Testing Large Transmissions

The design of large, high-power, helicopter drive systems requires the support of advanced testing techniques. As size increases, it empha­sizes the importance of understanding the behavior of gears and bearings operating at high velocities and centrifugal forces. L'oad paths are long and complex and are subject to significant thermal- and stress-related deflections. Undamped high­frequency vibratory forces can severely impact gear integrity. Development of large transmissions has been an ongoing program at Boeing Vertol under U.S Army, DARPA, and NASA sponsorship. Test requirements include the need to understand the relationship of tooth contact patterns to the stress field, as well as to evaluate the effects of vibrato­ry excitations at operating speed. To accomplish this, new instrumentation techniques have evolved to measure, transmit, and reduce large amounts of data from multiple meshes. The purpose of this paper is to provide a brief overview of requirements, procedures, and techniques devised for the evaluation of large transmissions, including the use of multiplex telemetry systems. This work is being carried on with the sponsorship of the Applied Technology Laboratory, AVSCOM, Fort Eustis, Virginia, and under the technical cognizance of Millard Pedersen of that facility.