The powertrain describes the mechanism that generates power and propels a vehicle. Over the years, powertrain structures have been improved to make cars more reliable, more fuel efficient and so on. But fine tuning one particular system can only go so far, before each adjustment puts something else out of kilter. The step change is to design a completely fresh system.

In 1948, the Royal Automobile Club employed ex-farmer, James Wilson Brown to turn a wartime airfield and farm into a race track for the first RAC International Grand Prix.

On 2 October 1948, a crowd of 100,000 gathered to see Luigi Villoresi beat a field of 22 in his Maserati.  A piggery in the middle of the race circuit was protected by hay bales and ropes, with canvas barriers around the outside to keep everyone on the course.  The track was Silverstone and the history of Formula 1 racing was in the making.

Always edgy and inventive, these early racing cars were technical miracles in their day – built for ‘the purpose of earthbound flight’ – made up of chassis, cockpit, panels, engine, tank, wheels – and nothing else. Cooper and Lotus put the UK at the forefront of Formula 1 in the late 50s.  This was a time when lots of engineering took place at the back of someone’s garage or workshop, often during some spare time after work. Engineer and racing enthusiast Charlie Cooper built the first chassis for a rear engine Cooper – which was to transform Grand Prix racing – in such a workshop.  Colin Chapman built the first Lotus around an Austin Seven engine in a lock-up garage behind his girl friend’s house.


These pioneers of Formula 1 were inventive and talented, and they spent many hours tinkering and trying out new ideas.  For them there was one simple goal – speed.

Hugo Spowers is chief engineer at Riversimple. Spowers also comes from the racing world. He left motorsport in order to “pursue, systematically, the elimination of the environmental impact of personal transport”.  Rasa is Riversimple’s first production prototype and the powertrain is based upon a small hydrogen fuel cell and a bank of super-capacitors.

A capacitor is basically something that can carry electrical energy, consisting of conductive plates separated by a non-conductive layer called the di-electric. When an electric current enters the capacitor, the di-electric stops the flow and a charge builds up and is stored in an electric field between the plates. Batteries, meanwhile, store electrical energy in a chemical form.  This means that capacitors have some advantages over batteries: they weigh less and they can be charged and discharged quickly and many times without wearing out.

Rasa powertrain_chassisSince ordinary capacitors don’t hold a charge for long, super-capacitors are a natural evolution. The Rasa prototype super-capacitors have a coating of charcoal and lithium ion to give them greater capacity to hold energy.

The RASA powertrain is intended to recover energy that is traditionally wasted during braking, whilst allowing recaptured energy to flow precisely where it is needed, when it is needed, and only as much as is needed. This is managed by purpose-designed Riversimple software – that’s the integrated brain of the car – ensuring that:

The light fuel cell maintains cruise

When braking, the motors in each wheel hub recover the kinetic energy and feed it into the bank of super-capacitors

Cruise and acceleration are “de-coupled” as separate functions

Energy recaptured from braking system boosts acceleration

The result is a car that can cruise along very efficiently on a tiny fuel requirement, but can also pack a big punch when asked to accelerate or climb a hill. In other words everything you need and nothing that you don’t.

Version 2

Riversimple anticipate that the commercial RASA will be more than 3 times as efficient as other fuel cell cars currently on the market.

So here’s to the pioneers. To the engineers who go beyond. To those prepared to struggle for something. And to those who may have started in a small workshop or at the back of a garage, but end up showing the world what is possible.



R Francis.



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