Title: Tractor Performance
1 WELCOME
2Tire inflation and its influence on drawbar
characteristics and performance
- Presented by
- Utpal Kumar Mishra -
12AG61R05
3 Need Of Research
- Drawbar performance Ability of tractor to
develop sufficient drawbar pull, within the
acceptable range of slip in the on road or
off-road condition. - About 20-55 of energy transferred to drive wheel
is wasted in soil-tire interaction. This energy
is useless or causes soil compaction. - Common speed of tractor during field operation is
3kph to 15 kph, unfortunately within this range
slip gets its maximum value.(Reducing slip means
more Tractive efficiency ). - Ways to reduce slip -
4Need cont
- Enlargement of the tire contact area reduces
negative effect of tractors movement on the
field and it restricts physical degradation of
soil characteristics (structure damage,
compaction, etc.). - On deformable surfaces, high inflation pressure
results in increased ground penetration work ,
thus higher rolling resistance. - Tire inflation has significant effect on contact
area between tire and soil and so on the tractive
efficiency.
5Objective
- To evaluate the advantages of low inflation
pressure and its effect on drawbar pull. - Application of obtained results in measurement
with a mounted plough.
6Theoretical analysis
- Gross traction, moving the tractor forward is a
result of interaction between soil and the engine
toque transferred onto tires Circumference. - The transfer circumference force causes the soil
shear stress, which is a direct proportional to
the tangential force, and the indirect
proportional to shear area, in which the force
acts.
7 Theoretical analysis
contda. Shear plate apparatus for measuring
soil strength b. Shear force versus shear
displacement curve for various loads
8 Theoretical analysis contdFmax AC
W tan f Fmax / A C (W/A) tan f
C p tan fFor loose sand and most of the
soil, the shear stress increases rapidly with
shear displacement and then approaches a constant
value. This shear stress shear displacement
relationship is proposed by Janosi and
Hanamoto.(2 , 8)
Here, j Shear displacement and
K Shear deformation modulus
9K is the measure of magnitude of the shear
displacement required to develop maximum shear
stress. Value of K determines the shape of the
curve. Its value is
represented by the distance between the vertical
axis and the point of intersection of the
straight line tangent to the shear curve at
origin and Horizontal line represent maximum
shear stress.
Theoretical analysis contd..
10Total tractive force
11 Theoretical analysis
contd..Measured surface pressure distribution
(in psi) under a smooth tire for the same
vertical load but different inflation pressure.
Above at 10 psi, below 6 psi. (off road Vehicle
engineering principles, C E Goering, M L Stone, D
Smith P K Turnquist)
12 Theoretical analysis contd..Three - dimensional
views of pressure distribution under a smooth
tire on soil A, Inflation pressure, 14 p.s.i.
B,10 p.s.i. C, 6 p.s.i. (Vanden Berg and Gill,
Amer. Soc. Agr. Engin. Trans. (460).(soil
dynamics in tillage traction, W R Gill )
13 Drawbar performance curve
(Theory of ground vehicles, J Y Wong.)
14 Relation between drawbar power and slip
with drawbar pull
(Theory of ground vehicles, J Y Wong.)
15 Tire Description
- Measurements of tire in?ation in?uence on drawbar
characteristics and performance, were performed
with the use of radial tire sets. The ?rst step
in the research was to measure drawbar
characteristics. In the next stage, the tractor
was equipped with a plough under the same
conditions. - The following radial-ply tires were used
- I. Tires with narrow treads
- Front tire 14.9 R28
- Rear tire 18.4 R38
- II. Tires with wide treads
- Front tire 520/60 R28
- Rear tire 650/60 R38
16Tires and inflation pressure used during test
Axle Tire description Inflation pressure (kpa) Static weight (kg)
Front wheel 14.9 R28 170 4540
Rear wheel 18.4 R38 170 3240
Front wheel 14.9 R28 255 4540
Rear wheel 18.4 R38 255 3240
Front wheel 520/60 R28 75 4580
Rear wheel 650/60 R38 65 3360
Front wheel 520/60 R28 180 4580
Rear wheel 650/60 R38 180 3360
17Soil and other sensors used
- Soil type loam soil, moisture content from
21.69 to 22.9. - Speed range of 5, 8 and 10 kph with full fuel
supply. - A RDS TGSS radar sensor was mounted onto tractor
frame for measuring actual velocity of tractor. - Tire footprint was obtained by multiple elevating
and lowering of wheel along horizontal plane till
clear footprint profile was obtained. - Lucia G evaluation software was used for
measurement of contact area. - After drawbar test, measurements with a plough
were carried out with same inflation and
adjustment settings. - Real and theoretical velocity, fuel consumption,
engine speed, depth and width of plough were
recorded.
