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6
Ahmetov Adilbek Agabekovich, d. t.s, main specialist in coordination of SRECW, Special design bureau "Tractor" UE, Tashkent, the Republic of Uzbekistan
Ahmedov Sherzodbek Anvarhon o*g*li, the design engineer, Special design bureau "Tractor" UE, doctorant TIAMI,
Tashkent, the Republic of Uzbekistan E-mail: sheran1@mail.ru
ABOUT AGROTECHNICAL PASSABILITY AND STABILITY OF THE 4-WHEELED UNIVERSAL-ROW TRACTOR
Abstract: The article presents the results of the investigation of the influence of the position of the clearance on the stability of the tractor. Researches have shown that change of clearance of the tractor with low-clearance on high-clearance leads to deterioration in both longitudinal, and cross stability of the tractor. Whereas change of clearance of the tractor, on the contrary, with high-clearance on low-clearance leads to improvement of both longitudinal, and cross stability of the tractor. At the same time static stability of the tractor increases: cross up to 9,42%, and longitudinal on a bias up to 6,25% and on rise up to 26,39%.
Keywords: tractor, agrotechnical gleam, clearance, wheel, front axle, rear axle, gravity, lifting, gradient, angle of heel, stability, controllability.
Increased agrotechnical patency of the 4-wheeled universal tractor can be achieved by changing the low clearance for high ground clearance. However, our researches have shown [1, 46-50] that changing the clearance of the front and rear bridges leads to change not only in the agrotechnical clearance, but also length of the base and the parameters of the coordinates of the center of gravity of the universal tractors.
Change ofparameters of coordinates of the center of gravity of any tractor, including 4-wheeled universal row leads tractors to change and loss of its stability, therefore, to a spontaneous deviation from the set direction, to side sliding or capsizing.
To capsizing there corresponds such rising ofwheels over a basic surface at which the angle of heel of a skeleton reaches extreme value and its further movement in the direction of a list by gravity and inertia becomes irreversible. Such phenomenon occurs in case
on cma6 (1)
where, M - the overturning moment, Nm;
'on o ' '
M , - the moment from forces seeking to return the
cmuo O
tractor to a starting position, Nm.
The main criteria of stability 4-wheeled universal row tractors against capsizing are characteristics of his geometrical parameters and the arrangement of the center of mass of rather basic wheels defining limits of static stability. And limits of static stability are defined by extreme values of angles of lead, descent and a side list.
The property of the tractor to resist the overturning movement around a cross axis of capsizing is called longitudinal stability of the tractor against capsizing. At the same time capsizing happens because of redistribution of basic reactions on bridges of the tractor and at equality of zero one of them.
To determine the effect of the clearance on the stability of the 4-wheeled universal tractors, we analyze its longitudinal (fig. 1) and transverse (fig. 2) stability in the high-steep (I) and low-lance (II) positions to rollover and to lateral slip.
Insufficient longitudinal and lateral stability when moving 4-wheeled universal tractor either during descent or during the work on a slope can lead tractors on a bias to irreparable consequences, i. e. to its overturning. Therefore in order to avoid undesirable situations carry out calculation on longitudinal and cross stability ofthe tractor in advance.
Figure 1. The settlement scheme to definition of longitudinal stability 4 - wheeled universal row tractors
When determining longitudinal stability 4-wheeled universal tractors are accepted the following assumptions:
- resistance of air isn't enough as the speed of the movement of the tractor no more than 30 km/h, therefore, Pw = 0;
- the tractor moves evenly at which P. = 0;
- traction loading is absent, i. e. P = 0.
O ' Kp
The greatest angle of lead at which the slowed-down tractor can stand, without overturning, call a limit static angle of lead ann.
The corner of the beginning of capsizing of the tractor in static situation on rise depending on options of a type of clearance decides on adjustable clearance by expression
aZl = arctg
(H(II> - aI(II>)
\ um '
h
I(II>
um
(3)
= arrtg
. hI(II> . um
(2)
where, anm , hnm - respectively by clearance options the
horizontal and vertical coordinate of the center of gravity 4-wheeled universal row tractors, mm;
Li(u) - respectively by clearance options base 4-wheeled universal row tractors, mm.
Further, in view of work [2, 83] we define a corner of the beginning of slipping
= arctg (°), (4)
where, fc - coefficient of coupling with the soil.
The angle of slipping a^01 ) respectively at the slowed-
down back driving wheels is determined by expressions on rise by options of clearance of the tractor
From fig. 1 it is visible that at a limit static angle of lead if not to consider force of resistance to swing, the vector of gravity passes through an axis of capsizing of 02.
Unlike a limit static angle of rise the limit static angle of descent a is determined from expression
a'(n) = arctg
<f>(L(n> - a'(">)
~c \ um /
, Htu> - h""
y U"
c y
on the slope
a",(I1 > = arctg
- O
, H(II> + hI(II>, ,
y U" Tc 1
(5)
(6)
,i (II )
re-
Critical angle of an inclination of the road axpcK spectively by options of clearance of the tractor under the terms of coupling of buses with a reference surface in case of which sliding of driving wheels can begin, is defined by expression
Condition of the guaranteed stability of the tractor against tilting [3, P. 338]
aT* >a^ (8)
npQO Kp.CK \ /
and at sharp braking
a'(II) = arctg
кр.ск О
ф ■ (¿(U) - а""') - f ■ L
~c \ цт ' J
(im - hm ■ф)
TI(II)
а
'I (II )
>Ф,.
