DETROIT -- Dodge truck engineers in the Chrysler Group of DaimlerChrysler AG have selected iron over steel for use in a pair of suspension system lower-control arms installed in the redesigned Dodge Ram 2500 and 3500 pickup trucks due out next fall as 2003 models. The decision to use iron was based on projected reductions in weight as well as parts.
If Chrysler builds 120,000 of the heavy-duty pickups every year, it is estimated that enough ferrous scrap and other foundry materials to produce 8.2 million pounds of iron control-arm castings will be needed annually for the new suspension system applications--replacing almost 9.4 million pounds of steel.
As unusual as it is in the auto industry for iron to be chosen over another material for weight-saving purposes, that was one of the reasons for the engineers' decision. According to Chrysler sources, the decision to substitute iron for steel in the new trucks' control arms was made after studies projected that the foundry-made iron castings would save several pounds apiece and also require fewer parts than weld-assembled steel arms like those used in previous Ram 2500 and 3500 pickups.
The new control arms, which weigh 34 pounds apiece, reportedly will be supplied by Citation-Texas Foundries Inc., Lufkin, Texas.
Automotive engineers do not often select iron over other materials, but the design of the new control arms reportedly had a lot to do with the decision, as did lower projected assembly costs, Chrysler sources said. The new 23-inch-long lower control arms were designed without the need for bushings, such as those employed in the previous steel parts, which will make assembly operations simpler and less expensive.
The new Dodge Ram 2500 and 3500 pickups will have a substantial cast iron content because of other parts applications in which the metal either beat out aluminum or had no competition, including certain axle, power-train and driveline parts, such as cylinder blocks, crankshafts and exhaust manifolds.
Austempered ductile iron will be used in the lower control arms, each weighing about 5 pounds less than a comparable steel arm assembly, or 10 pounds less per vehicle.
Heavy-duty pickups like the Ram 2500 and 3500 models are used for business and commercial purposes involving towing, service work, on-site support and hauling, as well as for personal use by people who buy them for recreational purposes. Unlike light-duty trucks, they are not subject to legislated corporate average fuel economy (CAFE) standards, although automakers try to keep their heavy-duty trucks as light and fuel-efficient as possible.
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