Abstract: A self-actuating traction drive speed changer has a movable force input element having a planar drive surface, and a movable force output element having a planar drive surface which is connectable to an output load. One or more movable roller elements has a planar drive surface operatively connected for movement to the input element, and are in frictional engagement with the planar drive surface of the output element so that movement of the input element will cause the planar drive surface of the roller element to engage and frictionally move the output element.

Abstract: A self-actuating traction drive speed changer has a movable force input element having a planar drive surface, and a movable force output element having a planar drive surface which is connectable to an output load. One or more movable roller elements has a planar drive surface operatively connected for movement to the input element, and are in frictional engagement with the planar drive surface of the output element so that movement of the input element will cause the planar drive surface of the roller element to engage and frictionally move the output element.

Abstract: A feedback mechanism for providing an implement position signal includes a rotary potentiometer mounted on the implement frame adjacent the rockshaft with the axis of the potentiometer shaft extending parallel to the rockshaft. A linkage structure includes a potentiometer arm connected to a rockshaft arm by a link such that the angle the potentiometer arm forms with the link is acute when the implement is in the transport position and obtuse when the implement is in the lowered field-working range. At the lowermost position of the implement, the link and potentiometer arm approach an overcenter position. The linkage structure provides amplified rotation of the potentiometer shaft relative to the rockshaft when the implement is in the field-working range of positions, while rotation of the shaft is reduced relative to rockshaft rotation when the implement is raised above the field-working position. In the preferred embodiment, rotation of the rockshaft 10.degree.