The invention relates to a mechanical speed controller used for controlling running speed of a tube cleaner and a defect detection device in a
pipe cleaning and defect detection process of
natural gas pipes on active service and a pressure test and discharging process of pipelines under construction. The controller can control the speed of the tube cleaner to be in a certain range and solve the problem that the existing tube cleaner is impacted due to the fact that the speed cannot be controlled and a
detector is inaccurate in detection due to the fact that the speed is too high. Four support wheels are arranged at two ends of a
barrel body respectively, and two speed collection wheels are symmetrically arranged on two sides of the
barrel body through support rods and connected through a spring. A belt wheel A is coaxially installed on the speed collection wheels and connected with a belt wheel B on the end portion of a central shaft through a belt. A sleeve is installed in the middle section of the central shaft, a fixed
barrel is installed on the
tail section, and a rotating barrel is sleeved on the outside of the fixed barrel. One end of a connection rod A and one end of a connection rod B are hinged to a
mass block, the other ends of the connection rod A and the connection rod B are connected with the sleeve and the rotating barrel respectively, a connection rod C is connected with the end portion of the fixed barrel and a friction block, and a connection rod D is connected with the end portion of the barrel body and a friction block. The speed controller is simple in structure, free of delaying, safe and reliable and has no electric appliance components.