Way back in the mists of history, the blue blazer brigade at the FIA determined that Formula 1 cars would run on 13” diameter wheels. I seem to recall that the logic was to force a reduction in the size of brake discs that could be used and therefore ensure the cars would have nice, long braking distances, so there could be lots of overtaking. Yeah, sure!

It didn’t take too long for the designers to work their way around that impediment with the technology that existed at the time. Chapman at Lotus used inboard chassis mounted front brakes driven by a brake shaft. It was the failure of one of those shafts that caused us to lose Jochen Rindt in 1970 before he could celebrate his world championship.
Cooper put the brakes inside the upright, which compromised the suspension geometry and scared the daylights out of Brian Redman when a wishbone broke causing the mother of all crashes and the death of two bystanders. Ken Tyrrell tried twin discs with a sandwich pad between them and Ron Tauranac at Brabham experimented with wheels which were 15” on the inside and 13” on the outside, necessitating special tyres that no company was particularly willing to make.

Regardless of the technical solutions, which all became irrelevant with the introduction of Carbon Brakes by Brabham in the mid 1970s, F1 was left with 13” wheels and the resultant balloon tyres.
In the late 70s, ground effects came along and with it we saw the demise of suspension travel as the designers sought to keep the car close to the ground for aero downforce reasons. Suddenly, suspension travel became less than tyre compression.

Car suspension is provided by two springs in series – the road spring and the spring in the tyre. The road spring can be damped, but damping in the tyre is only provided by the hysteresis in the tyre body and possibly by the gas used to inflate it. (You didn’t really believe that story about Ferrari putting Freon in their tyres to ‘air condition’ them, did you?). This is less a problem in most forms of motorsport because they use real tyres with sensible aspect ratios, but the balloons used in F1 cause issues because their undamped oscillations / vibrations excite the contact patch and so reduce tyre grip.

In 2005, Renault introduced a ‘tuned mass damper’, in the nose of the chassis, to damp the uncontrolled vibrations from the front tyres. Mass dampers are used in many applications to lower the frequency of vibration. They successfully kept the existence of the damper a secret until it was revealed in mid 2006. At the 2006 German Grand Prix at Hockenheim, the blue blazer determined the mass damper to be illegal on the grounds that it was a ‘moveable aero device’.

Craig Scarborough's drawing of the Renault Mass damper

A mass damper was incorporated in the Citroen 2CV – introduced in 1948 and which could never be considered as aerodynamic in any sense. But, Renault were forced to remove their damper and get on with tuning the car to race without it. Meanwhile, up the pit lane at McLaren, the team were struggling to maintain a straight face.
A mass damper is a mechanical analogue of a capacitor as used in electrical circuits, in that it absorbs some energy and then gives it back in a delayed fashion. McLaren had been using a device called the J-Damper since the Spanish GP in 2005, where Kimi Raikonnen won with it. It looked like a coil spring/damper unit and was mounted between the suspension rockers, so it looked exactly like a third spring to control heave, dive and pitch motion. It was in fact, a form of mass damper.

Inerter Drawing

The inverter principal was invented by a Dr. Malcolm Smith at Cambridge University in 1997. No, before you ask, this is not the Malcolm Smith of ‘On any Sunday’ fame. Inside the J-Damper there were no pistons, valves and hydraulic fluid. Instead, there was a heavy metal flywheel driven by screwed rods as the ‘damper’ worked. The inertia in the flywheel supplied the damping effort to reduce excitement at the tyre contact patch.

Inerter application

In the second ‘spy scandal’ in F1, concerning McLaren and Renault in 2005/06, Renault had gained knowledge of the J-Damper but obviously did not comprehend its operation and so went their own way to develop a cruder solution with their own 9kg vertically sprung mass in the nose of their car.
The inerter technology was sold to McLaren and Penske Industries.
These days, the Inerter technology is available to any F1 team, although Renault, or Lotus, or whatever they are called this week have chosen to develop and patent their own hydraulic inverter and the Blue Blazer Brigade seem perfectly happy with it.

Pat Clarke