Enclosure rotation on the Large Binocular Telescope

James Howard; Robert Meeks; David Ashby; Warren Davison; James Wiese; Jeff Urban; Rick Hansen; Jared Schuh

doi:10.1117/12.926493

17 September 2012 Enclosure rotation on the Large Binocular Telescope

James Howard, Robert Meeks, David Ashby, Warren Davison, James Wiese, Jeff Urban, Rick Hansen, Jared Schuh

Proceedings Volume 8444, Ground-based and Airborne Telescopes IV; 84443Y (2012) https://doi.org/10.1117/12.926493
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

After several years of operation the enclosure rotation system of the LBT is exhibiting wear and other performance issues that may impact operations. This paper reviews the system design and assumptions used, describes the current performance and observed symptoms, and discusses recent improvements made to improve performance and reliability. The rotating enclosure of the LBT is a 2200 ton structure riding on four bogies with a total of 20 wheels. Identified deficiencies include wheel bearing capacities, bogie misalignment, and rail loading. These are partially due to excess enclosure weight, which was supposed to be 1600 tons, but also due to design errors. The most serious problem was the failure of several wheel bearings. The bearings were not designed for field serviceability, so a crash program began to determine how to replace them. This got us back on sky quickly, but a review of the engineering calculations identified an error which led to the use of undersized bearings. A method of installing a larger bearing was found, and these have been installed. One set of bogie wheels are misaligned so severely the structure makes loud popping and banging noises when the direction of building rotation changes. The bogie needs to be rotated about its vertical axis, but there was no provision in the design for this. The circular rail the bogies roll on is wearing faster than expected. The rails are extremely difficult to replace, so the short term plan is to study the problem.

Citation Download Citation

James Howard, Robert Meeks, David Ashby, Warren Davison, James Wiese, Jeff Urban, Rick Hansen, and Jared Schuh "Enclosure rotation on the Large Binocular Telescope", Proc. SPIE 8444, Ground-based and Airborne Telescopes IV, 84443Y (17 September 2012); https://doi.org/10.1117/12.926493

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