Technical insight: Renault's J-damper

This year's technical innovation has taken a while to appear. But from first mentions in the Renault spy case to teams discussing the technology more openly in the first races, it seems there has been a return to Mass Dampers. At first this appears to be a new development, but the J-Damper actually predates the Mass Damper. And, bizarrely, isn't even a damper at all.

Unlike the Mass Dampers of 2006, these solutions are smaller and more integrated into the car's suspension. Initially co-developed by McLaren and Malcolm Smith, a Cambridge engineering don, these are technically known as 'Inerters'.

They are more commonly known as J-dampers, which was McLaren's internal nomenclature for the device and appears to have stuck. But the 'J' was not, in fact, for Jounce - a term for a bouncy/jumpy movement - but simply a random letter used by McLaren as a decoy.

Little has been detailed about the J-damper. It is known now that they are a solution like the now-banned mass dampers. The evidence given in the Renault spy case mentioned a mass spinning inside a damper, but the benefit of this in a conventional damper defied any logic. This is probably why Renault did not at first work out the use for the McLaren J-damper.

The Inerter solution was first considered by Smith back in 2003. Although tested during 2004 and first raced by McLaren as far back as San Marino 2005, it has taken several years for other teams to adopt Inerters.

Pictures of the Ferrari in pre-season testing revealed a large damper-like device fitted to the rear of the car, adding the belief that Ferrari is now racing this technology. Indeed, many people now point to the failures on the Ferraris at Monza last year as being a fault with the J-damper.

Additionally, BMW Sauber, Toyota and Red Bull are on the list of suspected J-damper users, but recent comments by Christian Horner suggest that his team is yet to race the damper.

At the moment Pat Symonds has alluded to Renault developing a system, its adoption of the technology delayed by fears that any similarity to McLaren's system might be seen as taking advantage from the McLaren spy pictures.

This seems unfair, as other teams have adopted similar solutions without collusion. Indeed the technical details of Smith's design are available freely on the web. No team has thus far questioned the legality of the devices, which aim to replicate the mass damper effect of maximising contact patch load. Equally as the FIA chose to ban the mass damper, but not the McLaren Inerter which was also racing at the time.

Moreover McLaren have exclusive license to race the design in F1. Thus the other team's adoption of it could be construed as a breach of this agreement. This potentially leaves McLaren free to protest its use by other teams. But the team have chosen not to do this as a matter of sporting fairness.

As the FIA banned mass dampers on a side issue of influencing aero, its poor choice back in 2006 may come back to haunt it in preventing the spread of J-dampers. In essence, the J-damper aims to reduce the bounce a tyre puts back into the suspension by spinning a weight inside a device fitted to the front and rear suspensions of the car.

This adds less weight to the car than the near-10kg mass damper and fits easily into the existing space around the suspension. However the effort in understanding and tuning the new damper will be far greater. The benefit of this could be up to two tenths a lap, clearly an advantage worth having, just as it was with the mass dampers of 2006.

Mass Dampers

Not to be confused with the j-damper, tuned Mass Dampers (TMD) were introduced by Renault in 2005 to overcome the natural frequency of the tyres.

A car's suspension is sprung/damped by both the conventional suspension and the bounce in the tyres. While the team can tightly predict and control the suspension movement, the effect of the tyres is largely outside the control of the team and to some extent the tyre supplier.

Formula One rules demands small, 13 inch (33cm) diameter wheels but large diameter tyres (66cm). Thus, the tyres have tall sidewalls which deflect both vertically and laterally. It is the vertical movement that affects the suspension, and this alters the pressure that the cars puts on the tyre's contact patch.

As the tyre deflects vertically, they work against the rest of the suspension and can lessen the load on the contact patch, reducing grip as well as making grip inconsistent.

Offsetting this movement is hard to achieve with conventional springs and dampers, which is why Renault developed the TMD, tuned to the same frequency of the tyre's natural spring rate.

