The planet and sun gears mesh so that their pitch circles roll without slip. A point on the pitch circle of the planet gear traces an epicycloid curve. In this simplified case, the sun gear is fixed and the planetary gear(s) roll around the sun gear.
WThe bookwheel 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 and, though now obsolete, inspires modern artists and historians.
WThe Ravigneaux gearset is a double planetary gear set, invented by Pol Ravigneaux, who filed a patent application on July 28, 1949, in Neuilly-sur-Seine France. This planetary gear set, commonly used in automatic transmissions, is constructed from two gear pairs, ring–planet and planet–planet.
WRohloff 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.
WThe Rohloff Speedhub is an epicyclic internal hub gear for bicycles, developed and patented by Rohloff AG. It has been manufactured and marketed by that company since 1998. The Speedhub 500/14 has 14 equally spaced sequential non-overlapping gear ratios operated by a single twistgrip. The overall gear range is 526%, meaning the highest gear is 5.26 times as high as the lowest gear. Individual gear shifts when shifting up give an increase of about 13.6%.
WThe Sachs Elan was an epicyclic internal hub gear for bicycles, developed and manufactured by the bicycle division of the German company Fichtel & Sachs. It was considered heavy and production units were plagued with quality issues. The gear hub was discontinued before the turn of the 2000 millennium.
WA Schlumpf Drive is a two-speed planetary gear assembly for use on bicycles. It is distinct from other bicycle planetary gear assemblies in that it is located behind the chainring rather than in the rear hub. A push-button on each side of the axle allows the rider to switch between high and low ratios. These are operated by the rider's heel.
WAlfine is the name of a comfort and urban oriented product series by Shimano. It is mainly known for internally geared hubs, but includes also hydraulic disc brakes and levers, chain tensioners, dynamo hubs, cranksets, shift levers, and complete wheels.
WShimano Nexus is a brand of bicycle components which includes products such as epicyclical gear hubs, cranksets, shifters, brake levers, hub brakes, hub dynamos, and a CPU for automatically changing gears. The series is primarily aimed at the "comfort" market such as urban commuters and tourers, and as such is not made to withstand the rigours of off-road or mountain biking. The free-wheeling Nexus internal gear hubs are compatible with Shimano's "roller brake", its version of a drum brake, but not with the Shimano disc brakes used with the higher-end Shimano Alfine internal gear hubs.