It was in 2013 that we first heard about the Rubbee, a device featuring a motorized roller that could be added to any bicycle to turn it into an e-bike. A new-and-improved version followed the next year, and now the even-newer-and-more-improved Rubbee X has just hit Kickstarter. Among other things, it's lighter, less wired-up, and can take multiple batteries.

Like the original Rubbee, this model simply clicks in and out of a mount on the bike's seat post – that process is reportedly quicker now, taking just one second instead of the previous seven. This means the device can be taken off of the bike and carried inside to charge the battery, and to keep it from being stolen.

In non-e-bike mode, the Rubbee X sits up above the rear tire, not touching it. When you want an electric boost, though, you flip a lever to lower it down. This causes its powered rubber roller to press down against the tire, held in contact using a pneumatic spring. A pedal cadence sensor detects when you're pedalling, and automatically instructs the motor to kick in accordingly. That sensor is now wireless, unlike the previous version which was hard-wired.

Additionally, while the previous models had one integrated lithium-ion battery pack, the X allows you to use anywhere from one to three replaceable batteries. The range varies from 16 km (10 miles) with a single battery, up to 48 km (30 miles) with all three. A new regenerative braking feature, which is activated by pedalling backwards half a revolution, helps boost that range.

The 250-watt motor manages a top electric-assisted speed of 25 km/h (16 mph). If you go for all three batteries, however, you can opt for a 350-watt motor upgrade, which makes possible a top speed of 32 km/h (20 mph). A smartphone app is used to select how much eletrical assistance is provided.

Another new feature is an integrated 14-LED brake light/turn indicator, which is controlled by an onboard accelerometer. And yes, the X is lighter than its predecessors – at 2.8 kg (6.1 lb) with a single battery, it actually weighs about half as much. Even with three batteries, it remains lighter at 4 kg (8.8 lb).

If you're interested in getting a Rubbee X of your own with a single battery, a pledge of £269 (about US$355) is required. Shipping is estimated for next June, if all goes according to plans.

It can be seen in use, in the video below.

Source: Kickstarter

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