Bicycle drivetrain systems are used to transmit power on bicycle

Bicycle

A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

s, tricycle

Tricycle

A tricycle is a three-wheeled vehicle. While tricycles are often associated with the small three-wheeled vehicles used by pre-school-age children, they are also used by adults for a variety of purposes. In the United States and Canada, adult-sized tricycles are used primarily by older persons for...

s, quadracycle

Quadracycle

A quadracycle is a four-wheeled human-powered vehicle. It is also referred to as a quadricycle, quadcycle pedal car or four-wheeled bicycle, amongst other terms....

s, unicycle

Unicycle

A unicycle is a human-powered, single-track vehicle with one wheel. Unicycles resemble bicycles, but are less complex.-History:One theory of the advent of the unicycle stems from the popularity of the penny-farthing during the late 19th century...

s, or other human-powered vehicles from the riders to the drive wheels. Most also include some type of a mechanism

Transmission (mechanics)

A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...

 to convert speed

Speed

In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...

 and torque

Torque

Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 via gear ratio

Gear ratio

The gear ratio of a gear train is the ratio of the angular velocity of the input gear to the angular velocity of the output gear, also known as the speed ratio of the gear train. The gear ratio can be computed directly from the numbers of teeth of the various gears that engage to form the gear...

s.

History

The history of bicycle drivetrain systems is closely linked to the history of the bicycle

History of the bicycle

Vehicles for human transport that have two wheels and require balancing by the rider date back to the early 19th century. The first means of transport making use of two wheels, and thus the archetype of the bicycle, was the German draisine dating back to 1817...

. Major changes in bicycle form have often been initiated or accompanied by advances in drivetrain systems. Several early drivetrains used straight-cut gears that meshed directly with each other outside of the hub. Some bicycles have used a double-sided rear wheel, with different-sized sprockets on each side. To change gears, the rider would stop and dismount, remove the rear wheel and reinstall it in the reverse direction. Derailleur systems were first developed in the late 19th century, but the modern cable-operated parallelogram derailleur was invented in the 1950s.

• Draisine
• Penny-farthing
  Penny-farthing
  Penny-farthing, high wheel, high wheeler, and ordinary are all terms used to describe a type of bicycle with a large front wheel and a much smaller rear wheel that was popular after the boneshaker, until the development of the safety bicycle, in the 1880s...
  
  
• Safety bicycle
  Safety bicycle
  A safety bicycle is a type of bicycle that became very popular beginning in the late 1880s as an alternative to the penny-farthing or ordinary and is now the most common type of bicycle. Early bicycles of this style were known as safety bicycles because they were noted for, and marketed as, being...
  
  

Power collection

Bicycle drivetrain systems have been developed to collect power from riders by a variety of methods.

From legs

• Crankset
  Crankset
  The crankset or chainset , is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain, which in turn drives the rear wheel...
  
   and pedals
  Bicycle pedal
  A bicycle pedal is the part of a bicycle that the rider pushes with their foot to propel the bicycle. It provides the connection between the cyclist's foot or shoe and the crank allowing the leg to turn the bottom bracket spindle and propel the bicycle's wheels...
  
  
• Treadle bicycle
  Treadle bicycle
  A treadle bicycle is a bicycle powered by a treadle instead of the more-common crank. Treadles were one of the mechanisms inventors tried in order to position the pedals away from the drive wheel hub before the development of the bicycle chain or in lieu of it...
  
  
• Vertical foot motion that mimicks that of a climbing exercise machine
• Elliptical foot motion that mimicks that of an elliptical trainer
  Elliptical trainer
  An elliptical trainer or cross-trainer is a stationary exercise machine used to simulate stair climbing, walking, or running without causing excessive pressure to the joints, hence decreasing the risk of impact injuries...
  
  

From whole body

• Rowing
• Hand and foot

Power transmission

Bicycle drivetrain systems have been developed to transmit power from riders to drive wheels by a variety of methods. Most bicycle drivetrain systems incorporate a freewheel

Freewheel

thumb|Freewheel mechanismIn mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft...

 to allow coasting, but direct drive and fixed-gear systems do not. The later are sometimes also described as bicycle brake systems

Bicycle brake systems

A bicycle brake is used to slow down or stop a bicycle. There have been various types of brake used throughout history, and several are still in use today...

.

Direct

Some human powered vehicles, both historical and modern, employ direct drive. Examples include most Penny-farthings, unicycles, and children's tricycles.

Rotating

• Chain
  Bicycle chain
  A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics. Nickel also confers a measure of...
  
  
• Micro drive
  Micro drive
  Micro drive is a term used to describe the drivetrain, mostly BMX and MTB, that use smaller than standard sized cogs. The smallest rear sprocket that fits on a freehub body is an 11-tooth, but with the use of a cassette hub, sometimes called a micro drive rear hub, sprockets as small as 8 teeth may...
  
