Secrets of the inerter revealed
A Cambridge University invention which was kept a closely-guarded secret because of the hidden advantage it offered to a Formula 1 racing team is finally being made available for widespread use.
“It was very difficult to believe that nobody had thought of it before and I presumed that either it had been done already, or there was some sort of snag.” — Professor Malcolm Smith, Department of Engineering
For years, the mysterious “J-Damper”, a vehicle suspension device described as the F1 technical innovation of the year, was carefully codenamed and concealed to prevent it from being copied by rivals.
McLaren agreed an exclusive right with the University to exploit the technology, but confidentiality restrictions ensured that other F1 teams were kept in the dark. Internet fan-sites and blogs began to buzz with speculation about what the device actually was.
Now, with the lifting of the confidentiality agreement, the secret of the “J-Damper” can finally be revealed. Cambridge Enterprise, the University’s commercialisation office, has signed a licence agreement with the American firm Penske Racing Shocks, enabling Penske to supply them to any team in F1.
In fact, the device was first conceived by its creator, Professor Malcolm Smith, as long ago as 1997 and raced for the first time by McLaren in 2005, when Kimi Raikkonen achieved a victory for the team at the Spanish Grand Prix.
The term “J-Damper” itself was merely a codename to keep the technology secret from potential competitors for as long as possible. Its proper name is an inerter. Many specialists spent time and energy trying to establish what the “J” stood for; but in fact it was just a meaningless decoy added to keep opponents stumped.
Although they are currently being used to improve mechanical grip, inerters have a wide range of potential advantages, many of which are still being explored. Broadly, they offer greater flexibility in a vehicle’s suspension system.
Standard suspension systems are based around two components – springs and shock absorbers (dampers). Together, these contribute to the car’s ride and handling: they keep vehicle occupants comfortable even though the vehicle is traversing an uneven road surface and is subjected to acceleration and cornering.
No matter how the system is tuned, however, there is always a compromise taking place between handling, comfort and grip. Even in F1 cars, where comfort is less important, the suspension needs to be set to allow both sensitive handling, which requires a harder suspension, and a good mechanical grip, for which the suspension would normally be softer. The upshot is that there is still some oscillation as the load on the tyres varies, which impedes the vehicle’s grip and therefore slows it down.
Professor Smith realised that this poor trade-off between handling, comfort and grip could be better resolved if a third type of component was added to a suspension system to make it more flexible: the inerter.
The inerter looks superficially 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 the rotation of a flywheel inside the device 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 thus helps the car to retain a better grip on the road.
Though they remain the preserve of F1 for now, inerters have many other potential applications. In time, they could extend far beyond the realm of motorsport and be incorporated into conventional road vehicles and motorcycle steering systems, to name just two areas.
“I was nervous about talking about the idea at first because it seemed so elementary a concept,” Professor Smith said. “It was very difficult to believe that nobody had thought of it before and I presumed that either it had been done already, or there was some sort of snag.
“As I discussed the idea with colleagues, however, I began to realise that it hadn’t been done and it was possible to achieve this trade-off to improve vehicle suspension. The next question was can it be done – and once I had worked out what it should look like, that was a fairly simple matter. It’s very pleasing that what began as a theoretical idea is now being used in motor sport, and hopefully it will gradually be incorporated into other types of vehicle as well.”
Photo credit: McLaren F1 Lewis Hamilton, by jiteshjagadish via flickr