NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Making an artificial horizon
From: George Huxtable
Date: 2011 Jan 21, 00:16 -0000
From: George Huxtable
Date: 2011 Jan 21, 00:16 -0000
Jim Wilson wrote- | All this talk about mercury reminds me that the one hundred inch Mount | Wilson telescope is floated in mercury to minimize bearing loads. There's | not much of it, since a thin layer is all that's required. I thought the | idea ingenious. Yes, but not novel. It had been used for years in lighthouses, to support the heavy rotating lens/mirror assembly. The idea was to minimise the energy needed to drive it, which came from a falling weight, wound back up to the top of the tower at intervals, by hand. Also, to provide an effective draught-excluder in gale conditions. I imagine that in both examples, the flotation relieved the supporting bearing of most, but not all, of the load, so that the bearing still provided precise location of the rotating assembly. Perhaps it was the Mercury, rather than the isolation, which caused the dementia to which lighthouse-keepers were prone. George. contact George Huxtable, at george{at}hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.