A comparison of KERS Formula One installations
The Formula One powertrain regulations have allowed the use of hybrid systems since 2009 (although in 2010 the teams chose not to use them). These systems were not considered when the engines to which they would be attached were conceived, however; the engines had been basically the same since 2006, and the adaptations to them in order to fit the KERS motors were very varied.
Both Mercedes and Renault powertrains have been photographed numerous times (the photos can be found easily on the internet) and show clearly that the KERS motors are mounted to the front of the engine close to the crankshaft, indicating that they are probably geared directly to a gear on the crankshaft or through a single idler. It would certainly be the preference of the chassis engineers to have the motor mass close to the centreline of the car and as low down as possible, which illustrates the close relationship between the chassis and engine design departments when the systems were conceived.
There are also photos on the internet of the proposed Honda installation, although with its withdrawal at the end of 2008, a KERS-equipped Honda Formula One engine never competed. Honda had examined both flywheel and electric hybrids, eventually choosing the electric hybrid route, possibly based on its use of this technology in some of its roadcars.
Honda’s approach to the mounting of the motor was completely different from that of Mercedes and Renault. It chose to take a drive from the timing gears on the left bank of the engine and, using a number of idler gears, it had the motor mounted out to the left side of the engine. This was a highly unusual approach and was clearly based on a different logic from the Mercedes and Renault installations. It is thought that Ferrari also has its motor motor/generator mounted in front of the engine. There are a number of photographs on the internet showing a driveshaft protruding from the front of the engine.
The other ‘headache’ that hybrid systems present is where to place the battery and power electronics. Mercedes has been the happiest to talk about its KERS system and its development, showing detailed pictures in Race Engine Technology magazine issue 67 (Dec 2012/Jan 2013). Initially its 2009 KERS system had separate enclosures for power electronics and battery, one mounted each side of the car, requiring a cross-car cable to transfer power.
By 2011, Mercedes had developed a neat ‘one box’ solution, with power electronics and battery in a single enclosure, doing away with the need for the cross-car cable. The single-box solution is neat for a number of reasons, notably the fact that only a single recess and a single set of mounting points are required in the chassis to retain these components. Honda released photos (again which can be found using a web search) of its proposed car installation, showing the power electronics mounted in the sidepod to the left of the driver, and the battery pack being mounted below the driver’s legs.
The single-box scheme also makes component cooling slightly simpler. At one race in 2013, there was TV footage of a Renault KERS module being removed, apparently full of fluid sloshing about. This shows that the battery, and possibly the power electronics, are liquid cooled. If two separate boxes require cooling, there are extra hoses and fittings to consider and an increased number of seals, each of which could potentially cause a leak. Reliability is very much a case of eliminating risks, as well as solving problems as they occur.
Written by Wayne Ward