Ferrari: Rear Dual Rate Anti Roll Bar

Ferrari rear suspension package: copyright- Liubomir Asenov

When comparing the fortunes of the three leading teams, one stand out feature has been Ferraris kindness to its tyres and its great traction. Although both these traits are hugely complex and achieved by a variety of factors, we have been able to identify a solution in Ferraris rear suspension that may be providing some of this mechanical grip. As one of the few leading teams to retain pushrod suspension in 2011, Ferrari have at least given a chance to see the clever mechanical set up at the of the car. We have already discussed the relative merits of pushrod Vs Pullrod and looked at the rear end packaging of the Ferrari (see the links at the end of this article). But what this detailed shot by Liubomir Asenov shows us, is the clever arrangement of the rear Anti Roll Bar (ARB). Ferrari have developed sprung drop links to create a dual rate ARB, which gives the team the advantage of soft roll control for low speed grip and stiff roll rates for high speed aero grip.

A typical Anti Roll Bar. copyright: Craig Scarborough

An Anti Roll Bar (ARB) is a spring that helps the chassis resist roll when cornering. Typically in a racecar this is a relatively simple “U” shaped arrangement, with levers acting on a torsion bar. Drop links lead from the rocker to the ARB. When the car rolls one rocker goes down and the other goes up. The links twist the ARB, which in turn provides the spring effect to resist the cars roll. A stiff rear ARB will be good for maintaining the underfloors attitude to the track, in order for the diffuser to work at its best. However at lower speed, a softer ARB will aid grip by allowing each tyre to maximise its contact with the track. Clearly some tracks will favour aero over mechanical grip, but laptime gains be found if the car can improve both aero and mechanical grip.

What Ferrari has done is to replace the drop links that lead from the suspension rocker to the ARB levers with small coil springs. Now when the car rolls, the softer coil spring compress first, these provide a soft initial ARB rate, which provides good mechanical grip. Then as their movement is taken up, the coil springs act like solid links to the ARB and the stiffer main ARB provides the tighter roll control to aid the underbodies aerodynamics.

This solution appears to be unique to Ferrari in F1, but is a known solution in other race series.
Andrew Thorby (Designer for Panoz, Lister, McLaren MP4-12c GT3) pointed out to me that Lola is known to have used this solution in some of their cars, using either coil springs or belleville springs. He also pointed out that although small; these Ferrari coils springs are mounted quite high up, over what is already a relatively high suspension package, thus upsetting the cars Centre of Gravity slightly. Other teams achieve similar variable rate ARBs with the geometry of the drop links and levers. Whether pushrod or Pullrod, any team could conceivably employ these spring links to provide this variable roll rate.

Analysis of Ferraris rear end packaging
https://scarbsf1.wordpress.com/2011/03/23/ferrari-rear-end-exhaust-and-drs-mechanism/

Analysis of pushrod versus pullrod
https://scarbsf1.wordpress.com/2010/10/10/red-bull-pull-rod-suspension-what-is-looks-like-how-it-benefits-aerodynamics/

10 thoughts on “Ferrari: Rear Dual Rate Anti Roll Bar

  1. Presumably the fact that these are notionally working in ‘tension’, means that they have no impact on pitch? But they still work in roll because it’s actually the off-side spring that is compressed?

    • I can’t confirm either way, indeed it might even vary by track. Clearly the Ferrari is designed to have the option of torsion bars, Piolas sketch earlier this season of the front of the gearcase shows torsion bars. These pass down to mount towards the floor of the gearcase.

      Also not drawn in my sketch (ran out of time) are the heave elements. Ferrari run quite complex rockers, beneath the set up I’ve drawn is another lever that operates the heave spring, then a lower rocker is splined to the upper rocker. This sits inside the gearcase and operates the Inerter. I’ll try to add these to my drawing once I get get a bit more time.

  2. Just thought I would point out that NASCAR, until a few years ago when it was outlawed, was coil binding their springs and running on the shocks only.

  3. I’ trying to work out if there would be benefit to using dampers rather than springs in this mechanism. Springs being displacement sensitive and dampers being speed sensitive. So for example with a damper you might use low high speed damping to reduce the roll bar effect on bumps whereas on low speed damping you’d make it higher rate to reduce cornering roll. Assuming of course the difference in the two situations is great enough that the damper can be engineered to behave correctly.

    By speed obviously I mean wheel speed up – down rather than vehicle speed.

    • Good point, I had asked this to Andrew Thorby, he explained it wouldn’t be a good idea as… “the damping in roll will be higher than in pitch/heave: that’s opposite to the generally accepted view”

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s