This document discusses disc harrows, which are farming implements used for secondary tillage operations like breaking up soil clods and destroying weeds. It describes the different types of disc harrows including single action, double action, and offset harrows. The parts of a disc harrow like the frame, discs, arbor bolt, and scrapers are defined. Forces acting on disc harrows and factors to consider when selecting a disc harrow are also summarized.

1. Agro Machine
Engineering
Mr. Matin A. Shaikh M.E. Design
Mr. Matin A. Shaikh

2. Course objectives:
 To explore various agro machinery related operations such as
ploughing, harrowing, threshing etc.
 To learn the working mechanisms of different agro machines.
 To make the student to know about design aspects of different
agro machines.
Mr. Matin A. Shaikh

3. Course outcomes:
After completion of this course, a student will be able to
 Distinguish between various agro operations such as ploughing,
harrowing, threshing etc.
 Select and design mechanism for various agro machines
Mr. Matin A. Shaikh

4. Chapter No. 3
Secondary Tillage Equipments
 Tillage: Mechanical manipulation of soil which is performed in order to
obtain a seedbed of desired tilth favorable for the seed emergence and crop
growth .
 Tillage operations are generally carried out before sowing or planting.
 The tillage can be classified in to two main categories,
 Primary tillage
 Secondary tillage
 Secondary tillage: To improve the seedbed by increased soil pulverization,
and to cut up crop residues, is accomplished by use of various types of
harrows.
 While plowing/ploughing cuts, granulates, and inverts the soil, creating
furrows and ridges, disking breaks up clods and surface crusts.
Mr. Matin A. Shaikh

5. Continued..
 Additionally, disking improves soil granulation and surface uniformity.
As one of the most important soil preparation practices, disking is
beneficial for provoking the weed growth and destroys already
emerged weeds.
 It also assists in the important task of incorporating crop residues into
the soil.
 Secondary tillage is any working completed after primary
tillage and is undertaken for
 reducing clod size,
 weed control,
 incorporation of fertilizers and
 leveling soil surface
Mr. Matin A. Shaikh

6.  Harrows: Harrows are used for shallow cultivation in operations such as
preparation of seedbed, covering seeds and destroying weed seedlings.
 Harrows are of two types:
 Disc harrow and
 Blade harrow.
 Disc Harrow
 The disc harrow consists of a number of concave discs of 45 to 55 cm in
diameter. These discs are smaller in size than disc plough, but more
number of discs are arranged on a frame. These discs are fitted 15cm
apart on axles.
 Two sets of discs are mounted on two axles. All the discs revolve
with axles. The discs cut through the soil and effectively pulverise the
clods.
 A disc harrow is a farm implement that is used to till the soil where
are to be planted. It is also used to chop up unwanted weeds or crop
remainders.
harrow - दंताळे फिरवणे/
शेतातील ढेकळे िोडण्यासाठी वापरतात ते दंताळे
Cultivation - मशागत
Shallow – jaast Kaola nasaNaaro
Mr. Matin A. Shaikh

7.  Disc harrows are farming implements used to prepare the soil
for planting or sowing by breaking up the clods and surface crusts, thus
improving soil granulation and destroying the weeds. They consist
of concave cutting blades (disks), mounted on a common shaft, that
form a gang.
Continued..
Mr. Matin A. Shaikh

8.  Blade harrow: The blade harrow does not go deep in the soil
therefore, can be used for killing weeds where only shallow ploughing
desired. The width of such type of harrow varies between 38-108cm.
Continued..
Mr. Matin A. Shaikh

9. Parts of disc harrow:
 1. Frame; holds and supports the disc harrow
 2. Disc; circular concave cutting blade made of steel. There are the two types
of discs:
 Smooth edge disc; also called plain edge disc; consists of plain discs used for
normal soil conditions
 Notched edge disc, also called cut-away discs or scalloped edge discs with
serrated edges; used for cutting crop residues and weeds
Mr. Matin A. Shaikh

