FLWO 48" INCH TELESCOPE REALUMINIZING PROCEDURE

Revised 6/22/00 NC

Items needed:
*Notify SO and confirm that schedule is OK.
*Sign Agreement and forward to SO.
*Issue PO for the work.
*Aluminum mirror lifting device
*Yellow bar
*Yellow hoisting tool
*Yellow milk stool
*Mirror box and lid
*Plastic tarps to cover mirror box and cell in case of rain
*Foam mirror cover
*Crown fork lift
*Pallet jack
*2 short lifiting straps
*Mechanical Hoist

Removal Procedures

  1. Remove Dec primary bearing cover (west fork).
  2. Move telescope to ~60 north so that access to the western cell bolts
     (particularly the southern most of the three) can be had. Loosen the
     two bolts. This is done because these bolts can't be fully accessed
     when telescope is at zenith.
  3. Return telescope to zenith.
  4. Pin telescope at zenith.
  5. Bring secondary mirror all the way toward primary (low numbers) with
     the telescope control program.
  6. (optional) Remove all filters from top box, using TCS.
  7. Move all guide probe motors to 0 using TCS and disconnect motor power.
  8. Remove instrument and cabling. Disconnect cabling to top box.
  9. Remove north electronics mounting plate.
 10. While standing on closed mirror doors, remove seconday baffle.
 11. Remove secondary mirror by removing the two bolts that hold the collar
     on, One person should hold the mirror while the other loosens the
     bolts.
 12. After the secondary is moved to a working surface, remove secondary
     mirror mount by removing the 6 screws that hold the washers on at the
     front, and gently twist the mirror with respect to the mount until the
     mirror can be twisted off.
 13. Place secondary mirror in box for shipping
 14. Remove top box assembly. Raise the lifting table to the level of the
     top box, and then remove the bolts that hold the spacer plate onto the
     cell.
 15. Remove the primary baffle.
 16. Remove cell cover plates.
 17. Deactivate the axial actuators by turning allen head screws until
     counterweights are pinned to cell.
 18. Install yellow bar at top ring using two short straps around the top
     ring. Bar should be aligned north/south. One person will remain on top
     of mirror doors to work with hoist.
 19. Install mechanical chain hoist.
 20. Bring chain down to floor level, and hook it onto the yellow hoisting
     tool (flange with stem).
 21. Raise hoisting tool to bottom of mirror cell. Bolt tool to cell.
     Tighten up chain.
 22. Loosen and remove cell bolts. Note that the rightmost bolt on the East
     side is shorter than the others.
 23. Lower cell to about 3 feet off the floor. Be careful of cell/telescope
     clearances.
 24. Working above the mirror, remove the earthquake/baffle ring.
 25. Remove the radial dial indicators.
 26. Remove the radial actuator connections to the radial load spreader bar.
 27. Back off the radial hardpoints. (The actuator covers will have to be
     removed for this purpose.)
 28. Place milk stool (3 legged cart) underneath cell, and line up posts
     with holes in cell that allow passage to mirror.
 29. Lower the cell onto the cart, making contact with the glass.
 30. Slowly lower the cell until the mirror extends out of the cell by about
     1.5 inches. The cell/tool should now be sitting on the cart.
 31. Install the aluminum triangular mirror lifting fixture. Lift the mirror
     off of the milk stool.
 32. Remove the radial load spreader bars from the mirror.
 33. Roll the cell out of the way. Take care not to run a wheel over a
     trench where the floor is weak.
 34. Use the pallet jack to roll the box under the mirror.
 35. Lower the mirror into the box.
 36. Remove the lifting fixture
 37. Put the top on the box.
 38. The mirror box is 64"x64"x 19". The 19" includes the blocks on the
     bottom to provide fork lift access. The box weighs 550 pounds. The
     mirror weight 330 pounds. The total weight of the box and the mirror is
     885 pounds.
 39. Load the mirror box in the flat bed truck. The Crown 15M hand forklift
     will lift 1500 pounds at 20". There is a chance that the mirror box
     could tip forward, therefore, the mirror box should be attached to the
     fork lift with a harness. The height of the loading dock is 25" from
     the drive. Lady's bed is 40" from the drive. The front part of the
     mirror box is first set in the truck and then the mirror box is pushed
     in with the fork lift and people. This works better than it sounds.
 40. No special padding is required. Drive flat bed truck to Sunnyside.

Reinstallation

In general, the reverse of disassembly. The following notes may be useful.
When lifting the box from the truck and moving into the dome, be certain
that the 4x4's on the box clear the front fork wheels as well as the forks.

Install bars on mirror before installing mirror in cell. The pucks on the
glass are not quite in the right place, thus the bars must be offset
slightly. The S and SE bars are centered; the N and NE bars should be offset
3/32 clockwise w.r.t. the cell; the NW and SW bars are offest 3/32 counter
clockwise.

Remove radial actuators before installing mirror, to avoid obstruction
problems. Also remove radial dial indicators before installation,

Get rotation correct before lowering mirror all the way into cell. Now lower
mirror onto axial hard points.

To get level correct, first remove axial hard points or at least lower them
so that mirror rests on the cell (nylon pads).  Reset the axial dial
indicators.  Now raise up mirror using the hard points, making sure
indicators read the same value.  It's a good idea to check level from top
surface as well.

Mirror should rest on hard points giving load cell readings of around 100
pounds. If lower than this, mirror may be stuck on something. Install axial
actuators before doing final centering, to allow ease of motion.

Check out the hysteresis of the axials by tilting the cell + primary without
installing the radial counterweights, only install the radial hardpoints.

Height of mirror: Edge of mirror should be 1.25 inches below mirror cell
mounting flange. According to drawing, the bottom of the mirror should be
1/2 puck thickness above nylon pad, or 0.0875". This corresponds to 2.8
turns on the screw adjustment for the axial hard point. So once the hard
point makes contact, in principle, one would turn each hard point 2.8 turns
more to put the mirror at the right height.

Move mirror radially via moving the radial hard points, monitor the
re-installed dial indicators for motion. Hard points are quite springy, so
some relaxation must occur before taking readings.

Radial actuators should be installed with 3 washers to space the actuators
out. Bearing that attaches to bar has two screws. These must allow some play
when attached to bars. Turn screws until 1 kg of force is achieved at
counterweight center of gravity.

Remember to install short bolt rightmost of the three on the East side. Only
two bolts are installed on this side (middle and rightmost). Put these two
in with fingers first, then when telescope is movable, move telescope far
south so that a wrench may be used for final tightening.

********************************