Experience indicates that the trial weight should be approximately equal to the weight of the rotating parts divided by 10,000. Ideally, the weight should be located 180º plus the lag angle
- in the direction of rotation - from the high spot to counter the unbalance. Therefore, the mass should be attached to the rotor arm nearest this location. In most cases, the lag angle will be unknown and in that event assume it to be 45º. Throughout this bulletin, angles are measured in the direction of unit rotation with respect to rotor arm No. 1 - the reference point.