https://blog.gongquiz.com/2020/11/26/%ec%9b%90%ec%8b%ac%ed%8e%8c%ed%94%84%ec%9d%98-%ed%9a%8c%ec%a0%84%ec%88%98%ea%b0%80-1200rpm-%ec%9d%bc-%eb%95%8c-%ec%96%91%ec%a0%95-15m-%ec%86%a1%ec%b6%9c%ec%9c%a0%eb%9f%89-2-4-m3-min-%ec%b6%95/