Abstract: A vibrator has a hydraulic circuit connected with a hydraulic power unit. An electromagnetic valve disposed at the hydraulic circuit is regulated for the time for actuating a switch valve through a control signal. A plunger capable of bearing a load of an object to be tested at an upper end portion thereof has an oil chamber for pressurizing the plunger in such a manner as to be able to move upward and downward. An oil passage communicates with the oil chamber and with the electromagnetic valve. A vibration applying cylinder is capable of vibrating the plunger at a desired amplitude and frequency through hydraulic oil which is fed from the electromagnetic valve. A lift means lifts the vibration applying cylinder to a predetermined height. A controller capable of outputting, as a control signal, a setting signal for setting at least the amplitude and frequency of the plunger is provided. A control unit actuates the hydraulic power unit and the electromagnetic valve in accordance with the control signal.

Abstract: A less expensive and less bulky motor vehicle performance test apparatus is disclosed which conducts various tests of a motor vehicle, such as a running test of a four-wheel drive vehicle and an evaluation test of a viscous coupling of a four-wheel drive vehicle, The apparatus comprises a synchronizer including a belt drive whereby the peripheral speed of rollers of a front wheel roller assembly is equalized with the peripheral speed of rollers of a rear wheel roller assembly, eddy-current dynamometers fixedly coupled with the front and rear wheel roller assemblies, respectively. An electromagnetic clutch is arranged to interrupt the drive connection by the synchronizer. The electromagnetic clutch is engaged to conduct a running test of a vehicle under test. The clutch is disengaged and excitation current is introduced to at least one of eddy-current dynamometers to conduct an evaluation test of a viscous coupling of a four-wheel drive vehicle.