Splitters Explained

Although low down in a dark area of the car and hidden behind bargeboards, the front splitter has been a critical part of the F1 car for many years. Known by many other terms, such as the shadow or legality plate, T-tray or bib, I’ll refer to this part as the splitter.

Since 1983 F1 cars have needed a flat floor in-between the front and rear wheels, then this floor needed to be stepped since 1995. In the late eighties when designers were slimming and raising the nose of the cars, there was a need to create a floor section under the front of the monocoque to meet the flat bottom rules. The most obvious first splitter was the Tyrrell 019 with its fully raised nose, since then the splitter has been more and more exposed as teams seek to raise and narrow the chassis cross section for aerodynamic benefit.

A splitters regulatory role has been to form the flat bottom of the car and from an attachment for the ‘plank’ running along the length of the flat floor. Thus the splitter must form the flat floor at reference plane level (the datum level where all bodywork measurements are, although the plank sits below this level). The splitter must also shadow the plan profile of the monocoque, such that the monocoque cannot be viewed from beneath the splitter.

However the need to have this bodywork forming the floor has been exploited and the splitter now forms aerodynamic and chassis functions of its own. As the term suggests the splitter separates the airflow passing under the raised nose between that which passes above and below the floor, equally its boats ‘bow’ shape above where it meets the monocoque also splits the airflow passing over the floor between left to right. Air then spills off the upper surface of the splitter and some of this will make its way under the floor and towards the splitter, thus the teams make use of this powerful flow to alter the pressure distribution across the underfloor to further improve airflow through the diffuser. allied to the fences, vortex generators and previously bargeboards, the splitter forms a critical role in the onset flow for the diffuser.

Brawns 2009 ballasted splitter

Being mounted low and far forward, the splitter also forms the location for ballast. Depending on the prevailing tyre and aerodynamic issues, teams can run as much as 50% of the cars weight on the front axle. with a rear engine car, the only way to do this is the ballast the front of the car and the splitter has been known to be made entirely from metal in order to maximise front end weight bias. Under the current aero and tyres rules, weight is somewhat more rearwards and the splitter is less heavily loaded with ballast

Deflection
In 2001 when the technical regulations demanded raised front wings (excluding the middle 50cm section) teams found the raised front ride height, cost downforce. Attempts were made to artificially lower the front wing when on track, both by flexing and by lowering front ride height. such is the geometry of the car, that the car cannot achieve enough rake to lower the front ride height without either excessive rear ride height or the splitter hitting the ground. A high rear ride height will cost rear downforce and stability, so the splitter needed to be moved out of the way. Teams found that deflecting the splitter upwards as it hits the track surface under braking allowed for lower ride heights. making the splitter far less stiff than it needs to be allowed the splitter to ride up without undue wear to the plank and skids which are measured in scrutineering for wear. Excessive wear to the skid block will bring penalties for the teams and drivers.

Hinged splitters allow lower front ride heights

However the FIA became wise to this practice and along with other deflection tests carried out on the he scrutineering rig, a test with push a hydraulic ram up from under the splitter was introduced. The car is bolted to the rig and the ram applies 200Kg of pressure to the front edge of the splitter, only 5mm of movement is allowed. this forced teams into running stiffer splitters and hence higher ride heights.

A hydraulic ram rises from the test rig to measure deflection to the floor

In order to regain the lower ride heights teams once again worked around the rules, by making the floors deflect at loads higher than the 200kg test. by hinging the splitter at its rear mounting and then making the front mounting a preloaded to 200kg. thus the floor will be be able to meet 200kg FIA test with little movement, but at loads over 200kg the front mounting will start to deflect and allow upwards movement for lower ride heights and more downforce. In Ferraris case this was a mounting with a small coil spring to provide the resistance to the 200kg load. McLaren had a pre-buckled stay, acting like a leaf spring between the floor and splitter. The justification for these very visible mechanical mounting was to avoid damage to the now very heavily ballasted splitter, when running over kerbs and bumps etc.

Ferraris 2006 preloaded sprung splitter support

One of the issues to fall out from the technical interchange between McLaren Mike Coughlan and Ferrari Nigel Stepney was Ferraris use of the splitter mounting. Knowing how Ferrari used the mounting allowed McLaren to ask the FIA technical delegate Charlie whiting for permission to use such as a system. this approach is a subtle workaround to a formal protest of another teams design, but ends up with the same result, either acceptance or a clarification banning the design. This issue arose at the start of 2007 and by the Spanish GP the teams were asked to remove deflecting splitter mounts, necessitating a redesign for most if not all teams. some people within the sport suggest Ferrari performance advantage from the previous few years was eroded by this rule change. since then teams run far stiffer splitter mountings and although several teams have been asked to revise their mountings since then by Charlie whiting, it is felt that there is little that can be done to deflect the splitter for performance benefit.

As you can see, FW Ride height is restricted by the splitter, unless the splitter deflects upwards

One of the explanations for the low wing ride height on the RB6 are suggested to be the splitter is allowing lower ride height by deflecting. Certainly trackside images suggest the Red Bull and the Ferrari are running significantly more rake in the set up at speed (i.e. nose down). Other teams suggest that this level of rake and low front wing ride height cannot be achieved with normal rear ride heights. But do not suggest how the car may be able to run that low. But the inference is that the splitter is in someway deflecting to allow this. I’ve not seen the detail of Red Bulls splitter mounting, but I doubt they are able to deflect the splitter without any obvious compliance in its mounting or undue wear to the skid blocks.

On a side note, it was Coughlans assertion that the Ferrari splitter of 2007 was also being sprung to create a mass damper effect, with mass dampers being banned the previous year.

Quote from Racecar-engineering.com “One of the defences used by McLaren was that Stepney, the former Ferrari employee, was ‘whistle blowing’ – something the court struggled to accept covered the whole affair, but it did certainly have an effect at the Australian Grand Prix. Ferrari won the race, but the FIA later outlawed the car’s floor. McLaren contended that the Ferrari that won was illegal, and a letter from Stepney to the FIA sent after the hearing revealed that it may well have been, as it was in effect a mass damper. Such devices were banned last season as they were controversially deemed to be a moveable aerodynamic device.
Stepney reveals in detail the exact workings of the floor that was used at the race: ‘The front floor is attached to the chassis via a mechanical hinge system at its most rearward point. The most forward support is a body with one compression spring and one tension spring inside which can be adjusted according to the amount of mass that is fitted to the front floor. There is also a skirt that seals the floor to the chassis, which is made out of rubber and Kevlar to help flexibility and reduce friction in the system.
‘If the system had been allowed it could have meant a huge cost of development for other teams in such areas as chassis and under trays etc to make way for the provision for storing the system and the variable quantity of mass. The possible long-term consequences of such a system would be quite substantial because the system is in a crude state of development.’
The system detailed by Stepney allowed the F2007 to ride kerbs harder due to the 14-15mm deflection at the leading edge of the floor, which means the Ferraris could straight line chicanes more than other chassis. Front plank wear would also be reduced, allowing the car to run lower at the front, giving an aerodynamic gain.
Stepney also explains the dynamic behaviour of the car, and the advantages the flexing floor gives: ‘From around 160-180km/h (100-112mph) the car is about 7-8mm lower at the leading edge of the floor, which multiplies up to nearly 19-20mm lower front wing height. The benefits in terms of ground effects and efficiency would be gained all around, with components like turning vanes and front wings at a reduced height relative to the ground.’ “