In the meantime, electric wheel truck faces serious challenge from various hydraulic mechanical drive trucks with large loadcapacity which appeared in the markets successively.
与此同时，多种大载重量液力机械传动汽车的竟相出现，使电动轮汽车面临严重的挑战。
2
A dual variable-diameter wheel pumping unit, which has long stroke and low pumping speed and large loadcapacity, is designed based on conventional beam pumping units.