Thousands of studs await the heat-treat process.
For those of you who think race car technology takes a back seat to aerospace, this article may surprise you. If you think the options for fasteners are either a Grade 5 or Grade 8 bolt, well, you really have something to learn. And if you're serious about racing, quality fabrication, and engine building, you must read this article.
Racing fasteners are just that-nuts, bolts, screws, and studs that hold the race car together. How well they do that will make the difference between winning and losing races, and will determine whether your engine and other important components can withstand the severe conditions of racing: large load demands, high and changing temperatures, vibration and harmonics, and cycling of stresses. By obtaining proper fastener performance, costly repairs can be avoided that could result from the use of lower quality fasteners or incorrect applications.
To get the lowdown on fastener technology, we went to the king of race car fasteners: Automotive Racing Products (ARP). For more than 30 years, this company has been one of the industry's pioneers in adapting state-of-the-art materials and manufacturing technology to the motorsports market. From NASCAR, NHRA, Formula 1, and IndyCar, to late-models and go-carts, ARP is heavily represented in every type of race car fastener.
Types of Fasteners
To be sure, race car fasteners include all bolts, studs, nuts, and connecting hardware within the engine-nowhere else will you find the extreme loads put on such critical pieces. Although there are basic applications of fasteners used for holding automotive components together-such as air-cleaner studs, water-pump bolts, valve-cover bolts, wheel studs, and body hardware-the real magic of technology shows itself in the important connections of items like rocker-arm adjusters, head and main studs and bolts, and the most critical of all connecting bolts: rod bolts. This is where a single failure could not only cost the race, but also result in wasting a $20,000 to $50,000 engine.
ARP's cold-forging machines perform five quick operations faster than you can blink an eye
"The application of fastener requirements to race car engines is unique," says Robert Florine, vice president of ARP. "Unlike most aircraft fastener connections, where redundancy is part of the design criteria, each connection within the racing engine is basically the weakest link. If a rod bolt breaks, that engine is history-it will probably fail catastrophically. In aircraft, even in the engines, a (fastener) failure should not lead to a catastrophic failure. There is a lot of overdesign in aircraft."
"Race cars don't have that luxury. A single failure can end the race and be extremely costly. That is why the quality of fasteners and their correct application is critical to good engine building and proper fabrication of the car. Connection failures cannot be an option in racing, and to eliminate failures it takes a good understanding of each important connection, the fastener requirement, and correct installation and maintenance."
Not every connection requires the quality of a fastener used in rod bolts and other high-stress applications. Chassis fasteners, for example, may need only the amount of strength required for a single bumper impact. The key to selecting the proper type and grade of fastener is to know the type of loading the fastener will endure and the rate, in cycles, it will encounter.
Loading of Fasteners
Two basic types of loading occur in fasteners: shear loads and tension loads. Many chassis bolts and studs are put under shear loads. This occurs when two forces move laterally in opposite directions-the bolt or stud is in shear tension. Fasteners such as these infrequently see material structure failure; it is not difficult to engineer good-quality bolts and studs that can withstand tremendous levels of shear loading. Drive-plate bolts and wheel studs are good examples of fasteners operating under shear loading.