Bicycle drivetrain systems
Bicycle drivetrain systems are used to transmit power on bicycles, tricycles, quadracycles, unicycles, or other human-powered vehicles from the riders to the drive wheels. Most also include some type of a mechanism to convert speed and torque via gear ratios.
History
The history of bicycle drivetrain systems is closely linked to the history of the bicycle. 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.[1] 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.
Power collection
Bicycle drivetrain systems have been developed to collect power from riders by a variety of methods.
From legs
From arms
From whole body
From multiple riders
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 to allow coasting, but direct drive and fixed-gear systems do not. The later are sometimes also described as bicycle brake systems.
Direct
Some human powered vehicles, both historical and modern, employ direct drive. Examples include most Penny-farthings, unicycles, and children's tricycles.
Rotating
- Belt
- Shaft
- Wire rope as in the Stringbike and Rowbike
Non-rotating
Two-wheel drive
Steve Christini and Mike Dunn introduced a two-wheel drive option. Their AWD 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 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.[6]
Speed and torque conversion
A cyclist's legs produce power optimally within a narrow pedalling speed range. 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.
- Retro-Direct
- Lever and cam mechanism, as in the Stringbike
Control
Theory
Single-speed
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.
See also
Gallery
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Elliptical foot motion on a modern treadle bicycle -
Hand crank on a tricycle
References
- ^ Frank Berto (2009). The Dancing Chain: History and Development of the Derailleur Bicycle (Third ed.). Cycle Publishing. pp. 23–28. ISBN 978-1-892495-59-4.
- ^ "3G Stepper Bike: A Fitness Monster that Beats Your Gym Membership". Popular Mechanics. October 1, 2009. Retrieved 2010-07-13.
- ^ "A Different Kind Of Bicycle". Gadgetopia. Retrieved 2010-05-26.
- ^ a b c Wallack, Roy M. (30 November 2009). "Going Beyond the Basic Bike". LA Times. Retrieved 2011-05-12.
- ^ Richard Peace (Mon 11 Jan 2010). "ElliptiGO seatless bike launched". BikeRadar.com. Retrieved 2010-07-13.
{{cite web}}: Check date values in:|date=(help) - ^ Michael Embacher (2011). Cyclopedia. Fontaine & Noë / Lannoo. pp. 46–47. ISBN 978-90-72975-08-9.
External links
- Additional alternatives not yet notable enough for their own article
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| Drivetrain | ||
| Cabling | ||
| Peripherals | ||