How Skarper partnered with the Red Bull Formula One team to develop its rotor-driven ebike conversion system

We’ve reported on Skarper’s unique drive system since the ebike conversion kit, which uses a disc brake rotor to drive the bike, broke cover in June 2022.

Back then, we saw an early prototype and followed up with a test ride on a pre-production Skarper system with six-time Olympic champion Sir Chris Hoy in September 2023.

Both stories sparked a significant amount of interest with our readers here on BikeRadar – Skarper is a system that, in theory, could turn any disc-brake bike into an electric bike.

This week we headed back to Skarper’s HQ in Camden, London, to get the inside story on how the brand turned the concept into a reality with the help of Formula One team Oracle Red Bull Racing’s Advanced Technologies division.

The beginning

Skarper’s relationship with Red Bull started before inventor and co-founder Alastair Darwood had begun developing the tech. 

“Back in 2020, at the start of the pandemic, I worked on a design for a low-cost ventilator for the NHS,” Darwood, a medical doctor with an engineering PhD, told BikeRadar. “The UK Government’s cabinet office connected me with Red Bull Advanced Technologies to develop my idea.”

When Darwood then began his development and prototyping of the original Skarper ebike conversion kit, early investor Sir Chris Hoy demonstrated a prototype of the device to Oracle Red Bull Racing’s CEO, Christian Horner, who was impressed by its potential. 

With a connection already established between Darwood and Red Bull Advanced Technologies, they agreed to help co-develop the system.

The challenges

Darwood and the team at Skarper had the idea in place and were running prototypes, but wanted to ensure strength and longevity, while also making the system as compact as possible. 

When presented with the opportunity to join forces with the engineering know-how of a Formula One World Championship-winning team, Darwood and Skarper’s group realised they could get to market faster by utilising the Finite Element Analysis and simulation capabilities of Red Bull Advanced Technologies.

From there, Red Bull enlisted its engineers to make the gearing inside the device smaller and more powerful, one of the key hurdles of making Skarper’s system viable.

The result is a compact drive system that clips onto Skarper’s DiskDrive (which replaces the rear disc rotor on any bike), converting a non-assisted bike into an ebike – and back again, if needed – in seconds, based on our experience.

Testing, testing

The development continued through 2023, with Skarper and Red Bull concentrating their efforts on refining the system’s size and weight to ensure its suitability for any road-going bike, without upsetting the ride quality.

Darwood says Red Bull Racing also helped to co-develop the gearbox in the motor unit and the bearing design. Testing – split between physical tests and simulations – included running the unit at its maximum torque output continuously for more than 1,000km and then extrapolating that data through simulated test runs over 25,000km.

The production-ready Skarper unit measures 34x16cm and contains a 250-watt motor, accompanied by a 240Wh battery pack to give a claimed range of up to 60km.

“This partnership with Skarper demonstrates how F1 expertise can help to improve everyday technology for the benefit of the public,” says Horner. “The device is an incredibly clever piece of engineering and we have been able to make it smaller and more powerful thanks to our own talented engineers.”

What’s next?

Skarper’s debut drive unit will be available later this year and we have a test unit arriving in March, followed by a long-term setup in June.

However, while at Skarper’s HQ, we managed to peek behind the curtain into the firm’s development lab and spotted a clever new hub that enables the drive unit to run on a rim-brake bike. This will require a wheel build, but the drive unit (without rotor) is incorporated into the non-driveside hub flange. We’ve already requested this setup to try out. 

The second product in development is a mountain bike version of the Skarper unit, designed to work around a 180mm rotor. Red Bull is said to have done a lot of the early R&D on this to validate the design and ensure a similar DiskDrive system can deliver sufficiently high torque and power. “We just wanted to be exactly sure that the physics work,” says Skarper’s Darwood.

For now, the original Skarper unit is available for pre-order ahead of the official launch.