F1 Technical series. Part 3 of 5 – Suspension

                                                            The suspension on a Formula 1 car is very important. It has an effect on the aerodynamics of the car. It is also the only way for the weight and...

The suspension on a Formula 1 car is very important. It has an effect on the aerodynamics of the car. It is also the only way for the weight and loading on the car to be transferred through the wheels/tyres to the road, so its geometry (toe, castor and camber) is crucial to the handling of the car. Formula 1 suspension has to meet 3 requirements. These are to reduce the amount of unsprung mass (any part of the car in which its weight is not supported by the torsion bar), disrupt the airflow as little as possible and be strong enough to withstand the high loadings that they are placed under. There are a couple of examples where loading can be too much, especially if there is a small flaw in the elements. The most recent of which was Sebastien Buemi in Shanghai 2010, where the pushrods had a small fracture in them, and the high loading placed on them under braking for turn 14 after the long straight caused them to fail. Another case is Kimi Raïkkonen’s accident in 2005 at the Nurburgring. There a flat-spotted tyre caused huge vibrations in the suspension, eventually causing it fatigue stress at which point it failed and he crashed in turn 1.

The suspension also plays a crucial role in controlling the tyre temperatures. The camber of the tyre affects how evenly distributed the loading on the tyre is, and therefore how hot each part of the tyre gets. Every F1 car will run with a slight degree of negative camber where the outside top of the tyre is further in than the bottom. Too much can cause blistering of the tyre on the inner shoulder, which leads to shorter tyre life and even less grip. There is a good effect of running negative camber however, and that is that as the car goes through the corner, the roll of the tyre forces the outer tyre to be moved slightly further inwards, which stretches the outer sidewall and gives a larger contact patch. If the car ran with positive or no camber at all this would impair the grip from the tyre. The geometry of the suspension, particularly that at which the wishbones are angled and controls tyre motion over bumps, kerbs and changes of direction is particularly important as having a car that can ride the kerbs better than others can seriously improve lap times, especially in lower speed corners.

The front suspension wishbones are attached directly to the chassis which fives them optimum stiffness. However the rear suspension is attached to the gearbox, which is only attached to the car through the engine. Which is only attached to the car through the backplate of the chassis. It is for this reason why some cars may sport a strengthening arm or 2 linking the gearbox to the chassis. Ferrari have been using it so far this year, but was originally brought into the sport by Renault.

The uprights which house the wheel hubs&bearings, brakes, brake cooling and wheel attachment must be made out of Aluminium. In previous years Metal Matrix Compound or MMC was used as it is stronger than aluminium and lighter too. However it was very costly to manufacture, so was dropped in favour of the cheaper alternative

With the exception of the Ferrari, the setup of the front and rear suspension is different. Every other car uses a pushrod-actuated front suspensions system and a pullrod-actuated system at the rear. Ferrari however use pullrod on the front too. There is a small aerodynamic advantage to this. There is also a mechanical advantage as the front torsion bar (spring), ARB (Anti-Roll Bar) and multimatic dampers could be mounted lower in the chassis, which gives a lower CoG (Centre of Gravity) and improves the handling of the car at lower speeds.

Formula 1 car utilize a very simple double wishbone and inboard suspension setup on both the front and rear. By contrast most modern cars (with the exception of some Honda models) use a typical MacPherson strut type suspension where there is just one lower control arm attached to the lower half of the wheel hub and the strut (which houses the springs and the dampers) attached to the top of the wheel hub.

The components of an F1 car suspension are as follows

Top/bottom wishbones – Control wheel angle (camber and castor) and wheel movement. Also houses the mandatory wheel tethers which are required by the regulations to hold the wheel close to the car as long as possible in the event of an accident.

Pushrod/Pullrod –  Transmits the suspension and car loading through from the upright to the rockers (bell cranks) or to the tyres.

Rockers (Bell cranks) – Transfers the vertical reciprocating movement of the push/pullrod into rotational movement at the torsion bar.

Torsion bar (springs) – The torsion bar acts as the spring that absorbs shock loads from the suspension movement. Its strength is controlled by the alloy mixture, its thickness and the length. Most F1 torsion bars are of equal length and its diameter only changes in the middle as the outer ends need to be the same size to fit in the splined holes in the chassis and on the rockers. Stiffer torsion springs increase the handling responsiveness at that end of the car, but reduces overall mechanical grip in the middle of the corner. Cars are also less pitch-sensitive as the car changes its pitch a lot less under braking/acceleration loadings

Heave spring – The heave spring controls how stiff the car is when both sides of the cars suspension are compressed together for example under braking, or acceleration, or over a hefty bump. Cars are less pitch-sensitive as the car changes its pitch a lot less under braking/acceleration loadings when the heave springs and dampers are stiffer. This means the car may have more grip going into a corner, and may have better traction on the exit of the corner.

4-way Adjustable damper – These are fully adjustable dampers. They are adjustable in 4 ways. High and low speed bump, and high and low speed rebound. Bump settings are the compressing of the damper, rebound is the extending. So when a wheel moves upwards it compresses the damper, when it moves downwards it extends the damper. The dampers are critical for fine-tuning the handling of the car. The softer the damper the easier it is to compress and the more oscillation from the torsion bars you get and vice versa. When talking about the speed of the damper we don’t talk about the speed of the car, we talk about how quickly the damper is moved. Low speed is a slow extension/retraction and high speed is a fast extension/retraction. There are 3 dampers at the front and 3 at the rear of most F1 cars. 2 directly attached to the rockers and one that connects both front rockers together. The 3rd damper is often called the ‘heave’ damper and controls how the car reacts when both front wheels move together.

Track rods – The track rods controls the steering of the wheel hubs. They are normally attached to the front of the wheel hub, and quite often run in front or in the wake of the lower wishbone, which slightly reduces drag and

http://www.bbc.co.uk/sport/0/formula1/17742439

ARB – The anti-roll bar links both sides of the car together through the suspension elements. This means that the car is less sensitive to roll. The balance of the car can be fine-tuned by altering the stiffness of the ARBs. Softer front/stiffer rear  ARBs give less understeer and stiffer front/softer rear give more understeer.

Raïkkonen’s suspension failure 2005 – http://www.youtube.com/watch?v=lFG4mdEVmKQ

Buemi Suspension failure 2010 – http://www.youtube.com/watch?v=ek3ybBIq

Ferrari gearbox-chassis linking arm – http://www.formula1.com/news/technical/2012/865/948.html

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