I wish to rotate a short cylinder (thick disc) by 150 degrees. I chosed to use a double torsion spring for this (as the picture below). The picture shows only one side.
Yes. To reduce wear, material fatigue, and strength needed to turn it, you should use a couple coils of the spring, leave enough play so it won't seize when tensioned, and obviously the disc needs to sit on an independent bearing/bushing/hinge to turn, spring only providing tension - it's no replacement for a bearing.