Drag the rotor balancing machines have lap band Transmission drag, drag and self-drive coupling. 
Drag ---- lap band is the use of rubber endless belt or silk endless belt, dragging the rotor from the motor pulley, thus dragging the circle with the requirements of the rotor surface must have a smooth cylindrical surface, advantages lap belt does not affect the drag rotor unbalance, high precision balance. Lap Band balancing machines 
Drag ---- coupling joints using the balancing machine shaft coupled to the rotor. Characterized by a coupling for the dragged irregular outer rotor, large torque can be transmitted, for large windage drag rotor fans, etc., are disadvantages of the drag coupling joint itself will unbalance rotor impact (and therefore its coupling to the balanced before use), will be introduced to balance the accuracy of interference, in addition to a large number of connections made to accommodate the different types of the disc rotor. Single vertical balancing machines