In this article we will discuss about:- 1. Components of Disc Harrow 2. Penetration of Disc Harrow 3. Care and Maintenance.
Components of Disc Harrow:
A disc harrow mainly consists of:
1. Disc
2. Gang
3. Gang bolt or Arbor bolt
4. Gang angle
5. Gang control lever
6. Spools or spacer
7. Bearings
8. Transport wheels
9. Scraper and
10. Weight box.
1. Disc:
It is a circular, concave revolving steel plate used for cutting and inverting the soil. Disc is made of high grade heat treated hardened steel. Tractor drawn disc harrows have concave discs of size varying from 35 to 70 cm diameter. Concavity of the disc affects penetration and pulverisation of soil.
Usually two types of disc are used in disc harrows:
(a) Plain disc and
(b Cut-away disc
Plain discs have plain edges and they are used for all normal works. Most of the harrows are fitted with plain discs only. Cut-away discs have serrated edges and they cut stalks, grasses and other vegetative matter better than plain discs. Cut-away discs are not very effective for pulverisation of soil but it is very useful for puddling the field especially for paddy cultivation.
2. Gang:
It is an assembly of concave discs mounted on a common shaft with spools in between.
3. Gang Axle or Arbor Axle:
It is a shaft on which a set of discs are mounted. The spacing between the discs on the gang bolt ranges from 15 cm to 23 cm for light duty harrows and 25 to 30 cm for heavy duty harrows.
4. Gang Angle:
The angle between the axis of the gang and the line perpendicular to the direction of travel is called gang angle.
5. Gang Control Lever:
A lever which operates the angling mechanism of the disc harrow is called gang control lever.
6. Spool or Spacer:
The flanged tube, mounted on the gang axle between every two discs to retain them at fixed position laterally on the shaft is called spool or spacer. It is just a device for keeping the discs at equal spacing on the axle. It is usually cast in special shapes and sizes and is generally made of cast iron.
7. Bearing:
Bearing is essential to counteract the end thrust of the gangs due to soil thrust. Disc harrow bearings are subjected to heavy radial and thrust loads. Chilled cast iron bearings, ball bearings or tapered roller bearings may be used on disc harrows. Oil soaked wooden bearings are very common for disc harrows, because they are cheaply available. Chilled cast iron bearings are also used due to their durability.
8. Transport Wheel:
In trailing type disc harrows, transport wheels are provided for transport work on roads and for preventing the damage of the roads. This also helps in protecting the edges of the discs. Mounted type disc harrows do not require wheels for transport purpose.
9. Scraper:
Scraper prevents the discs from clogging. It removes the soil that may stick to the concave side of the disc.
10. 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 discs in the soil.
Penetration of Disc Harrow:
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 disc 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.
In short, the following are a few adjustments for obtaining higher penetration:
i. By increasing the disc angle
ii. By adding additional weight on the harrow
iii. By lowering the hitch point
iv. By using the sharp edged discs of small diameter and lesser concavity and
v. By regulating the optimum speed
Care and Maintenance of Disc Harrow:
i. Bearing must be thoroughly greased at regular intervals.
ii. All the nuts and bolts must be checked daily before taking the implement to the field.
iii. Blunt edges of the discs should be sharpened regularly.
iv. During slack season, the worn parts including bearings should be fully replaced.
v. It is better to coat the outer and inner surfaces of the discs when the harrow is lying without use in slack season.