The locomotion device is an input interface, which can sense the walking pace and direction of the user, for the virtual reality system. This paper presents a new type of locomotion device called Omni-direction Ballbearing Disc Platform(OBDP), which allows the user to walk naturally inside the virtual environment. Instead of using the 3D tracker, arrays of ball-bearing sensors on a disc are used to detect the pace and an orbiting frame to identify the walking direction. No other sensor, except the head tracker to detect the user's head rotation, is required on the user's body. In addition, the ball-bearing on the sensor slips the user's foot back to the center position of the disc. A prototype of the overhead crane training simulator that fully explores the advantage of the OBDP is also designed and introduced in this paper.