Hello List

I'm a newbie to Gazebo and have been experimenting with it for the last 
couple of days.
So now I have a small problem, I wrote a simple 4 wheels robot (attached 
to this email) which spawns perfectly in gazebo. Now whenever I apply a 
body wrench, I get the following warning in
Gazebo
"[ WARN] [1299848525.581625793, 11872.099000000]: ApplyBodyWrench: 
reference frame and reference_point not implemented yet, force is 
defined and applied at the body frame"

rosservice call gazebo/apply_body_wrench '{body_name: 
"car::left_front_wheel" , wrench: { force: { x: 0.1, y: 0, z: 0 } , 
torque: { x: 0.0, y: 0 , z: 0 } }, start_time: 10000000000, duration: 
1000000000 }'

The car moves actually the way I want, but it I'd understande from that 
warning that the force is applied to the base_link and not to the wheel 
the way I want. Or did I miss something?

Thanks alot for the help
Best regards
Moataz