In a foreign country hence communication is not good. Customer low speed balanced a 45000 kg generator rotor at 250 rpm. IRD print out tabulates the calibration runs (ie micrometers and phase for each plane)but no listing of calibration weight used or angle. When asked the reply was "something was placed on top of the pedestal to do the calibration and it was correct' was the answer. I am fairly familiar with the IRD balance machines and have always noted the use of a 'test weight and angle' to complete the balance machine's calibration prior to undertaking the corrections if necessary. Have I missed something!!!!!

IRD have/had? a as far as I know very unique/special thingy to make soft machines to compete with stiff as test runs was not required as a builtin "unbalance generator" a rotating excenter is builtin or mounted on the piedestals to create a known force at a known speed and thereby "calibrating" basically using the effect of mass etc. of the rotor on the known vibration force and thereby avoiding testruns. It´s not as accurate as real testruns but do work. I have used it. Olov

These "shakers" were mounted on the rear of the bearing assembly and were/are used to measure the effect of a known amount of unbalance by operating each side independent of the other pedestal. They are technically known as rectilinear shakers and are simply a couple of nylon gears with 1/2 moon weights attached so that they only show movement from front to back, just as the suspension senses movement of the unbalanced part. They are operated in a static mode before spinning the part and, thus, would give a first run readout of the unbalance of the part once spun. As OLI says, they work well for rotors between bearings, but not quite as accurate as actual trial masses used in the part itself. They were used with the IRD 220, 260 and 290C instruments.