# Revision history [back]

### URDF parser eliminating inertialess non-fixed links

Hello,

The urdf loader in Gazebo 9.0.0 seems to be eliminating all links, including a "revolute" link, that don't have an inertia tag. As an example, the following macro produces a model with model->GetJointCount() > 0:

<xacro:macro name="fin" params="name parent_link xyz rpy">
<!-- First, define the link -->
<link name="${name}_link"> <visual> <origin xyz="0 0 -0.0762" rpy="0 0 0"/> <geometry> <mesh filename="package://shiny_robot/mesh/fin.stl"/> </geometry> <material name="orange"/> </visual> <inertial> <origin xyz="0 0 0" rpy="0 0 0"/> <mass value="0.1"/> </inertial> </link> <!-- Now apply the offsets --> <joint name="${name}_servo" type="revolute">
<parent link="${parent_link}"/> <child link="${name}_link"/>
<axis xyz="0 0 1"/>
<limit lower="-${pi/4}" upper="${pi/4}" effort="10" velocity="10"/>
<origin xyz="${xyz}" rpy="${rpy}"/>
</joint>
</xacro:macro>


Interestingly, this keeps the link in place despite the inertial tag failing to parse because there's no inertial tensor. I note this is a change in behavior from earlier versions of Gazebo. Anyone know what's up with this?