Abstract: The present invention relates to a linkage unit (101) for a roller chain link assembly of a caterpillar track, the unit comprising a bushing (102) which has a body and a seat (103) retaining a sealing member (104) at each of the respective axial ends of the body, an outer roller (105) mounted on the bushing (102) for rotation relative to the bushing (102) and means for reducing friction (106) disposed between the internal surface of the outer roller (105) and the outer surface of the bushing (102). The present invention also relates to a roller chain link assembly (110) having the aforementioned linkage unit (101) and a caterpillar track (301) suitable for use in track-type machines employing the roller chain link assembly (110).

Abstract: Amphibious construction equipment comprising a working unit supported on a pair of elongate, parallel, buoyant pontoons (2) each of which carries a caterpillar track (3) driven by sprockets mounted on an axles (5), the axles (5) being positioned at or towards the ends of each pontoon (2) on its upper surface, wherein each axle (5) is driven by at least one hydraulic motor (4), all the motors (4) being powered by a single hydraulic pump (7), the motors (4) on each pontoon (2) being arranged such that they run synchronously as to both direction and rate but not necessarily in the same direction or at the same rate as the motors (4) on the other pontoon (2).