5.3 Calculation of the common traction resistance of a cultivator
This calculation begins with determination of forces operating on paws forward and back rows according to their width of capture by depth of processing and type of the soil.
In a general view the traction resistance of one paw is calculated on q specific resistance, and capture width in
(20)
where q - a specific resistance of the soil, N/mm;
in - width of capture of a paw, mm.
Specific traction resistance of lancet paws with a width of capture of domestic cultivators by the 240-300th at traveling speed of 10 km/h is specified in tab. 1. tab. 1. Specific resistance of lancet cultivator paws
Глубина обработки, см. |
6 |
8 |
10 |
12 |
14 |
Удельное сопротивление, Н/мм |
0,8-1,0 |
0,9-1,3 |
2,1-2,7 |
3,0-3,8 |
3,9-4,7 |
At
increase in traveling speed of a cultivator by 1 km/h (over 10 km/h)
resistance of paws increases by 10%
Рисунок 11.Схема действия силы Rxz сопротивления почвы на лапу.
We accept q=3,8 of N/mm as depth preseeding processing makes - 12 cm. We choose capture width maximal in =300 mm.
However
resistance of paws of a forward row exceeds resistance of paws of a
back row (with the same width of capture) approximately twice. It
needs to be considered when determining traction resistance of a
separate paw
(21)
(22)
Then
the traction resistance of paws is determined by analogy on a
formula:
(23)
(24)
Besides traction resistance, the paw is affected still by vertical resisting strength of the soil of Rz. (fig. 8).
m=tgΨ coefficient characterizing the relation of size of the vertical paw of Rz composing resistance to horizontal Rx depending on sharpness of an edge, hardness of the soil and depth of processing can change over a wide range and have both positive, and negative value. The negative value of a corner Ψ appears at solid dry soils and the blunt edge.
The
direction of net force Rxz is defined by a corner Ψ
and depends on the angle of dyeing β
and a sliding angle φ:
As the angle of dyeing β from paw parameters, and a sliding angle φ – from properties and a condition of the soil, and a corner Ψ will be depends on them.
With a
depth of course of 10 - 12 cm that corresponds to average humidity of
the soil and a fine edge Ψ
= 22-280. We
accept Ψ = 31.
We calculate traction resistance for a forward number of a cultivator of Rxz a per:
We
calculate traction resistance for the second and third ranks of a
cultivator of Rxz the back:
The
provision of a cross point of a force direction Rxz is characterized
by the size h which depends on processing depth:
(25)
We
calculate Rxz point of application:
The common traction resistance of a cultivator is calculated by a formula:
Р= Rхz пер*n+ Rхz зад*n+ Rхz зад*n (26)
where n-the number of paws among
As on the first row the number of paws of n = 5 pieces,
On the second row - n = 5 pieces,
On the third - n = 4 pieces, that common traction resistance will be: Р= 1459*5+896*5+896*4= 15359Н
We accept a traction class of the tractor of 30 kN. In that specific case we will take the tractor of the T-150K brand. 6 Design calculations.