18Measured and calculated parameters at testing tire
Tires with narrow tread
Tires with wide tread
Axle Inflation pressure (kpa) Tire footprint (cm²)
Front wheel 75 2123
Rear wheel 65 2390
Front wheel 180 1702.1
Rear wheel 180 1822.5
Axle Inflation pressure (kpa) Tire footprint (cm²)
Front wheel 170 1527.8
Rear wheel 170 1569.5
Front wheel 250 1373.1
Rear wheel 250 1181.4
19 Vehicle traction ratio versus
slipHighest values 0.57 0.61 .VTR increased by
7.01 and tire footprint area by 21.25.
(Tire with narrow tread )
20Drawbar power specific fuel consumption
characteristics versus drawbar pull.
(Tire with narrow tread)
21 - Highest values 0.66 0.74. VTR increased by
12.12 and tire footprint area by 28.23. - (Tire with Wide tread)
22Tire with wide tread
23 Results contd
- The maximum drawbar power is increased at 5, 8
and 10 kph by 9.1, 9.6, and 14.6,
respectively. - The tire footprint increased at the rear and
front tires by 31.1 and 24.7, respectively. - The specific fuel consumption at maximum drawbar
power was reduced at 5, 8, 10 kph by 3.4, 8.1,
and 16, respectively in comparison with higher
inflation pressures. - If the tractor works with lower tire inflation by
setting travel speed at 5 kph, it reaches fuel
consumption saving up to 1.64 l h1.
24 Result of ploughing set measurement
Width (mean) (m) Depth (mean) (m) Tractor speed (kph) Slip Effective performance (ha/h) Fuel consumption ( l/ha)
2.71 ( with wide tread, front 75kpa, rear 65kpa ) 0.25 4.70 19.11 (13 ) 1.27 (8.5 ) 24.33 (8.8)
2.68 ( Both tire 180 kpa ) 0.26 4.35 21.99 1.17 26.68
2.64 ( with narrow tread, 250 kpa) 0.25 4.44 24.73 1.17 26.55
2.60 ( 170 kpa ) 0.25 4.66 20.74 (16 ) 1.21 (3.4 ) 25.53 (3.8 )
25Conclusion
- The results of test measurements revealed that
reducing tire inflation of appropriate tire types
can improve the drawbar characteristics and,
consequently, fuel consumption. - However, low tire inflation does not guarantee
better drawbar characteristics in all cases. - From the results of the above-mentioned
experiment, it can be concluded that lower tire
inflation has the largest influence on
performance at aggregation with implements,
requiring a lower working speed and a large
demand of drawbar force, therefore practical
benefits are in the case of field operations with
increased drawbar pull requirements.
26Conclusion contd
- The tractor should only be operated until the
value of slip where VTR reaches its maximum. - In case the VTR grows monotonously, the slip
should not go over the transitional zone into the
linear part of the curve. - The results show that the slip should not exceed
15 because it causes a decrease of engine power
efficiency transmitted to the surface. - As follows from the presented characteristics,
the tractor transferred larger drawbar pull to
the surface at the same ground speed and lower
inflation pressure. - Larger transferred drawbar pull means an increase
of drawbar power and thus tractor performance.
27References
- 1 Grec?enko A. Vlastnosti terennich vozidel.
VS?Z v Praze 1994 118 s.ISBN 80- - 213-0190-2 in Czech.
- 2 Bekker MG. Introduction to terrain-vehicle
systems. MichiganUniversity of - Michigan Press 1969.
- 3 Burt EC, Lyne PW, Meiring P, Keen JF.
Ballast and inflation effect on tyre efficiency.
- Trans ASAE 198326(5)13524.
- 4 Gaultney L, Krutz GW, Steinhardt GC,
Liljedahl JB. Effects of subsoil compaction on - corn yields. Trans ASAE 1982(3)5639.
- 5 Lyasko M. Slip sinkage effect in soilvehicle
mechanics. doi10.1016/ - j.jterra.2009.08.005.
- 6 Vermeulen GD, Perdok UD. Soil compaction in
crop production. Amsterdam - Elsevier 1994. p. 44778.
- 7 Wong JY, Huang W. Wheels vs. tracks a
fundamental evaluation from the traction - perspective. J Terramech 2006432742.
- 8 Wong JY. Terramechanics and off-road
vehicles. Amsterdam Elsevier 1989. - 9 Wong JY. Theory of ground vehicles. 3rd ed.
New York Wiley 2001.
28Thanks