Abstract: An endless loop tractor drive mechanism has equally spaced pushers meshing with a bucket train where its filled circular buckets are traveling along a substantially straight ascending path to a dumping support wheel. Wire rope cables or other flexible tension elements extend between the buckets. The pushers have drive rollers for pushing the buckets, and additional rollers for guiding the cables. Additional support wheels guide the bucket train along a catenary loading span where the buckets are dragged through bulk material to fill the buckets. At least two pushers engage at least two successive buckets at all times, to distribute and share the lifting load among two or more buckets. Due to the straight ascending path, the cables are not flexed when the lifting load is applied. Thus, the combination of high tensile stresses and high cable flexure is avoided. Wear and tear on the cables are thereby minimized. Fraying and breakage of the cables are no longer problems.