# Revision history [back]

### Ball joint in sdf not moveable

Hi, I have this universal joint that works that I want to convert to ball type.

The joint description:

<joint name="forearm1_arm1" type="universal">
<parent>arm1</parent>
<child>forearm1</child>
<axis>
<xyz>0 1 0</xyz>
</axis>
<axis2>
<xyz>1 0 0</xyz>
</axis2>
<pose> 0 0 0.17 0 0 0 </pose>


</joint>

Now when I change it to type ball the joint becomes fixed.

<joint name="forearm1_arm1" type="ball">
<parent>arm1</parent>
<child>forearm1</child>
<pose> 0 0 0.17 0 0 0 </pose> </joint>


There's no moveable axis after changing it to ball.