In this paper, the frictional characteristics of a test motor are investigated experimentally using three different types of hydraulic oil. The test motor is a pressure-balanced type vane motor, and the test oils are turbine oil, anti-wear type hydraulic oil and friction-modified type hydraulic oil. All of the test oils are available in the market. In the friction-modified type hydraulic oil a kind of fatty acid is added as a friction-modifier.
As the result of this investigation, it became clear that the magnitude of frictional torque at start and in low speed range was very different according to the types of hydraulic oil. For example, in the case of the friction-modified type hydraulic oil, the magnitude of frictional torque at start is only one half of that of the turbine oil, and in the case of the antiwear type hydraulic oil, the magnitude of frictional torque at start takes the intermediate value between that of other two test oils.
In the case of the turbine oil, the frictional torque becomes largest at start, and it reduces with increase of rotational speed. But, in the case of the anti-wear hydraulic oil and the friction-modified hydraulic oil, the frictional torque at 10rpm is larger than that at start.

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The performance of filter elements is generally evaluated by particle separation capability, contaminant retention capacity and degree of resistance to the flow of fluid.
In this paper, we propose a method for making quantitative evaluation of these characteristics. (1) Particulate Removal Characteristics: Particle separation rate for each particle size interval is shown graphically. (2) Contaminant Retention Characteristics: Hydraulic conductance of a filter element versus amount of the retained contaminants is shown graphically. The hydraulic conductance is expressed by the flow rate divided by the pressure difference and the contaminant retention is defined by the total contaminant shadow area which is calculated on the basis of the particle size distribution analysis of fluid samples.
The proposal is available for making clear the results of either multi-pass or single-pass filteration performance tests. It will not only provide an absolute filter rating technique but also elucidate the possible correlation of the resistance to the flow of fluid with the contaminant retention. We show here some applications of the proposed method to the evaluation of paper type filter elements and examine the contaminant retention characteristics theoretically with an assumption of both the contaminant capture mechanism and the flow mechanism within the filter elements.

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