Studios on the Improvement of Stationary Onion Topper

Abstract

Experiments on onion topper were conducted for different types of retarder to determine the effects on topping performance. The results obtained are summerized as follows;
1. Fixed type rertader
Two types of retarder, net covered and tined type, were used (Fig. 2). The net covered type retarder did not give satisfactory topping performance. The tined type retarder was a little mare effective than net covered type and miss-topped bulbs were reduced to 7.4% when the harvesting rate of bulbs was less than 2.6ton/hr.
2. Rotary retarder
Higher revolving speed of retarder resulted in higher topping performance. However, greater harvesting rate of bulbs resulted in more miss-topped bulbs. On the other hand the topping performance at different angle of screen slope was not evident. When the harvesting rate of bulbs was less than 5ton/hr and topper was set at 35-50rpm revolving speed of retarder and at the angle of screen slope of 1.5-3.0 degrees, miss topped bulbs were able to be reduced to 1.5%.
The topping performance at different harvesting term was investigated. In these experiments topping was done at the rate of 5ton/hr and topper was set at 48.7rpm revolving speed of retarder and at the angle of screen slope of 3 degrees. In the case of early harvesting term (September 12), the stripped and damaged bulbs were only 0.7%. However, miss-topped bulbs reached about 24% under non-curing tops condition (a moisture content of tops was 69.1% and a green tops ratio was 59.4%). In the case of latest harvesting term (October 2), miss-topped bulbs were decreased 4.0% and the stripped and damaged bulbs were 1.3% (a moisture content of tops was 28.6% and a green tops ratio was 0.0%).
Through these experiments it was found that this topper could be used in practice between mid-September and early-October.