Renault placed a weight (mass) and allowed it slide up and down on a shaft controlled by springs and damper. As the tyres bounced, the mass damper counteracted the forces that the tyres fed into the chassis to maintain a more consistent load on the contact patch.

Renault enjoyed an exclusive period with the TMD, but soon other teams found out about and adopted TMDs to the point in mid-2006, when over half the grid was racing with front TMDs.

Meanwhile, Renault had developed a rear-mounted solution, placing the weight above the gear cluster and via a lever controlled it with a spring/damper.

It was at this stage the FIA stepped in and outlawed these devices. Teams were rumoured to be running masses of as much as nine kilos in the detachable nose cone and although safety was an issue, the FIA chose to ban the device on its effect on aerodynamics.

It was initially believed the devices were to reduce the pitching of the nose during braking, thus making the front wing and floor more aerodynamically efficient. Renault disputed this theory, although the benefit still appears to be possible from the TMD.

Many teams that eschewed the device felt it contravened the movable ballast rules, but the FIA chose not to follow this route. The other teams felt the device was legal as it was part of the suspension and reacted only to changes in load, which is demanded in the rules. Regardless of the rights or wrongs of the FIA's decision, TMD were banned and the teams continued without them until the recent development of J-dampers.

J-dampers

Rumours have persisted since the banning of TMDs that top teams had a system that replicated the effect. One suggestion was the use of active damping using magneto-rheological or MR dampers.

These dampers use a magnetic fluid that thickens when an electric current is applied to it. This would require the dampers to have a power cable attached to them - clearly not something the FIA would look kindly on.

There is an MR damper solution that creates its own electricity via a spinning mass inside the damper, thus making do without external power and strictly speaking, only reacting to changes in suspension load. But any of these would immediately fall under the continuing ban on active technologies, and although attractive to the road car manufacturers, these aren't believed to the new solution in use this year.

In fact, the so called J-damper is a far simpler solution. It was alluded to in the World Motor Sport Council evidence, in that engineer Phil Mackereth brought drawings of McLaren's J-damper to Renault. Described quite simply as a "damper with a spinning mass", its exact detail and purpose were not expanded upon.

It now transpires that the adoption of Inerters by McLaren predated Renault's debut of the mass damper by nearly half a season. McLaren first raced it in San Marino in April 2005, whereas Renault didn't race the TMD until Brazil in September.

The Inerter works quite simply by spinning a mass when the suspension moves. This conversion of the linear movement of the suspension rockers to a rotation in another direction takes the energy away from the tyres and dissipates it, keeping it from affecting the normal suspension of the car.

Tuning the mass and its damping will ensure it only works to offset the tyre's frequency and not other parts of the suspension.

To create the rotating effect, the mass fits inside a damper-like body, which is fitted to a thread running along a sliding rod. The mass will spin when the rod moves in and out of the body. Bearings on the side faces of the mass allow the mass to spin freely when it presses against the end caps of the body.

Understanding how the spinning mass takes energy away from the suspension is at first hard to comprehend. The best analogy is that of a child's spinning top; the type with the plunger to make it spin. You press hard downwards and the energy from your arm is taken away by the spinning of the top, just as the tyre's energy is taken away by the J-damper.

Unlike the TMDs, the Inerter is fitted as part of the suspension. Being fitted in place of the heave (also known as the 'third') damper, the device is only used when the both sides of the suspension are moving at the same time (i.e. not when the car is rolling).

As the unit fits in place of an existing suspension piece, being both a similar size and shape, it's hard to spot and easy for the designer to package.

Additionally, it's easy for the teams to fit a Inerter both front and rear. As it would be recognised as a conventional part of the suspension, the FIA is less likely to outlaw it.

To date is it believed that the teams are racing with these devices, and one suspects it's with some FIA knowledge. It's certainly common knowledge in the pitlane, and unless someone protests the solutions, it is plausible the devices will remain to be seen as legal and be adopted by all teams.

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- The Autosport.com Team

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