Effect of Gear Composition and Soil Interaction on Surface Wear of Worm Gear of Self Propelled Rotary Hoe

This study was conducted on a self-propelled locally made rotary hoe to overcome a problem of frequent transmission failure. The machine is used for mechanical weed control and hoeing.It was observed that the worm gear used in its transmission often failed due to surface wear of gear teeth. Worm gears made from three different copper alloys were tested against soil resistance in sandy loam soil bin. The gears were formed of commercial gun metal (Cu 87.76%, Sn 7.74, Zn 1.52%), gun metal (Cu 88%, Sn 7.38%, Zn 1.78%), and gear bronze (Cu 85.92%, Sn 4.96%, Zn 2.93%, Ni 1.23%). The gear compositions were determined using atomic absorption. The gears under test exhibited significant difference in surface wear among each other. As compared to gear bronze commercial gun metal and gun metal showed surface wear of 245% and 109% respectively. The highest surface wear was observed in commercial gun metal whereas lowest surface wear was observed in gear bronze. It was concluded that gear bronze may be the best material composition for use in the worm gear of the rotary hoe transmission box as compared to the other two alloys tested.4