Balancing of high-speed shafts

Details Balancing of high-speed shafts Balancing of high-speed shafts

1978-03-20

1979-10-16

Gill, James J.

Measuring and testing

Rotor unbalance

73462, 73468, 73622, G01M 132

Patent

active

041708962

ABSTRACT:
In some helicopters power is transmitted from a gearbox adjacent the engine to the tail rotor by a long shaft. To minimize weight, a tubular shaft is used, which rotates at supercritical speeds. Vibrations resulting from shaft unbalance are magnified by resonance as the shaft passes through its critical speeds making it essential that the shaft be finely balanced. This is accomplished by slowly rotating the shaft about its axis while measuring at a chosen station along its length both the wall thickness of the tubular shaft and the distance from a fixed reference plane to the outer surface of the shaft. From these data are determined the local cross sectional area and the location of the center of gravity at the chosen station. From the latter two quantities are determined both the amount of counterweight required and its required angular location around the shaft, for the chosen station. The measurements are repeated at a large number of stations along the shaft. Self-adhering aluminum tape is used as the counterweight, which is applied to the outer surface of the shaft in a continuous manner along its length. The number of layers of tape and their width determine the amount of weight applied. It is assumed that the variation in mass density of the shaft is negligible.

REFERENCES:
patent: 3071972 (1963-01-01), Koenig
patent: 3426437 (1969-02-01), Rebhun et al.
patent: 3604248 (1971-09-01), Altmann et al.
patent: 4114456 (1978-09-01), Dory

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