879. A New Design Weight and Center of Gravity Determining Fixture

Paper

Abstract

The Ormond Inc. Mass and Center-of-Gravity determining system, model
WCG-91-2-10K was uniquely designed by Ormond Inc., Santa Fe Springs, California,
under the technical direction and to the specifications of Thiokol Chemical Corporation.
It is being used to measure mass and determine balance data for Minuteman Third Stage
loaded chambers and pre-fired and post-fired motor assemblies. A description of the
equipment, the principles of operation, calibration data and technique, accuracies,
errors, and repeatability of the fixture are presented. The system is the largest device
ever built which uses a mechanical beam balance for measuring mass and a separate
and distinct system composed mainly of two electronic load cells for measuring center of
gravity moment. The load cells measure only the off center force and, therefore,
their measurement of the center-of-gravity moment is independent of the amount of
weight applied to the table. Calibration data obtained during the past year demonstrates
a 3sigma mass measurement repeatability of 0.023 percent and an accuracy of 0.032 percent
or better of applied load throughout the usable range of 500 thru 10,’OOO pounds. Obtained
center-of-gravity accuracies are 0.013 in. longitudinal, and 0.005 in, lateral and vertical
(3sigma ).