Lhasa Wednesday, 03/16/11 11:23:04 AM Re: None Post # of 195 One Wheel Forward, One Back for Tata's Pixel From Automotive Engineering International Online A city car concept for Europe, the Tata Pixel has a rear engine and a turning circle radius of 2.6 m, thanks mainly to the effects of its infinitely variable transmission, which can control each rear wheel independently, allowing rotation in opposing directions when parking. Tata's rear-engine Pixel, shown in concept form at the 2011 Geneva Motor Show, was conceived as a city car for Europe. At just over 3 m (9.8 ft) long, it is based on the Nano and is claimed to be the most package-efficient four-seat (for adults) car in the world. Carl-Peter Forster, Group CEO of Tata, said the company believes there is an opportunity for such a car in Europe, particularly one with exceptional maneuverability. That maneuverability comes from the use of a prototype toroidal traction-drive IVT (infinitely variable transmission) from Torotrak, which has been developed to assist rotation of the outer rear wheel forward and the inner rear wheel backward as the front wheels turn at acute angles. The resultant turning radius is a remarkably compact 2.6 m (8.5 ft). The Pixel’s transmission comprises Torotrak’s traction-drive and epicyclic technology. When the car is driven normally, the transmission provides seamless ratio changes, said Torotrak Product Development Manager Rob Oliver. "But when parking and when very tight maneuvering is needed, its ability to control each rear wheel independently is used to enable rotation of those wheels in opposite directions," he said. He added that by linking the vehicle’s steering system with the control mechanism for the IVT, the car could pivot about its rear axle. “Zero turn capability provides tremendous opportunities to deliver new technology solutions for urban drivers,” he said. The Pixel’s maneuverability is complemented by very short overhangs, and scissors-action doors provide added accessibility in tight spaces. Connectivity is also central to the Pixel’s design, with key functions controlled by the driver’s smart phone. The concept has a 1.2-L three-cylinder turbocharged diesel engine with stop-start facility. The engine is fitted with variable coolant and oil pump operation plus rapid warmup technologies. Low rolling resistance tires are fitted. Claimed economy figures include a European combined (NEDC) fuel consumption figure of 3.4 L/100 km and CO2 emissions of 89 g/km. Torotrak is working closely with Tata. Torotrak's technology focus is on traction-drive systems, developing main-drive transmissions and variable-speed drives for flywheel-based hybrids. Its variable drive technology is also being developed for use in engine auxiliary systems including superchargers, turbochargers, and fan systems to help facilitate engine downsizing. Its core technology platform is a full-toroidal traction drive designed to deliver improved fuel economy and reduced emissions in parallel with high levels of performance.