3D motion blur will use the motion from one frame to the next - if you're setting your beginning and end pose in frame 1 and 30, you'll end up with very minimal differences between the frames, thus barely any blur. As Raven wrote - set your start and end pose in frames 1 and 2, enable 3D motion blur in the render settings (use FireFly) and render frame #1. The quality of the motion blur is controlled with the pixel samples setting.