Getting joint angles for passive urdf model

I'm a bit confused about how to get joint states. I'm trying to set up an inverted pendulum on a two-wheeled cart. I've successfully attached differential drive, and also control of the revolute joint for the pendulum rod. But, now I want to remove any actuators and simply access the state of the passive model. E.g., I want to view the angle of the rod as it collapses under gravity from vertical to about horizontal. Do I nevertheless need a joint_state_controller, or even position controllers? I'm simulating in gazebo, of course. The joint_states I see published are empty.
---
header:
seq: 105994
stamp:
secs: 2120
nsecs: 302000000
frame_id: ''
name: []
position: []
velocity: []
effort: []
---
Here are links to the relevant files as they stand now... URDF: [http://pastebin.com/MTkTgZmH]( http://pastebin.com/MTkTgZmH) YAML: [http://pastebin.com/eD0jK7AZ](http://pastebin.com/eD0jK7AZ) Launch: [http://pastebin.com/Zwrrb](http://pastebin.com/ZwrrbGtT) 
My setup...
ROS Indigo, Gazebo 2.2.6.
Linux Mint 17.3 (Rosa) 64-bit.
(3.19.0-32-generic #37~14.04.1-Ubuntu SMP Thu Oct 22 09:41:40 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux) I'd love to get angular position and velocity for the three joints (turret_to_rod, motor_to_wheelleft, motor_to_wheellright). Thanks!