Abstract
In a potato harvester, the tuber damage is mainly caused by the primary web. In this reseach, the relations of web speed, ratio of web speed to forward speed and tuber size to tuber damage were investigated. The speed monitor was developed to measure and display wed speed, forward speed and speed ratio. The tuber damages were evaluated by DAMAGE POINT and DAMAGE INDEX that had been defined by the extent of wounds and bruises.
The results obtained were as follows:
(1) The tuber damage became severer as web speed or its speed ratio was greater. This fact shows that soil on web acts as a cushioning stuff. Covering structure, by rubbers or soft materials released the soil from cushioning duty. However, as bruising occured by small shock which did not make wound, the web speed should be less than 1m/s with the forward speed of less than 0.5m/s.
(2) The grade and number of damages on one tuber tended to become greater, as tuber size became greater.
(3) The wounds were distributed evenly on all part of tuber. On the contrary, 70-80% of the bruises were located on the top and bottom part of tuber. Therefor, potato harvester should be designed on the basis of no occurence of bruising on top/bottom part of tuber.
