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Motion System Design

Good vibrations down on the farm

The shakes, rattles, and rolls that drivers of agricultural vehicles feel are things of the past on new machinery with technology from Lord Corp., Cary N.C., and Sears Seating. The operator seats in large row-crop tractors from agricultural vehicle manufacturer CNH Global, Lake Forest, Ill., use magnetorheological (MR) fluid technology to reduce vibration and shock.

According to Douglas F. LeRoy of Lord's MR Solutions unit, “The MR fluids respond to a magnetic field with a dramatic change in rheological behavior. They can reversibly and instantaneously change from a free-flowing liquid to a semi-solid with controllable yield strength when exposed to a magnetic field.”

The study of MR fluids began in the 1940s; Lord began to research their use in commercial damping applications in the 1980s and 1990s. Now their use is only expected to increase, as new vibration level regulations will be put in place in Europe next year.

“Today, most devices use MR fluids in a valve mode or direct-shear mode. The rheological properties of MR fluids depend on the concentration, size, distribution, and shape of the iron particles, the carrier oil properties, additional additives, applied field, temperature, and other variables,” LeRoy says. Application-specific MR fluid formulations range from dry mix technology to highly viscous fluid material with advanced shear thinning chemistry.

Lord's patents on MR fluid formulations, devices, and systems include additives, lubricants, and suspension aids to keep iron particles in place while preventing them from grinding away at seals, gaskets, and metal components.

The VRS (Vibration Reduction Suspension) 2000 Seat System from Sears uses Lord's MR fluid technology to automatically adapt to the driver's body weight and continually changing levels of shock and vibration, improving operator productivity while reducing fatigue.

The VRS 2000 is the first air suspension vehicle seat that combines semi-active damper technology, exclusively marketed and developed by Lord, with a low natural frequency air spring system, developed by Sears Seating, to provide high vibration isolation during normal vehicle operation while maintaining smooth ride control during rough terrain inputs.

Lord is currently working with two European agricultural vehicle OEMs to commercialize MR technology in their cab suspensions. Production will begin in the next 18 months.

For more information, visit or e-mail the editor at [email protected].

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