My Shutter modification for Wye Mountain Observatory.

The Modification consists of a furniture wedge kit (about $2.00) and a little hand work.
View of the modified furniture wedge kit mounted on dome.

History: The shutters worked fine for the first year I used the dome. Then one day on a observatories Yahoo group someone had to go and complain that theirs was jamming. Well I proudly proclaimed how well mine were working. A couple of days later I started having the same shutter opening difficulties. The shutter would start binding about 30 percent open and sometimes the cables would pop out of the PVC guides.

Development. After careful study of what might be causing the bind it was determined the front shutter was opening about 30 percent and binding on the rear permanent window panel. As the front shutter opens it sometimes twists due to normal cable tension from the windlass. This twist or unalignment on the dome would have the rear overlapping corner of the front shutter engage the front overlapping edge of the permanent rear panel. Some damage to the front shutter is obvious in the picture (chipped onleading edge).
View of the furniture wedge kit.

Phase 1: Start by smoothing one side of the plastic wedge with whatever tool you find useful. I used a large flat file and sandpaper. With the movable shutters out of the way hand place the wedge against the dome flange and the wide part end of the flange against the rear panel. Mark on the thin edge where you might have to trim out a place for the existing nylon button to clear. If trimming is necessary simply use side snips and cut in a triangle or rough out a round part to match the button.
Closeup view of the furniture wedge in place.

Finally drill a small hole in the thick end of the wedge (I used about a 1/8" diameter counter shank machine screw) and countersink the hole a bit so the screw will be flush with the surface of the plastic. Before mounting the wedge place a bit of glue or silicon on the inside of the thin piece for extra holding power.
Second closeup view of the furniture wedge in place.

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© , 2011

Created:2/17/2011, by Don Lewis, Last update 2/17/2011