Balancing of high-speed shafts

US4170896A · kind A · utility

Assignee

• The Summa Group Limited · US

Inventor

• Gregory J. Korkosz · Malibu, US

Key dates

• Filing date: Mar 20, 1978
• Grant date: Oct 16, 1979
• Expiry date: Mar 20, 1998

Classification

• Technology area (CPC G): Physics
• CPC primary: G01M1/32
• WIPO field: Measurement
• WIPO sector: Instruments

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 we…