Development of special purpose silk thread through reverse engineering and yarn geometry for use in engines of battle tanks

Abstract

One of the Engine factories in India is manufacturing three types of engines that power various types of battle tanks. While operating the tanks, the crank shaft main journals and pins need lubrication for smooth running with minimum friction and to dissipate the heat produced. In order to prevent the leakage in the lubricating system, special purpose silk thread is wound around the threaded portion of the bolt before tightening the nut with gasket and washer that has to withstand the oil pressure of 14 kg/cm2 at a temperature of 140 °C. The expected life of the engine is 10 years approx. (500 h of actual running), so the special purpose silk thread should have self-life of more than the engine life. Earlier, the special purpose silk thread of 77.2 Tex (maximum) that would have a breaking load of 2 kgf (minimum) with 18% elongation at rupture (minimum) was sourced from Japan indirectly. Due to decline in the silk production in Japan, the supply chain broke and ceased to exist. The technical know-how on yarn manufacturing was unknown but details of eight thread characteristics were available. CSTRI, Bangalore, with the data, manufactured the special purpose silk thread through reverse engineering by designing the yarn geometry using indigenously produced multivoltine raw silk reeled on multiend reeling machine. Subsequently, the special purpose thread was produced in commercial scale and supplied to the Engine factory, Avadi that is being used as oil seal in the engines of battle tanks after getting the performance test report from the Defence quality control agency. This research paper deals with process of reverse engineering and design of yarn geometry in achieving the desired characteristics of the special purpose silk thread.