[机] bottom filling of tank cars

yoú cáo chē dǐ bù zhuāng yoú ㄧㄡˊ ㄘㄠˊ ㄔㄜ ㄉㄧˇ ㄅㄨˋ ㄓㄨㄤ ㄧㄡˊ