Mounted on shaft A is round box member 1 with a number of concentric grooves a. The grooves are partly filled with a liquid and the box is closed by cover b. As the shaft begins to rotate the liquid is at rest with respect to the walls of the groove. Owing to friction, the liquid begins to rotate and finally reaches a speed equal to that of box 1. Owing to its inertia and viscosity, the liquid tends to maintain a constant shaft speed, notwithstanding variations in speed in the drive.
$3726$SHP,M$