Fatigue Life for Small Gear Boxes


The static torque Four-Square method of testing gear boxes is economical and can be effective. Disadvantages inclued: (1) reduction of torque due to gear and bearing wear; (2) variation of load during each revolution; and (3) application of load before a dynamic oil film and dynamic equilibrium are established. A strain gaged shaft and slip ring assemgly were used to determine the significance of these difficulties. Quantitative indications of the pertinent parameters were determined for a typical type of static torque facility. Component wear reduced the torque as much as 36 percent. The torque varied plus or minus 6. 7 percent in one revolution. The torque dropped as much as 24 percent from static to dynamic conditions. Frequent retorquing can compensate for losses due to component wear. Testing gear boxes which have previously been used for a break-in-period can reduce the variations that occur in a given revolution, and will minimize the change that occurs in the static-to-dynamic transition.


Mechanical and Aerospace Engineering

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Article - Journal

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© 1979 American Society of Mechanical Engineers (ASME), All rights reserved.

Publication Date

01 Jan 1979

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