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VIS (PR3)
fabian.arellano - 17:32 Tuesday 30 March 2021 (16355) Print this report
Comment to Tightening the locating clamps for the piano wire. (16348)

With Hirata-san and Washimi-san.

Summary: we successfully tightened the screws of the locating clamps of the piano wires. Tomorrow we will proceed to reassemble the system.

See pictures in album PR3 Remedying Work.

  • We removed the outer locating clamps for the tungsten wire. They are named:
    • -Y side: #5
    • +Y side: #8
  • We released the mirror from the RM. The gaps between the stop screws and the mirror were set relatively large for the sake of safety.
  • In order to lift the RM the lower side stop screws were not enough because of their orientations. We needed to improvised. The security structure has a hole right underneath the RM. We inserted an hexagonal tool (#8) through the hole and the tool was supported with a jack (M38 × 3 mm per thread). See this picture. The tip of the tool did not interfere with the tungsten wires underneath the RM.
  • We lifted the RM a total of 2 mm, in steps of 500 um (3 mm / 6). The tungsten wire became loose enough to be pushed aside and allow the insertion of the torque wrench into the inner locating clamps screws. This was a three persons job. One would move the jack up and the other two would move the lower side screws of the RM into provide support and avoid large tilts. We put a bubble level on top of the multi-purpose cube as a guide. See this diagram
  • Then we locked the mirror to the RM.
  • When tightening the screws we realized the four of them were completely loose.
  • We checked that the piano wires were in the grooves. It was difficult because access is very limited. They all seemed in the grooves.
  • We tightened with a torque of 2 Nm.
  • After another inspection we had the impression (from a blurry picture)  that one wire (-Y side) was not exactly within the groove but a little off. However, in other pictures it looks in place. We tried to measure the size of the remaining gap and tried to insert the thickness gauges. From 100 um to 10 um, none of them went in. This suggests the wire is properly clamped rergardless whether it's entirely in the groove or not.
  • We released the mirror from the RM.
  • We moved the jack down in steps of 500 um at the time. At each step we withdrew a bit the lower stop screws for the RM.
  • We removed the jack and the rod completely.
  • At the RM sides, we removed the PEEK spacers that were between the RM and the tungsten wires below the wire breakers.
  • When hanging free, it was clear that the RM was slightly tilted in pitch. The wires had more tension in the lower side. This is likely due to the absence of the coil bodies.
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