Shock tactics

Technology that improves cars’ road grip may soon be available outside of the highly secretive world of F1 racing. Siobhan Wagner reports

A former ‘top secret’ McLaren Formula One component will be available to all race teams following a deal between its UK developers and a US motorsport technology group.

The suspension device, code-named the ‘J-Damper’ has been used by McLaren since 2005 under a confidential arrangement between the team and Cambridge University. Called an inerter, it is used to improve mechanical grip but can offer greater flexibility in a vehicle’s suspension system. Standard suspension systems are based on two components—springs and shock absorbers (dampers).

These systems are designed to keep vehicle occupants from rolling around when the car corners, springing back when it speeds up or feeling discomfort travelling down a bumpy road.

Yet, no matter how well a suspension system is designed, there is usually a compromise between handling, comfort and grip. Even in F1 cars, where comfort is less important, the suspension needs to be set to allow sensitive handling and good mechanical grip. But sensitive handling usually requires harder suspension, and good mechanical grip usually needs a softer suspension. So there is still some oscillation because the load on the tyres varies and this impedes the vehicle’s grip, slowing it down.

In 1997 Prof Malcolm Smith of Cambridge University realised the compromise between handling, comfort and grip could be resolved if a third type of component was added to a suspension system to make it more flexible. Thus, the concept of the inerter.

This looks to the average observer like a conventional shock absorber with an attachment point at each end. For example, one end may be attached to the car body and the other to the wheel assembly.

A plunger slides in and out of the main body of the inerter as the car moves up and down. This causes a flywheel inside the device to rotate in proportion to the relative displacement between the attachment points. The result is that the flywheel stores rotational energy as it spins. In combination with the springs and dampers, the inerter reduces the effect of the oscillations and helps the car keep a better grip on the road.

Smith said he was nervous talking about the idea of the inerter at first because it seemed such an elementary concept. He could not believe it had not been done before. When he realised it hadn’t, the next question was, could it be done?

‘That step was very quick because I realised what was required in principle,’ he said, adding that the embodiment he had in mind was a simple rack-and-pinion device. ‘Finding the most convenient way to do it in a car suspension evolved over a period of time.’

The inerter concept was given the seal of approval at the Spanish Grand Prix in 2005 when it was used in the winning car driven by Kimi Raikkonen. Cambridge Enterprise, the university’s commercialisation arm, recently signed a licence agreement with the US company Penske Racing Shocks, to enable Penske to supply the devices to any team in F1.

While they are being used only in F1, Smith said his research group is working on finding applications for the inerter outside the realm of motorsport — in passenger vehicles and motorcycle steering systems.

However, it is not going to be a simple case of just bolting on the same device used in F1 cars to passenger vehicles and motorcycles.

‘In translating this to road cars the performance measures are very different,’ he said. ‘The suspensions are totally different. They’re much more softly sprung.’

Smith said they still need to determine if there would be a huge advantage in having these in regular road cars. ‘In Formula 1 the margins are so tight that if you have a device that gives you a small percentage gain, then it’s of definite interest.’ he said. ‘If we can give Lewis Hamilton a couple tenths of a second, then that is very important.’

‘There could be an advantage for road cars but we need to know how much of an advantage. Whether the gain is big enough for the amount of money it costs to manufacture these devices is something that remains to be seen.’