Load sharing analysis of high contact ratio spur gears in military tracked vehicle application

Military tracked vehicles demand a very compact transmission to meet mobility requirements. A compact transmission with low operating noise and vibration is desirable in military tracked vehicles to reduce weight and improve power to weight ratio. It is also necessary to increase the rating of existing transmissions in military tracked vehicles, like prime movers, to accommodate the additional weight required for ballistic protection. Hence, it was decided to apply high contact ratio (HCR) spur gearing concept which will reduce noise, vibration and enhance load carrying capacity, for a 35 ton tracked vehicle final drive. In HCR gearing, the load is shared by a minimum two pairs of teeth as in helical gears. It was decided to analyze the load sharing of the normal contact ratio (NCR) gearing used in sun-planet mesh of the existing final drive, and also, to analyze the load sharing of HCR gearing which will be used to replace the NCR gears without any change in the existing final drive assembly except sun, planet and annulus gears. This paper deals with analysis of load sharing percentage between teeth in mesh for different load conditions throughout the profile for both sun and planet gears of NCR/HCR gearing using finite element analysis (FEA). Also, the paper reveals the variation of bending stress, contact stress and deflection along the profile of both NCR/HCR gearing.