When the engine reaches the highest speed, the mixer drum rotating speed should be lower than 15rpm. Otherwise, the drum body and the mixing blades will be premature worn down. During working, the rotating speed of the drum should be adjusted by the operation system. During unloading, the rotating speed of the drum also should be adjusted higher than 10rpm to ensure the quality of the mixing material. There is a round nut on the drum roller which is used for setting and adjusting the slack of the bearings.
