“Scorching hot desert sand…” – Opel‘s International Technical Development Center (ITDC) reproduces climatic conditions comparable to the Sahara desert. In Rüsselsheim in the middle of winter, the mercury is at 60 degrees Celsius and the sweat is pouring. In the middle of it all, the new Astra Sports Tourer defies the adverse conditions. Calmly and smoothly, it bounces up and down on the heat test bench while the earsplitting racket from the ventilation system fills the 60 square meter room.
One day later, same place, same time, but the observer is confronted with a completely different scenario: the Opel Astra Sports Tourer is all wrapped up in a white outfit that is covered with a thin layer of ice. The compact station wagon’s spacious interior is not visible from the outside, as the windows are completely frozen over. The temperature is -40 degrees, and without warm winter clothing no one can last in here. “We want to see how the materials in the Sports Tourer react to extreme conditions. We also check if its appearance changes and if extreme heat or cold have an effect on, for example, gap width,” explains Otto Hemmelmann, Lead Engineer Test Methods. With his interdisciplinary team from various specialist areas, he is responsible for this foray into scorching and freezing conditions.
Extreme climatic testing for higher customer satisfaction
The heat and cold test bench – also called thermal cycling testing – is part of the compulsory program in Opel vehicle development, just like the acoustic and electronic lab tests. “After all, our customers around the world drive the Astra in all different climate zones,” says Hemmelmann. In general, every new vehicle is tested during the development phase, here a completely standard Astra Sports Tourer. This ensures that exactly the materials that are later used in customer vehicles are actually put to the test. During the two-week phase, temperatures change daily. “Sealing, bonding, plastic parts and materials, rubber – all this has to work properly, meaning constant elastic constricting and stretching like a rubber band, without bearing any traces of it,” explains the Chief Engineer.
Even direct sunlight can be simulated in the climatic chamber with the help of special radiators. “If the Sports Tourer is parked outside in the summer, interior temperatures can reach 90 degrees,” says Hemmelmann. With the help of the sun simulation, the team tests the interior materials’ stress tolerance. “But we also test how long the air conditioner has to be on until the temperature is bearable again.” In addition, the so-called four-post test bench moves the Sports Tourer up and down under its wheels. This enables testers to ensure that comfort in the car is not compromised even under extreme conditions and that the interior materials make no irritating noises or smells during driving despite high strain and stress.
Intelligent tailgate and FlexFold rear seat back tested
The Astra Sports Tourer is not specially prepared for the heat/cold test bench. It is fitted with commercial tires and belts secure the compact station wagon on the four-post test bench. Nevertheless, the vehicle is thoroughly checked before the test. Because after the hot/cold treatment, the engineers look at the Sports Tourer through the customer’s eyes and identify differences. “We look at what impression the car makes on us and take measurements to determine if anything has become distorted or misaligned,” says Hemmelmann.
The team’s systematic examination puts a special focus on the installed plastic parts such as bumpers and side sills. “The gap width is extremely important in these cases, because of course the components must not be protruding.” Employees from the respective specialist areas also check all functions in the interior. For instance, does the glove compartment open smoothly and easily? Can the FlexFold rear seat back be seamlessly adjusted in all situations? And above all, does the sensor-controlled tailgate also open and close at -40 degrees with a simple kicking motion under the bumper? After all, this practical function makes its premiere in the new Astra Sports Tourer. Only when all components, body and add-on parts are tested and cleared has the Astra Sports Tourer passed the thermal cycling test – and then it is ready for its daily job as a comfortable business or multi-functional family car.