Monga gawo lamphamvu la chotengera, pulley yoyendetsa imagawidwa m'mitundu iwiri: Smooth pamwamba ndi pulley yokutidwa ndi mphira.Pansi pa mphamvu yochepa komanso kutentha kochepa kozungulira, pulley yosalala ingagwiritsidwe ntchito.Pamalo a chinyezi, mphamvu yayikulu komanso kutsetsereka kosavuta, pulley yokhala ndi mphira iyenera kugwiritsidwa ntchito.