Wheel Balancer Articles

Merrill Wheel Balancing System

In 1945, Marcellus Merrill developed an electronic dynamic wheel balancer.  Before this, all methods of wheel balancing were static and required the wheel to be romoved from the vehicle.  Merrill's wheel balancer allowed the wheel to stay on the vehicle and be spun at high speeds while detecting vibrations.  With the wheel jacked off the ground, he would spin the wheel and then analyze the vibrations.  The vibrations were monitered by an electronic pickup on the floor and was attached to the bumper of the car by a magnet.  The signal would trigger a proboscope light which made the wheel appear to stand still.  The light would show the point where the balance weight should be placed on the rim and help show the amount of weight to be added for a proper balance.  The front wheels would be spun by a "spinner" which included an electric motor with a large flat pulley pressed against the wheel.  To balance the rear wheels, one wheel was lifted up and spun with the vehicles engine.

At the time, the Merrill wheel balancer system worked very except that the electric motors on the wheel spinners were subject to frequent failures.  Marcellus Merrill contacted General Electric, the manufacturer of the motors, regarding the problem.  General Electric assigned the problem to Jackson F. Fuller, a young field engineer in it Denver office.  The motors were failing because the energy required to accelerate the wheels to a high speed exceeded the design capability of the motors.  Mr. Merrill resisted using larger motors as a solution because they would require more current from their electric supply circuits.  This could exceed the electric circuit capability in some applications.  The problem was sovled by changing the insulation materials and installing a larger cooling fan.  Elements of this wheel balancer are still used today in some applications.