Iscar Metals
An Exercise In Utility: Developing A Suspension Without An Order

ArvinMeritor put the "independent" in its independent rear suspension module when it designed, engineered, and developed a bolt-in unit for a current vehicle without a P.O. Even if the OEM in question never buys it, the supplier knows it has gained valuable knowledge for that time when the money really is on the table.

Somebody designed and built an independent rear suspension for a current light truck/SUV without anyone asking them to do it? That's right.

"We undertook this project ourselves without a request, or a contract, from an OEM," says Bob Carlstedt, vice president, ArvinMeritor Modular Suspension Systems. "It's an independent rear suspension for a large light truck and SUV currently on the market that can be swapped with the current solid axle in order to give both the OEM and the vehicle buyer the greatest flexibility possible in meeting their needs."

Still, this is Detroit. People don't go to lunch in this town without a Request For Quote (RFQ). There must be more to this story–and there is.

Arvin and Meritor merged just over one year ago, which was about the same time Carlstedt was charged with forming the team responsible for this project. Its goal was to learn as much as possible about the problems and opportunities facing OEMs, the resources (testing, development, and supply) available, and how to meld both with needs and desires of the vehicle buyer.

Approximately three months were spent selecting the 14 people who would design, develop, and deliver this module. Nine months were spent actually doing the work. This timeframe was tighter than most suspension design cycles, Carlstedt admits, but it forced the group to focus on utilizing the best tools available while producing a fully engineered property for display at the 2001 Frankfurt Motor Show.

The ArvinMeritor Performance System (AMPS), a lean manufacturing process created when separate Arvin and Meritor disciplines were combined, includes adherence to what the company calls S3, or Six Sigma Shainen solutions. This process helped the team determine the things that were most important to producing a high-quality product and process by looking at effect-and-cause, rather than cause-and-effect.

"One of our goals," says Carlstedt, "was to institutionalize these processes as much as possible right from the start. Producing a product that allows our customers to bring a product to market more quickly is no good if you can't ensure the quality of what you provide. So we made certain that we made quality an integral part of the culture of this group right from the start."

Which brings us to another goal, finding high-quality suppliers. "We had to discover who we could work with, and who would bring the experience and ideas that would make the design, engineering, and build processes work better," says Carlstedt. "Looking at the problem from the OEM's perspective helped us become a better supplier with better solutions. Understanding what the supplier is up against let us see how everything relates, who is giving the best information and taking the long-term view, and whether or not the information received is the best possible."

Targeting a current vehicle for upgrade allowed the team to create a proof-of-concept that didn't put a multi-billion dollar program in jeopardy, evaluate their work against an established baseline, and use this information to upgrade their processes. It didn't hurt that the result could be placed into production at the completion of the project, recouping the monies spent thus far.

The independent rear suspension module has a large stamped and welded carrier that supports the differential and provides mounting points for the upper and lower suspension arms. It bolts into the space between two existing frame members, while the complete unit utilizes the same mounting points as the current solid axle. Putting it there wasn't a simple case of taking out the old and putting in the new, however.

"Packaging the exhaust system was a problem," Carlstedt says, "so we went to our exhaust system group for help. They came up with an elegant solution that meets our needs."

The team also utilized the expertise of Meritor Suspension Systems Company, a joint venture with Mitsubishi Steel Manufacturing Company, and ArvinMeritor Ride Control. Along with help in tuning the suspension system, the former supplied the coil springs and stabilizer bars, while the latter provided the shock absorbers.

"The buyer wants his vehicle to ride just as well whether he's pulling a 35-ft boat, on the construction site, or driving down the road with no cargo," says Carlstedt. "Tapping into the experience necessary to meet those needs, and understanding how it all fits together was important to this project."

So was understanding the OEM's production process.

"We worked with the OEM to understand how we could fit this module into the assembly line with minimal disruption," says Carlstedt. "And that included making provisions for delivering complete units to the line for either low-volume or high-volume applications, if that's what the OEM wants."

In the meantime, Carlstedt's group continues to optimize the design. As might be expected, the addition of an IRS module to a vehicle not originally designed to accept one has exposed many areas ripe for improvement. "By making some minor changes to the frame," remarks Carlstedt, "we know we can optimize the fuel tank space, lessen the cut of the rails, make it easier for the OEM to switch our module with the solid axle unit, and lower the weight of the structure. And there are other things we can do because our module is lighter than the standard unit."

Production might be just around the corner. And wouldn't that be the ultimate proof for this proof-of-concept?