Rolling resistance
The rolling resistance of a tractor is mainly caused by the deformation of the tires and soil. Under the weight of the tractor, the tires are flattened and the soil is compacted. During the rolling process, the various parts of the tire that come into contact with the ground along the circumference of the circle are continuously flattened and deformed, and the soil in front of the wheel is pressed down to deform the soil and form a wheel track, which creates rolling resistance that hinders the forward rolling of the wheel. There are many factors that affect rolling resistance, mainly related to the size of the vertical load on the solid and moist ground. For the same tractor, if the ground conditions are different, its rolling resistance is also different. For example, when driving on asphalt, cement, or dry hard ground, the rolling resistance is small, and the tractor traction is large. Under the same usage conditions, the greater the weight added to the tires, the greater the vertical deformation of the soil, and the greater the rolling resistance. Generally speaking, reducing the deformation of the tire itself and the vertical deformation of the soil is beneficial for reducing rolling resistance. If the tractor is driven on soft ground, using low-pressure tires and increasing the tire support area can reduce soil deformation in the vertical direction, lower rolling resistance, and thus improve traction. Due to the fact that tractors are mainly used for field operations and often drive on soft ground, in order to reduce soil deformation in the vertical direction, tractors generally use the lowest pressure tires, and the same principle applies to widened tires. We should pay attention to the differences in the use of low-pressure tires, widened tires, and high-pressure tires in our operations.
Traction resistance
Traction resistance is the resistance that a tractor needs to overcome to drive agricultural machinery during operation. It is equal to the traction force transmitted by the tractor to the agricultural machinery through a connecting device. Since traction is equal to driving minus rolling resistance, increasing driving force and reducing rolling resistance are effective measures to improve traction.
Driving force
It is the horizontal reaction force of the road to the driving wheel. Therefore, the magnitude of the driving torque Mk transmitted by the internal combustion engine to the driving wheels through the transmission system indicates that the driving force Pk of the tractor is also greater. However, since Mk is determined by the power of the internal combustion engine, Pk is also limited by the power of the internal combustion engine. At the same time, Pk is limited by soil conditions and cannot be infinitely increased, because when the soil's reaction force, i.e. the driving force Pk, increases to a certain extent, the soil is destroyed, the driving wheel slips severely, and the driving force Pk cannot be increased any further. We call the maximum reaction force that the soil can produce on the driving wheel "adhesion". From this, it can be seen that the maximum value of the driving force Pk is not only limited by the internal combustion engine rate, but also by the soil adhesion, and cannot be infinitely increased.
