A guard is a device designed to prevent injury from rotating machinery.
Three concentric and rotating shafts would be known as a contra-rotating device. Currently, several machines like these are being designed, according to the US Patent Office.
a device that uses a positive means such as a lock to hold an energy isolating device in a safe position and prevent the energizing of the equipment and/or machinery being worked on
A wheel clamp, is a device that is designed to prevent vehicles from being moved. In it's most common form, it consists of a clamp that surrounds a vehicle wheel, designed to prevent removal of both itself and the wheel.
There are lots of device that rotate; one of them is a wheel.
a propeller
a Propeller
a engine
knuckle joint
a flywheel
propeller.
propeller
It is the propeller.