(9)
(7)
where, f - coefficient of resistance to self-movement.
When calculating cross stability define a corner of the beginning of capsizing and a corner of the beginning of slipping on a slope (fig. 2).
Figure 2. The settlement scheme to definition of
The corner of the beginning of capsizing ßn on a slope depending on options of a type of clearance of the tractor is defined according to work [2, 83] as expression
ßI(") = arctg
Í А (II ) Л
hI (п ) V Цт У
(l0)
where, Ayn) - a shoulder of stability of the tractor, mm;
Km - vertical coordinate of the center of gravity of the tractor.
The corner of the beginning of slipping on a slope according to work [2, 83] can be accepted
cross stability 4 - wheeled universal row tractors
arctg(0,8 -fr ). (11)
In the presence of dynamic influences from micror-oughnesses of the path a dynamic lateral stability angle according to [4, 270]
F™ = (0,4 * 0,6)(ii) . (12)
According to the stated technique it is defined the key parameters estimating longitudinal and cross stability 4-wheeled universal row tractors in two options: in high-clearance and low-clearance, also we enter them in table 1.
Table 1
Name of indicators, symbol and unit of measure Value of indicators by options Increase (+) or reduction (-),%
I II
1 2 3 4
1. Longitudina stability
Corner of longitudinal static stability (rise) anpJ(II), degree 32.72 4l.35 26.3S
Corner of longitudinal static stability (bias) a'npJ(n), degree 47.3S 50.34 6.25
1 2 3 4
Corner of longitudinal stability. The tractor moves evenly on an eddish (rise) anpJ(II), degree 30.67 39.52 28.85
Corner of longitudinal stability. The tractor moves evenly on an eddish (a bias) a'npJ(II), degree 48.64 51.60 6.07
Critical angle of an inclination of the road on which sliding of driving wheels under the terms of coupling of buses with a reference surface on an eddish of a . 1 (II), degree 29.73 24.63 -17.15
Condition of the guaranteed stability of the tractor against capsizing on an eddish {a , > a . } done done
Corner of the beginning of slipping of the a* degree
on an eddish 34.99
on the dirt road 33.02
on a concrete covering 37.23
An angle gaucherie delayed The tractor of ascension and a^(II), degree
on an eddish 36.47 31.34 -14.06
on the dirt road 33.21 28.63 -13.79
on a concrete covering 40.44 34.65 -14.31
An angle gaucherie delayed the tractor on slope a ^(II), degree
on an eddish 23.57 16.86 -28.46
on the dirt road 22.06 15.99 -27.51
on a concrete covering 25.32 17.85 -29.5
At emergency brake application of the tractor condition {
on an eddish Accomplished (done) Accomplished (done)
on the dirt road Accomplished (done) Accomplished (done)
on a concrete covering Accomplished (done) Accomplished (done)
2. Cross sta bility
Corner of cross stability of fip (II), degree 31.58 34.55 9.42
Corner of the beginning of slipping on a slope (eddish) degree
on an eddish 29.25
on the dirt road 27.47
on a concrete covering 31.30
Dynamic corner of side stability of the (II), degree 12.63 13.82
Results (tab. 1) of the calculations have shown that in both options of clearance the condition of the guaranteed stability 4-wheeled universal row tractors against rollover is fulfilled. But, despite this, the change in the clearance of the tractor from the low-level to the high stance position leads to a deterioration in the overall picture of both longitudinal, and lateral stability of the tractor. The change in the clearance of the tractor from
the low-level to the high stance position, on the contrary, leads to improvement of both longitudinal, and cross stability of the tractor. At the same time static stability of the tractor increases: cross up to 9,42%, and longitudinal on the slope up to 6,25% and on rise up to 26,38%.
Thus, one of the effective ways of increasing the stability of 4-wheeled universal row tractors, both in longitudinal, and in the cross direction, especially when
performing transport works, is decrease in his center Therefore, for carrying out transport and field works by
of gravity due to reduction of clearance of the tractor. the same 4-wheeled universal tractor, its clearance must
Whereas when performing interrow processings of tall be adjustable from low-clearance to high-stance position.
cultures, for example a cotton, for providing get prettier Proceeding from this consideration the TRCS TR carries
fits in row-spacings and agrotechnical passability the out NI and ROC on the creation of a 4-wheeled universal
clearance 4-wheeled universal row tractors has to be high. row tractors with adjustable clearance.
References:
1. Akhmetov A. A., Akhmedov Sh. A., Karimov A. K. Researches of influence of change of clearance on technical and operational parameters of the tractor with adjustable clearance // Problems of mechanics, - 2017. - No. 1. -P. 46-50.
2. Anilovich VYa., Vodolazhchenko Yu. T. Designing and calculation of farm tractors. - M.: Mechanical engineering, -1976. - 83 p.
3. Miroshnichenko A. N. Bases of the theory of the car and tractor. - Tomsk: TGASU publishing house, - 2014. -338 p.
4. Chudakov D. A. Bases of the theory and calculation of the tractor and car. - M.: Ear, - 1972. - 270 p.
