Research on designing devices for uprooting trees after harvest

Dao Vu, To Quoc Huy

Forest Industry Research and Technology Transfer Center                                                                  

Uprooting trees on natural forest, especially plantation areas after harvest for preparing soil for planting requires many laborers and much time and money. In Vietnam, this work is usually done by hand and in some regions of Vietnam, done by bulldozer with knife or bailer-shaped blades. These methods have a low productivity and effectiveness.

To have a specialized tool for effectively uprooting trees, research on designing and producing them is necessary to meet the demands of our present forestry sector.

Methodology: Investigation, collection of documents regarding characteristics and features of research matter; Calculation methods for designing agricultural devices; Methods for experimenting on agricultural devices.

Investigation research

Topography, soil and vegetation      

The northern mountainous topography is quite complex, and the area for forest production is divided and has steep slopes. Soil in this area is mainly feralit soil with much laterite. Vegetation includes a number of main species, such as: some species of Mytarcaece with 1-1,5m  high and 3-10cm in diameter.       

The tree stumps on the scene after harvest, for example: stumps of Eucalypts, Acacia and Pine have 12-20 cm in height, 15-45 cm in diameter and the density of stumps is approximately 1500 stumps per hectares and the root system sticks into soil about 40-150 cm deep.

* Equipment, Machines           

The main equipments used for uprooting trees and vegetation is a chain bulldozer with a capacity of over 100 horsepower, such as T-130, TZ-171, Komatsu D65, D85A, or Fiat, combined with a dumper or the machines which have toothed wheels for falling trees and collect roots. In general, using these machines gives us low productivity and in the slope areas, it causes soil erosion. These machines are only suitable for clearing natural vegetation or grass-plots.

Design and manufacture

* Basic design parameters

+ The maximum depth of teeth: 700 mm

+ Rising angel: α = 25 – 300 

+ Device frame shaped into a circle, the places where the toothed wheels are installed are designed so we can change the depth when the machines work.

*Selection of motive power           

 Based on the results of calculating the suitable capacity for digging up stumps which are 40 cm in diameter, we selected the chain pulled Komatsu –D65A which the capacity of 155 horsepower.

Machine test results           

The initial results show that the new devices designed for uprooting work quite well. The productivity is higher than other uprooting machines by about 20 – 25%. Fuel costs and the price will reduce by at least 20%. Soils are prepared better and soil erosion is reduced.           

For Eucalyptus stumps with a diameter of 10-35 cm, the productivity of LHM achieves an average of 650- 800 stumps per 7 hours. It uses 125 lit diesel per 7 hours. The tree uprooting devices are researched, designed and produced on the basis of the suitability of the characteristics of the work.

The device is installed at the end of chain puller with the capacity obtain 150 – 180 horsepower, and they can uproot the stumps with the diameter of 10 – 60cm. The productivity achieves 650-800 stumps per 7 hours with the diameter of  10 – 35 cm.Machine union works stably, giving high productivity, low fuel costs and the price is reduced by  20%, lower than other uprooting machines.

Our project has not tested this device in a wide area, where geography with the different tree stumps kinds, time for testing is limited so we can not estimate all working efficiency and economic efficiency of this device. Thus, the device need to be researched completely and tested in the bigger scale for defining the characteristics of them. Research on designing, producing the uprooting devices for installing in the tractors which have higher capacity for uprooting stumps are over 60 cm in diameter. 

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