That’s how the 3D-measuring arm works
The Technical DTM regulations, comprising 200 pages, massively restrict the car designers’ scope for creative solutions. All the more they focus on finding smart detail solutions. And in this area, admissible tolerances represent a key factor as even in the computer age, manufacturing certain components accurately to the hundredth of a millimetre and positioning it just as precisely on a car is virtually impossible. This applies in particular to the carbon-fibre components a DTM vehicles body is made of. But these tolerances mustn’t be exceeded and to make sure that this isn’t done, Dekra relies on highly sensitive monitoring technology – the so-called 3D measuring arm.
For the assembly of a DTM vehicle, maximum precision is a must. After all, the carbon-fibre components of a car make a major impact on its aerodynamic performance and could bring the team valuable seconds. A low mounted roof, for instance, would allow for more of the airstream flowing to the rear wing, thus making for additional downforce. Or a rear diffuser with an angular degree set just half a degree steeper than allowed could help the driver quickly gaining several tenths of a second. And this sensitivity applies to all the components having contact with the air flow. So, it comes no surprise that the vehicle engineers are sailing closer and closer to the wind.
Therefore measuring tapes and templates have completed their service as monitoring device for the form and position of components years ago. Today, both the manufacturers involved and Dekra – responsible for monitoring of the cars – are taking along so-called 3D measuring arms to the circuits. The high-quality precision devices remind of robot arms equipped with a small, ruby-red sphere at the top.
But before the robot arm can start measuring, somebody has to show it where it actually is – it must be calibrated. For this purpose, seven reference points have been stamped into the monocoque of every DTM vehicle, providing the measure arm with the urgently needed X, Y and Z coordinates, with X standing for the longitudinal direction (related to the driving direction), Y for the width position and Z for the height position.
Prior to the beginning of the measuring, the aforementioned red sphere is taken to at least three of the seven reference points that then are identified by the measure arm’s software. Only now, the robot arm knows where in the car its measuring top currently is placed and the monitoring of the stipulated dimensions can begin. The calibrated measuring arm can effortlessly be moved to any desired position in or on the DTM car. The measured value at the respective position is saved by pressing a button and compared with the regulations.
But the incredible precision of this measuring method also entails risks – particularly for the car engineers. Should they dare to move too close to the limits stipulated by the regulations, it easily can happen that certain components are slight pushed out of their position – for instance due to contact with other cars or even by driving hard over the curbs – and consequently are found the not be within the permitted tolerances, in the scrutineering following the respective session or race. Should this be the case, the driver possibly will have to face disqualification – and his engineer a telling-off by the Team Principal.