A disconnect mechanism is provided which, upon a suitable trigger event, such as excess temperature causes a camming element 40 having a tapered head 52 to move under the urging of a compression spring 60 such that the tapered head 52 becomes trapped between a rotating element 32 and a support 42. This gives rise to frictional inter-engagement which prevents further rotation of the rotating element 32 and thereby locks the rotating machine against further rotation. This is turn causes the shear region to fail thereby drivingly disconnecting the machine from its prime mover.