Hub dynamo
Encyclopedia
A hub dynamo is a small electrical generator
built into the hub of a bicycle
wheel that is usually used to power lights
. Most modern hub dynamos are regulated to 3 watt
s at 6 volt
s, although some will drive up to 6 watts at 12 volts.
with their Dynohub of the 1930s-1970s. This competed effectively with contemporaneous bottle dynamo
s and bottom-bracket generators, but the Dynohub was heavy with its steel housing and was discontinued in the 1980s. Around 2009, Sturmey-Archer released new hub dynamo/drum brake units with an alloy housing, designated X-FDD and XL-FDD.
The Schmidt Original Nabendynamo
(SON) can power two 6-volt lamps in series at speeds above about 12 mph, and Schmidt manufactures lamps designed to facilitate this. These lamps have optics based on the Bisy FL road lights. The efficiency of the SON is quoted by the manufacturers at 65% (so just over 5W of the rider's output is diverted to produce 3W of electrical power) but this applies at only 15 km/h (10 mph). At higher speeds the efficiency falls. Automotive alternators, in contrast, achieve efficiencies over 90% by using electromagnets to adjust the field current. Bicycle dynamos instead use permanent magnets to eliminate the need for a battery to excite the field and initiate electrical generation.
Shimano
offers a variety of hub dynamos under the "Nexus" brand, such as the DH-3N70/DH-3N71, advertised as having significantly less drag than the Nexus NX-30. Some of the Shimano units come with an automatic light-sensitive switch.
SRAM manufacture the i-Light
hub dynamo. The D7 series is available for both rim and disc brakes while the D3 series features several of rim brake varieties. In a 2006 review by the German Stiftung Warentest
, the efficiency at 15 km/h of a D1 series i-Light hub dynamo was 66%, 10% better than a SON-28.
SR Suntour
offer the DH-CT-630 hub dynamo series with integrated overvoltage protection.
reviewed seven different hub dynamos in 2005. The SON28 was found to be the most efficient, although its cost was significantly higher than models from Shimano.
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
built into the hub of a 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....
wheel that is usually used to power lights
Bicycle lighting
Bicycle lighting improves the visibility of the bicycle rider to others in dark conditions, i.e. to increase the rider's conspicuity and to enhance the ability of the rider to see, illuminating the way forward. Both reflectors and active lights are used to make the rider more visible, and many ...
. Most modern hub dynamos are regulated to 3 watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
s at 6 volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
s, although some will drive up to 6 watts at 12 volts.
Models
The market was largely pioneered by Sturmey-ArcherSturmey-Archer
Sturmey-Archer is a manufacturing company originally from Nottingham, England. It primarily produces bicycle hub gears but has also produced motorcycle hubs....
with their Dynohub of the 1930s-1970s. This competed effectively with contemporaneous bottle dynamo
Bottle dynamo
A bottle dynamo or sidewall dynamo is a small electrical generator for bicycles employed to power a bicycle's lights — or to charge batteries for electronic devices including cellphones or GPS receivers....
s and bottom-bracket generators, but the Dynohub was heavy with its steel housing and was discontinued in the 1980s. Around 2009, Sturmey-Archer released new hub dynamo/drum brake units with an alloy housing, designated X-FDD and XL-FDD.
The Schmidt Original Nabendynamo
Schmidt Original Nabendynamo
Schmidt Original Nabendynamo is a German maker of high-efficiency and low-drag bicycle hub power generators and other electric bicycle gear....
(SON) can power two 6-volt lamps in series at speeds above about 12 mph, and Schmidt manufactures lamps designed to facilitate this. These lamps have optics based on the Bisy FL road lights. The efficiency of the SON is quoted by the manufacturers at 65% (so just over 5W of the rider's output is diverted to produce 3W of electrical power) but this applies at only 15 km/h (10 mph). At higher speeds the efficiency falls. Automotive alternators, in contrast, achieve efficiencies over 90% by using electromagnets to adjust the field current. Bicycle dynamos instead use permanent magnets to eliminate the need for a battery to excite the field and initiate electrical generation.
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...
offers a variety of hub dynamos under the "Nexus" brand, such as the DH-3N70/DH-3N71, advertised as having significantly less drag than the Nexus NX-30. Some of the Shimano units come with an automatic light-sensitive switch.
SRAM manufacture the i-Light
I-Light
The i-Light is a hub dynamo manufactured by SRAM as part of their i-Motion bicycle product series.The initial D1 series was replaced by the D3 and D7 series in 2007....
hub dynamo. The D7 series is available for both rim and disc brakes while the D3 series features several of rim brake varieties. In a 2006 review by the German Stiftung Warentest
Stiftung Warentest
Stiftung Warentest is a German consumer organisation and foundation involved in investigating and comparing goods and services in an unbiased way. It was founded on 4th. December 1964 by the Federal Republic of Germany as an independent foundation under civil law. It is based in Berlin.- Aims and...
, the efficiency at 15 km/h of a D1 series i-Light hub dynamo was 66%, 10% better than a SON-28.
SR Suntour
SunTour
SunTour or SR Suntour is a manufacturer of bicycle components. It was Japanese owned and managed, based in Osaka, until the mid 1990s when its name was sold to a Taiwan conglomerate. Its products ranged from suspension forks to derailleurs...
offer the DH-CT-630 hub dynamo series with integrated overvoltage protection.
Efficiency
Bicycle QuarterlyBicycle Quarterly
Bicycle Quarterly is a magazine that examines the history of bicycles, their design, and evolution; with emphasis on Randonneuring bicycles. Articles evaluate equipment and bicycles for performance and function, and articles include footnotes. It is published and edited by Jan Heine, of Seattle,...
reviewed seven different hub dynamos in 2005. The SON28 was found to be the most efficient, although its cost was significantly higher than models from Shimano.
External links
- Sturmey-Archer hub dynamo
- Audax UK - Generators Compared.
- http://www.myra-simon.com/bike/dynotest.html Testing by Chris Juden at Wilfried Schmidt Maschinenbau.
- http://bike.shimano.com/publish/content/global_cycle/en/us/index/products/0/nexus.html Info on the Shimano Nexus system.