1704. A New Mass Properties Program for the IBM PC and Compatibles


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A B Burns: 1704. A New Mass Properties Program for the IBM PC and Compatibles. 1986.



Analyzing the mass properties of a physical object entails two basic steps: 1) configuring an analytical model consisting of geometric elements whose shapes, sizes, locations and orientations reasonably reflect the distribution of mass within the object, and 2) computing, transforming and integrating the mass within properties of the several shapes. A recently published, personal-computer-based program is described which trivializes the burden of the second part of the process – the computation – and, in so doing, substantially frees the constraints long imposed by the computation burden on the first part of the process – configuring the analytical model. The basic capabilities of WCGI, a forgiving mass properties program for the IBM PC and compatibles, are summarized. Its fifteen geometric modeling elements include rectangular, conical, ellipsoidal, and prismatic forms and accommodate positive and negative densities and optional element weight specification. Special ”given” modeling elements provide for specifying elements whose properties are already known. WCGI’s powerful coordinate transformation capability, which includes translation, rotation, scaling, mirror imaging, and concatenations thereof, is described and illustrated. The required and allowable contents of the input data file needed for program execution are demonstrated with an example which also illustrates the content of the resulting output files. The principle solution file reports the weight of the whole body, its cg location, its moments and products of inertia reckoned with respect to the reference axes, and the magnitudes and orientations of its principal moments of inertia. A second output file reports, in a compact format suitable for subsequent use in input data files, the inertia properties of each of the several elements (or selected groups of elements) included in the model. The program’s comprehensive syntax checking and associated error diagnostics are illustrated. Product ”radius of gyration” is introduced as a convenient, physically meaningful concept for representing product of inertia. The paper closes with the author’s own appraisal of the program’s utility and includes two generalized recommendations to the weight engineering community.


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