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Suspension trends

The past few years have seen the leading Formula One teams continuously evolving their suspension systems, with designers taking some radical approaches to both front and rear set-ups. For the front suspension, the most significant trend was a move by Ferrari and McLaren to a pullrod- instead of pushrod-actuated system. Ferrari made the first move in 2012 with the F2012, and McLaren followed in 2013 with the MP4-28.

The main impetus behind this switch was to optimise the front aerodynamic package. A pullrod front suspension system allows for a higher nose position, which helps the flow from the front wing to the underfloor. The pullrod design must be properly executed though, otherwise the suspension geometry can be compromised to a point where the performance gain given by the improved aerodynamics is largely cancelled out by a reduction in mechanical grip due to loss of suspension compliance.

Looking at McLaren’s MP4-28, the location of the horizontal suspension members were positioned in such a way as to smooth the airflow from the front wing. This is achieved by moving the suspension members clear of the front-wing vortex (shed from the inboard end of the front wing flaps). This vortex is important for downstream flow around the barge boards and underfloor. Thanks to the location of the spring and damper units at the bottom of the nose assembly (rather than the top, as in a pushrod system), there is also a small benefit to the centre-of-gravity height

Rear suspension systems have also been developed extensively by some teams. One general trend has been a move by most of them to pullrod-actuated rear suspension systems, thanks to the tighter rear bodywork packaging such a set-up allows. The gains teams have found must be considerable in order to account for the widespread adoption of the layout, given the compromise it presents in terms of suspension performance. Notably, that fact that lifting the rear lower wishbones and toe links up to rear axle height – as in a pullrod design – significantly reduces rear suspension stiffness.

The biggest suspension-related talking point of the 2013 season was the public appearance of Mercedes’ interlinked suspension system, dubbed FRIC (Front Rear Interconnect). Interlinked front and rear suspension is not a new concept in Formula One – it was a feature on active suspension cars such as the Williams FW-14B in the 1990s – but since such systems were outlawed it has taken engineers a long time to develop passive systems that are both effective and fall within the regulatory requirements.

In 2011, both Mercedes and Lotus developed passive systems, although the details of their operation have been kept under wraps, and evidence of the Mercedes system’s existence only came to light during 2013. Lotus initially developed an hydraulic set-up linked to the braking system, but this was deemed to contravene the technical regulations and so was outlawed. Mercedes, however, has managed to develop a system that controls the pitch of the car using linked front and rear hydraulic systems; it is thought that the system also controls roll.

The intention behind such systems is to maintain a constant ride height, regardless of whether a car is braking, accelerating or pitching. This in turn ensures that the aerodynamic balance is kept as consistent as possible, ensuring maximum downforce. It is thought that several other teams have developed similar systems, although none have been willing to reveal details. However, Ross Brawn has been quoted as saying that since Formula One cars were invented and aerodynamics understood, the compromise between suspension and aerodynamics has always been a compromise. Essentially, the FRIC allows this compromise to be reduced, allowing for some chassis compliance while also ensuring a predictable aero platform.

Given the creativity of some teams within the bounds of the outgoing technical regulations, it will be fascinating to see the new approaches – and technical loopholes – the 2014 rules will bring to light.

Written by Lawrence Butcher

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