As per of aim of study, a desired type of seed cum fertilizer drill machine was designed and developed to suit with the SHRACHI power tiller, model: SF 15 DI. Engine S 1100 N, 4 -stroke Diesel Engine (Horizontal Type), manufactured /supplied by M/S Bengal Tools, Pvt. ltd. Calcutta.
(i) Easiness of seeding attachment.
(ii) To accommodate in available space between rotary tiller and riding seat (Varshney et al., 2004)
(iii) Details of major components of the machine are shown in Table 1 and detail-design is next described.
Seed and fertilizer box
The seed and fertilizer box of 2 mm MS sheet was designed for about 16 kg wheat seed and 14 kg paddy and for 10 kg DAP/ IFFCO granular fertilizer capacity. Considering density of seed and fertilizer and working capacity of power tiller, the size of box is about 0.021 m3.
Four rigid tines, made of MS flat size 40 x 5 mm were mounted on a tool bar for seeding at a varying spacing of 18 to 22 cm suiting to wheat and paddy. Reversible narrow shovels mounted on each tine. Design methodology, materials and methods used for the study for individual components are next described.
Design of seed and fertilizer box
In literature, the box capacity for different type of manually, animal and tractor drawn seed drills are available but not for power tiller (Varshney et al., 2004). Therefore, as per design consideration of seed and fertilizer box, the dimentions were decided. The box was made from MS sheet rectangular in shape and shown in Figure 2. Horizontally, the seed cum fertilizer box was located between roto-tiller and riding seat behind the hood of rotary tiller. Vertically, the box height was limited by upper main transmission gear-lever, rotory transmission gear-lever and handles. Finally the size of seed box was determined as:
L x W x H = 680 x 180 x 170 mm3
= 0.02081 cubic meter
The size of fertilizer box, L x W x H = 560 x 100 x 100 mm3
= 0.0056 cum.
And the theoretical capacity of seed box = 0.2081 cum x 800 kg /cum
= 16.640 kg for wheat and for Paddy grain 12.5 kg.
The seeding capacity of the developed machine, with paddy and wheat seed is worked out based on actual observations as given below:
Theoretical capacity (ha/h),
Where, W = working width, m = 4 x 0.20 = 0.80 m, S = speed, kmph (1.45 - 3.0 km /h)
Thus, the designed box size for seed capacity is found satisfactory. Therefore, the net designed seed box capacity of 16 kg wheat would be sufficient for about 2 working hours.
Design of tool bar
A tool bar of square section, made by joining two angle iron was designed and fabricated for mounting of tractive tynes. The tool bar was made of square section of 40 x 40 x 5 mm joining two MS angle iron of size 35 x 35 x 5 mm and its length was kept 720 mm as shown in Figure 3. The short design calculation for forces and strength was calculated and the dimension of tool bar was determined using standard formulas.
In order to select the size of material requiring for tool bar, The following assumptions are made.
(i) Number of tines = 4
(ii) Maximum depth of operation, cm = 15
(iii) Width of furrow opener, cm = 3
(iv) Maximum ground clearance of tool bar and height of tines, cm = 34
(v) Center to center distance between two tines, cm = 20
Area of furrow cross section = width x depth = 3 x 15 = 45 cm2
Therefore, the draft requirement for each tine = 45 cm2 x 0.6 kg /cm2 = 27 kgf. (Assuming draftability of sandy clay soil in friable moisture condition = 0.6 kgf /cm2)
The tool bar is subjected to torision and bending moment due to induced draft.
The tool bar consist with four tines in one row.
Total Draft = 27 x 4 = 108 kgf = 108 x 9.8 = 1058.4 N
The design was calculated based on maximum load. Maximum load was calculated considering factor of safty equal to four for agricultural machines (Paul, 2003; Verma, 2005) as follows:
Total draft = 1058.4 x 4 = 4233.6 N
Torque on the tool bar by each tine = Draft x ground clearance
= 27 x 0.34 = 9.18 kgf -m = 89.96 N –m
Total torque on the tool bar with 4- tines = 89.96 x 4 = 359.84 N -m
In addition to torque on the tool bar, bending moment would also be produce. The tool bar was considered as simple supported beam on the fram.The maximum bending moment:
Where, w = Total weight / force on the fram, l = Total length of tool bar, cm
= 762.048 N -m
Equivalent torque ue to torision and bending moment was calculated as:
The maximum shear stress developed on the tool bar was obtained by using torsional formula as:
fs / R = T / J (3)
Where, fs = Shear stress at any section, R = Distance of the section from nuetral axis = d / 2,T = Equivalent torque, J = Polar moment of inertia.
