Talking about how to irrigate farmland by rollover. It was invented and manufactured by Ma Jun during the Three Kingdoms period.

1, dumper, is a scraper type continuous water extractor, also known as keel waterwheel, which is one of the most famous agricultural irrigation machinery in ancient China. It is recorded in the Book of the Later Han Dynasty that Bilan made a rollover, which was improved by Ma Jun of the Three Kingdoms. Rollover can be driven by hands, feet, cows, water or wind. Keel blades as a chain, lying in a long rectangular slot, leaning against the river or pond. Sprockets and wheels are lowered. Send the water to the upper end of the long trough. Through this continuous circulation, water can be transported to the needed place, and water can be taken continuously, with greatly improved efficiency, convenient operation and transportation, and the water intake point can be transferred in time. The earliest application of chain drive in ancient China was rollover, which was a great improvement of agricultural irrigation machinery.

2. Lanzhou waterwheel, also known as crown block, rollover and tiger car, was built by Jinshi section in Jiajing period of Ming Dynasty. According to "Gaolan County Records", Lanzhou people continued to be knowledgeable and scholars, and Zeng Huan traveled to several southern provinces and benefited a lot. After returning to Li, the official referred to what he saw in the south. "It was ingenious to create a rollover and pull the Yellow River backward to irrigate the fields." The spoke diameter is about 20m, and the spoke diameter is10m, and the water can be lifted up to15-18m. The center of the spoke is a folding shaft, and 40-50 wooden barrels with a length of 1 m and a width of 30-40 cm are obliquely installed around the round wheel, one more than the wooden barrels. The wheel rotates slowly counterclockwise. At this point, the bucket that sank into the water was full of water. When it rises to the top of the round wheel, the river will pour into the pre-arranged groove and flow into the farmland, and then the empty bucket will return to the water with the round circle for the next cycle.