Chain drive
A method of transmitting mechanical power using chains and sprockets.
A chain drive is a method of transmitting mechanical power from one location to another, commonly used in vehicles such as bicycles and motorcycles, as well as in a wide variety of machines. The power is typically conveyed by a roller chain passing over a sprocket, with the gear's teeth meshing with holes in the chain links. The oldest known application of a chain drive appears in the Polybolos, described by the Greek engineer Philon of Byzantium in the 3rd century BC, though this device did not transmit power continuously. The first continuous and endless chain drive was depicted in the horological treatise of the Song dynasty by the Chinese polymath Su Song (1020–1101 AD), who used it to operate the armillary sphere of his astronomical clock tower.
- type
- Mechanical power transmission system
- earliest known application
- Polybolos, described by Philon of Byzantium (3rd century BC)
- first continuous chain drive
- Depicted by Su Song (1020–1101 AD) in Song dynasty China
- common types
- Roller chain, Morse chain, duplex chain
- alternatives
- Belt drive, drive shafts
- key design feature
- Gear ratio altered by varying input and output gear diameters
Lore & Background
The oldest known application of a chain drive appears in the Polybolos, described by the Greek engineer Philon of Byzantium (3rd century BC). Two flat-linked chains were connected to a windlass, which by winding back and forth would automatically fire the machine's arrows until its magazine was empty. Although the device did not transmit power continuously, the Greek design marks the beginning of the history of the chain drive, as no earlier instance of such a cam is known, and none as complex is known until the 16th century. The flat-link chain, often attributed to Leonardo da Vinci, actually made its first appearance here.
Reader's Guide
The chain drive has been a fundamental method of mechanical power transmission for centuries, with its earliest known application in the Polybolos of Philon of Byzantium and the first continuous chain drive in Su Song's astronomical clock tower. It became a key feature of the safety bicycle introduced in 1885, differentiating it from the penny-farthing and remaining a basic bicycle design element. In automobiles, many early cars used chain drive as an alternative to the Système Panhard, with Frazer Nash employing a system using one chain per gear selected by dog clutches, effective for fast gear selections in racing cars of the 1920s and 1930s. The last popular chain drive automobile was the Honda S600 of the 1960s. Chain drive remains a fundamental design decision in motorcycles, alongside belt drive and drive shafts, and is used in a wide variety of machines beyond vehicles.
Did You Know?
- The oldest known application of a chain drive appears in the Polybolos, described by the Greek engineer Philon of Byzantium in the 3rd century BC.
- The first continuous and endless chain drive was depicted by the Chinese polymath Su Song (1020–1101 AD) for his astronomical clock tower.
- Duplex chains are essentially two chains joined side by side, allowing for more power and torque to be transmitted.
- Chain drive was the main feature that differentiated the safety bicycle introduced in 1885 from the penny-farthing.
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