Studies on the Mechanical Harvesting of Tree Fruits (III)
Dynamics of a Boom Type Tree Shaker
1974 Volume 36 Issue 2 Pages 303-310
Details
1974 Volume 36 Issue 2 Pages 303-310
This study principally purposed to analyze the vibrating system which consisted in a shaker body, a boom and tree limbs, and to find the design criteria for a boom-type shaker. It was so difficult to express this system mathematically that the system was assumed to be a lumped-constant model as shown in Fig. 1. In this experiments, a boomtype shaker mounted on 4-wheel tractor was used and limbs of cherry trees were shaken at various frequencies and strokes. The boom was made of an aluminium tube of about 5m in length and 6cm in outer diameter. The main results obtained were as follows;
1. With the heavy shaker-body and the light and stiff boom, large shaking forces could be effectively transmitted to limbs, from the shaker. For ω>>ω0 (where ω0=natural frequency of limb), the shaking force and power increased proportionally to the square and the cube of the frequency, respectively.
2. The average shaking force in practice was about 400kg and the maximum force came up to 1000kg. The maximum force was nearly equal to the calculated value. The total power was 10-20PS and the net power required for limb shaking was 5-46PS.
3. There was an inflection at 1000-1200cpm in the both curves of the force and the power versus frequency. It seemed that the natural frequency of limb was 1000-1200cpm.
4. The vibration intensity, the effective value of acceleration, was approximately 40G at the clamp position on the limb and the peak value of acceleration reached 120G. The net power per 1G was 0.15-0.4PS and it increased as the clamp position approached the crotch of limbs.
5. The actual strokes at the clamp position were smaller at 800-850cpm than those set by the shaker, but were larger at 1000-1200cpm than those by the shaker. The shaker-body was shaken in the displacement of 0.3-0.6cm due to the shaking reaction of limbs.
6. By the correlogram and the power spectrum analysis, it was found that the most distinguished frequency of limbs was that set by the shaker However, there were some higher frequencies effected by the boom deflection, engine revolution, supporting manner of the shaker and the others in the vibration of the shaker body.
