454. Weight Synthesis in Preliminary Design
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Paper
Abstract
The method and machine for performing actual tests of mass moment of inertia upon various types of hardware, as discussed in this paper, were developed by the Research and Advanced Development Division of Avco Corporation. In its present configuration, the machine is extremely accurate and relatively simple to operate. Basically the machine consists of a turntable which supports a test article. Rotary motion is imparted to the turntable by means of a falling weight attached to a cable which is wrapped around the turntable perimeter. Acceleration of the turntable, including test article, is measured when the weight is falling and deceleration is measured during the coast down which occurs after the weight has disengaged. These measured values are instantaneously fed into an integrating digital voltmeter and printer. The read-out, in radians per second squared, is converted to moment of inertia by means of a modified form of the equation for torque ( T = I a ). To calibrate the system, a standard was obtained by constructing a slug consisting of a simple geometric shape whose mass and moment of inertia could
be accurately measured and calculated, During a preliminary calibration run on the latest version of the moment of inertia machine, accuracies of 0. 04 percent were obtained. The system could be conservatively rated at 0. 20 percent. The fact that the new machine will give this accuracy with a single run represents a significant improvement. With the older machines, it is necessary to take the average of several runs to approach this accuracy. ‘The missile and space industry should find many applications for a moment of inertia machine of this indicated accuracy.
