Roller rack type trochoidal gear assembly has been developed which consists of a series of roller train and a mating cam pinion. Motion principle for the mechanism has been analyzed. To avoid undercut which occurs at the dedendum, we applied some amount of "profile shifting". The optimum value of the profile shifting coefficient is discussed in relation to contact factor and pressure angle. Roller diameter and tooth height also affects to the mechanism design. A prototype of roller rack trochoidal gear assembly was constructed using the optimal values. The accuracy and the smoothness of the motion proved to be sufficient for practical applications.
