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.