901. From Hi-Shears to Hi-Loks – A Decade of Change

Paper

Abstract

The Hi-Lok fastening system development is traced from the factors of simplicity of design, weight saving and cost saving of the Hi-Shear rivet in 1941. These factors are shown graphically to give the comparison between the Hi-Shear rivet, conventional aluminum alloy rivets, and the AN bolt series that were prevalent in aircraft structure at that period of time.
The Hi-Lok fastening system is compared to the features of the Hi-Shear rivet and the added feature of quiet assembly by the use of installation tools powered by air motors instead of vibratory rivet guns. Illustrations show the use of specialized installation tools which allow the designer the capability of using much reduced clearances and considerable weight savings.
A weight comparison is made between the tension type Hi-Lok and the 12 point MS21250 bolt series. Weight and strength comparisons are made between three types of countersunk head Hi-Loks and also show how fastener head height has afforded the designer the opportunity of saving weight by reducing flange widths and reducing chem-milled pad-up thicknesses for countersunk fasteners.
A chronological summary of the aircraft that use Hi-Loks, from the Lockheed Electra in 1959, to the present design of the B-1 and F-15 that are just starting their first stages of manufacture. The summary of aircraft includes the following: Lockheed Electra prop-jet, Northrop T-38, Convair B-58, Boeing 707, 720, 727 , and 737 , Douglas A4D-5, Convair F-111A , Lockheed C-5A, Boeing 747, Lockheed L1011, Lockheed S-3A, Grumman F-l4A, McDonnell Douglas DC-10, McDonnell Douglas F-15, and North American Rockwell B-1.