where: - S is slip, percent;
- An is the advance under no load conditions per wheel or track revolution,
m(ft);
- A1 is the advance under actual load conditions per wheel or track revolution, m(ft).
Draft force required to pull many seeding implements and minor tillage tools operated at shallow depths is primarily a function of the width of the implement and the speed at which it is pulled. For tillage tools operated at deeper depths, draft also depends upon soil texture, depth, and geometry of the tool. Typical draft requirements can be calculated as: D = F*I [ A + B + C(S) where: - D is implement draft, N (lbf);
- F is a dimensionless soil texture adjustment parameter (table 1);
- i = 1 for fine, 2 for medium and 3 for coarse textured soils;
- A, B and C are machine-specific parameters (table 1);
- S is field speed, km/h (mile/h).
- W is machine width, m (ft) or number of rows or tools (table 1);
- T is tillage depth, cm (in.) for major tools, or equals one for minor tillage tools and seeding implements.
(PDF version of this table,
11KB)
where: - Pdb is drawbar power required for the implement, kW;
- D is implement draft, kN;
- s is travel speed, km/h;
or,
where: - Pdb is drawbar power required for the implement, hp;
- D is implement draft, lb;
- s is travel speed, mph.
where: - Ppto is power-takeoff power required by the implement kW (hp);
- w is implement working width, m (ft);
- F is material feed rate, t/h(ton/h) wet basis;
- a, b, and c are machine specific parameters (Table 2)
(PDF version of this table, 8KB)
where: - Phyd is hydraulic power required by the implement, kW;
- F is fluid flow, L/s;
- p is fluid pressure, kPa;
or,
where: - Phyd is hydraulic power required by the implement, hp;
- F is fluid flow gal/min;
- p is fluid pressure, psi.
where: - Pel is electric power required by the implement, kW;
- I is electric current, A;
- E is electric potential, V;
or,
where: - Pel is electric power required by the implement, hp;
- I is electric current, A;
- E is electric potential, V;
where: - PT is total implement power requirement, kW (hp);
- Et is traction efficiency (expressed as a decimal);
- Pdb is drawbar power required for the implement, kW (hp);
- Phyd is hydraulic power required by the implement, kW (hp);
- Ppto is power-takeoff power required by the implement, kW (hp);
- Pel is electric power required by the implement, kW (hp);
- Em is mechanical efficiency of the transmission and power train.
- This coefficient is typically 0.96 for tractors with gear transmissions.
NOTE: Additional power is required to accelerate and overcome changes in topography, soil and crop conditions. Additional power is also required for operator-related equipment such as hydraulic control systems, air conditioning, etc.
where: - Ca is area capacity, ha/h;
- s is field speed, km/h;
- w is implement working width, m;
- Ef is field efficiency, decimal;
or,
where: - Ca is area capacity, acre/h;
- s is field speed, mile/h;
- w is implement working width, ft;
- Ef is field efficiency, decimal.
NOTE: Typical ranges of field efficiency and field speed can be found in Table 3. (PDF version of this table,
6KB)
where: - Cm is material capacity, t/h;
- s is field speed, km/h;
- w is implement working width, m;
- Ef is field efficiency, decimal;
- y is unit yield of the field, t/ha;
or,
where: - Cm is material capacity, ton/acre;
- s is field speed, mile/h;
- w is implement working width, ft;
- Ef is field efficiency decimal.
- y is unit yield of the field, ton/acre.
NOTE: Typical ranges of field efficiency and field speed can be found in Table 3. This information in this document was adapted from American Society of Agricultural Engineers Standards.
Information provided by:
Wayne E. Coates wcoates@u.arizona.edu, Research Professor, Arid Lands College of Agriculture and Life Sciences, The University of Arizona Revised July 2002. |
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