A small electric motor is used to directly drive a plain steel shaft that is housed in a bearing as part of the device. On the shaft, the bearing is supported freely and is sealed at the motor end. The control unit carefully regulates the motor speed, and the motor end is sealed. The motor speed can be operated in either direction and is accurately controlled by the control unit. The bearing has four pressure taps along the axis and twelve evenly spaced pressure taps around the circumference. All are connected to the manometer via a thin, flexible plastic tube, allowing for simultaneous observation of the pressure heads at all sixteen points. By adding weight to the arm that is supported beneath the bearing, it can be loaded.