The present invention relates to a system to float an automobile on water. In particular, a method of downloading multimedia content from a server to a user equipment and a system for performing the method are disclosed. The tool changer further comprises a service life end detecting section for counting the number of times of the operation performed by the tool changer mechanism and judging whether or not the count of the number reaches a reference operation number serving as a basis for the detection of the end of the service life of the bearing.