Germany 2012 Free Practice 2

Time of Session:

ToS (h:m:s)**

01:11:50          Glock sitting in the garage debriefing with his engineer, reports “for some reason” the quick-shift adjustment lever for brake balance is stuck “very hard” with him needing to “really hammer on it” to be able to move it. Engineer responds, “So, presuming you can’t do it with your left hand anymore, huh?” Glock replies can indeed move it, but only after pushing it “hard”

** 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.

We often hear about drivers adjusting brake balance to compensate for rotor temperatures, KERS dynamics, or corner entry issues, but what really is it and how do they adjust it?

There are two separate master cylinders on two separate hydraulic circuits that actuate the brake calipers, with one master for the front calipers and another master for the rear calipers. Both cylinders are actuated together by the one single brake pedal. Any 4-wheeled car obviously requires more braking energy across the front axle to manage inertia of the mass of the vehicle, but how is more energy achieved at the front when there is only one single brake pedal?

The two separate master cylinder pistons are connected to the chassis from the brake pedal via a “balance bar” or also known as a “bias bar.” The balance bar mechanically dictates the ratio of piston displacement between the front and rear cylinder as the pedal is pressed. Basically, for any given distance the pedal is displaced, the front cylinder will be displaced more than the rear cylinder. With more piston displacement in the front cylinder, the front hydraulic circuit will experience a higher pressure than the rear which has less piston displacement. There are other means of fine tuning hydraulic pressure through piston and cylinder diameters, but we don’t need to discuss that for this basic explanation.

The balance bar is adjustable to mechanically alter the ratio of piston displacement. Mechanical adjustment is available to the driver in the cockpit as a “quick-shift” lever for large macro adjustments or a knob for finer adjustments. Levers can be set to make adjustments as large as 1.5% in one fast movement. The direction of lever actuation is usually intuitive for the driver to be able to use it without thinking too much about it or looking down at it. For example, moving the brake balance rearwards involves pulling the lever back, with pushing it forward to move balance towards the front. On in-car camera feeds, Schumacher is often seen actuating the quick shift lever multiple times during a lap from corner to corner.

What is the brake balance number we often hear about over the radio? Often when engineers request a driver to change brake balance, they not only ask for the percent of change, but also discuss the final total percentage. Formula 1 cars usually operate with a brake balance of approximately 56-60%. That percentage number is the ratio of total hydraulic pressure in both circuits, relative to the front axle. Basically, just keep in mind that it essentially means, 56-60% of the total braking force is being applied to the front brakes.

How is brake balance calculated? A hydraulic pressure transducer sensor is located at each master cylinder. Each sensor will thus have its own calibrated parameter in the data system. With the logged brake pressure data from each separate hydraulic circuit, we can then calculate brake balance with the follow basic equation:

First, let’s set up our 2 variables:

Fpress = Front Brake Hydraulic Circuit Pressure                                                        Rpress = Rear Brake Hydraulic Circuit Pressure

Brake Balance =

[(Fpress) / (Fpress + Rpress)] * 100%

As you can see, all the equation did was to determine the ratio of front force to the total force and multiply that number by 100 to present it as a percentage. On some in-car photos and videos, you can see the brake balance percentage designated on the steering wheel dash as “BBal.” Now you know how the data system and engineers measured and calculated that number we hear so often.

Monaco 2012 Free Practice 2

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Time of Session:

ToS (h:m:s)**

-00:02:00        Vitaly will leave garage “straight away” right when session goes green. Will do a “few” laps because team doesn’t expect prime tires to put in good times “on the first timed lap”

-00:01:00        De La Rosa given choice to run same amount of laps as ran in FP1. Told to pit within 5-6 laps if he’s determined balance of car to then make setup changes

01:30:00         Hulkenberg to do a bite point find at the end of pitlane

01:27:35         Rosberg told team expecting rain between “Five and quarter past” the hour “so you’re just going to get a couple of laps”

01:12:08         Petrov reports rain on-track. Team Repsonse: “OK, OK we will prepare wet helmet”

01:10:35         Petrov told only 2 other cars went out on super-softs

00:56:23         Caterham expects rain to return in 8 min and tells Petrov they think tires need one timed lap to be in the best track conditions. Team will send car in 3 minutes. Vitaly wants to wait and not be first on-track, doesn’t think “track is ready”. Team agrees, but says cannot wait too long to give a 2 lap advantage to other cars, due to “risk” that by the time tires reach optimum, more rain will come. Team says Petrov will be sent as soon as other cars set flying laps due to the impending rain

———-            RIC to add 3-4 turns of front wing

———-            Heikki fueled for 7 total laps

00:44:15         Rosberg reports “a warm up issue” with the super softs. Mid corner understeer. Rear of car “not fantastic”

00:42:25         Ricciardo reports rain in T5,6,7,8,10. Still fighting understeer. Asks for +2 or 3 turns front wing “if we still have room to go”

00:41:03         Caterham analyzing data, says Petrov may benefit from +2 clicks forward on brake balance to help locking into T5 & T6. Engineer reminds him locking in T6 is natural because inside front wheel is “unloaded” through corner. Told not to judge brake balance from those 2 corners and Vitaly agrees. Engineer also reminds him that under damp conditions, the driver is to make final decisions

00:38:28         HRT expects a “tiny” gap in rain. “If anything, there’s a lot more rain coming.” De La Rosa says, “OK, but you only need a few drops here to be very slippery”

00:37:32         Heikki told to go minus 1% brake balance which equals 1 “full turn” on his adjuster. Reminded to only use the “quick shift” balance adjuster for T10. As he examines driver data in the car, told to focus improvement on exit of “last three corners”

00:34:45         VER told to pit if he feels he is “destroying the tires”

00:34:28         Petrov going out on softs until track is “really good” then will do a pit stop practice onto super softs until end of session practice launches on grid.

