Impact speed of 64 km/h with up to 81g (1g = 9.8 m/sec2 (3.2 ft/sec2) on the wrist of a dummy in an automobile body. The automotive specialists at DEKRA had never performed a test like this before, and it remains unique to this day.
The conventional industry stress tests for watches provide a good indication of the reliability of these timepieces. SINN Spezialuhren zu Frankfurt am Main went a step further with two watches from the 756 and 900 series and had them tested under extreme conditions by DEKRA at the Technology Center in Klettwitz (Brandenburg, state of Germany).
Have you ever heard of the town of Klettwitz? Several hundred years ago, the kingdoms of Prussia and Saxony clashed there. Today, objects clash against each other here in a very precisely planned manner. The DEKRA Technology Center, where material tests for the international automobile industry are conducted under the toughest conditions imaginable, is located at the Lausitzring, a 5.8 km speedway in Klettwitz. The center employs 70 technicians and engineers.
The DEKRA testing center was the location of a watch test that remains one of a kind. Sinn Spezialuhren is known for using unconventional technologies and materials in manufacturing its watches. Thus, one of the most unusual stress tests carried out under standardized conditions at DEKRA was ideal for our purposes.
The Duochronograph 756 equipped with a case featuring TEGIMENT Technology, a back made of nickel-free stainless steel, Dehumidifying Technology and Magnetic Field Protection up to 80,000 A/m (100 millitesla or 1,000 gauss).
Crash tests for the automobile industry are part of the daily routine at the DEKRA Technology Center. A watch on the wrist of a 75-kilogram dummy had never been launched from the compressed air catapult before. For real human passengers in an automobile, the simulation test would correspond to acceleration forces of up to 81 g at a speed of 64 km/h. Without the use of safety belts and airbags, the chance of survival in a real crash would be zero. The dummy in the DEKRA test was buckled up – and with it, the watches from SINN. This was a routine test, but the engineers and technicians at DEKRA watched with interest. First, the acceleration system for the test had to be prepared: the auto body was fastened to the catapult, the seat installed, the dummy positioned in the “vehicle” using a hoist, the watch fastened to the dummy’s wrist, and the high-speed cameras (1,000 images per second) and the lighting system (60,000 watts) brought into place. All of the screwed-on, specifically positioned and adjusted parts were re-checked.
Then the countdown started as if for a spaceship and the technicians left the launch ramp. Buckled up in his seat and wearing his SINN watch, the dummy looked rather lonely. The final launch preparations got underway behind a thick glass window in the control center above the test hall. Behind sound-insulated walls, a compressor filled a set of air tanks to 150 bar. The catapult was held in front of the launch jet with several brake cylinders connected in series.
The pressure mounted as the countdown continued – ten seconds left. With a bang, the dummy and his watch were flung into the safety belt in 60 milliseconds. The dummy’s upper body shot forward like lightning. The arm with the watch waved through the opening of the side window. After 20 meters, the vehicle body braked to a stop.
The team with SINN’s CEO engineer Lothar Schmidt and the technical developers Dr. Wolfgang Schonefeld and Dr. Ronald Boldt (CEO of SUG) approached the catapult. Would they find a “time bomb” ticking there, or merely an extremely durable watch? By comparison, aerobatic and jet pilots are exposed to acceleration forces of “only” 11 g. The DEKRA test was much tougher!
The initial inspection revealed that the dummy was fine, the watch that was knocked against the car body showed no external signs of wear, the spring bars of the watch band were just as straight as before the launch, and the watch was running.
The subsequent measurement on the timing machine showed how the mechanical movement withstood acceleration forces up to 81 g. Compared with the values recorded before the test, the new measurement data were practically identical. After the second test with the multifunctional chronograph 900, the DEKRA and SINN teams recognized that this was no “time bomb” ticking away, but a perfectly functioning, extremely robust mechanical wristwatch. Here as well, there were only minimal changes in the amplitude values in the range of hundredths of a second. In addition to robust watch mechanisms, hardened cases and sapphire crystal glass surfaces also contribute to the enduring beauty and reliable functionality of these watches in everyday use.
DEKRA has officially certified this unusual watch stress test.