Torotrak, Xtrac and Flybrid Systems have joined hands to develop highly efficient and compact CVTs

Torotrak announced a licence agree ment with Xtrac Ltd recently to use traction drive technology to develop highly efficient and compact continuously variable transmissions (CVTs) for application in a new mechanical kinetic energy recovery systems (KERS) proposed for Formula 1 (F1) motor racing. A major F1 racing team has become the first customer for the mechanical KERS. This F1 team will be supplied with KERS technology through Silverstone based Flybrid Systems LLP, an innovative engineering company focusing on research and development of hybrid vehicle technology, that will source Torotrak's full-toroidal CVTs used in their KERS directly from Xtrac Ltd.

Dick Elsy, chief executive at Torotrak, stated, "The rapid movement from concept to application with a significant F1 racing team highlights the benefits of the mechanical KERS and its ability to contribute to improved performance. This is also a significant step towards acceptance of Torotrak's technology for use in mainstream road cars to provide improvements in performance, fuel economy and greenhouse gas emissions." This development demonstrates the level of interest and confidence within F1 in the mechanical KERS based upon Torotrak's full-toroidal traction drive technology. Furthermore, it highlights the benefits of using Torotrak's technology to meet the requirement outlined by FIA president Max Moseley -of developing technology directly relevant to improving fuel efficiency in road cars - by recovering energy from the vehicle under braking and subsequently re-using that energy to accelerate and drive the vehicle.

The toroidal variable drive technology consists of components within each variator that include an input disc and an opposing output disc. Each disc is formed so that the gap created between the discs is 'doughnut' shaped; that is, the toroidal surfaces on each disc form the toroidal cavity. Two or three rollers are located inside each toroidal cavity and are positioned so that the outer edge of each roller is in contact with the toroidal surfaces of the input disc and output disc. As the input disc rotates, power is transferred via the rollers to the output disc, which rotates in the opposite direction to the input disc. The angle of the roller determines the ratio of the Variator and therefore a change in the angle of the roller results in a change in the ratio. So, with the roller at a small radius (near the centre) on the input disc and at a large radius (near the edge) on the output disc the Variator produces a "low" ratio. Moving the roller across the discs to a large radius at the input disc and corresponding low radius at the output produces the "high" ratio and provides the full ratio sweep in a smooth, continuous manner.

The transfer of power through the contacting surfaces of the discs and rollers takes place via a microscopic film of specially developed long-molecule traction fluid. This fluid separates the rolling surfaces of the discs and rollers at their contact points. The input and output discs are clamped together within each variator unit. The traction fluid in the contact points between the discs and rollers become highly viscous under this clamping pressure, increasing its 'stickiness' and creating an efficient mechanism for transferring power between the rotating discs and rollers.

Speaking about the agreement, Adrian Moore, technical director of Xtrac, said "We are delighted to be working with Flybrid, which has an important role to play in the development of an energy efficient KERS for F1. It is also exciting to be involved in the development of this new technology, which ultimately has the prospect of helping road cars to be more fuel efficient." The mechanical KERS system utilises flywheel technology developed by Flybrid Systems to recover and store a moving vehicle's kinetic energy, which is otherwise wasted when the vehicle is decelerated. The energy is received from the driveline through the Torotrak CVT, engineered and supplied by Xtrac, as the vehicle decelerates, and is subsequently released back into the driveline, again through the CVT, as the vehicle accelerates.

The FIA have defined the amount of energy recovery for 2009 season as 400kJ per lap giving the driver an extra 80hp over a period of 6.67 seconds. Compared to the alternative of electrical-battery systems, the mechanical KERS system provides a significantly more compact, efficient, lighter and environmentally-friendly solution. According to Jon Hilton, Flybrid's managing partner, the Torotrak solution offers the smallest and lightest package for the power output required and that the inherent torque controlled nature of the device ideally suits the application.

Torotrak is a world leader in the development of full-toroidal traction drive technology for use in automotive, truck, bus, off-highway, OPE and ancillary drive markets. Xtrac, at the other end, specialises in vehicle transmission technology focussed on clients in the aerospace, automotive, defence, marine and motorsport sectors. Flybrid Systems LLP is an innovative engineering company taking a fresh look at hybrid vehicle technology in F1, motor sport and automotive applications.