  
• Chainless
  Chainless bicycle
  A chainless bicycle is a bicycle that transmits power to the driven wheel through a mechanism other than a metal chain.Examples:* Directly driven "ordinary" bicycle * Shaft-driven bicycle* Belt-driven bicycle...
  
  
• Belt
  Belt-driven bicycle
  A belt-driven bicycle is a chainless bicycle that uses a toothed synchronous belt to transmit power from the pedals to the wheel. The belts are typically made by the same manufacturing companies that produce timing belts for automobiles, machineries, and other synchronous belt drive...
  
  
• Shaft
  Shaft-driven bicycle
  A shaft-driven bicycle is a bicycle that uses a drive shaft instead of a chain to transmit power from the pedals to the wheel. Shaft drives were introduced over a century ago, but were mostly supplanted by chain-driven bicycles due to the gear ranges possible with sprockets and derailleurs...
  
  
• Wire rope
  Wire rope
  thumb|Steel wire rope Wire rope is a type of rope which consists of several strands of metal wire laid into a helix. Initially wrought iron wires were used, but today steel is the main material used for wire ropes....
  
   as in the Stringbike
  Stringbike
  The Stringbike is a bicycle that uses a wire rope and pulley drive system instead of a traditional bicycle chain and sprockets. It uses two steel wire ropes attached to pulleys attached to swinging lever and cam mechanisms, one on each side of the bike. These mechanisms replace the round sprockets...
  
   and Rowbike
  Rowbike
  A rowbike is an example of a rowing cycle, hybrid fitness/transport machine that combines a bicycle, generally considered a recumbent bicycle, and a rowing machine. "Rowbike" is a trademark of the RowBike company. The RowBike company was founded by Scott Olson, the inventor of Rollerblade inline...
  
  

Two-wheel drive

Steve Christini and Mike Dunn introduced a two-wheel drive option. Their AWD

Four-wheel drive

Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...

 system, aimed at mountain bikers, comprises an adapted differential that sends power to the front wheel once the rear begins to slip. In the late 1990s, 2WD 'Dual Power' mountain bikes were sold in Germany under the Subaru

Subaru

; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...

 name. They used one belt to transfer power from the rear wheel to the head tube, a small gearbox to allow rotation of the front fork, and then a second belt to transfer power to the front wheel.

Speed and torque conversion

A cyclist's legs produce power optimally within a narrow pedalling speed range

Cadence (cycling)

In cycling, cadence is the number of revolutions of the crank per minute; roughly speaking, this is the rate at which a cyclist is pedalling/turning the pedals...

. Gearing is optimized to use this narrow range as best as possible. Bicycle drivetrain systems have been developed to convert speed and torque by a variety of methods.

Implementation

Several technologies have been developed to alter gear ratios. They can be used individually, as an external derailleur or an internal hub gear, or in combinations such as the SRAM Dual Drive, which uses a standard 8 or 9-speed cassette mounted on a three-speed internally-geared hub, offering a similar gear range as a bicycle with a cassette and triple chainrings.

• Derailleur gears
  Derailleur gears
  Derailleur gears are a variable-ratio transmission system commonly used on bicycles, consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another...
  
  
• Cogset
• Crankset
  Crankset
  The crankset or chainset , is the component of a bicycle drivetrain that converts the reciprocating motion of the rider's legs into rotational motion used to drive the chain, which in turn drives the rear wheel...
  
  
• Hub gear
  Hub gear
  A hub gear, internal-gear hub, or just gear hub is a gear ratio changing system commonly used on bicycles that is implemented with planetary or epicyclic gears. The gears and lubricants are sealed within the hub-shell of the bicycle's rear wheel, as opposed to derailleur gears, where the gears and...
  
  
• Continuously variable
• Retro-Direct
  Retro-Direct
  Retro-direct is a gearing mechanism used on some bicycles in the early 20th century, which provides a second gear ratio when pedaled backwards.-History:...
  
  
• Lever
  Lever
  In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to either multiply the mechanical force that can be applied to another object or resistance force , or multiply the distance and speed at which the opposite end of the rigid object travels.This leverage...
  
   and cam
  Cam
  A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
  
   mechanism, as in the Stringbike
  Stringbike
  The Stringbike is a bicycle that uses a wire rope and pulley drive system instead of a traditional bicycle chain and sprockets. It uses two steel wire ropes attached to pulleys attached to swinging lever and cam mechanisms, one on each side of the bike. These mechanisms replace the round sprockets...
  
  

Integration

While several combinations of power collection, transmission, and conversion exist, not all combinations are feasible. For example, a shaft-drive is usually accompanied by a hub gear, and derailleurs are usually implemented with chain drive.

External links

• Additional alternatives not yet notable enough for their own article