Metaldyne: Engineering A Better Suspension

Metaldyne is seeking to change the world of front vehicle suspensions with the advent of a system that reduces weight, improves ride and requires fewer parts to manufacture.

As OEMs fight for every ounce of weight reduction possible in the development of new vehicle platforms, Metaldyne (www.metaldyne.com; Plymouth, MI) has devised a way to drop as much as 24 lb. of excess weight from a vehicle via simple changes made to the front suspension. Based on the Link-X system devised by Todd Wagner, CEO of Wagner Engineering (see: Too Good To Be True?), the suspension—now called “Metaldyne Suspension System” (MSS)—is based on a modified short-long-arm design which removes the necessity for a front sway bar. The original configuration Wagner thought up more than five years ago, consisting of a larger single arm designed in a physical “X” configuration, failed to achieve the lower production cost and weight targets. The latest iteration, however, uses existing manufacturing technology and lightweight materials—high strength machined steel and forged aluminum—to achieve the targets and provide additional weight savings. The support arms—which are more conventional in size—are configured in a way that one extends between the lower ball joint and a pair of upper body mount connection points, while the other extends between the upper ball joint and a pair of lower body mount connection points, allowing them to cross one another via the creation of a virtual “X” pattern.

The intersection point, or the center of the “X”, is where the instant center for the front elevation of the vehicle is located, making it adjustable by modifying the position of the arms via their location points on the frame. The elimination of the front sway bar allows energy to be isolated at each wheel, such as when a vehicle hits a bump in the road. Traditional sway-bar dependent systems allow the energy to be transmitted through the bar, affecting the performance of the entire front suspension system. The changes designed in MSS result in a suspension that is said to reduce head toss, energy transfer and provide a smoother ride. The design is also claimed to provide tangible safety benefits, enabling double-lane changes on a prototype vehicle to be taken safely at 62.05 mph, an improvement of nearly 5 mph when compared to a commercially available baseline model. An additional benefit: The prototype generated 40% less rolling velocity, which aids in preventing a potential rollover scenario. Tire wear was also reduced by 31% since the contact patch remains relatively flat during normal driving maneuvers.

Inventor Wagner admits without Metaldyne buying into the system a year ago his idea would have withered on the vine: “They brought a lot of things to the table, most importantly in terms of computer modeling and simulation, which helped move the development four or five levels further.” Daniel Brinker, vice president of sales and engineering at Metaldyne’s chassis group credits his company’s acquisition of DaimlerChrysler’s New Castle, IN, casting and forging facility, along with its recently completed merger with Japan’s Asahi Tec, as integral events that facilitated the advancement of the MSS. “We really got everything together on this in the last year. When we acquired the New Castle facility that brought us into the control arm and ball joint side of the business and that completed our portfolio, especially since we were already great at knuckles and wheel ends. With Asahi Tec we can investigate new lightweight and higher strength materials, including Hyper-ductile iron,” Brinker said.

Metaldyne engineers recently completed retrofitting a Hummer H3 with MSS and will begin showing the system to OEMs, with hopes that a contract can be signed for a clean-sheet vehicle program sometime after 2010. A passenger car model was recently selected for retrofitting with engineering changes to be completed in May. “This is going to be a culture change and that’s the biggest hurdle,” said Brinker. “Now that we have a prototype vehicle…we can address a lot of the OEMs’ questions and concerns and get moving. If we had a clean sheet we could have prototypes on the road within a year.”