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The National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST) located on the summit of Haleakalā, Maui is the largest solar telescope in the world. Housing a 4-meter off-axis primary mirror and a highly advanced adaptive optics system, DKIST is enabling observations of specific regions of the Sun in higher resolution and greater detail than any preexisting ground-based telescope. The DKIST Enclosure Azimuth Mechanism is responsible for accurate positioning of the Enclosure in azimuth and provides a second degree of freedom to the altitude movement of the Enclosure Shutter which enables an overall position accuracy of 19 arcmin point-to-point at the Enclosure Aperture. The mechanism is primarily comprised of sixteen track rail segments, eight driven bogies, and two idler bogies, and it serves as the interface between the fixed support building Ring Girder structure and the rotating Enclosure structure. Visual observations and control system torque data have shown evidence of a loss of contact at the interface between the individual bogie wheels and the track rail. This loss of contact results in imbalanced loading conditions that impact performance and reliability as loads are varied in proportion to the number of wheels in contact. In addition, visual inspections have shown early indications of rolling contact fatigue at specific azimuth locations of the track rails due to high contact stresses. As a result, a project was initiated to improve load sharing and maintain tracking accuracy by minimizing pointing error deviations that result from rail flatness tolerances variations, unanticipated mechanical deformations from load imbalances, and varying control systems demands. In addition, equalizing the load balance will reduce unintended fatigue loading of the structural and mechanical components as well as reduce contact stresses in the rail sections improving overall mechanism reliability. The investigation, implementation, and evaluation of this process is presented herein.
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