Gears are extensively used in many applications, such as: automotive, drive trains, industrial gearboxes and machine tools. They are designed to transmit power and rotational motion from the input shaft to the output shaft. In the design process of a gearbox, factors such as: load capacity, size, lifetime or manufacturing cost are often taken into consideration. However, precise measures of efficiency are frequently forgotten issues in the design process. Such shortfalls relate to oil churning, windage, oil squeezing during gear mesh, or the friction processes at the level of the gear pairs, seals and bearings. This paper presents a calculation method used to determine the efficiency of helical gear transmissions. The method was validated by experimental measurements. Finally, influence factors on the gearbox efficiency, such as transmitted load and operating speed are presented.
