The Effect of Gang Angle of offset Disc Harrows on Soil Tilth, Work Rate and Fuel Consumption

2. Seminar on
“The Effect of Gang Angle of offset Disc Harrows on Soil
Tilth, Work Rate and Fuel Consumption”
By
SHAIKH AMIR JAMEER
2012AE/54B
DEPARTMENT OF FARM MACHINERY AND POWER
COLLEGE OF AGRICULTURAL ENGINEERING AND
TECHNOLOGY
VASANTRAO NAIK MARATHWADA KRISHI VIDYAPEETH
PARBHANI 431 402

3. INTRODUCTION
Offset disc harrow:-
It is a secondary tillage implement which pulverises,
smoothens, and packs the soil in seed bed preparation and
control weeds.
 In offset disc harrow two gangs are fitted one behind the
other.
 The soil is thrown in both directions because discs of both
gangs faces in opposite directions.
 The angels between the gangs of disc harrow can be
adjusted to meet field condition.

4. Components of Disc Harrow
Disc :-
Gang:-
Gang axel:-
Gang angle:-
Gang control lever:-

5. Fig 1. Offset Disc Harrow

6. Working Principle
 off-set disc harrow is based on the working principle that side
thrust against the front gangs is opposed by the side thrust of the
rear gang.

7. Objective:-
The effect of gang angle of offset disc harrow on
Soil tilth,
Theoretical work rate, and
Fuel consumption

8. Material and Methods
1) Tractor
A four-wheel drive, 59 kW (44 hp) tractor equipped
with a tractor performance monitor, which provide
relevant information such as: engine speed, actual
forward speed, wheel slip and fuel consumption per
hour.
Tyres Axial Load
kn
Inflation pressure
kpa
Dimensions of tyres
Front 29.15 152 13.6R 24
Rear 29.10 124 16.9R 34

9. 2) Implement
A trailed-type medium-weight offset disc harrow with
the following specifications was used in the field trials.
3) Data acquisition system
A portable computer-based recording system was
developed, which analyses the signals from the tractor
performance monitor sensors as well as the information
from a 50 kN load cell based pull measuring system.
Disc
Diameter,
mm
Number of
discs
Static weight
per disc, N
Disc spacing,
mm
Max. working
width, mm
610 20 650 230 2350

10. RADAR
Actual forward speed
FUAL FLOW
Consumption per hour
MAGNETIC PROXIMITY
Engine speed
MAGNETIC PROXIMITY
Wheel speed
POSITION
timing active
SENSORS
Tractor performance
monitor
LOAD CELL
Drawbar pull
TERMINAL
BORARD AND
CONDITIONE
R
Data
acquisitio
n board
PORTABLE
COMPUTER
DERIVATION

11. 4)Soils
Two fields with different soil types were selected
(a) Site 1:- clay loam; and
(b) Site 2:- loamy sand.
These fields, located on private farms, soil conditions in each
site are presented in following Table.
Soil condition: Average result in the 200 mm top layer

12. 5) Test Procedure
At the maximum angle between disc gangs, and throttle set to
1800 rpm, a preliminary test was run, with the operator shifting to
a higher gear, step by step.
Same test was repeated at a lower angle between disc gangs.
After the two combinations of throttle, gear and gang angle were
set, defining two treatments, the actual measurements were taken
in 50m runs, with four replications.
Average depth of soil layer was obtained from at least 20 value
along 50m run
Average working width was obtained from 12 direct
measurements across each 50 m harrowed path .

13. Result and Discussion
 At site 1 (clay loam), the maximum gang angle between
the disc gangs was found to be 46o
,while at the site 2
(loamy sand) it was found to be 33o
.
 The gang angles were re-adjusted to 37o
and 25o
at site 1
and site 2 respectively. At the same time, the speed was
increased from 5.8 to 6.9 km/h at site 1 and from 4.9 to 6.6
km/h at site 2. and the results observed are tabulated in table
no 4.

14. Average results from four replications at each gang angle, at sites 1 & 2.
Angel
betwee
n
gangs,
degree
Engine
speed
under
load,
rpm
gear
Forwar
d
speed,
km/h
Worki
ng
depth,
m
Wheel
slip
%
Theore
tical
work
rate
ha/ hr.
Fuel
consu
mption
, l/ha
Drawb
ar pull
Kn
Drawb
ar
power
Kw
Site 1
46
(Max.)
1670 15 5.80 0.194 7 1.21 11.69 18.68 3.11
37 1681 17 6.90 0.188 5 1.46 9.96 15.16 29.05
Site 2
33
(Max.)
1712 13 4.93 0.270 16 1.09 11.06 15.28 21.67
25 1626 17 6.61 0.270 11 1.46 9.34 11.79 20.91

15. Angle
between
disc
gangs ,deg
Mean ,mm Standard
deviation
,mm
46 44.2 7.4
37 42.8 12.7
Table 5
Adjusted MWD at each angle between disc
gangs at site 1
Table 7 .
Adjusted MWD : At each angle between disc gangs at site2
Angle between
disc gangs ,deg
Mean ,mm Standard
deviation ,mm
33 12.9 7.9
25 11.1 4.8

16. K value Source
Degrees
of
freedom
Sum of
squares
Mean
square
F value prob
1 Replications 7 759.037 108.434 1.0048 0.4976
2 Angle 1 8.702 8.702 0.0806
-3 Error 7 755.418 107.914
total 15 1523.157
Table 6
Adjusted MWD : analysis factorial ANOVA for replications (1-8)
and angles (46 and 37)at site 1.

17. Forwardspeedkm/h
Fig. 1:- Variation in forward speed at each gang angles
Theoreticalwork
rateha/hr
Fig. 2:- Variation in theoretical work rate at each gang angles

18. Fig. 3:- Variation in fuel consumption at each gang angles
Fuelconsumption
l/ha
Fig. 4:- Variation (%), after reducing the angle between the gangs

19. Conclusion
 In the light soils tested, higher work rates and lower
values of fuel consumption per unit of cultivated area were
attained with no visible difference in soil tilth.
 operating the disc harrows at a lower gang angle and
shifting to a higher gear in the tractor.

20. References:-
 The effect of gang angle of Offset disc harrows on soil tilth,
work, and rate and fuel consumption by Joao M.serrano; J.O.
Peca; M.Carvalho; M. Nunes; Ribeiro; F.santos
 Universidad de Evora, Departamento de Engeharia Rural,
Nucleoli da Mitra Apartado 94, 7002-554 Evora, Portugal.
 White WM (1993) Dry aggregate distribution in soil
sampling and method of analysis, pp 659- 662. Levis
publisher Canada
 Singh jay; Ganguly Purnima; Singh K N (1978) Effect of
soil and implement parameter on the depth of penetration of
disc harrow.

21. Topic Is Open For Discussion