Intelligence for All Wheel Drive - Haldex

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Double disc, double perform Haldex and SKF from Sweden have jointly developed an advanced wheel end for commercial vehicles. Its typical features include a fixed caliper brake with two discs and the compact SKF hub unit. Text Michael Kern Photos Haldex, Gigant 12 Haldex Dynamix 1/2007 www.haldex.com
ance www.haldex.com Closing the gap in stopping distance requires a better bite in truck brakes. DISC BRAKES have a fairly long history in cars. But in commercial vehicles, especially in heavy trucks, this type of brake has been used only for a relatively short period of time. That’s due to the fact that hydraulics are not really a practical power transmission medium for the brakes of such vehicles, which typically weigh about 40 tonnes. And it was not until the mid 90s that purely pneumatic brakes reached the level of maturity required for fi eld operation. Manufacturers Scania and Mercedes were the pioneers, and it took about ten more years before the last European truck builder switched over to disc brakes. Today the standard both in trucks and trailers is sliding caliper brakes with one brake disc each. But there’s still plenty of room for technological advancement. After all, the wheel ends have to meet the same expectations as the truck as a whole. Today, more than ever, the trend is towards increased effi ciency with reduced weight and lower costs. Haldex’ Development Engineer Joakim Gripemark explains what this means with regard to brake clamping forces – in other words, the “bite” of the brakes: “We expect that clamping forces of up to 35 kNm will be required in future, compared to some 27 kNm today.” From a technical point of view, it would be no problem to make today’s sliding caliper brakes fi t for such fi erce forces. But due to the required reinforcements, the result would be a roly-poly that would be diffi cult to incorporate in the available installation space – especially at the front axle where space is extremely restricted. So it was a logical step for Haldex to undertake the design of a fi xed caliper with dual discs. Thanks to the fi xed caliper, the entire unit is no wider than the sliding caliper brakes used today. A support is not required. Development began in the year 2000 and immediately looked very promising. So the idea started to form in the minds of the engineers to do it thoroughly and completely to be able to develop an entire wheel end. At this stage, skf became involved as an extremely experienced hub bearing unit manufacturer and contributed �Expertise The new fixed caliper dual disc brake reduces life cycle costs to a considerable extent. with a tailor-made integrated slim-line hub unit. Designed for one million kilometres of maintenance-free operation, it boasts a decisive advantage: When the discs are worn down, they can easily be drawn off the axles as soon as the wheel fl ange has been dismounted and the locking device opened. IT’S NOT WITHOUT REASON that skf was selected as a partner. The company took up series manufacture of compact truck hub units in 1990. Having produced more than fi ve million such units to date, skf is the most experienced manufacturer worldwide in this fi eld. But let’s take a detailed look at the so-called “ModulD” solution developed in cooperation with Haldex. The hub unit is of extremely slim design and offers precisely adjusted interplay between the bearing, grease and seals. It has been designed for a service life of one million kilometres. Conception of the unit was assisted by sophisticated calculation programs that made it possible to anticipate fi eld conditions at the laboratory stage. During fi eld tests, the impressive expected life of one million kilometers was � proven to be achievable. 1/2007 Haldex Dynamix 13
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Page 9 and 10: to get a kit of parts,” says Gerd
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