Interlinked Suspension and Mercedes FRIC

[The King of Spa 637]

Teams have been using interlinked suspension for a number of years now in order to control either 'Roll' or 'Heave' or in the case of Mercedes both, which allows them to control 'Pitch'. The advantages of running such systems can be two-fold, helping with mechanical grip and aiding in a consistent aerodynamic platform.

 

 

Suspension is a push / pull area between what the driver wants in slower speed corners vs the designers demands for downforce in the high speeds ones. A driver likes a softly sprung car as it helps him feel the car much more making the grip tangible whilst the designer requires a much more stiff platform for his aerodynamic principles to work across a wide spectrum. An F1 car goes through a rollercoaster of attitude adjustments through the course of a lap and of course that then becomes a fight between Aerodynamic efficiency and Mechanical grip, both of which can be very subjective to driver feel during the switching points.

 

Aerodynamicists will argue that given a stiff car / rigid aero platform they can create enough downforce that the suspension becomes irrelevant, with the forces acting on it regulating the drivers ability to corner as the car is effectively sucked to the ground. The most recent account of this would be Off Throttle Exhaust Blown Diffusers with the rest of the car being setup taking account for the fact that by virtue of creating a 'Sealing' effect with the exhaust plume at all times, rear downforce is generated on a consistent level. This gave the driver a buffer or zone to work within as he knew the car, unless a failure occurred would have sufficient downforce to make corner entry at speed as downforce was continuously fed to the car even when they were in the braking phase.

 

If we look back through F1 and moreover a topic that I have covered most recently in my section on the Williams FW14B for Grand Prix Merchandise teams have been looking to bridge the gap between a rigid aerodynamic platform and Downforce for some time. 'Active Suspension' created this bridge back in the 80's, early 90's with the driver given a more consistent window of downforce as the computers fought the car's wantant needs to pitch or roll. The interlinked suspensions of today are doing a similar thing but passively through the use of Hydraulics.

Lets start out with a few scenarios without interlinked suspension so that we can understand what the teams are trying to achieve:

Scenario A: The driver is entering the braking phase from a speed of 180mph into a slow left hand corner, as he decelerates the balance of the car shifts forwards destabilizing the rear of the car. This is what we refer to as 'Pitch'

NB: In this example the height of the diffuser increases as the car pitches forward, coupled with the loss of the exhaust plume's sealing effect (as the driver is off throttle), means the Diffuser is subjected to 'Tyre Squirt' and results in a less compliant rear end)

Scenario B: As the driver completes the braking phase in Scenario A he turns into the left corner the car rolls to the right. This will result in the car leaning on the right tyres as the car's weight transfers (This is why you sometimes see drivers fighting opposite lock / oversteering out of a corner as the transmission of speed is too much for the force applied on the given tyre)

 

Scenario C: As the driver straightens the car from Scenario B he applies the throttle and the balance of the car pitches rearwards (Squatting)

Interlinked suspension helps to manage these effects retaining a more stable aerodynamic platform, in all three scenarios an interlinked suspension can counter the car's natural tendency to shift forward, sideways or rearwards. This allows the aerodynamics to be much more aggressive and tailored to a much smaller operating window. Mercedes (and Lotus to a smaller extent) are the only team I'm aware of using Left to Right and Front to Rear interlinked suspension thus they control the whole platform of the car as it pitches or rolls. Some of the other major teams including Red Bull, Ferrari & McLaren are all believed to have left to right interlinked systems that help the car adjust it's attitude in Roll.

 

It's not a fool proof system by any means though with Mercedes utilising their system for around 3 years now, also Caterham share rear end technology with Red Bull purchasing their gearbox and rear suspension from the Championship winners. So why do some have more success than others using the system? If we were back in the days of unlimited testing I'm quite sure the teams would have it nailed by now but with limited track time and the effects difficult to model on conventional suspension design systems the teams have had to invest time and money in the tools required to model it.

