Whether you're cycling to the office and don't want to arrive too sweaty and out of puff, or you just need some help getting up a steep hill, e-bikes can be a great way to get around. For many though, buying a brand new bicycle when you already have a perfectly good one just doesn't make sense. That's where add-ons like the Copenhagen Wheel and the Rubbee come in, transforming an existing two-wheeler into an e-bike. The latest to join the add-on kit party is UK-based Revolution Works, with the three-part Revos system.

Currently raising production funds over on Kickstarter, Revolution Works reckons that riders will be able to go from standard non-powered bicycle to pedal-assist e-bike in under 10 minutes with no special tools. The kit will come as a drive unit, a pedal-assist sensor and a battery.

The 250 W aluminum alloy drive unit is clamped on the seat tube, between the seat stays, with the unit's roller resting on the tire of the rear wheel. A battery holder is mounted on the down tube, in place of a bottle holder perhaps. Then one of two available Li-ion battery packs (100 Wh or 209 Wh) is slotted into the holder and cabled up to the drive unit. Finally the magnetic pedal sensor is zip-tied to the chain stay and directed toward the cassette at the rear. The sensor is also cabled to the drive unit.

Once fitted, all a rider needs to do is start pedaling, the sensor will detect movement of the cassette and the Revos drive unit will kick in and help out until a speed of 15.5 mph (25km/h) is reached. The drive unit will only engage while a rider is pedaling, so will stop while coasting. And if you want to turn the unit off completely during a trip, you simply back pedal by half a turn. Then if you notice a particularly threatening incline approaching, the system can be reactivated with another half turn back pedal.

"The drive unit (patent applied for) and motor controller ensure that pedal assist is provided extremely efficiently," company director Mark Palmer told us. "This gives the rider a very positive experience as well as maximizing the available energy stored in the battery. When people see Revos, their first reaction is that its too small give significant help. Once around the car park and they've changed their minds."

The Kickstarter campaign has already met its crowdfunding goal, with a little over 2 weeks left to run. Pledges start at £349 (US$465) for a 100 Wh battery kit, and £439 (US$585) for the 209 Wh version. If all goes to plan, shipping is estimated to start in October. The video below has more.

Sources: Revolution Works, Kickstarter

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