ABSTRACT
The crawler-(track) type tractor unit is designed for those jobs requiring high traction effort and working on low bearing capacity soil. They are usually rated by size or weight and power. Crawlers are more widely used than wheel tractors (Sain and Quinby, 1996). Table 3.1 provides a comparison of crawler-tractor and wheel-tractor utilisation. An advantage of wheel-type tractors as compared with crawler tractors is the higher speed. However, in order to attain a higher speed, a wheel tractor must sacrifice pulling effort. Also, because of the lower coefficient of traction between rubber tires and some soil surfaces, the wheel tractor may slip its wheels before developing it’s rated pulling effort. The crawler tractor is used where high speed is not possible but high drawbar pull and good traction are mandatory. The most essential operating characteristic of the crawler tractor is that it is a powerful, versatile machine best used for rough work over short distances (Russell, 1985). As we consider very soft clay in this study, our attention is drawn to the crawler tractor.
