This electric bike conversion kit uses the disc brake to assist the rider

Buyer demand for electric bikes is sparking the imagination of some engineers looking to offer a cheaper and simpler alternative through the conversion kits for electric bicycles. Skarper has devised one of the simplest and easiest to install systems on the market. You do not need to modify the frame or install complex accessories on it. It just requires a bracket on one of the chainstays to mount it, swap the rear wheel brake disc for the DiskDrive rotor and fit a wireless sensor on the crank of one of the pedals to start the system.

There are kits on the market to convert a conventional bicycle into an electric bicycle. The most complex ones require placing an electric motor on the bottom bracket or on the hub of one of the wheels and feeding it through a battery that hangs from one of the frame bars. Other simpler options are based on replacing one of the wheels with another that has the entire system integrated. Finally, the simplest ones are those that are placed on a support that allows them to rub against the deck by means of a wheel to transmit energy.

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The motor, battery and “brain” of the system are remarkably compact, weighing just 3.5 kilograms.

The originality of Skarper’s system is that uses the rear wheel disc brake to provide the assistance. The installation, as described by the company, is very simple. Put tabs on one of the rear chainstays to hold the kit in place, a wireless cadence sensor on the pedal cranks, swap out the rear brake disc for the included DiskDrive rotor, and the conversion is done. Once this first operation has been carried out, the kit can be removed and attached to the bike in just five seconds since the rest of the components can remain in it. The total weight of the entire assembly, including the kit and the brake disc, is 3.5 kilograms.

So while most conversion kits can’t be easily removed due to the effort involved in changing a wheel, cables, batteries and accessories, Skarper’s new system eliminates that problem by containing everything within a single compact unit that has a unique and patent protected design.

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Skarper’s patented DiskDrive rotor replaces the bike’s original disc brake, and the control system’s sensors and algorithm combine to deliver the power you need when you need it.

The kit hangs from the tongue, being attached to the lower part of the chainstay and rubbing against the brake disc. The electric motor that it incorporates is of 250W and assists the pedaling until the 25km/h, complying with the regulations for EPAC vehicles (the American version reaches up to 32 km/h). The battery that powers it has a capacity of 202 Wh that can offer assistance for approximately 60 kilometers, depending on the weight of the cyclist, the power demanded, the orography and the weather. The time it takes to recharge is 2.5 hours.

Disk Drive assists the cyclist’s pedaling by driving the rear wheel through the brake disc. Through the cadence sensor connected by Bluetooth to the motor, it knows when it can start and when it should stop assisting if you stop pedaling or reach 25 km/h. In addition, the embedded software orders to increase or decrease the assistance power since it is capable of detecting the slope of the road and the pedaling cadence. Although Skarper’s system is practically autonomous and self-controlled, the brand is also working on a smartphone app which allows the owner to make custom settings and receive firmware updates. A lights and buttons interface It allows you to select the assistance modes among the three available: Eco, Standard and Turbo, in addition to checking the battery level and Bluetooth connectivity.

An interesting detail is that the system also works as a brake on the rear wheelalthough this does not imply that the original conventional caliper brake, whether mechanical or hydraulic, does not continue to work.

Skarper says it has a team of more than a dozen engineers and designers working at its London base. The director of development is the inventor Alastair Darwoo who has behind him many innovations associated with his training as a doctor. These include orthopedic and anesthetic medical devices developed while working for the NHS.

Economically, Darwood’s innovative electric bike conversion kit features the investor support from a group of cyclists who have privately backed the company. They include sir chris todaya six-time Olympic champion and 11-time world champion who has also been heavily involved in the testing and development of the unit.

As he explains, “I have always been an advocate for more people to use bicycles, regardless of their fitness, ability or age, and I discovered that electric bicycles can play a very important role in making cycling more accessible for all”.

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The unit integrates a rear light in its locking lever and an interface of lights and buttons allows you to select the assistance modes among the three available, check the battery level and Bluetooth connectivity.

Skarper has not provided full details on this product. The presented prototype is adapted to road and city bikesalthough it is already working, together with Red Bull Advanced Technologies, to offer an off-road version.

Skarper says its unit “offers power and torque which means you can use it to take it to the top of the mountain, unhook it, stow it in your pack, and then hit the trails without carrying your extra weight on the bike, at the same price as a bike. simple mountain bike.

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The Skarper is not just for city bikes it can also be adapted to road bikes, gravel bikes, mountain bikes or any bike with disc brakes.

According to the planning of the company Skarper foresees that the system be available next year at a price of 1,000 pounds sterling (1,160 euros at current exchange rates). He claims to be in talks with major bike brands about the opportunity to fit the DiskDrive disc brake rotor as standard.

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