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After over a year since registering the world record, Dr. Dennis Freiburg, a former member of staff of the Institute of Machining Technology (ISF) at TU Dortmund University, has also officially received the certificate for the world record for the lightest e-bike in the world. Weighing just 6.872 kg, the record was officially confirmed by GUINNESS WORLD RECORDS© under the title “The lightest electric bicycle prototype”.
“Once the design for the e-bike, which was developed at TU Dortmund University, was completed, there was still a long way to go before it was finally entered in the book of records,” explains Dr. Freiburg. Independent performance tests on the battery and the drive system had to be conducted. But now he’s made it: The officially lightest e-bike in the world comes from Dortmund and is more than just extremely light. Anyone thinking now that savings were made in the prototype’s performance just to achieve the lowest possible weight is mistaken: The drive system can accomplish far more than the prescribed 250W and was only throttled due to legislation. The rechargeable battery is naturally smaller than that of conventional e-bikes, but here too GUINNESS WORLD RECORDS© set down a fixed target. Depending on the degree of support provided by the motor, a range of 19 to 35 kilometers is possible.
What concept lies behind this world champion e-bike? You take a bicycle frame plus wheels made of an ultralight material, the electric motor for a remote-controlled model helicopter, a water bottle, a rechargeable battery and small electrical parts, combine all this with German engineering expertise, add customized components, season with self-developed software – and the lightest electric bicycle in the world is ready to go. However, developing the bike was naturally not quite so simple: Dennis Freiburg, mechanical engineer, mobilized a lot of know-how and support among his colleagues in order to put the ultralight model on the road.
The rechargeable battery is housed in a water bottle
The e-bike’s frame is made of carbon. It was produced and placed at Freiburg’s disposal by Merida, German manufacturer of top-of-the-range bicycles. He attached the electric motor under the frame with a custom-made mount. The motor transfers its power via a friction roll to the rear wheel. “This is a very direct type of drive,” says Freiburg. He considers slightly increased wear of the rear wheel to be a disadvantage of this kind of power transmission.
Freiburg, an engineer who previously worked at the Institute of Machining Technology of TU Dortmund University, has housed the rechargeable battery in a commercially available water bottle, which he adjusted on the inside so that he was able to accommodate not only the battery but also the control electronics. Freiburg installed the software for his bike via a USB port in the bottle.
Functional parts from a 3D printer
In general, the e-bike can easily be used as a normal bicycle, as it weighs only about half a standard bicycle. To activate the e-drive, Freiburg turns the cap of the water bottle. He has redesigned this “lid” to form an on/off switch. In addition, he can regulate the power and level of support provided by the electric motor by turning the cap. This is possible because Freiburg has substituted the original lid with a cover that houses the corresponding electronics. He used a 3D printer to make this “lid” as well as other components, for example the brake mounts.
The battery power is enough for about 25 to 40 kilometers when the electric drive is switched on. “For a longer range, I can simply attach a second battery,” says Freiburg. Sensors on the rear wheel transmit speed data to the bicycle’s electronic control unit, sensors in the chainring tell it whether the rider is pedaling. The electric motor operates when the e-bike is going at speeds of to 25 kilometers per hour. “That’s the legal limit,” says Freiburg. “From 25 kilometers onwards, I’m naturally considerably faster when I use muscle power. After all, the bike doesn't weigh much.”
Dr. Freiburg remarks: “Without the people who supported and vouched for me as well as my wife’s patience, the project would have been impossible.” He particularly thanks the Institute of Machining Technology of TU Dortmund University, including Professor Dirk Biermann, bicycle manufacturers Merida, and Yan Rudall, who all supported the project from the outset. His thanks also go to the Institute of Electrical Engineering (ETI) of the Karlsruhe Institute of Technology and to velotech, a cycling equipment company, which both supported the project in its final phase.
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The campus of TU Dortmund University is located close to interstate junction Dortmund West, where the Sauerlandlinie A 45 (Frankfurt-Dortmund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is "Dortmund-Eichlinghofen" (closer to Campus Süd), and from B 1 / A 40 "Dortmund-Dorstfeld" (closer to Campus Nord). Signs for the university are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dortmund.
To get from Campus Nord to Campus Süd by car, there is the connection via Vogelpothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at Campus Nord and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.
TU Dortmund University has its own train station ("Dortmund Universität"). From there, suburban trains (S-Bahn) leave for Dortmund main station ("Dortmund Hauptbahnhof") and Düsseldorf main station via the "Düsseldorf Airport Train Station" (take S-Bahn number 1, which leaves every 20 or 30 minutes). The university is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duisburg.
You can also take the bus or subway train from Dortmund city to the university: From Dortmund main station, you can take any train bound for the Station "Stadtgarten", usually lines U41, U45, U 47 and U49. At "Stadtgarten" you switch trains and get on line U42 towards "Hombruch". Look out for the Station "An der Palmweide". From the bus stop just across the road, busses bound for TU Dortmund University leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dortmund main station to the stop "Dortmund Kampstraße". From there, take U43 or U44 to the stop "Dortmund Wittener Straße". Switch to bus line 447 and get off at "Dortmund Universität S".
The AirportExpress is a fast and convenient means of transport from Dortmund Airport (DTM) to Dortmund Central Station, taking you there in little more than 20 minutes. From Dortmund Central Station, you can continue to the university campus by interurban railway (S-Bahn). A larger range of international flight connections is offered at Düsseldorf Airport (DUS), which is about 60 kilometres away and can be directly reached by S-Bahn from the university station.
The H-Bahn is one of the hallmarks of TU Dortmund University. There are two stations on Campus Nord. One ("Dortmund Universität S") is directly located at the suburban train stop, which connects the university directly with the city of Dortmund and the rest of the Ruhr Area. Also from this station, there are connections to the "Technologiepark" and (via Campus Süd) Eichlinghofen. The other station is located at the dining hall at Campus Nord and offers a direct connection to Campus Süd every five minutes.