This apparatus is majorly a round disc which is placed horizontally on three legs attached to a foundation. A 360 protractor is set centrally on the plate and three pulleys on clamps permit the load hanger cords to run toward a ring dropped over the center. The apparatus is best to express the conditions of equilibrium for three coplanar forces acting on a circular disc.
Conditions of equilibrium can be obtained by centralizing a small ring available over the central pin with cords to load hangers where the loads and lines of action are variable. In this way, it is possible to construct the triangle of forces in equilibrium and to find the resultant of two known forces.