In the Han dynasty, a new type of water lifting tool-rollover appeared. According to the Book of the Later Han Dynasty, in the Eastern Han Dynasty, Bilan invented rollover and "set a locomotive to divert water". The working principle of the dumper is: the upper and lower sprockets drive, and the turning plate around the wheel is the transmission chain. This turning plate is also a workpiece for lifting water, which drives the dumper to rotate and lift water at the same time. For a long time, dumper has become the most widely used and important water lifting machine in rural areas of China.

Ma Jun improved the dumper and made a new type of dumper, which has exquisite structure, can continuously lift water and greatly improve the efficiency. This new type of rollover is also labor-saving, and children can also turn. Later, this kind of dumper developed into a keel waterwheel, which played an important role in the development of agricultural production in China.

Introduction of subway vehicles

Also known as "water-turning bucket car", it is a water-lifting tool that appeared in the Tang Dynasty. Water-powered tools for irrigating fields. The principle is as follows: hit two hard piles on the bank where the water is very fast to make a big wheel, and the shaft of the big wheel is placed on the pile fork. The upper part of the big wheel is higher than the embankment, and the lower part is immersed in water and can rotate freely. The bamboo tube is obliquely tied to the water receiving plate on the outer side of the wheel spoke, and there is a water tank on the bank of the wheel near the water receiving pipe.

When the water receiving tray of the big wheel is impacted by the rapids, the wheel rotates and the water tank is filled with water. When the wheel top rotates, the cylinder mouth inclines downward, and water just pours into the sink and flows to the field along the sink. This kind of truck irrigates the land day and night, without the help of people and animals, with high efficiency, which was produced in Sui and Tang Dynasties.