A hydraulic oscillator is advantageous due to its power amplification ability and strong durability while being placed under strenuous applications.
In the previous report, we pres e nted the theoretical characteristics regarding new type hydraulic oscillators-an oscillator with a dead zone restoring force and an oscillator with low-supressed restoring torque with a small vibratory displacement.
This paper presents an experimental analysis of these vibratory characteristics. That is, it has been experimentally confirmed that the vibratory characteristics of the oscillator with a quasi-dead zone restoring force agree very well with the theoretical characteristics of the oscillator with a perfect dead zone restoring force on condition that the values of parameter 1/k_o are less than 0.15. As regarding the oscillator with a low-suppressed restoring torque, the experimental vibratory characteristics have been compared with the theoretical ones which were obtained from analogue simulations computed by using the restoring torque measured experimentally, and it was shown that the new type oscillator has lower frequency characteristics than the former oscillators.

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Swath-plate type variable delivery axial piston pump is commonly applied to in small-size agricultural and construction machines as the power source for hydrostatic transmission. The use of hydrostatic transmission is increasing for the above types of machines due to its ease in control. In most of applications, however, the pump is operated manually.
It becomes very important to study not only static but also dynamic characteristics of the operating moment. The latter delicately affects feeling in manual operation and noise level. The authors found, however, that there are few studies on the dynamic operating moment of the variable delivery axial piston pump for manual operation.
In this paper, static and dynamic characteristics of the operating moment of a swath-plate type variable delivery axial piston pump, in which roller bearings are used to support the swath-plate, have been studied experimentally as well as theoretically. The effect of the tilt angle supporting system was considered.
The following results were obtained in this study.
(1) Average values of experimental operating moment were in good agreement with those of theoretical exciting moment which is derived from pressure measured in the cylinder block (measured cylinder pressure) without considering the dynamic characteristics of the tilt angle supporting element. Concerning the waveforms, however, experimental and theoretical values do n ot always coincide. (2) By taking the dynamics of the tilt angle supporting element into consideration, waveforms of the operating moment based on measured cylinder pressure are calculated. They were found to be in good agreement with those of experimental values. (3) Finally, combining the conventional calculation method of cylinder pressure and the calculation method of the dynamic behavior of the tilt angle supporting element, the operatin g moment was able to be derived. The calculated value by this method showed good agreement w i th that of experimental value of the pump in which the valve plate with wide, short and deep knotc h es were used.

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