Tailored load-displacement mechanisms are a type of nonlinear mechanisms that can be designed to obtain a specific desired load-displacement curve. In order to achieve tailored torque-twist curves, these mechanisms often need to be complex; requiring multiple parts that sum up to the desired curve. In this work a revolute compliant mechanism, based on a helicoidal shell, is adapted so that it can achieve positive tailored torque-twist curves, using a single part. The goal of this paper is to make a tool that allows this tailorable property to be fully realised using the the rate of twist along the spinal axis as the design variable, whilst the radius and thickness are kept constant. This tool has an analytical model as a basis that predicts the numerical result of a Kirchoff-Love shell model. The model is dimensioned by linking numerical results to shape factors of the helicoidal shells as well as observed deflection behaviour. The resulting design method is demonstrated with the creation of a few tailored torque-twist curves: A linearly increasing, as well as a linearly decreasing curve, and two sinusoidal curves, designed to be used as gravity balancers. Subsequently these designs are produced and measured.
Related dataset 4TU.ResearchData: https://doi.org/10.4121/d87be8e0-38bb-4bdd-a703-70c3e856b1ca