Ball-and-Socket or String Action: Which is Best?

by Engelbert Schmid

Many amateurs order ball and socket linkages, but almost all professionals prefer string. If you examine the mechanism the reason is clear.

Valve at beginning of stroke



In its starting position the ball and socket action  is at an angle of 135°, not really bad, but not ideal. The vertical distance between the center of the ball and the center of the rotor determines the mechanical advantage.

Halfway through stroke



Half-way through the stroke the ball and socket reaches the optimal angle of 90°, where the vertical distance is greatest and the maximum mechanical advantage is reached.

Valve at the end of the stroke



Entirely depressed, the ball reaches the less-than optimal angle of 135 °. Since the mechanical advantage is less the rotors need more pressure to move and the stroke is uneven. The large initial angle causes the mechanism to have more resistance at the beginning of the stroke.

String Action Valve



Since a string action always pulls at the optimal  90° angle, the action is even and the stroke can be made very short. A ball and socket action can be made to feel more quick and even by increasing the distance between ball and centerline, but at the expense of a longer stroke.

String actions have other advantages as well: They are silent and the height of the levers can be easily adjusted. Modern string materials will not break or stretch and need be replaced rarely.


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