Force India: New beam wings and enlarged cooling outlets
Continuing their current theme of innovation Force India (FI) produced a revised rear end for the VJM03 in the latter days of the Barcelona test. This included a revised beam wing set up and enlarged cooling outlets.
Originally it appears that the FI used a very tall diffuser and a split rear beam wing. In Actual fact the car used a lower diffuser, but what appears to be the top section of diffuser was a second full width beam wing, sat ahead of the split one. Although the rules demand ‘one closed section’ (i.e. one element) for the area containing the beam wing, there is a free zone for bodywork sat ahead of it. Last year both Ferrari and Toyota exploited this area for a second beam wing sat in tandem ahead of the other one.
With the update there are now two full width beam wings, the rearward one no longer split but instead hooking up over the rear crash structure. However the forward beam wing remains (yellow) and sits in a cascade with the diffuser, to create a high expansion ratio diffuser by effectively making a taller exit (light grey). Also aiding the diffuser exit are a pair of fins attached the outside faces of the diffuser and stack of winglets affixed the rear brake ducts.
Allied to the diffuser changes the hump enclosing the rear of the sidepods around the gearbox was cut open to allow for greater cooling in the opening flyaway races. Allied to the rear end of the coke bottle shape, the exhaust outlets and a gaps made for the suspension that allow hot air to escape the sidepods (all shown dark grey).
McLaren added these floor details (yellow) as part of the Barcelona update
McLaren ran a variety of new details on the MP4-25 in Barcelona, which included this new duct in the floor. Sitting just ahead of the tyre, this lets air pass from above to below the floor, which then passes the coved section of florr beside the diffuser. The coved (ridged) section was first used on the RB5 and has been copied by several teams. However so far no one has gone as far as McLaren in makign the top deck of the diffuser reach up as far the full width of the beam wing. McLaren have even added a slot to this section to keep the flow attached.
McLaren ran this vent with both a rear facing outlet and louvers
Additionally the team ran with different cooling outlets by the cockpit, some of these featured both an rear facing outlet and louvers along its top and side surfaces.
Red Bull surprised everyone with their revised car that appeared on the last day of testing. As the car sported revised exhaust systems with a low exit that aims the exhausts over the diffuser. While exhaust driven diffusers were popular in the nineties before periscope exhausts became the norm, to have the exhaust play over the top of the diffuser is a relative novelty. However the Newey designed solution on the RB6 is a little more complicated than it first appeared. In one shot we can see the upper deck of the diffuser features a window (Arrowed) to allow the exhaust gas to pass inside the diffuser, rather than solely over it. With the aim that the high speed exhaust gas will drive more flow through the diffuser to increase downforce.
One criticism aimed at exhaust driven diffuser is their sensitivity to the throttle position and hence the speed of the flow through the exhaust and in turn the amount of downforce it adds to the diffuser. This issue was mainly related to when the exhausts were placed right on the kickline between the floor and diffuser, thus their effect on downforce was much more pronounced. Placing the diffuser further up the diffuser reduced this sensitivity. Newey knows a thing or two about blown diffusers, the McLarens retained diffuser exhausts exits all the way to the MP4-17, even then the switch to periscope exhausts was largely driven by other engine packaging factors. Even the still born MP4-18 aimed to have diffuser exiting exhausts. The placement of the exhaust some way upstream of the diffuser exit should allow a better compromise between downforce and sensitivity.
try a simplified front wing and deeper sidpod fins, not visible in this pic, but they have new exhaust outlets too
NOTE: Update on McLarens Snorkel\Rear wing here http://wp.me/sNdA9-235
As McLaren continue to use testing rigs to map their cars aerodynamics, the importance of the snorkel on the top of the chassis is becoming apparent. On Friday The car lapped with an array of sensors attached to the rear wing. However, there was an additional sensor mounted inside the snorkel. Raising the question why would you want to test rear wing and driver cooling simultaneously?
This Snorkel, is an apparently innocuous looking part, which was at first believed to be solely an inlet to cool the cockpit. Several teams add similar inlets in this area to supplement the inlet in the tip of the nose. The cockpit houses the power steering rack, hydraulic lines and electronics boxes, so cooling is often required. However the initially simple inlet has been superceded by at least two more shapely snorkel-like derivatives each with an apparently unnecessarily complex double wall construction creating smooth narrow inlet and a streamlined outer surface. This snorkel has been present ont he car through out all the cold and wet testing sessions, suggestion its purpose goes beyond a simple primary purpose of cooling.
One rumour around the internet suggests the inlet is linked by a duct to the shark fin\blown rear wing. At first appearing to be simply a wild rumour, that the snorkel is blocked by the drivers knee to alter the rear wing airflow. However the presence of the airflow sensor along with the rear wing test rig, suggests there might be a link after all. The rumours suggest the drivers left braking leg, which sits unused on long straights could be used to alter the flow from the snorkel to the rear wing duct, where a valve alters flow through the blown slot to stall the rear wing. This would reduce downforce and also drag, which would allow a higher top speed. Then the driver moves his leg to start to brake for the next turn the valve switches airflow back to normal, the wings airflow reattaches and provides the downforce needed for the turns. This sounds both feasible and far-fetched at the same time.
It would be hard to link the rear wing and snorkel with any certainty, but any input from the driver that would alter the cars aerodynamics as the rumours suggest would certainly be an area of greyness in the rules and liable to protest come Bahrain.
Force India: The undernose hump may reduce lift and also house ballast
Not new developments, merely ones not spotted on the car at its launch.
Under the nose the car sports a hump, similar to that employed in 2009 by Renault and Williams (in early testing at least). This is used to offset the lift created by the neutral central section of the front wing (as mandated by the rules). Additionally Force India appear to have an access hatch in this hump, which suggests that there might be Ballast placed inside it, not as effective as ballast mounted in the wing by usefully a few centimeters lower than inside the main nosecone.
Force India: splines to mount the wheel to the hub speeds pitstops
Then the front wheel and hub assembly is innovative. usually the front wheel is prevented from rotating on the hub by four or so drive pins. In fitting the wheel during pitstops, the holes in one need to correspond with the drive pins in the other. Thus four drive pins means the wheel will fit the hub in four orientations each 90-degrees apart. Thus the more drive pins the less the mechanic has to rotate the wheel to fit it to the hub. This year Force india have specially made wheels with a splined detail, to match that on the hub. I can around 20 splines on the wheel suggesting the wheel will fit in one of 18 positions. making the aim of the sub three second pitstop that little bit easier.