ira_laser_tools merger doesn't subscribe to topics from laser in gazebo

Hey together, please see edit #1 and #2. The node for the laser scanner won't subscribe to the topics given in its parameters in the launch file. But the scan topics are published correctly. I am trying to merge 3 laserscans together to one. For this I am trying to use the ira_laser_tools packaged and in this the laser_multi_merge. My setup is following: 3 simulated Lasers in gazebo mounted to my robot, publishing 3 different topics. I am able to view the scan topics in rviz with no problem. After launching the laser_multi_merger with following launch file part: `rostopic list` comfirms that the topics `/scan_hokuyo1` `/scan_hokuyo2` and `/scan_ibeo1` are being published. It also shows the topic `/scan_multi_merged`, but if I subscribe to it whit `rostopic echo /scan_multi_merged` the following output appears: rostopic echo /scan_multi_merged WARNING: no messages received and simulated time is active. Is /clock being published? If i enable via rqt the debug level of the node it also says that something is wrong with the /clock topic. Output of ROS_DEBUG message: [DEBUG] [1453887963.432518126, 100.157000000]: Incoming queue full for topic "/clock". Discarding oldest message (current queue size [0]) Can someone of you lead me to the right way and show me my faults I did? Thanks in advance :) Edit #1 Output of `rosnode info /laserscan_multi_merger` rosnode info /laserscan_multi_merger -------------------------------------------------------------------------------- Node [/laserscan_multi_merger] Publications: * /laserscan_multi_merger/parameter_descriptions [dynamic_reconfigure/ConfigDescription] * /merged_cloud [sensor_msgs/PointCloud2] * /rosout [rosgraph_msgs/Log] * /laserscan_multi_merger/parameter_updates [dynamic_reconfigure/Config] * /scan_multi_merged [sensor_msgs/LaserScan] Subscriptions: * /tf [tf2_msgs/TFMessage] * /tf_static [tf2_msgs/TFMessage] * /clock [rosgraph_msgs/Clock] Services: * /laserscan_multi_merger/set_parameters * /laserscan_multi_merger/set_logger_level * /laserscan_multi_merger/get_loggers contacting node http://aschultz-ThinkPad-T450s:42260/ ... Pid: 21244 Connections: * topic: /rosout * to: /rosout * direction: outbound * transport: TCPROS * topic: /clock * to: /gazebo (http://aschultz-ThinkPad-T450s:33525/) * direction: inbound * transport: TCPROS * topic: /tf * to: /vehicle_state_publisher (http://aschultz-ThinkPad-T450s:55570/) * direction: inbound * transport: TCPROS * topic: /tf_static * to: /vehicle_state_publisher (http://aschultz-ThinkPad-T450s:55570/) * direction: inbound * transport: TCPROS Edit #2: Changed launch file because Laser merger is not subscribing to topics Output of `rostopic info /scan_hokuyo1 /scan_hokuyo2 /scan_ibeo1` rostopic info /scan_hokuyo1 Type: sensor_msgs/LaserScan Publishers: * /gazebo (http://aschultz-ThinkPad-T450s:51633/) Subscribers: * /rviz (http://aschultz-ThinkPad-T450s:55316/) rostopic info /scan_hokuyo2 Type: sensor_msgs/LaserScan Publishers: * /gazebo (http://aschultz-ThinkPad-T450s:51633/) Subscribers: * /rviz (http://aschultz-ThinkPad-T450s:55316/) rostopic info /scan_ibeo1 Type: sensor_msgs/LaserScan Publishers: * /gazebo (http://aschultz-ThinkPad-T450s:51633/) Subscribers: * /rviz (http://aschultz-ThinkPad-T450s:55316/)