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Automotive Design


Fig. 2. The prototype Flybus is based on an Optare Solo midibus with an Allison automatic transmission and a flywheel-based energy recovery system.


which makes it smaller and easier to package. The CVT, which manages the flywheel’s speed 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


Fig. 3. Tata Motors has used a Torotrak prototype transmission in its Pixel concept car. The Torotrak IVT (above).


Image courtesy of Tata. www.engineerlive.com 7


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