Helicopter rotor balancing tool.
https://diqn32j8nouaz.cloudfront.net...ncing_tool.jpg
Previously:
https://www.homemadetools.net/forum/...024#post145074
https://www.homemadetools.net/forum/...010#post160551
https://www.homemadetools.net/forum/...731#post159637
https://www.homemadetools.net/forum/...178#post149795
https://www.homemadetools.net/forum/...200#post145824
