Module 1. Tractor Mechanics
Module 2. Traction
Module 3. Introduction to Transmission System
Module 4. Clutch System
Module 5. Gear Box
Module 6. Differential and Final drive
Module 7. Brakes
Module 8. Steering system
Module 9. Hydraulics
Module 10. Power Transmission
Module 11. Human Factors
Lesson 8. Traction aids
A number of factors influence the development of traction force by a traction device, which in our case usually is a pneumatic tyre. These factors include area of contact on the soil by the traction device, rolling resistance, tyre inflation pressure, etc. In addition to this a lot of aids can be used for enhancing the traction developed.
Effect of Inflation pressure
Inflation pressure affects the traction as is evident from the Newton Mohr expression. The tyre thrust can be increased if the area of contact on the ground surface is increased specially in case of soils which are cohesive in nature. Hence, as the tyre pressure is decreased, the contact area increases, and traction can be increased, and vice versa. However, the tyres can get cracked or can get damaged due to low pressure.
Tread Pattern and Design
Tyre tread pattern and design is also important for enhancing the traction. The tyre tread pattern depends upon:
Tyre inflation pressure
Direction of motion
Normal load on the tyre
Tracks have been used as a traction aid in loose ground surface. This is not only used in loose soil in field conditions but also in icy and snowy conditions. This helps in traction by reducing the bearing pressure. These also tend to be a costly option, although a quite a efficient one.
Tyre chains are used around the tyre and helps in improving traction by increasing adhesion in slushy conditions.
The normal load on traction wheels can be increased by putting water or air inside the pneumatic tyre-tube. Filling water in the tube is water ballasting, and filling sand in the tube is sand ballasting. Generally the tube is filled upto maximum of 75% by the ballasting material and rest with the air at the rated air pressure.
Additional weights are also used