SM-1430 consists of a beam mounted on two supports which is subjected to point loads. The beam is cut at one point. At that point there is a low-friction hinge with one degree of freedom. The bending moment occurring at the section is recorded by a force gauge acting on a fixed lever arm. An adjuster nut on the force gauge is used to align the beam horizontally and balance out any lowering.
The reactions are determined from the static conditions of equilibrium. To investigate the effect of the point loads in the beam, it is notionally split into two segments. Applying the method of sections, the internal forces and moments are plotted onto the two segments and calculated by way of conditions of equilibrium.