Gears are mechanical machines which are used primarily to change the speed or direction of rotation. Gears have found tremendous use in the our lives; in the mechanical gadgets which we use in our day to day lives; starting from clocks to cars. Almost all of us must have used or at the known about changing the gear in bicycles. Here the for transmission speed the gear ratio changes where gear ratio can be simple stated as ratio of number of teeth on the input gear to the output gear. In general higher the gear ratio higher is the torque.

If a bicycle has front gear smaller than the back gear then it is said to have power ratio which will be helpful in easy movement in uphill. If the bicycle has back gear smaller than the front then it is said to have speed ratio which helps it to move downhill easily. Gear ratios can also be given as the ratio of engine speed of the car to the rotation of the drive wheels. This in higher gear one turn of shaft would produce one turn of the wheel while at lower gear more turns of the shaft would be required to produce one turn of the wheel thus producing more torque at the wheels.

Though gears are of great use in any mechanical device it definitely requires proper maintenance. For a longer and a safer run of the gear, regular monitoring is required. Grease and oils should be applied on the gear to avoid corrosion and rust. This also makes it chemically and thermally stable and thus increases the life of gear. The gear boxes should be checked thoroughly for damaged parts, elongation of chains used, condition of the sprockets, etc. All damaged parts should be replaced immediately before the machinery starts working. Cleaning of internal parts should be done with good washing liquids and thus in increases the performance of the machine