In Greek mythology, Porus was the personification of expediency. He married Penia at a feast. He was sometimes considered the son of Metis and father of Eros.
... to a smaller extent by the slipping friction.
The device is covered by US patents 3,726,146 (1973) and 5,353,655 (1994) by L.A. Mishler and US patent 5,800,3 ...