6. Always ensure that your lens is level and plumb. To determine whether
the lens is level, place a torpedo level on the base. Check in two places
using the "T" method. Larger lenses require that a line be stretched tightly
across the base ring of the lens. A hanging level (line level) is used to
determine if the lens is plumb. Repeat at 180 degrees to ensure that the
lens is level in both directions. By looking up from the center of the larger
lenses, you can determine if the lens is out of plumb (with respect to the
torque applied to the lens may cause it to twist or rack causing lens
elements to loosen and possibly fall out. Some large lenses use roller
supports at the top of the lantern room. Be sure that the chariot wheels on
these upper supports move freely, do not have excessive clearance, or
bind on the race as it may cause the lens frame to twist allowing lens
elements to loosen. If problems are apparent, contact your CEU for
assistance.
Figure 3-3. Out of Plumb
7. Inspect the chariot wheels and bearing surface for indications of abnormal
wear. Observe the rotation mechanism in motion, listening for any noise
such as creaking, chatter, groaning, or squeaking that may indicate
improper wear. Ensure all wheels are rotating freely and not dragging, and
look for metal shavings and uneven wear spots on wheels and bearing
surfaces. Some wheels are crowned to minimize wear while traveling in a
circular path while others are tapered. Once this crown or taper is worn
off, the horsepower requirements to rotate the lens increase and evidence
of wear (metal shavings, see Figure 3-4) is more apparent. Measure the
3-3
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