Design Engineering

Trunk Lid Mechanism Design Defect

Case Synopsis: A vehicle owner was leaning into the open trunk of his late model sedan, reaching for groceries, when the trunk lid suddenly closed, striking him in the back causing permanent nerve damage.  The owner sued the auto manufacturer claiming the trunk lid mechanism was designed defectively and in a way that permitted the lid to close unexpectedly.

Expert Analysis: An engineering evaluation followed, and included an inspection of the incident vehicle, an analysis of trunk lid hinge and support mechanism, and research of similar trunk lid designs by both the defendant manufacturer and its competitors. The inspection revealed that the vehicle, and in particular, its trunk lid hinge and support mechanism, was in the same condition as it was when it left the control of the manufacturer, and that the trunk lid was equipped with a factory-installed airfoil, or “spoiler.”  Testing revealed that only a few pounds of force were required to initiate lid closing and that once the lid moved a few inches from the open position, the lid would free-fall closed without any resistance.

Subsequent research revealed the vehicle design had evolved since that model’s introduction a few years earlier.  In particular, the trunk design originally did not include a spoiler; however, a review of the part numbers for the hinge and support structure revealed that the support springs remained the same.  Calculations demonstrated the trunk support springs were adequate to support the lid without the spoiler; however, additional calculations combined with the inspection testing results showed the springs were inadequate to support the combined weight of the lid and spoiler.

Result: These observations and results provided the basis for the expert conclusion that the vehicle possessed a design defect and facilitated an early settlement.

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