Germany 2012 Free Practice 3

Time of Session:

ToS (h:m:s)**

00:36:53          Grosjean reporting issues with gear shifting, asks, “are you sure everything is really right with the gearbox? Downshift don’t seems good.” Engineer confirms they can see the issue occurring over telemetry data, asked to then box and select neutral gear to coast down pit lane into the box. Grosjean responds, “but I can’t pull downshift.” Then the engineer asks him to “try not to shift” gears, but continues to ask him to shift into neutral to coast in the box when he comes in. Finally, the team confirms to Grosjean the issue is “we lost clutch LVDT”, so the team is working on a solution to be able to “keep running.”

** 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.

What happened? The clutch slave cylinder is instrumented with a displacement sensor that is vital to all clutch operation and that is what failed for Grosjean. There are displacement sensors on the steering wheel clutch paddles as well. The outputs of both sensors are input factors into a multi-dimensional map with clutch slave hydraulic pressure as the dependent function. In a basic sense, the displacement of paddles and slave cylinder are mapped together to control how much the slave is displaced to release the clutch diaphragm. The clutch map is constantly tuned for driver preferences and clutch parameters. Bite point find procedures are fundamental to this tuning, but we’ll discuss those at another time.

What is an LVDT? The acronym stands for “Linear Variable Differential Transformer.” In our basic discussion here, we don’t need to go into how the sensor actual works. Just remember that it outputs physical linear displacement as a voltage to the data system, which is then calibrated to a parameter within the software. For a bit more information on LVDT sensors used in clutch slave instrumentation, please visit Active Sensors site here: http://www.activesensors.com/motorsport-position-sensors/clutch-position-sensors

Active Sensors is one of a few popular suppliers of LVDT sensors for motorsport use and most importantly, will work closely with teams to develop bespoke sensors for specific packaging requirements.

How did they fix the issue for Grosjean to continue? There are many redundant systems and protocols designed into a Formula 1 car to be able to compensate for failures. It would be reasonable to believe that maybe the clutch slave actuation was mapped only to hydraulic pressure, thus eliminating the failed LVDT from closed-loop control.

Great Britain 2012 Free Practice 2

POST SESSION COMMENTARY

00:06:15          Button reports a “false neutral” on entry into turn 1. Engineer acknowledges issue and informs him Glock is the next car behind in traffic and that there is a “large gap” behind Glock if he needs space.

00:02:01          Button debrief, says he “didn’t get any clear space” in traffic due to his previous “false neutral into turn 1” in addition to the other cars running intermediate tires causing traffic, “who are really struggling out there”.

** 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

What is a “false neutral?” In general, a false neutral is a situation when the gear indicator on the steering wheel dash indicates gear engagement of a particular gear, but mechanically, there is no output of the drivetrain. The word “false” is derived from the data system indicating an engaged gear, but that indicated gear is not mechanically engaged. The word “neutral” is derived from the gearbox mechanically functioning as if it were in neutral, without gear driven capabilities, such as forward drive or engine braking.

In Button’s situation, he reports the issue occurring on entry into turn 1. Thus, it is obvious he was downshifting when the issue arose and utilizing engine braking. In a basic sense, engine braking is a significant contributor to the energy used to slow the car down through providing force against the drivetrain from engine drag. As a driver loses a gear on downshift, not only will they be massively distracted, but now they must use the brakes, quickly sort their thoughts,  and try to grab other gears, all in an instant before having to still turn in and make it through the corner.

Jenson was obviously able to successfully engage a gear and continue on because he did not come back to the garage for repairs. A false neutral is primarily caused by software or sensor issues. If it were a mechanical failure, Jenson would have definitely felt and heard it, in addition to being unable to select any other gears. There are sensors monitoring the position of the gear selector barrel working together with other sensors as inputs into the gearshift strategy maps controlling the hydraulic valves that actuate gear engagement. In basic terms, the mechanical tolerances of those sensors or the exact timing of calculations performed in a map output may induce an error, failing to actuate a gearshift, but at the same time falsely indicate to the driver that the shift has been mechanically completed. Requesting alternate shifts, via the paddles from the driver after experiencing a false neutral, essentially forces the software to refresh map calculations and start over from selecting another gear.