Zhang, a 37-year-old local farmer, who is interested in scientific inventions, has made six miniature submarines with several fellow engineers, one of which was sold to a businessman in Dalian at a price of 100,000 yuan ($15,855) last October. The submarines, mainly designed for harvesting aquatic products, such as sea cucumber, have a diving depth of 20-30 metres, and can travel for 10 hours, local media reported. Amateur inventor Tao, 34, made a fully functional submarine, which has a periscope, depth control tanks, electric motors, manometer, and two propellers, from old oil barrels and tools which he bought at a second-hand market. He took 2 years to invent and test the submarine which costs 30,000 yuan ($4,385). Farmer Wu Yulu drives his rickshaw pulled by a self-made walking robot near his home in a village at the outskirts of Beijing. A woman rides an unicycle at a park in Shanghai. The unicycle was designed by Chinese inventor Li Yongli who called it "the number one vehicle in the world." Zhao Xiuguo and his brother Zhao Xiushun built the car from scrap metal and said that they wanted to design and build the first Formula One racecar in China. The round steel flying device, which cost more than 20,000 yuan ($3,135), is the fifth model made by Shu, a junior middle school graduate. It measures around 5.5 meters (18 feet) in diameter, and is powered by eight motorcycle engines. Shu managed to hover for 10 seconds at about 1 metre (3.3 feet) above ground during a recent test flight.