Electronic gear-shifting system
Encyclopedia
An electronic gear-shifting system is a method of changing gears on a bicycle
, which enables riders to shift with electronic switch
es instead of using conventional control levers
. The switches are connected by wire or wireless
ly to a battery pack
and to a small electric motor
that drives the derailleur
, switching the chain
from cog to cog. An electronic system can switch gears faster, and because the system does not use Bowden cable
s and can calibrate itself, it may require less maintenance.
at the 1992 Tour de France
. It was a prototype, but it achieved neither technical success nor commercial application. A development of this was used by Chris Boardman
to win the opening time trial (prologue) of the 1997 Tour de France
.
In 1994 Sachs introduced the Speedtronic.
In 1999 Mavic introduced the Mektronic, its second electronic shift system but again without commercial application.
During the 2000s both Shimano
and Campagnolo
(2005) experimented with electronic shifting in professional cycle races.
The first commercial electronic gear shift system for road bicycle
s was introduced by Shimano in 2009, the Di2. Three professional teams used the Di2 in the 2009 Tour of California: Columbia High Road, Garmin Slipstream, and Rabobank
; and several teams and riders, including George Hincapie
, used it during the 2009 Tour de France
Also in 2009 Giant
released a bicycle equipped with the Shimano Di2 and Trek
began providing a battery mount and Di2-specific cable routing and stops on its Madone frames.
's Di2 (Dura-Ace 7970) for road bicycle
s. While the traditional method of gear shifting uses mechanical control levers that pull and release Bowden cables and spring-loaded derailleurs, Di2 is controlled by solid-state switches located either in the integrated shift levers and/or at the end of time trial bars. The switches send signals through a wiring harness to a battery pack, placed near the bottom bracket
. The rechargeable lithium-ion battery pack supplies power to the derailleur motors, which move the derailleurs via worm gears
. Shimano
estimates that their 7.4-volt battery pack can last up to 1000 kilometres (621.4 mi) per charge. The system also has an LED light to warn when it needs a charge.
The rear derailleur has shift times similar to mechanical systems and a break-away system to protect it in case of a crash. The front derailleur, however, switches gears almost 30% faster. On traditional bikes, the front derailleur is problematic because the chain can be under tension and has to make a large vertical jump between chainring
s. The electronic system's controlled motion overcomes these problems. The Di2 can also trim the front derailleur to eliminate chain rub and calibrate itself to adjust for wear and tear. Finally, the entire 7970 groupset
weighs approximately 113 grams (4 oz) less than the 7800 it replaces but 68 grams (2.4 oz) more than the new 7900.
In 2011 Shimano introduced the Ultegra Di2 electronic gear change set, a cheaper version of the electronic Dura-Ace system.This seemed set to provide an electronic option within reach of a wider audience. Campagnolo
introduced their first system of electronic shifting in the same year. Cyclists began to see a growing market in electronic alternatives to traditional mechanical shifting for derailleur gears
.
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....
, which enables riders to shift with electronic switch
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....
es instead of using conventional control levers
Shifter (bicycle part)
A bicycle shifter or gear control or gear levers is a component used to control the gearing mechanisms and select the desired gear ratio. Typically, they operate either a derailleur mechanism or an internal hub gear mechanism. In either case, the control is operated by moving a cable that connects...
. The switches are connected by wire or wireless
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
ly to a battery pack
Battery pack
A battery pack is a set of any number of identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density...
and to a small electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
that drives the derailleur
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...
, switching the 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...
from cog to cog. An electronic system can switch gears faster, and because the system does not use Bowden cable
Bowden cable
A Bowden cable is a type of flexible cable used to transmit mechanical force or energy by the movement of an inner cable relative to a hollow outer cable housing...
s and can calibrate itself, it may require less maintenance.
History
In 1992 the first electronically controlled gear shift mechanism, the Zap, was introduced by the French manufacturer MavicMavic
Mavic is a French bicycle parts manufacturer, its name an acronym for Manufacture d'Articles Vélocipédiques Idoux et Chanel, founded by Charles Idoux and Lucien Chanel. The company is noted as a manufacturer of bicycle wheels. Mavic is based in Annecy, France...
at the 1992 Tour de France
1992 Tour de France
The 1992 Tour de France was the 79th Tour de France, taking place July 4 to July 26, 1992. The total race distance was 21 stages over 3983 km, with riders averaging 39.504 km/h...
