[机] positive infinitely variable driving gear

wú xiàn biàn sù chuán dòng zhuāng zhì ㄨˊ ㄒㄧㄢˋ ㄅㄧㄢˋ ㄙㄨˋ ㄔㄨㄢˊ ㄉㄨㄥˋ ㄓㄨㄤ ㄓˋ