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Types and components of Secondary tillage implements
Harrow
Classification of disc harrow Based on power source, they are classified as Tractor drawn and bullock drawn disc harrows. a) Single action disc harrow Fig. 14.1 line diagram of disc arrangement in single action disc harrow b) Double action disc harrowFig. 14.2 line diagram of disc arrangement in double action disc harrow c) Tandom disc harrowIt is a disc harrow comprising of four gangs in which each gang can be angled in opposite direction as shown in Fig.14.3. Fig. 14.3 line diagram of disc arrangement in tandom disc harrow d) Off-set disc harrowFig. 14.4 line diagram of disc arrangement in offset disc harrow (Courtesy: http://www.sumoindia.com) Gang: Each set of discs that are mounted on a common shaft is called the gang.Plate : 14.2 Different types of disc used in disc harrow Gang bolt or arbor bolt: It is a long heavy of square headed bolt from the other end, a set of discs are mounted on the gang bolt. The spacing between the discs on the gang bolt ranges from 15 to 25 cm for light duty and 25 to 30 cm for heavy duty harrows. The angle between the axis of the gang bolt and the direction of travel is called the gang angle. Gang control lever: A lever, which operates the gang mechanisms of the disc harrow, is called the gang control lever. Spool or spacer: The flanked tube, mounted on the gang bolt between every two discs to prevent the lateral movement of the disc on the shaft is called the `spool’ or `spacer’. It is just a device for keeping the discs at equal spacing on the gang bolt. It is usually cast in special shapes and sizes and is generally made of iron. Bearing: Bearing is essential to counter act the end thrust of the gang due to soil thrust. The harrow bearings are subjected to heavy radial and thrust loads Chilled cast iron bearings are used for heavy radial and thrust loads and they are also used due to their durability. Transport wheel: In trailing type disc harrow, the transport wheels are provided for transport work on roads and for preventing the edges of the discs from damage. Mounted type disc harrows do not require wheels for transport work. Scraper: It prevents disc from clogging. It removes the soil that may stick to the concave side of the disc. Weight box: A box like frame is provided on the main frame of the harrow for putting additional weight on the implement. Additional weight helps in increasing the penetration of the disc in the soil. There are several factors which affect the penetration of disc harrow in the field. If the disc gangs are set perpendicular to the line of draft, the penetration is not adequate. Penetration can be increased by adding some additional weight on the frame of the harrow. For obtaining maximum penetration, the gangs should be set with the forward edges of the discs parallel to the direction of motion. If the hitch point is lowered, better penetration is achieved. A sharp edged disc has more effective penetration compared to blunt edged disc. It is observed that penetration is better in low speed than in high speed. The following are a few adjustments for obtaining higher penetration i. By increasing the disc angle ii. By adding additional weight in harrow iii. By lowering the hitch point iv. By using the sharp edged discs of small diameter and lesser concavity v. By regulating the speed. |
Last modified: Tuesday, 26 June 2012, 1:33 PM