Subject: 3.5-m enclosure wheel repair

From: gillespi@galileo.apo.nmsu.edu

Submitted: Thu, 18 Jan 1996 16:36:59 -0700

Message number: 41 (previous: 40, next: 42 up: Index)

To all 3.5-m users:

Most of you know that the enclosure (aka "dome") wheels for the 3.5-m are
cracked and getting worse to the point that we fear that a wheel will start
spalling, leaving chunks on the rail and causing significant damage.  This
could happen at any time and would necessitate closing the telescope until
repairs are made.  We are monitoring the cracks with frequent wheel
inspections and limiting the use of azimuthal slews.

An attempt to repair the worst wheel (of 4) in place was made in November
but was ineffective because of unexpectedly high forces needed to remove
the wheel shaft from its bearings.  A new plan which involves removing the
entire wheel assembly is being devised and will be implemented by L&F
engineer Terry King.  Terry was at the site yesterday and today to assess
their plan, and feels that the single wheel repair could be accomplished
during or around the scheduled 3.5-m shutdown 29 January through 4
February.  The actual start and finish dates are not certain at this time,
and may require pre-empting scheduled science programs.  Repairing the
other 3 wheels would be done at a later time because parts with long
lead-times would need to be fabricated.

More will be posted when available. It is also our decision based on
several recommendations (including Terry's), that we will continue
telescope operation until the shutdown, provided the wheels remain intact.

Our thanks also to Patrick Waddell and the engineering group at UWashington
for their advice and help in getting L&F to respond quickly to our
difficulty.

Bruce Gillespie


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