2/28/2010
Emhart Cites Fastener’s Role in Greener Vehicles
Emhart Technologies envisions new fastener technology may help automotive sales, reduce recalls and warranty rates and lead to “greener” cars.
“We’re at the beginning of a fastener revolution in automotive,” Ray Genick, Emhart Technologies director of new business development, declared. “It’s being driven not only by a need to lower recall and warranty costs, but also to raise fuel efficiency while reducing weight and environmental impact.”
A new report projects the automotive fastener market will reach $12.2 billion by 2012. “Automotive fasteners assume high significance owing to the increasingly complex nature of vehicular designs, which is expected to necessitate stronger, improved and durable fasteners,” according to a news release for “Automotive Fasteners: A Global Strategic Business Report,” published by Global Industry Analysts Inc.
Failure of fasteners is one of the leading causes of vehicle recall in North America and Europe, according to the report.
The typical threaded joint, produced by a standard nut and bolt, has existed since the 19th century. Technical writer Del Williams explained the problem is that when a fastener loses its clamp load, thenn safety, recall, or warranty issues occur. Locking devices from wires and washers to chemical and drypatch adhesives may be added to retain clamp load. While adding weight and complexity, they don’t guarantee holding up under shock, vibration, or temperature extremes.
Traditionally an overdesign ‘belt and suspenders’ mentality has been used – such as putting eight bolts on an exhaust manifold when four might do, Williams wrote. “This has led to big, heavy, fuel inefficient cars that consumers will increasingly turn from in today’s cost, energy, and environmentally conscious climate.”
Hybrid cars, which combine gas engine with advanced electronics, are expensive. Electric cars have cost, battery life and electrical grid problems. Fuel cells have not reached a reliable level of distributing hydrogen fuel.
One technology is advancing. “Clean diesel will be the bridge technology to all-electric and fuel cell powered vehicles,” Genick told Williams. “Compared to conventional gas engines of equivalent displacement, its engine torque is 35% to 40% higher, its fuel mileage almost double in smaller engines, and its emissions much less.”
But the added drivetrain torque, heat and vibration of clean diesel increases the strain on fasteners.
In traditional locking fasteners with the standard 60-degree thread form, the gap between the crest of the male and female threads can lead to vibration loosening, Genick explained.
Stress concentration and fatigue at the first few engaged threads, increased chance of shear and temperature extremes expanding or contracting, can compromising joint integrity.
The Spiralock thread form adds a 30-degree wedge ramp at the root of the thread, which mates with standard 60-degree male thread.
The wedge ramp allows the bolt to spin freely relative to female threads until clamp load is applied. The crests of the standard male thread form are then drawn tightly against the wedge ramp, eliminating radial clearances and creating a continuous spiral line contact along the entire length of the thread engagement. This continuous line contact spreads the clamp force more evenly over all engaged threads, improving resistance to vibrational loosening, axial-torsional loading, joint fatigue, and temperature extremes.
Sprialock is currently used in the 2010 Dodge Ram 2500 clean diesel engine.
Audi, BWM, Chevrolet, Ford, GMC, Mercedes and Volkswagen produce clean diesel models.
Arlindo Marques, Spiralock director of Global Engineering, said Spiralock reduces fastener size or number and thus weight. “The key is Spiralock’s full contact along the entire engaged length of the thread,” Marques told Williams. “This reduces thread galling, or microwelding, especially in the heat-resistant nickel alloys becoming important in automotive. It enables fastener reusability up to 50 times, simplifying installation and maintenance. And it makes the thread form self-centering, which improves performance and eases the balancing of high-RPM diesel and turbo systems.”
Spiralock is currently used in ring gears, torque converters, chassis assembly, exhaust manifold joints and axle, turbine, or transmission housings. Caterpillar and Mack Trucks use Spiralock in diesel engines. Web: spiralock.com ©2010 GlobalFastenerNews.com
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