While there are plenty of add-on electric bicycle motors out there, the Rubbee takes a particularly interesting approach. The product of a successful Kickstarter campaign, it incorporates a powered polyurethane roller that rubs against the bike's rear tire (hence the name), helping to augment the rider's pedaling power by driving the wheel forward. The second version of the device is now available and it's reportedly easier to use, plus it'll take you farther.
Both versions of the Rubbee follow the same basic principle ... they're mounted on the bike's seatpost, allowing the motorized roller to be flipped down onto the tire only when needed. In fact, the whole Rubbee can be quickly installed or removed, via its quick-release mount. Power comes from an integrated 250-watt motor and a 14.4-volt 280-Wh battery pack, that can be fully charged from empty in three hours.
On the original version, the rider manually adjusts the motor’s output level via a handlebar-mounted controller that stays attached full-time. On the Rubbee 2.0, however, a permanently-installed Pedal Assist Sensor monitors how fast the rider is pedaling, while integrated software also keeps track of the speed at which the motor is running.
By analyzing that data, the Rubbee is able to determine how fast the bicycle is traveling. It then determines how much assistance it should provide, both in order to maintain the preferred cadence and the desired speed ... up to a maximum of 25 km/h (16 mph).
Other improvements include a 300-gram (10.6-oz)-lighter weight of 6.9 kg (15 lb), 30 percent more torque and a 35 percent increase in range, which takes it up to approximately 40 km (25 miles).
It's available now, for US$1,190.