THE designation, “hydrodynamic” power transmission, is used in this paper, and not “hydraulic” power transmission because fluid gears are discussed that operate by dynamic action like turbines or centrifugal pumps, not those working by means of static fluid pressure like piston pumps. It is the dynamics of turbines and centrifugal pumps which has to be understood when the action of a hydrodynamic gear is to be explained.
The basic ideas of the hydrodynamic power transmission are given, especially when applied to motor cars. A hydrodynamic gear which can take differences of torque between the primary and secondary shaft and which consequently is furnished with one or more fixed blade rows, is defined as a “hydraulic torque converter,” but such a gear, which consists of revolving blade rows only and, therefore, cannot take differences in torque is called a “hydraulic coupling.” Considerable data explaining the basic operating principles of various combinations of these hydrodynamic gears and mechanical gears are presented.
There are several reasons for the fact that automotive engineers have been comparatively hesitant to introduce the hydrodynamic gear into automotive engineering, the author concludes. Its characteristics are not as easy to understand as is the case with mechanical gears and, for motor drive, it will be necessary to develop special types for quantity production when proper and sufficient experience has been obtained. In so doing, the author predicts that many an advantage for their layout will turn up, and the overall economy will be increased still more.