10.  3. Arbor bolt; also called gang bolt, is a long heavy steel shaft on
which discs are mounted
 4. Spool or spacer; component mounted on arbor bolet between
every two discs to retain their fixed position and prevent any
movement of the disc
 5. Bearings; essential for providing rotation of the gang and
regulating the thurst.
 6. Scraper; removes the soil from the disks, keeping the concave
side of the disk clean, thus preventing the clogging of the discs
 7. Disc gang; each group of disks mounted on a common arbor
bolt with disc spacer, bearing, and bumper; may consist of 3 to 13
discs
 8. Weight box; included on the frame to provide additional weight
for increasing the penetration of the disc into the soil
Mr. Matin A. Shaikh

11. Mr. Matin A. Shaikh

12. Types of Disc Harrows:
 There are various types of disc harrows. Regarding of the operation
mode, there are three different types of disc harrows:
 Single action disc harrow: It consists of two disc gangs arranged in
opposite directions, it throws the soil in opposite directions creating
ridges and furrows.
 Double action disc harrow; also called tandem disc harrow: It consists of
two or more gangs, discs from the front gangs throw the soil in one
direction, while discs on the rear gangs throw the soil in the opposite
direction.
tandem - एकापाठी एक असे दोन घोडे जोडलेली
घोडागाडी/ जोड दुचाकी (दोन सीटस दोन पेड्लस
असलेली)
Mr. Matin A. Shaikh

13.  Offset disc harrow: It consists of two gangs in tendem ,capable of being off
-set to either side of the centre line of pull. The soil is thrown in in both
directions, because discs of both gangs face in opposite directions. There
Harrow are usually designed for right hand off-set operation.
tandem - एकापाठी एक असे दोन घोडे जोडलेली घोडागाडी/
जोड दुचाकी (दोन सीटस दोन पेड्लस असलेली)
Mr. Matin A. Shaikh

14.  In regards to the disc diameter, there are three different disc harrows:
 Light disc harrows; with a disc diameter of 20-30 cm
 Middle disc harrows, with a disc diameter of 30-50 cm
 Heavy disc harrows, with a disc diameter more than 60cm
Mr. Matin A. Shaikh

15. Force acting on Disc harrow & its analysis:
Mr. Matin A. Shaikh

16.  𝑒 𝐿 𝑓 + 𝑒 𝐿 𝑟 + 𝑏 𝑆𝑓 − 𝑏 + 𝑑 𝑆 𝑟 = 0
 𝑒 𝐿 𝑓 + 𝐿 𝑟 = 𝑏 + 𝑑 𝑆 𝑟 − 𝑏 𝑆𝑓
 𝑒 𝐿 𝑓 + 𝐿 𝑟 = 𝑏 𝑆 𝑟 + 𝑑 𝑆 𝑟 − 𝑏 𝑆𝑓
 𝑒 𝐿 𝑓 + 𝐿 𝑟 = 𝑏 𝑆 𝑟 −𝑆𝑓 + 𝑑 𝑆 𝑟
 𝑒 =
𝑏 𝑆 𝑟 −𝑆 𝑓 + 𝑑 𝑆 𝑟
𝐿 𝑓+𝐿 𝑟
Mr. Matin A. Shaikh

17. Selection of Disc harrow:
 Quality of Work:- After harrowing the field should have an even and level
surface with minimum number of ridges. The corner should not be left
undisced.
 Implement Adjustment:-
 Disc gang angle or cutting angle- An adjustment increasing gang angle improve
penetration.
 Disc harrow leveling- It is used for to eliminate uneven penetration and side draft.
 Depth Control- The depth at which the implement is required to work is controlled
hydraulically by raising or lowering the control lever on the tractor.
 Material of Disc harrow:- Cost of (cheap) cast iron harrow is less as compared
to other material used for harrow.
 Weight:- Weight of disc harrow is low so that load on tractor will reduced.
 Availability:- Spares are easily available and easily interchangeable.
 Maintenance Cost:- Less vibration during operation. Hence no damage to
harrow parts. Therefore maintenance cost will be less.
Mr. Matin A. Shaikh

18. Mr. Matin A. Shaikh