Imported model error

I have exported a tank model from blender. Then, I tried to set the rigidbody component to it and used gravity on it. When it was dropping down, it appeared as:
http://imageshack.com/a/img673/9281/0gxU2B.jpg

Did I miss some configurations before I export it??
Thank you.

Try disabling the animator component and then test it once.

Red