Determining the cause of an automobile accident is often encountered by the claims analyst. Was the accident a result of driver error, actions by another party or a mechanical failure of the vehicle? Detachment of a wheel from a vehicle, which is the subject matter of this case study, is known to cause severe accidents. Figure 1 shows the result of wheel detachment which caused a vehicle to roll over with severe injuries suffered by the occupants.

The left front wheel became detached, causing loss of control of the vehicle. Figures 2a & 2b are views of a typical wheel spindle which secures the wheel, bearings and hub to the vehicle. A castle nut (also called a castellated nut or slotted nut) with cotter pin is used to secure the wheel hub to the vehicle. (Figure 2a)

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