2024 ARP Catalog

18 There are literally hundreds of standards and specifications – for all types of applications, from bridges to rockets. None are as critical as those required for real-world motorsports applications. In an environment where lighter is faster there is clearly no room for redundant fasteners, like those found in military and aerospace applications. The mere nature of Motorsports requires designers to produce fasteners that are light; yet tough, fatigue-resistant and reliable beyond other acknowledged application standards. The design and production of fasteners, exclusively for racing, clearly involves many complex factors. Some are so unique and complex that no standards or design criteria exist. This means that everyone at ARP is entirely dedicated to the development and analysis of appropriate bolt designs exclusively for special applications. Our designs take into account the special loads that must be carried, the material selection, the manufacturing processes and the methods of installation required to deliver ARP quality and reliability. It is hoped that by providing an overview of the engineering, design and production techniques ARP applies daily, you – as the end user – will be better equipped to evaluate your initial fastener requirements, effectiveness and performance. Design Procedures for Automotive Bolts Presented by Dr. Kenneth Foster, PhD The design of automotive bolts is a complex process, involving a multitude of factors. These include the determination of operating loads and the establishment of geometric configuration. The process for connecting rod bolts is described in the following paragraphs as an example. The first step in the process of designing a connecting rod bolt is to determine the load that it must carry. This is accomplished by calculating the dynamic force caused by the oscillating piston and connecting rod. This force is determined from the classical concept that force equals mass times acceleration. The mass includes the mass of the piston plus a portion of the mass of the rod. This mass undergoes oscillating motion as the crankshaft rotates. The resulting acceleration, which is at its maximum value when the piston is at top dead center and bottom dead center, is proportional to the stroke and the square of the engine speed. The oscillating force is sometimes called the reciprocating weight. Its numerical value is proportional to: It is seen that the design load, the reciprocating weight, depends on the square of the RPM speed. This means that if the speed is doubled, for example, the design load is increased by a factor of 4. This relationship is shown graphically below for one particular rod and piston. Motorsports Fastener Engineering for the Non-engineer FASTENER TECH