While the technical and performance considerations of an observatory’s azimuth rotation system (ORS) are fundamentally distinct from those of a telescope’s azimuth rotation system (TRS), their impact on the capital cost, maintenance cost, and overall telescope uptime and reliability metrics can be equally impactful. Furthermore, due to its inherently larger scale, higher loads, extreme stiffnesses, and exposure to a larger variety of environmental forces, the design and construction of an ORS poses unique technical challenges that merit an appropriately unique approach. In particular, construction imperfections can have an unexpectedly outsized impact on ORS mechanisms loads, leading to underestimated design loads and premature component failures. In response, this study proposes a methodology of analysis, design, and construction of an ORS that is fundamentally distinct from that of a typical TRS. The need for extremely tight tolerances and high precision is deemphasized, in exchange for a more rigorous analytical approach that ensures that all performance and reliability objectives can be achieved while following tolerance schemes more typical of the commercial built environment. To do so, the proposed methodology derives mechanism and structural loads by pairing typical building codes with a Monte Carlo analysis; the presented techniques can be used to derive loads for various general arrangements of ORS mechanisms, including a variety of restraint schemes, structural and mechanism compliances, and tolerance envelopes. Representative simulation results generated with SAP2000 are presented along with general design guidelines for detailing an observatory rotation system with economical tolerances, reduced maintenance demands, and high long-term reliability.
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