Determination method of rational design parameters for four-shaft not-coaxial preselector transmissions of agricultural tractors

Developing the preselector transmissions for different vehicles, designers of machine-building enterprises face the absence of methods that would allow to define unambiguously the design parameters of those transmissions. Particularly, during determination of shafts arrangement diagram in four-shaft preselector transmissions with not-coaxial arrangement with necessity to keep the minimum overall width, there is the mutual interference of parameters of geometry and arrangement of gear wheels on each other and overall width simultaneously. For the solution of this problem, it is necessary to resort to using of graphical analytic method with a great number of iterations, which is labor consuming and does not provide a guarantee of result repeatability. The article deals with the method that allows to choose the rational parameters of main kinematic links to provide minimum overall width and to define unambiguously their position in space. During method preparation, the authors’ experience in development of transmissions for agricultural tractors of 4 drawbar category was taken into account. The design sequence of preselector transmission is reduced to choice of gear ratios and to forming of rational shafts arrangement diagram, due to which the minimization of overall width of preselector transmission is achieved. It is established that on the basis of kinematic parameters of links, it is possible to form the rhombus that completely defines shafts arrangement in transmission. For complete description of the rhombus geometry and its position in space, the analytical dependences are obtained. As a result, it is possible to determine accurately the overall dimensions of preselector transmission and the distance between input and output shafts without using graphical analytic method. The developed determination method of rational design parameters of preselector transmissions could be used in development of similar constructions for traction and transport machines.

agricultural tractor, preselector transmission, not-coaxial arrangement of shafts, synchronizer, friction clutch, gear wheels, synchronizer circuit, clutch circuit, shafts arrangement rhombus, minimum overall width