I work on very large (30+ tons) custom mining equipment that rotates side to side. One of the machines had its center of gravity above the axis of rotation. On it passing a certain point, the machine started rotating down on its own and almost smashed into the ground next to us. The spring applied brakes engaged and stopped it about 10in of the ground! If it had hit the ground, a multimillion dollar, one of a kind piece of equipment would have been ruined!