Effect of spring caused tensions to the resistance of polyamyde spur gears

Plastic spur gears have superiorities compared to metal ones, due to their plastic substance, the feature of self lubrication, resistance against corrosion etc. The small capacity of carriage of plastic spur gears, the small number of their thermal conductivity, and damages occuring on their surfaces are their disadvantages. The biggest problem during usage of spur gears is their low fatigue strength. The most commonly preferred plastic spur gear in the last years is polyamyde.Metal springs, consisting of an external diameter of 4.8 mm with a wire diameter of 1,2 mm and 7 windings, had been used by creating pretensioning, and the springs had been released after moulding. In the experiments, two different samples were used, of which one was with spring reinforcing and the other one without spring reinforcing. Experiments regarding statical rupture and fatigue had been undertaken, the results were compared with the calculations in accordance with BS 6168 standards, and it was observed, that the results were positive. Eventually, it was determined, that spring reinforcement expanded the life span of fatigue, although it has negative effects on substance in high loadings .