. It was a prototype, but it achieved neither technical success nor commercial application. A development of this was used by Chris Boardman
Chris Boardman
Christopher "Chris" Boardman MBE is a former English racing cyclist who won an individual pursuit gold medal at the 1992 Summer Olympics and broke the world hour record three times, as well as winning three stages and wearing the yellow jersey on three separate occasions at the Tour de France...
to win the opening time trial (prologue) of the 1997 Tour de France
1997 Tour de France
The 1997 Tour de France was the 84th Tour de France, it took place July 5–27, 1997. Jan Ullrich's victory margin, of 9' 09" was the largest margin of victory since Laurent Fignon won the 1984 Tour de France by 10' 32"...
.
In 1994 Sachs introduced the Speedtronic.
In 1999 Mavic introduced the Mektronic, its second electronic shift system but again without commercial application.
During the 2000s both Shimano
Shimano
Shimano, Inc. is a Japanese multinational manufacturer of cycling components, fishing tackle, and rowing equipment.In 2005, the company had net sales of US $1.4 billion. Bicycle components provided 75% of its sales income...
and Campagnolo
Campagnolo
Campagnolo is an Italian manufacturer of high-end bicycle components with headquarters in Vicenza, Italy. The components are organised as groupsets and are a near-complete collection of a bicycle's mechanical parts. Campagnolo's flagship components are the Super Record, Record, and Chorus...
(2005) experimented with electronic shifting in professional cycle races.
The first commercial electronic gear shift system for road bicycle
Road bicycle
The term road bicycle is used to describe bicycles built for traveling at speed on paved roads. Some sources use the term to mean racing bicycle...
s was introduced by Shimano in 2009, the Di2. Three professional teams used the Di2 in the 2009 Tour of California: Columbia High Road, Garmin Slipstream, and Rabobank
Rabobank (cycling team)
Rabobank is a professional bicycle racing team, sponsored by the Rabobank. The team consists of three sections: ProTeam , Continental , and Cyclo-cross...
; and several teams and riders, including George Hincapie
George Hincapie
George Hincapié Garcés is an American professional road bicycle racer currently riding for UCI ProTeam . Hincapie resides in Greenville, South Carolina...
, used it during the 2009 Tour de France
Tour de France
The Tour de France is an annual bicycle race held in France and nearby countries. First staged in 1903, the race covers more than and lasts three weeks. As the best known and most prestigious of cycling's three "Grand Tours", the Tour de France attracts riders and teams from around the world. The...
Also in 2009 Giant
Giant Manufacturing
Giant Manufacturing Co. Ltd. is a Taiwanese bicycle manufacturer which bills itself as the world's largest bicycle manufacturer. Giant has manufacturing facilities in Taiwan, Netherlands, and Mainland China.-History:...
released a bicycle equipped with the Shimano Di2 and Trek
Trek Bicycle Corporation
Trek Bicycle Corporation is a major bicycle and cycling product manufacturer and distributor under brand names Trek, Gary Fisher, Bontrager, Klein and until recently, LeMond Racing Cycles...
began providing a battery mount and Di2-specific cable routing and stops on its Madone frames.
Implementation
As of 2009, one system was commercially available from a major parts manufacturer: ShimanoShimano
Shimano, Inc. is a Japanese multinational manufacturer of cycling components, fishing tackle, and rowing equipment.In 2005, the company had net sales of US $1.4 billion. Bicycle components provided 75% of its sales income...
's Di2 (Dura-Ace 7970) for road bicycle
Road bicycle
The term road bicycle is used to describe bicycles built for traveling at speed on paved roads. Some sources use the term to mean racing bicycle...
s. While the traditional method of gear shifting uses mechanical control levers that pull and release Bowden cables and spring-loaded derailleurs, Di2 is controlled by solid-state switches located either in the integrated shift levers and/or at the end of time trial bars. The switches send signals through a wiring harness to a battery pack, placed near the bottom bracket
Bottom bracket
The bottom bracket on a bicycle connects the crankset to the bicycle and allows the crankset to rotate freely. It contains a spindle that the crankset attaches to, and the bearings that allow the spindle and cranks to rotate. The chainrings and pedals attach to the cranks...
