Farm Power & Machinery

Gear and gear box

• A tractor engine runs at high speed, but the rear wheel of the tractor requires power at low speed with high torque. Hence it is very much essential to reduce the engine speed and increase the torque available at the rear wheels of the tractor.

  The power available is given by

                                                                                          2?NT

                                                                     Power = -------------- ……………….Watt

                                                                                       60 x 1000

                           where,

                                        T - Torque in Newton-metre (N-m)

                                       N - Speed in rpm
• If the engine power is constant, it is obvious that for higher torque at wheels, low speed is required and vice versa. So the gear box (Plate 7.1) is fitted between engine and rear wheel for variable torque and speed. This is done by suitable design of gear and shafts. Speed varies according to the field requirements and hence a number of gear ratios are provided to suit the varying conditions. Gears are usually made of alloy steel.

  

  Plate : 7.1 Gear box of a tractor

  There are different types of gear box used in tractors such as Sliding mesh, Constant mesh and Synchromesh