Model UP-4 incorporates a special concept of the unipivot principle. The bearing consists of a hardened steel pivot resting in a concave, polished sapphire. The bearing is damped in all directions with silicone fluid.
The low positioning of the bearing provides for a greater stability compared to other unipivot arms. This is because a considerable part of the moveable mass of the arm is positioned above the pivot point, thus forming a physical pendulum together with the mass below the pivot point.
With the model UP-4 the azimuth adjustment is made by the way of the counterweights.
Vertical cross section of model UP-4 through pivot and sapphire.