Balancing_Machine_Drives

Balancing machines typically employ one of following three different drive configurations 
to spin the rotating assembly: 
  • Direct end drive 
  • Wrap-around belt drive 
  • Tangential belt drive 

Direct end drive: 
The direct end drive or universal joint connection is typically used with rotors having 
large moments of inertia or high windage losses. This drive design will transmit high 
torque forces for fast acceleration and safer braking. To attach the drive shaft, the rotor ends must be prepared to accept the U-joint directly or with an adapter. With this design, the drive system becomes a part of the rotor and must be considered in the balancing accuracy of the system. Before this type of the drive can be used to accurately balance a workpiece, the U-joint assembly, itself must be balanced. The desired end result is to be able to rotate the U-joint assembly 180 degrees without any variance in the balancingmachine readout. 

Wrap-around belt drive: 
For rotors weighing below 2250 kilograms and with at least one smooth surface, a wrap- around belt drive works very well. For this drive configuration, 2250 kilograms is about the maximum rotor weights that will allow adequate torque transmission to bring the rotor up to the required balance speed. A 180-degree wrap is required to provide adequate torque transmission to rotate the rotor and keep the applied torque in the vertical plane of the balancing machine pedestal. A belt drive of this type is considerably more accurate then a direct coupled end drive in that the drive mechanism does not influence the workpiece balance. 

Tangential belt drive: 
A tangential belt drive, either under the rotor or in an over-arm configuration, is frequently used in smaller capacity, high volume production oriented balancing machines for rotors weighing less than 450 kilograms. This type of drive configuration is used to bring the rotor up to the required balancing speed and the then the drive arm is moved away from the rotor and the unbalance data is collected.