Better Riding Through Electricity
Cadillac's magnetic-rheological shocks.
BY PAUL WEISSLER
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The electrical connector is at the shock’s bottom, where the piston rod is located, as the circuit goes through the rod to the electro-magnet in the piston. Orifices in the piston are nonmetallic, so the metal powder in the fluid won’t adhere to them.
There’s a sharp dip in the road, the kind that normally forces you to slow down suddenly, to prevent the car from becoming airborne. However, in the 2002 Cadillac Seville, we continue at more than 70 mph, and the car just hugs the road without the slightest hint of lift, maintaining the traditional Cadillac ride. This is all thanks to an ingeniously simple innovation—magnetic-rheological shock absorbers that respond instantaneously to a modulated current feed of only a few amps from a conventional 12-volt system.
The shock absorber fluid is about 40 percent iron powder, but with the current off, the oil flows freely. When the current is applied (up to five amps per shock), an electro-magnetic coil is energized in the shock absorber piston, thickening the fluid as it flows through the piston orifices. This "stiffens" the shock, and the amount of stiffness is infinitely variable depending on the amount of current applied. The response time of the shock is 1/1000 of a second, over 10 times faster than the premium-priced electronically-controlled valves in the shocks of today’s Cadillacs. Just as important, the thickening effect provides a much greater range of control for the entire chassis.
M-R as it’s known, is part of a long-studied technology that is finally ready for prime time. The more broad-