 

So now you know what the teams are doing I'm guessing you want to know how, well it's an area that is difficult to explain in it's entirety with images due to the teams hiding it and most of the system being enclosed under bodywork. But in a rare shot of the rear end of the Mercedes W02 we can see how the team are hydraulically linking both sides of the suspension.

 

In the image above found by @F1Talks – www.f1talks.pl and courtesy of www.suttonimages.com from the Korean GP in 2011, we can see a damper connected to the bottom of the Pull Rod which takes care of 'Roll' and/or 'Heave' (Heave is the up or down motion of the car) we can also see 2 Hydraulic pipes are connected to the damper and lead to a central valve block. A hydraulic pipe is connected to either the high or low pressure chamber of the damper which leads to the central valve block where it's counterpart or opposite from the other side of the suspension meets with the valve block too. This connection allows a displacement of hydraulic fluid on one side of the suspension to have a counter displacement on the opposite side of the car helping to level it.

Above: A very basic drawing breaking down what we can see in Sutton image above



In the case of Mercedes they went one step further than some of their counterparts (appears Lotus may have a similar system too) by connecting the Front & Rear to the interlinked system too (FRIC – Front/Rear InterConnected).

 

Above: Giorgio Piola illustrates the method employed by Mercedes to alter the level of hydraulic fluid present in the FRIC system

 

This means the team control the pitch angle, allowing the team to have a good handle on one of the biggest aerodynamic pitch sensitive issues fought by the teams: Rake

 

These interlinked suspensions therefore help to keep a more constant aerodynamic platform allowing the team to set the rake angle such that they need not fear it bottoming out, maximising the downforce that can be generated by the Diffuser / Exhaust Sealing.

With Pitch angle being able to be controlled we don't have the same issues we saw back in Scenario A as the car doesn't pitch forward under braking the way it normally would resulting in the Diffuser being able to retain the downforce generated for a more sustained period of time.

 

A trend seems to be emerging with teams both softening the rear suspension and lowering tyre pressures to further aid in the braking and turning in phase. This not only aids in reducing the Diffuser height as the suspension counteracts the car pitching in the braking phase but modulates the tyre, generating heat and grip.

 

In Malaysia we saw Red Bull and Mercedes soften their suspensions and run with less tyre pressures than in Australia having perhaps witnessed Lotus adopting this style. Meanwhile Lotus and moreover Raikkonen went a little backwards suffering perhaps with the aerodynamic changes made to his car whilst still running an aggressively soft car. (Raikkonen suffered with snap oversteer throughout the race)

 

http://youtu.be/V9ZUoEVIjFI

 

http://youtu.be/CCoI14v4eDI

 

It will be interesting to see how this plays out throughout the rest of the season especially as I see no reason why Pirelli should heed the calls of Red Bull to switch back to 2012's tyre construction. Furthermore Mercedes have spent 2 painful years already trying to perfect their more complex FRIC system which creates a link between the front and rear of the car and caters for Pitch and Roll. Therefor I don't see teams being in a rush to copy Mercedes this season especially as the gains aren't substantial in terms of overall pace when as much can be made up by key aero upgrades.

 

 

Below are a few images caught of the Mercedes W04 caught during build up

 

 

 

Posted by Matthew Somerfield

http://somersf1.blog...cedes-fric.html

 

Qua la traduzione automatica

http://somersf1.blogspot.co.uk/2013/04/interlinked-suspension-and-mercedes-fric.html

[The King of Spa 637]

Minardi fa scuola, dal LINK del 93 al FRIC dei giorni nostri

 

 

5 maggio 2013 – In questo inizio di stagione a tener banco tra i team di Formula 1 è stato il sistema FRIC, front and rear interactive control, adottato da Aldo Costa e Ross Brawn sulla Mercedes W04 di Hamilton e Rosberg. Si tratta di un sistema idraulico che permette alle sospensioni anteriori e posteriori di lavorare insieme ricreando così in parte i benefici delle sospensioni attive.

