Hello.

I am a new user to Gazebo and trying to create a mobile robot with universal omni-wheels in Gazebo. Followings are the steps which were followed.

1. Parts (Wheel hub, Roller, Base) were created in solidworks.
2. The parts of the robot were exported into .wrl format.
3. The .wrl parts were imported into MeshLab and saved as .dae files.
   
4. The .dae files were imported into Gazebo.
5. One complete universal omni-wheel was configured (Revolute joints) with 28 rollers and saved as a model file (.config and .sdf). [Intention was to use the saved wheel model file again and again]
6. In a new Gazebo file, the saved omni-wheel and base model files were imported and tried configuring joints using "Relative Pose" option under "Create Joint". But it "Relative Pose" option is frozen.

Any suggestion on this matter is highly appreciated. !