Brake expectations

Formula One’s 2009 season could see UK technology on the starting grid helping teams make use of energy recovery systems to boost acceleration. Jon Excell reports.

It’s often hard to argue with the notion that F1 has become little more than a dull procession of millionaire- propelled advertising hoardings whizzing round a track at high speed.

This is why, in what will certainly rank as one of his more sensible decisions, Max Mosley — boss of the sport’s ruling body the FIA — last year announced a raft of measures aimed at turning the sport into a proving ground for new hybrid technology, while simultaneously boosting its environmental reputation and reinjecting a bit of excitement into racing.

The main focus of this technical push is the development of kinetic energy recovery systems (KERS). Expected to make their first appearance on some of the vehicles racing in the 2009 season, these devices will store the energy that is otherwise wasted when a vehicle brakes and use it to boost acceleration coming out of corners and overtaking.

Intriguingly, in contrast to the freeze on engine design and other areas of F1 development, the FIA has decreed that teams are free to use any system they like providing that no more than 400 kilojoules/lap is recovered, and energy is only captured or released at a maximum rate of 60kW. F1 chiefs last week announced they are to discuss raising the cars’ 605kg weight limit to accommodate the new devices.

With numerous mechanical and electrical systems now enthusiastically vying for a spot on next season’s starting grid, Mosley’s effort to stimulate new automotive developments has apparently worked. And one of the most promising candidates is a fully mechanical, flywheel-based system jointly developed by a trio of UK automotive specialists — Torotrak, Xtrac and Flybrid Systems.

The 25kg system, which has already been licensed to two unspecified teams, is made up of a flywheel, a control system and an ancillary transmission, or variator, that provides a continuously variable connection between the flywheel and the vehicle driveline.

The device, which on an F1 car would be positioned directly above the trans-axle behind the driver, stores energy when the vehicle is slowing down by spinning the flywheel up to speed. This energy is then released when the vehicle speeds up again by slowing the flywheel down. The energy is received from the driveline, and released back into it through the variator.

Adrian Moore, technical director of Xtrac, explained how the variator — based on technology licensed from Torotrak — achieves the complex feat of matching the flywheel speed to the vehicle speed.

‘The flywheel has a speed range of 30,000-60,000rpm and the vehicle goes relatively slowly in terms of rpm and has a speed range of 62-124mph (100-200kph),’ he said. ‘You’ve got to match those speeds with some sort of gearbox and the logical way to do that is with a continuously variable transmission (CVT). You need a speed range of about 6:1 and by happy coincidence a Torotrak toroidal CVT is about 6:1.’

 


The flywheel-based kinetic recovery system is designed to help motorsport’s environmental reputation by using energy that would otherwise be wasted

The other key element of the system, developed by the Silverstone-based project leader Flybrid Systems, is the flywheel itself. Featuring a specially-designed hermetic seal that runs at 64,000 rpm and a containment system that addresses the safety concerns associated with running a flywheel at high-speeds, its developer claims that it represents a fundamental breakthrough in the development of mechanical KERS systems.

‘Our flywheel runs at least three times faster than any previously known vehicle-mounted example,’ claimed Flybrid’s Jon Hilton. ‘This makes it nine times smaller and lighter which reduces the size of our hybrid system enormously and gets us to a position where it could almost be considered an accessory.’

Designed to be activated manually by F1 drivers, Moore said the system could be deployed in a number of ways. ‘You can’t use it until you’re doing 100kph, but you could deploy it once you’ve reached that speed meaning you end up with a potential gain of several metres by the first corner. you could use it to improve your maximum velocity on the fastest part of the circuit — on some you could end up with a 20m or 30m gain by the end of the straight. You could use it as an overtaking tool or to prevent people from overtaking you.’

But while Moore and the rest of the team are keen to explore other opportunities for their system in motorsport (Le Mans, for example, with its numerous corners looks set to really benefit from KERS) the big potential for the technology is to make road cars and other vehicles more fuel efficient. ‘Motorsport provides a way of demonstrating that the technology is completely viable,’ said Moore.

Indeed, thanks partly to the rigorous challenges of designing a device for F1, Moore believes that the group’s fully mechanical system could have distinct advantages over the electrical hybrid solutions that are already on the road.

‘There’s a very big efficiency advantage because it’s mechanical,’ he said. ‘Obviously there are some mechanical losses, but the wheel-to-wheel efficiency is much higher than it is for electrical systems; you could be talking a 70 per cent-plus efficiency level, whereas electrical systems, which convert energy from kinetic energy into electrical energy, chemical energy and ultimately back in to kinetic energy are down in the 30s.’

And it looks like we may be seeing flywheel-enabled hybrids on the roads sooner rather than later. Hilton said he is engaged in vehicle discussions with a number of road car OEMS, while Moore claimed that the technology is likely to appear on a production prototype within the next three years.

Moore suggested that one way the device may be applied to road cars is as a bolt-on complement to existing electrical systems. ‘There are some advantages to using an electrical system and then a mechanical one for bursts of power if you suddenly want some acceleration,’ he said.

But unlike the F1 application, the consumer version of KERS is unlikely to feature a ‘big red button’. ‘You would have no driver input at all,’ said Moore. ‘the driver will just drive the car and if he requests a certain acceleration mode via the throttle the car would work out whether you do it by battery or whether you use some of the flywheel energy you have recovered.’

Straying even further from the world of motorsport, Moore said that the system could even help boost the efficiency of public transport. Trains, which have a highly structured start and stop cycle are ripe for a KERS device while buses, somewhat ironically given their lumbering nature, have a very similar duty cycle to an F1 car.

‘An F1 car goes through a corner very slowly and then accelerates very quickly down the straight and slows again and accelerates and stops every now and then for a pit stop. That’s pretty much what a bus does, ’ joked Moore.