 

Per la Formula 1 non si tratta però di una novità assoluta. Già negli anni ’90 il Minardi Team aveva dotato la sua M193 di un sistema analogo. Proprio per capire meglio il funzionamento e gli effetti abbiamo interpellato l’ingegnere Gabriele Tredozi, “papà” di numerose monoposto del team faentino. Arrivato alla corte di Gian Carlo Minardi nel 1988 come ingegnere di macchina di Adrian Campos e, successivamente, di Pier Luigi Martini, nel 1997, in seguito alla partenza proprio di Aldo Costa verso la Ferrari, divenne capo progettista della monoposto M198 e Coordinatore tecnico della squadra.

 

“Bisogna fare una premessa tornando indietro di circa vent’anni. Alla fine del ’92 spopolava una nuova tecnologia – sospensioni attive – che aveva la capacità di gestire elettronicamente la sospensione attraverso numerosi parametri come l’altezza da terra, il rollio e beccheggio. Tutto questo non veniva più fatto attraverso un sistema a molle, ma idraulicamente” introduce l’ingegnere di Brisighella “Il sistema era composto da attuatori posti sui puntoni. Il gruppo molla-ammortizzatore riceveva l’olio degli attuatori in pressione tramite una pompa e, attraverso i controllo elettronici, veniva gestita l’altezza da terra del posteriore, anteriore, il beccheggio e il rollio, ottenendo così un beneficio in termini aerodinamici. Tutto questo progetto si può scorporare in due parti: una parte passiva, con l’hardware delle sospensioni idrauliche, e quella attiva, ovvero elettronicamente” ci illustra Tredozi.

 

“La M193 di Martini e Fittipaldi era dotata di un sistema idraulico passivo: non c’era una pompa esterna che metteva in pressione e gestiva automaticamente l’altezza da terra, ma era dotata di sospensioni tradizionali mandate in pressione idraulicamente. Lavorava sulle molle comandate da condotti idraulici con il puntone che mandava in pressione il circuito. Questo era il punto di partenza per poi rendere completamente attivo il sistema l’anno successivo. Purtroppo la FIA bandì il sistema e così ci trovammo con una sospensione molto avanzata ma non sfruttabile. Continuammo però ad usarla nel 1994 senza renderla attiva”

 

Come funzionava il sistema: “L’obiettivo era minimizzare le variazioni di altezza tra anteriore e posteriore in frenata e accelerazione. Per gestire in modo passivo il beccheggio della vettura mettemmo in comunicazione, con un collegamento incrociato – LINK – l’asse anteriore con il posteriore. In questo modo, quando la vettura in frenata schiacciava l’anteriore l’attuatore creava un vuoto nel retro, occupato dall’ olio dell’attuatore posteriore in modo da far schiacciare a terra anche il posteriore. Così facendo si manteneva inalterata la differenza di altezza. Essendo incrociato dava un aiuto in più in curva: quando il carico maggiore era sulla ruota posteriore esterna, interveniva sulla ruota anteriore interna limitando il rollio. Il medesimo funzionamento, ma opposto, avveniva in accelerazione: il carico si trasferisce dietro facendo alzare l’anteriore. La pressione degli attuatori evitava proprio questo schiacciando il muso a terra. Così facendo si diminuisce il sottosterzo in potenza”.

 

“Alla fine del 1993 però il collegamento venne vietato. Con la M194 continuammo quindi con le sospensioni idrauliche, ma non più connesse. Una parte del beneficio venne quindi perso. Sulle Formula 1 di oggi invece è ricomparso questo Link, utilizzando quindi un sistema analogo al nostro di 20 anni fa”.

 

Quali sono i suoi vantaggi: “Il vantaggio è di minimizzare la differenza tra l’altezza anteriore e posteriore in frenata o accelerazione. Avere una macchina molto stabile in frenata vuol dire avere una più alta velocità in ingresso e, di conseguenza, più carico. Inevitabilmente si sfruttano meglio le gomme. Il pneumatico scivola e patina di meno e l’anteriore strappa di meno. E’ certamente un sistema che richiede del tempo per essere messo a punto, che si gioca sui diametri dei tubi”, conclude Tredozi.