Abstract: A coupling system for conduit and pipe is disclosed. First and second conduit sections are disclosed, each of which has first and second ends. The first end has an outside diameter, and the second end has a belled portion with an inside diameter greater than the outside diameter of the first end. The belled portion has an aperture and a raised lip surrounding the aperture. A threaded fastener is rotatably disposed in the aperture and engages threads of the aperture and an inner surface of the raised lip. The raised lip has a predetermined lip height that is selected to provide a minimum number of full threads engagement between the belled portion and the threaded fastener to ensure the belled portion has a predetermined pull out strength. Other embodiments are disclosed and claimed.

Abstract: A system of adjustable balancing weights is provided for a helicopter main rotor blade. The trailing edge of the rotor blade is formed with a plurality of recesses that each receive an aerodynamically shaped weight to adjust and balance the weight of the rotor blade. A forward weight recess and a forward weight are also provided on the rotor blade adjacent the rotor blade leading edge. The lateral spacing between the weight adjacent the rotor blade leading edge and the weights adjacent the rotor blade trailing edge provides greater flexibility in balancing the mass of the rotor blade.