We’ve seen lightweight e-bikes before, but none have ever come close to the 15.15 lb (6.872 kg) Freicycle e-bike built by mechanical engineer Dennis Freiburg.
Its featherweight e-bike recently set a new Guinness World Record for lightest e-bike – prototype.
The Freicycle took Freiburg a good part of the year to design and build, part of a project for his doctorate.
Built on a Merida Scultura carbon road bike, the Freicycle benefited from the start from an ultralight frame weighing less than 2.2 lbs (1 kg).
Freiburg cut the rest of the weight with as much carbon fiber as possible for critical load-bearing components such as the wheels, fork and cranks.
Other components that couldn’t be light enough were 3D printed, such as special ultralight pedals.
But of course, the heart and soul of any e-bike is the motor and the battery.
For the motor, Dennis relied on a decidedly low-tech but lightweight solution: a friction drive.
Lightweight hub motors and mid-drive motors exist, but they can’t compare to the minimalism of a properly designed friction drive.
These types of e-bike drives have been around for decades due to their simplicity. A motorized roller is pressed against the bicycle tire, requiring minimal assembly and zero gearing. Freiburg used a brushless RC helicopter motor capable of producing 600 watts of power, wrapped in an abrasive sleeve to provide grip for the rear tire.
Torque from the motor swings its single mount down and engages the rear tire. When power to the motor is cut, the spring mechanism pulls it out of the way of the tire. Simple. Effective. Light.
Since the Freicycle was built in Europe, the motor is limited to road-legal 250W and a top speed of 15.5 mph (25 km/h). But when unlimited, the Freicycle can apparently hit speeds of up to 30mph (48kph) with its 600W of power.
A simple way to save weight would be to install a small battery. A watch battery might spin the wheel a turn or two with a step-up converter, but that wouldn’t get you very far.
To cut down on shenanigans like this, Guinness needs a battery of at least 137 Wh for a valid record attempt.
Freiburg built a regulation battery and managed to store it in a lightweight drink bottle held in place by a 3D-printed bottle cage. The bottle cap even doubles as an on/off switch, which you can see in the video below.
The battery isn’t huge, but with enough pedaling it will apparently take the rider between 12 and 22 miles (19-35 km).
I’ve ridden lightweight e-bikes before taking the one-finger lift test, but I’ve never seen a 15-pound e-bike.
And while it’s obviously not something you can buy today, the DIY nature of the project is still impressive. We’ve showcased a number of DIY e-bike builds and even undertaken our own. But we have never seen anything like it!
As e-bike construction continues to evolve and more carbon fiber e-bikes enter production in the coming months, it will be interesting to see if a retail e-bike can ever challenge Dennis for the record.
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