An optimal design formulation is developed to minimize the contact loss in clearance joints. The objective taken is the ratio of the time derivative ($\acute{r}$) of joint force direction to the magnitude (R) of joint force, i.e., $\acute{r}/R$, as calculated from the nominal mechanism without clearances. Design variables are the magnitude and the location of an added mass to each link.
Several examples with an offset slider crank mechanism and a four bar linkage were considered. To check the suitability of the objective function taken for the stated purpose, the optimized and initial systems were simulated dynamically by integrating the system model equations and the phenomena of contact loss compared. It is found that, although $\acute{r}/R$ does not contain any parameters describing the clearances, it is a reasonable indicator in a relative measure for the contact loss phenomenon in a single clearance system. The shaking force and input torque variations were also obtained and compared. As far as the input torque is concerned, less variations were found in the optimized systems, which can be expected from the formulations.