. The rechargeable lithium-ion battery pack supplies power to the derailleur motors, which move the derailleurs via worm gears
Worm drive
A worm drive is a gear arrangement in which a worm meshes with a worm gear...
. Shimano
Shimano
Shimano, Inc. is a Japanese multinational manufacturer of cycling components, fishing tackle, and rowing equipment.In 2005, the company had net sales of US $1.4 billion. Bicycle components provided 75% of its sales income...
estimates that their 7.4-volt battery pack can last up to 1000 kilometres (621.4 mi) per charge. The system also has an LED light to warn when it needs a charge.
The rear derailleur has shift times similar to mechanical systems and a break-away system to protect it in case of a crash. The front derailleur, however, switches gears almost 30% faster. On traditional bikes, the front derailleur is problematic because the chain can be under tension and has to make a large vertical jump between chainring
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...
s. The electronic system's controlled motion overcomes these problems. The Di2 can also trim the front derailleur to eliminate chain rub and calibrate itself to adjust for wear and tear. Finally, the entire 7970 groupset
Groupset
A groupset or gruppo is a bicycle component manufacturer's organized collection of mechanical parts...
weighs approximately 113 grams (4 oz) less than the 7800 it replaces but 68 grams (2.4 oz) more than the new 7900.
In 2011 Shimano introduced the Ultegra Di2 electronic gear change set, a cheaper version of the electronic Dura-Ace system.This seemed set to provide an electronic option within reach of a wider audience. Campagnolo
Campagnolo
Campagnolo is an Italian manufacturer of high-end bicycle components with headquarters in Vicenza, Italy. The components are organised as groupsets and are a near-complete collection of a bicycle's mechanical parts. Campagnolo's flagship components are the Super Record, Record, and Chorus...
introduced their first system of electronic shifting in the same year. Cyclists began to see a growing market in electronic alternatives to traditional mechanical shifting for 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...
.
Advantages
An electronic system can have several advantages over a comparable mechanical system:- shift gears faster than a regular mechanical system
- eliminate the need for the rider to switch hand positions in order to shift
- allow for an accurate and effortless shift, even in difficult circumstances, such as if the rider has cold hands or is completely exhausted
- shifting performance is not affected by contaminated, stretched, or worn Bowden cables
- automatic trim function can eliminate chain rub
- the smoothness of electronics can reduce the shock on drivetrain components
- allow for two sets of gear controls, where cable shifted gears are limited to one. This is useful especially on Time TrialTime trialIn many racing sports an athlete will compete in a time trial against the clock to secure the fastest time. In cycling, for example, a time trial can be a single track cycling event, or an individual or team time trial on the road, and either or both of the latter may form components of...
bicyles.
Disadvantages
An electronic system may have some disadvantages when compared to a mechanical system:- There is currently no option for manual override when the battery is exhausted. This could pose a problem for riders, depending on the type of terrain on which they are riding.
- As currently implemented, each shift requires an individual button push, while many mechanical systems can move the chain multiple cogs with a single lever movement.
- Reliability issues have caused previous electronic systems to be withdrawn from the market.
- Cost: the system is extremely expensive compared with conventional mechanical derailleur systems. (The Shimano Dura Ace Di2 system costs in excess of $2500 in May, 2010).
- Weight: a Di2 system is heavier than the equaivalent Dura Ace cable shifted system.
See also
- Hub gearHub gearA 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...
- another bicycle gear shifting system alternative - NuVinci - continuously variable planetary transmission for bicycles
- Semi-automatic transmissionSemi-automatic transmissionA semi-automatic transmission is an automobile transmission that does not change gears automatically, but rather facilitates manual gear changes by dispensing with the need to press...
- electronic gear shifting for automobiles and motorcycles
External links
- Shimano's description of their Di2 with technical specifications and exploded views