In December 2019, Germany's Dr. Dennis Freiburg, mechanical engineer, stamped his name into the Guinness Book of World Records with the world's lightest ebike: the 6.872-kg (15.15-lb) Freicycle. Now, he's revealed how he did it – with a 600-watt friction drive motor.
The Freicycle started out as a 2016-model Merida Scultura – a carbon-framed climbing racer with a sub-1kg (2.2-lb) frame and rim-mounted brakes to cut down on weight as much as possible. Freiburg took things up a notch with a full carbon crank and 3D-printed pedals, and barely-there carbon rims. Every metal part was assessed to see if it could be replaced by something lighter and 3D printed, and the brake calipers were one example of something that was tossed for a lighter, 3D-printed design.
The motor and battery typically add a lot of weight to an ebike build, and here Freiburg got a little creative. Instead of a hub or mid-mounted drive motor, he took the small motor powering the main rotor of a model helicopter and fashioned it into a friction drive that rests against the rear wheel under power, and swings out of the way when it's not in use.
The motor is software-restricted to an EU-legal 250 W and 25-km/h (15.5-mph) maximum pedal assist speed, but when unlocked it can deliver as much as 600 W and push the bike to speeds up to 48 km/h (30 mph). Even in restricted mode, the Freicycle's ludicrously low weight makes it much easier to ride fast in an unassisted fashion than most ebikes, and the tiny motor adds no pedal drag when it's not touching the wheel.
To carry the Guinness-mandated minimum 137-Wh battery, Freiburg grabbed a lightweight, off-the shelf drink bottle, filled it up with batteries and control electronics, made a 3D-printed bottle holder, and wired the whole thing up to that. He 3D printed a new lid for the bottle that's also capable of acting as an on/off switch for the bike and an assistance level dial as well. Lightweight sensors in the crank and wheel provide the system with information on the wheel speed and pedal cadence.
The entire drive system weighs less than 2 kg (4.4 lb), and the battery is sufficient for a range between 19-35 km (12-22 mi). Freiburg says it's not too much of a pain to carry an extra drink bottle battery pack if he needs a little extra range.
The bike is just 72 g (2.54 oz) over the 6.8-kg (15-lb) minimum weight required by the UCI organization for international race events – although there are a fair few people pushing to have that minimum weight lowered or eliminated.
The project as a whole cost somewhere around €20,000 (US$23,790) to realize, which is a lot for a bike, but not a lot for a Guinness World Record. If you're looking for the lightest ebike you can actually buy, the lightest we can find is the 11-kg (24.3-lb) Invisitron R1, which rocks a 250-W motor and costs AU$3,300 (US$2,380) – and that's a much easier price tag to come at.
See the Freicycle in action in the video below:
Source: Freicycle
