Fig. 2. The prototype Flybus is based on an Optare Solo midibus with an Allison automatic transmission and a flywheel-based energy recovery system.
and the flow of kinetic energy, was built by motorsport firm Xtrac using Torotrak’s traction drive technology. Ford Motor Company is examining the potential for secondary applications for flywheel-CVT systems. Separate to this, a Volvo-led project to evaluate flywheel
technology will incorporate Torotrak’s CVT technology with the aim of boosting fuel economy (Fig. 1). The project, part- funded by the Swedish Energy Agency, will use Torotrak’s variable drive technology with flywheel technology from Flybrid Systems. Other partners in the kinetic energy recovery system (Kers) project include SKF and Volvo Powertrain.
Relatively cheap technology
Torotrak says that this project will demonstrate how mechanical hybrids could reduce emissions and improve fuel economy more cost-effectively than electrical hybrid systems. Torotrak chief executive Dick Elsy comments: “We sense real momentum in the growing markets for efficiency-enhancing
devices to reduce CO2
emissions. The industry needs cost-
effective hybrid solutions: using a Torotrak variable drive transmission, with a mechanical flywheel, has demonstrated the capability for double-digit improvements in fuel economy.” Another way of using flywheels is seen in the UK Flybus
project that is investigating alternatives to battery-hybrid buses (Fig. 2). The first prototype has now been built, based on an Optare Solo midibus with an Allison automatic transmission. The flywheel-hybrid unit attaches to an unused power take- off shaft, with Torotrak’s traction drive managing the flow of energy in and out of Ricardo’s high-speed carbon composite Kinergy flywheel. As well as being suitable for use on buses, the system could
be equally effective on commercial vehicles such as delivery vans and trucks operating stop-start schedules. With over 2.5 million medium and heavy commercial vehicles manufactured worldwide each year, the technology could make a significant contribution to reducing vehicle emissions globally.
Opposite directions
But CVT/IVT technology could capture more market share if it starts to be adopted for more small cars - which tend to be produced in higher volumes. Tata Motors has used a Torotrak prototype transmission in the Tata Pixel concept car that was revealed at this year’s Geneva Motor Show (Fig. 3). This four-seat urban vehicle uses an IVT to boost fuel economy and manoeuvrability. Rob Oliver, Torotrak’s director of product development, explains: “The Tata Pixel is an example of how IVT technology addresses the needs of small and city-cars. Features such as the IVT’s zero-turn capability provide tremendous opportunity to deliver new technology solutions to urban drivers.” The rear-engined Tata Pixel uses Torotrak’s traction-
Fig. 3. Tata Motors has used a Torotrak prototype transmission in its Pixel concept car. The Torotrak IVT (inset).
Image courtesy of Tata. 14
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drive and epicyclic technology to create an integrated IVT. In normal driving, the transmission provides seamless ratio changes. During tight manoeuvring, or parking, the transmission’s ability to control each rear wheel independently means that the wheels can be rotated in opposite directions. By linking the vehicle’s steering system with the IVT’s control mechanism, the car can pivot around its rear axle. Automotive components supplier Bosch also believes that
CVT technology will become more widely accepted: in April 2011 it opened a new factory in Vietnam to make CVT push
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