In addition to the cross-section of the bars and their length and the stiffness of the material, the upper and lower bearings have a considerable influence on the external force F that can be applied in the direction of the bar to the upper end of the still undeformed straight bar. Depending on the type of bearing, a sometimes quite small compressive force is sufficient here to cause the bars to buckle, which represents the failure.
In order to make these effects tangible for the students in addition to the teaching materials and to illustrate the buckling process to them, we have conceived, designed and manufactured our own Euler demonstrator as an illustrative object in a small project. On the demonstrator, which is made of aluminum and stainless steel, all 4 Euler cases are reproduced according to theory. The force acting on the rods is realized by a multitude of weights with masses between 6 and 285 grams in interaction with the acceleration due to gravity. For each of the cases shown, the weights can therefore be stacked "slice by slice" and the force acting on the rods thus increased until the critical force Fk is reached and the rods made of spaghetti buckle. This does not happen gradually, but suddenly. The deflection is limited in order to be able to represent the illustrations of buckled rods known from teaching in a non-destructive and yet as similar manner as possible.
In addition to a possible compressive loading of bars, there is, as already mentioned, depending on the application, the possibility of tensile loading and thus under certain circumstances a strength problem in which the bar length is irrelevant. In order to be able to reproduce this loading condition as well, the fixture was designed so that it can also be turned upside down and the weights cause a tensile load by clamping the fourth bar (right) on both sides.