Machine Design
According to I.B.R., the efficiency of a double riveted butt joint with double cover straps of equal width should be

45 to 60%
63 to 70%
70 to 83%
80 to 90%

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Machine Design
Elastic nut is a locking device in which

Through slots are made at top and a cotter pin is passed through these and a hole in the bolt, and cotter pin splitted and bent in reverse direction at other end
A slot is cut partly in middle of nut and then slot reduced by tightening a screw
Hard fibre or nylon cotter is recessed in the nut and becomes threaded as the nut is stewed on the bolt causing a tight grip
One small nut is tightened over main nut and main nut tightened against smaller one by loosening, creating friction jamming

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