Abstract
Experiments were carried out to know the magnitude of gyroscopic couple which occurs on piano-wire cutting blade during mowing work. The influence of gyroscopic couple on the physical stress of operator and ease of operation was also studied and compared with cut-away blade. The results are as follows:
1. The gyroscopic couple of piano-wire blade was approximately 1/5 and 1/20 of the 4 and 8 cut-away blades, respectively. The scattering of grasses mown by the piano-wire blade resulted in a fewer turn-over motions and smaller moment of inertia of the blade.
2. Owing to the above reasons, the use of piano-wire blade reduced the time required for mowing and the physical stress of operator.
3. Man-machine system which had a mechanical part consisting of a tapered ridge model were used for tracking task, and the performance of work was analysed dynamically. The human operator's adaptability to the change of differential constant T1 was experimentally investigated for preview tracking system, in which assumed transfer function was included. It is known that the differential constant T1 is dependent on the physical stress. Under the signal of tapered shape, differential constants T1 for piano-wire blade, 4 and 8 cut-away blades were 0.38, 0.43, and 0.90, respectively. The result gives good agreement with the magnitude of gyroscopic couple and the physical reaction of operator.
4. In mowing work with 8 cut-away blade, a large quantity of gyroscopic couple of 1.5kg-m or thereabout was occurred in stepping of feet and in turn-over motion of blade for brushing aside grasses. This value is equivalent to 3kg of force at handle grip.
5. In the tracking work using cut-away blade, the large phase shift and the large displacement (the distance between the cutting blade and ridge models) appeared even in low ground speed because of larger gyroscopic couple, resulting in difficult handling.
6. Judging from surface EMG, heart rate and rate of work, the most appropriate cutting width is considered to be 150-200cm.
