Germany 2012 Hockenheim Track Map
POST SESSION COMMENTARY
Time of Session:
–:–:– Ricciardo will do 2 timed laps with “constant passes” of constant speed aero testing on the straight after T6 and T11, in 4th gear, maintaining a speed of 200kph. After the first outing, he will box for a front wing flap adjustment before going back out again to do two more constant speed “passes” on his second timed lap.
–:–:– Heikki reminded to maintain “cruise control” mode engagement as long as possible on braking into T6 because they are performing their constant speed aero test on the straight before the hairpin.
–:–:– Kimi, running Lotus’ new double-DRS, is also reminded of his constant speed aero test parameters, with no DRS activation on his first timed lap, “aero cruise” steering wheel switch position “2”, in 6th gear, starting from the exit of T6.
–:–:– While on track for his install lap, Schumacher is reminded to activate “cruise mode 2, if possible”
–:–:– For Clos’ first timed outing, he is reminded of “what is important” is to “check the aero balance on the car”
–:–:– Grosjean asks to box for changes, with his engineer acknowledging the request and asking for a constant speed aero test with “aero” steering wheel setting position “2”, in 6th gear, on the straight after T6 on his inlap.
–:–:– As Clos sits in the garage before another outing, his engineer recounts the changes they just made to the car, including reducing front ride height for “correcting aero balance” and “tire pressure adjustments” to help with issues of mid-speed and high-speed understeer.
–:–:– Massa told to pass through pit lane to perform a practice launch start at the end of pit lane to go back out to run only one lap around with “a constant speed again on the inlap” for “aero mapping”
00:38:21 Heikki will make an outing on medium primes. The front wing flap angle has been adjusted with a “reasonable step to see if it improves the balance”
00:31:56 Alonso complains of lap traffic holding him up and requests to box. Engineer denies his request and asks for one more lap to do a “constant speed” before boxing
00:23:48 Massa asked to perform “constant speeds again” before boxing as the rain returns and increases.
** Time of session is the session time at which the message was heard on the television broadcast, as radio communications are delayed from when they actually occur. The messages without time of session notation is due to an FOM change in the Pit Lane Channel broadcasting lacking a ‘time remaining’ display during the entire session.
We already spoke a bit about what constant speed aero tests are for and what is aero balance for the Valencia Free Practice 1 post here: http://f1pitradio.com/2012/06/23/valencia-2012-free-practice-1/ , but let’s look at it in a bit more detail in seeing a bit of what makes it tangible and quantifiable to engineers and data.
Before we begin, let’s remember that aerodynamic downforce is the force acting upon tire contact patch from aero influences reacting to the geometric shapes of the car. Those aero influences are obviously due to the bodywork, such as wings and the floor attached to the sprung mass of the car, while the tire contact patches are essentially connected to the unsprung mass of the upright corner assembles. The primary connection between the sprung and unsprung mass is the push/pullrods. Aerodynamically induced force acting upon the bodywork is thus transferred to the contact patches via the push/pullrods. As the prime load paths of force between the chassis and tires, the rods are instrumented with axial load cell strain gauge sensors, with one sensor per rod. In the data system, each sensor will have its own calibrated parameter indicating the force applied to it at any given point on the track, able to be logged at a maximum of 400 kilosamples per second.
So, let’s say we’re analyzing a section of data from a constant speed aero test. In theory, let’s pretend the car drove perfectly straight, had no bumps in the road, and the platform of the car was perfectly managed by the cruise mode engine map, fixed drive gear, and constant vehicle velocity. With our hypothetically stable car, we will see our 4 load cells maintain stable values of force acting upon them from two things: The weight of the sprung chassis mass, and the aerodynamically induced downforce. With those 4 values, we can now calculate the aero balance of whatever setup we had on our car at the time. A basic calculation is as follows:
First, let’s set up names for all of our variables:
RodFL = Force measured at the Front Left rod RodFR = Force measured at the Front Right rod RodRL = Force measured at the Rear Left rod RodRR = Force measured at the Rear Right rod SprungF = Weight of the sprung mass forward of the center of gravity SprungR = Weight of the sprung mass rearward of the center of gravity
Aero Balance =
[((RodFL+RodFR) – (SprungF)) / ((RodFL+RodFR+RodRL+RodRR) – (SprungF + SprungR))] * 100%
As you can see, all the equation did was subtract out the weight of the sprung chassis to isolate what the aero forces have induced, and then found the ratio of the total aero force relative to the front of the car. F1 cars typically operate with a 38-40% aero balance, being 38-40% of the total induced aero dynamic downforce is acting on the front tires. If you don’t care about the math, just remember as you’re listening to radio messages what that number means when you hear them mention it.
What are some of the things teams can do with the final number of calculated aero balance? As Rob Smedley informed Massa of what parameters he needed to set for constant speed aero testing, he mentioned its importance for “aero mapping.”
What is an aero map? An aero map is simply a multidimensional plot with an aerodynamic factor as a dependent function, exactly similar an engine map. Many different input variables may be ride height, wing angles, or changes in the numerous bodywork parts afforded to an F1 car. Aerodynamic functions may include factors such as aero balance, total downforce, drag, lift vs drag efficiency, etc. Below is an example of a map of aero balance as a function of front and rear ride height. The bands of color in the z-axis represent ranges of aero balance in units of percentage and the front and rear ride heights are on the x and y axis in units of millimeters. Teams obviously possess maps generated from software simulation and wind tunnel testing, but this is their chance to validate those maps against real-world track conditions.
Aero Balance map as a function of front & rear ride height