mujoco

<mujoco>
  <extension>
    <plugin plugin="mujoco.sdf.gear">
      <instance name="gear1">
        <config key="alpha" value="0"/>
      </instance>
    </plugin>
    <plugin plugin="mujoco.sdf.gear">
      <instance name="gear2">
        <config key="alpha" value="15"/>
      </instance>
    </plugin>
  </extension>

  <asset>
    <mesh name="gear1">
      <plugin instance="gear1"/>
    </mesh>
    <mesh name="gear2">
      <plugin instance="gear2"/>
    </mesh>
  </asset>

  <option sdf_iterations="5" sdf_initpoints="20"/>

  <default>
    <geom solref="0.01 1" solimp=".95 .99 .0001" friction="0.2"/>
  </default>

  <statistic meansize=".1"/>

  <include file="scene.xml"/>

  <worldbody>
    <body pos="0 0 .2">
      <joint name="freewheel" type="hinge" damping="1000" axis="0 0 1"/>
      <geom type="sdf" name="gear1" mesh="gear1" rgba="0.4 0.4 0.4 1">
        <plugin instance="gear1"/>
      </geom>
    </body>
    <body pos="2.85 0 .2">
      <joint name="drive" type="hinge" damping=".1" axis="0 0 1"/>
      <geom type="sdf" name="gear2" mesh="gear2" rgba="0.7 0.7 0.7 1">
        <plugin instance="gear2"/>
      </geom>
    </body>
    <light name="left" pos="0 0 1"/>
    <light name="right" pos="1 0 1"/>
  </worldbody>

  <actuator>
    <motor name="drive" joint="drive" ctrlrange="-1 1" gear="1500" ctrllimited="true"/>
  </actuator>
</mujoco>