Considering each side of measured d mm and factor of safety 2 – 4 (we selected maximum safty of factor = 4) and ultimate stress of selected material, Fe = 360 N/mm2 (Verma, 2005).
Maximum working stress of 360 N /mm2 act at the center of toolbar. J is calculated by using formula as:
J = d4 / 4 (5)
Where, d = width of section
On substituting above values in the Equation (3), we get:
Therefore, equivalent size of tool bar of 40 mm , depending availability of material, was considered safe for the machine. The detailed diagram is shown in Figure 3.
The design considerations for the furrow opener were that they should be of self cleaning nature, easily un-clogging type and narrow shape to minimize draft requirement.
Design procedure of the tine
The height of tine ie ground clearance was taken as 340 mm which was calculated as:
(1) Maximum working depth in tilled soil = 150 mm
(2) Free length (to avoid clogging by tool bar) = 190 mm
Width and thickness
The width and thickness of the tine was calculated as follows. A reversible shovel was fitted with tine as cutting tool. The tine was made of mild steel flate plate having carbon content from 0.15 to 0.25 per cent (Verma, 2005) of size 40 x 10 mm. Width of reversible shovel was 30 mm, with 5.0 mm thickness and was made of MS sheet.
The furrow cross sectional area = 150 x 30 = 4500 mm2
The soil resistance = 0.0060 kg /mm2
Soil resistance exerted at the tip of each furrow opener /tine = 264.6 N
Ground clearance of tine = 340 mm
The bending moment = draft x distance
= 264.6 x 340 = 89964 N /mm2
Where, f = Bending stress, N /m2, C = Distance from neutaral axis to the point at which strain is determined, m.
The sectional modulas from the neutral axis is computed by using formula:
From the Equations 6 and 7, we get:
Taking bending stress equal to 49.05 N /mm2 (Sachin, 2000; Verma, 2005).
Section modulas of the furrow openers, the ratio between the thickness to width (t : b) can be taken from 1 : 3 to 1 : 4. (Sharma and Mukesh, 2008):
So, t : b = 1 : 4
Considering the factor of safty, availability of material of standard size, the thickness of tine was taken 10 mm. Therefore, width of the tine = 4.0 x 10 = 40 mm
Therefore, the narrow reversible shovel types openers were selected as shown in Figure 4. In order to overcome the problem of trash and clod collection, between the adjacent tines, the furrow openers were placed behind the rotary blades on the frame. So, that a narrow shallow slot could be tilled by the rotary blades for placing seed in direct conservation drilling.
Seed metering mechanism
Simple fluted rollers were used for the metering of seeds and orifice types arrangement made for the fertilizer. The simple knob mechanism is used to meter the desired quantities of seed. The detailed diagram and figure of the fluted roller is shown in Figure 5.
Ground wheel and other parts
The ground wheel was made of MS flat iron of size 25 x 3 mm and the ring was made of 360 mm diameter, with steel pegs of length 70 mm. The pegs were made of 25 x 3 mm size. Total numbers of pegs were taken 12 on the periphery. The numbers of spokes were 6, made of iron rod of size 9.5 mm. The detailed diagram and figure of the ground wheel is shown in Figure 6. The diameter was designed for minimum rolling resistance and easy operation of the ground wheel. So, the clods and stubbles height should not be more than one third of its diameter. Considering 15 cm height of stubbles/ clods, the diameter of ground wheel was designed for 45 cm and thus the tip to tips of peg, the diameter was taken = 50 cm.
The power is transmitted to ground wheel to metering shaft of seed and fertilizer without hindrance in the rotary tilling. During seeding, the tractive tines of seed cum fertilizer drill, place seeds and fertilizer behind rotary tiller instantaneously and perform tilling cum seeding operation in a single pass, conserving field moisture. The fabrication cost of the machine was found about Rs 6000.00. The machine was easily attached and detached and can be adjusted for different crops.