Abstract: A device for testing and evaluating the performance characteristics of a linear motion devices such as, for example, linear actuators, linear step motors and solenoids. Generally, the device of the invention provides a variable force, fixed simulated mass load to a device under test. The preselected fixed mass, variable force load is applied to the output rod of the device under test by a variable torque directly translated to a linear force by, for example, a rack and pinion arrangement. The torque generating means is built to reflect a predetermined mass so as to reflect a constant mass for the load simulated by the mechanical coupling of the rack to the output rod.