Testing worm gears with cooperating elements made of different materials

The author tested the efficiency, load-carrying capacity, and the type of friction in a meshing of a worm gear having the same parameters as worms made of carburized and quenched steel and worm-wheels made of steel, cast iron, and bronze. The type of friction was identified in case of worm gears with steel and cast iron worm-wheel at a volume temperature of the worm-wheel of 100 ℃; these gears did not demonstrate the tendency to seizure. The value of resistance of an oil film formed between the worm and the worm-wheel was accepted as the criterion of the existing type of friction in the meshing during mating of these two elements. The resistance of the oil film in the worm meshing was measured twice each time for two directions of the passage of electric current to avoid the effect of possibly occurring polarization phenomenon. Obtained values were averaged. During the course of the experiments, the image of friction was observed on the screen of an oscilloscope. Obtained values of the oil film resistance prove the low participation of fluid friction in the worm meshing with the worm-wheel made of steel as well as of cast iron. In case of the gear with the steel worm-wheel, the decrease of resistance in comparison with the bronze worm-wheel amounted to approximately 10 times and that of cast iron to almost 100 times. On the basis of the tests one can state that the application of steel worm-wheels and in particularly cast iron worm wheels makes it difficult for the fluid friction to occur while the application of a traditional material mating pair (a steel worm–a bronze worm-wheel) forms conditions for the occurrence of a mixed friction with a very high (approximately 99%) participation of fluid friction.