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• A tripod joint-CV joint transmission between parallel axis shafts can be homokinetic. • If connected to a CV joint, a tripod joint performs better than previously expected. • On cars, tripod joints can still be a good alternative to CV joints. • The transmission ratio of a tripod joint-CVJ driveshaft can now be exactly assessed. The paper presents a procedure to assess the instantaneous transmission ratio, in a generic configuration, of a driveshaft equipped with a tripod joint and a constant velocity joint of the fixed type. This mechanical transmission is used, for example, in automobiles to connect each half shaft of the differential to a driving wheel. After highlighting that the usual approach to evaluating the instantaneous transmission ratio is conceptually flawed, the paper proposes an original procedure to correctly assess the transmission ratio. The paper also proves that the considered driveshaft is homokinetic whenever the axes of the two end shafts are parallel. Numerical examples show application of the proposed procedure to case studies. [ABSTRACT FROM AUTHOR]

Exploring the motion characteristics in thread rolling process under varied center distance between rotation axes of workpiece and rolling die is important for accuracy evaluation and process control, and provides a basis for further study on motion compatibility condition in the thread and spline synchronous rolling process. The motion characteristics between the die and workpiece under varied center distance in the thread rolling process were investigated. Related mathematical models in the rolling process, such as the rotation angle and the angular velocity for workpiece, the transmission ratio, and the axodes of workpiece and die, were established. The results indicated that: (1) the relationship between rotation angle of workpiece and rolling time is approximately linearly dependent, transmission ratio almost presents the same change as angular velocity of workpiece; (2) the cross sections of the axodes of workpiece and rolling die are similar to Archimedes line, where the polar radius reduces with the reduction of center distance; (3) however, the changes of the angular velocity of workpiece, the transmission ratio, and the axodes are closely related to the shape of tooth profile. [ABSTRACT FROM AUTHOR]

This paper presents a study on a novel passively variable transmission (PVT) which is capable of operating in a wide range of transmission ratios. The developed device is light, bidirectional, and compliant, which is achieved by incorporating a twisted string actuator (TSA) in it. TSA is a cheap and mechanically simple actuator, in which twisted strings contract as a result of twisting and therefore act as a linear transmission. If one introduces a physical offset between the twisted strings, this changes the ratio between the output speed and force provided by the actuator. By introducing a passive element that changes the offset between the strings depending on the magnitude of external load force, we developed a PVT which inherited the advantages of conventional TSAs. This paper describes the basic operation principle and presents mathematical model and experimental evaluation of the proposed variable transmission mechanism. Advantages such as light weight, compliance, and passive bidirectional adjustment of transmission ratio make the proposed device attractive for implementation in various areas of haptics, teleoperation, and wearable and lightweight robotics. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the present work was the conjoint analysis of the efficiency and transmission ratio ranges that can be achieved with all the possible constructive solutions of four-, five-, and six-link planetary gear trains. We started from the graphs of these trains to determine all the structurally distinct kinematic inversions. We then obtained all the constructive solutions resulting from every possible combination of gear type and configuration. The result was thus the set of structurally and constructively different planetary gear trains. Next, we obtained the range of transmission ratio that can be achieved with each train, and the efficiency as a function of the transmission ratios within that range. This analysis revealed which trains allow both high transmission ratios and high efficiency, and are thus potentially most useful in the design of power transmission applications. They included a series of high efficiency trains whose potential utility had not as yet been investigated. Additionally, the study led to some interesting conclusions about the relationship between efficiency and transmission ratio in six-link planetary gear trains. [Copyright &y& Elsevier]