00:32:32         Caterham says latest weather info from Meteo France reports light rain expected to last until end of session. If track reaches condition for intermediates, the team will do so.

00:14:38         Glock reporting on extreme wet tires, says they gave him “more confidence” but with “movement” of the tread blocks, “if you push a little bit”, there is “massive movement and you destroy the blocks.” Team plans to do grid launch practice at end of session, so will not send Glock out on extreme wets, but may do a few laps on inters “to get a feeling”

00:11:45         Ricciardo reports tires going off as track dries, “so I had a bit more sliding on top of the surface instead of like a wet full slide, if that makes sense”

00:08:30         Pastor will be sent out at 7 minutes to go. “Not changing fuel level”

00:08:12         Vettel reminded DRS still available if he “wants to practice” and if he “thinks it’s safe”

00:08:59         Senna told track is now clear from Massa’s incident. Told Massa did “same as you, rear locking downhill”

00:06:40         Pastor’s front wing flap set to 18.5 degrees. Will stay out until end of session for grid launch practice.

———-           Petrov told to move brake balance 3 clicks to the rear and use 50% KERS harvesting map

———-           Heikki will run a 40 Kilowatt KERS map

00:05:52         Pastor told track “still looks slippery” in T5 and T6

00:04:54         Webber asking if team would like him to stay out on dry tires to collect more data and says, “Might not be a bad idea.” Team confirms and says, “stay out” and will do practice starts at end of session

00:04:11         Heikki says reverse doesn’t work, “I have no reverse on the dash, nothing happens, so I have to stop, went straight in turn 5, so that’s it”

00:00:00         Pastor told to use high gear with low revs to cool the engine on the in-lap

00:00:00         McLaren telling both drivers for practice bite point find grid launch to do 4 burnouts with 2nd gear launches, yellow ‘G’ steering wheel switch set to 1. Lewis to the left side of grid, JB on the right side

00:00:00         Di Resta debrief, reports trouble with getting front brake temps. “Couldn’t get the light to go out”, “Almost like the material had glazed.” Engineer agrees and says they saw a problem with the front right brakes and says, “this material will be changed for Saturday”

00:00:00         JB debrief, says, “got traffic on my last timed lap, but even so considering the fuel load, I don’t think it’s too horrendous, but the tires are going away quite quickly.” Says wettest part of track was T3 through to exit of tunnel, which “was eating up the tires pretty badly.” In reference to the fuel load, “in a good way, the rear isn’t moving around too much on the tire.” Still reports too much understeer in the car, but rear balance was OK

** 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.

POST SESSION COMMENTARY

As with FP1, mid-corner understeer is a major issue among all drivers and cars. The issue is primarily caused by the nature of the track being constructed on public roads featuring lateral road-crown. Public roads are obviously crowned with a slight convex curve to allow rain water to naturally drain away to the gutters. The crown curve, layout of the kerbs, and proper driving line, all combine in varying degrees at each corner to create sub-optimal corner camber. Therefore, the car cannot be setup to solve all understeer issues, but rather setup as a compromise to the track as a whole.  Allan McNish commented that every corner is essentially “off-camber.” To visualize track camber, think of an oval racing track with banking towards the inside of the track to aid in cornering. An opposite track angle, away from the inside radius of the corner, is known as “off-camber.” Part of what engineers and drivers take note of on track walks during setup day is to identify which corners are off-camber and how much so.

What does it mean when cars are fueled for “total laps”? The amount of fuel to be added to the car is calculated by multiplying the average flying lap consumption times the number of planned timed laps, plus the average outlap consumption, plus the average inlap consumption, plus fuel scavenge to remain in the tank. A quick generic free practice fuel load calculation is as follows:

(Avg Outlap consumption) + [(Avg Timed Lap consumption) x (Planned number of laps)] +

(Avg Inlap Consumption) + (Fuel Cell Scavenge to remain in tank) = Fuel Load

The engine obviously consumes different amounts of fuel on in- and outlaps because the car isn’t being pushed for timed laps and displaces different amounts of track distance due to track and pitlane configurations. Fuel scavenge is required as a buffer for not running the engine out of fuel and to compensate for calculation errors, deviation from average consumption per lap, and for parc ferme regulations at the end of qualifying.

As Ricciardo fought understeer, he first requested an additional 3 to 4 turns of front wing. Later in the session, he asked for an additional 2 or 3 more turns of front wing and says, “if we still have room to go.” I find that interesting because that implies Toro Rosso’s front wing flap adjuster may only have 6 to 7 turns of downforce increasing range of angle from its starting position.

During Di Resta’s debrief, he was reporting the inability to reach optimal brake temperature and said he, “Couldn’t get the light to turn out.” That tells us that he has an LED indicator light on his dash that stays illuminated until the brake rotors reach optimum temperature, as measured by infrared sensors on the uprights.