Pull, lift and side force characteristics of cage wheels with opposing circumferential lugs

This study was aimed at finding the effect of a lug parameter that has been considered less important in improving the performance of cage wheels. This was the lug arrangement or configuration like a rubber tire on the cage wheels, called opposing circumferential lugs. The experiments were carried out in a laboratory soil bin with clay soil of 49% average soil moisture content and 135 kN average cone index. Cage wheels with opposing circumferential lugs at four levels of circumferential angle, 0°, 15°, 30° and 45°, were evaluated and their performance compared with normal cage wheels. The lug spacing and wheel slip of the test wheels were varied from 20°, 24°, 30° to 40° and from 25, 40 to 55%, respectively. All tests were conducted at a constant lug sinkage of 7 cm and at 20 rpm rotational speed of the wheel. The characteristics of three orthogonal force components produced by the cage wheels with opposing circumferential lugs were obtained by using a triaxial dynamometer. The pull and lift forces of the opposing lugs at circumferential angles of 15° and 30° were significantly higher than those of the normal lugs due to increase in the shear area in the corresponding direction, caused by the increase in lug length at larger circumferential angle. However, the wheel forces were drastically affected by the influence of the opposing circumferential lug interference at 45° circumferential angle. The better balancing of side forces could be obtained by increasing the circumferential angle and decreasing the lug spacing. The cage wheels with opposing circumferential lugs at 15° circumferential angle, 24° and 30° lug spacing gave superior performances as compared to other combinations.