Conservation tillage

Final year project Design of Inline Seeder

Final Year Project Report Submitted Towards the Practical Fulfillment for the Requirements for the Award of B.SC. Degree in Mechanical Engineering

2006

AKNOWLEDGMENT

Many helping hands are in the completion of this project, both from in and out of Mekelle University. Consequently, first of all I am very thankful to my advisors Ato Solomon G/egziabher (MSc.), Ir.Fissiha Meressa (MSc.) and Ato Abebe Kebede; all are from the Farmtech project in the university, for their unreserved follow up and help through all levels of the project. Secondly my thanks go to those persons in the department of Crop Science (Mekelle University) in particular to W/ro Alemstehay ( ) for her precise information. And last but not least I would like to thank the mechanical engineering department and staffs, Friends here in Mekelle University and those who are away for their consistent moral and financial support; and their great concern to my project. TABLE OF CONTENT Contents page

1OBJECTIVES

3PART ONE

31. Literature

31.1. Conservation tillage agriculture

41.1.1. Soil tillage

101.1.2. Bed-Planting Systems (Ridge-Till)

121.2. Draft animals/ animal traction

151.3. Soil Texture and fertilizers

151.3.1. Fertilizer Material

151.3.1.1. Fertilizer Form

161.3.1.2. Fertilizer compounds

171.3.1.3. Fertilizer Placement

171.3.2. Fertilizer application techniques

171.3.2.1. Broadcasting

181.3.2.2. Band or storage application

191.3.2.3. Foliar application

191.3.2.4. Slurry

191.3.3. Crops type limitation on fertilizer application

201.4. Maize and Wheat/Barley

201.4.1. Maize

251.4.2. Wheat

271.4.3. Barley

301.5. Sowing and planting equipments

301.5.1. Traditional Sowing Methods

311.5.2. Functions of Seed-drills and Planters

311.5.2.1. Subsystems of Sowing and Planting Equipment

34PART TWO

342. Conceptual Design

342.1. Different mechanism of metering assessed

342.1.1. Model A

352.1.2. Model B

352.1.3. Model C

362.1.4. Model D

372.1.5. Model E

372.1.6. Model F.

382.2.Design matrix

402.3. Decision and Conclusion

43PART THREE

433. Design analysis and synthesis

433.1. Axle

463.2. Bearing

513.3. Wheel

603.4. Power transmission

673.5. Shaft

703.6. Metering discs

733.7 Frame and compartment

733.7.1. Vertical beam

753.7.2. Horizontal beam

763.7.3. Opener attaching beam

783.7.4. Pulling bars

793.7.5. Compartment/housing

803.7.5. Collecting tubes and guiding rods

813.8. Openers

843.8. Covering mechanism

87PART FOUR

874. Manufacturing

874.1. Data required for production

874.2. Basic requirements data mandatory for production

894.3. Weld design and selection

924.4. Material cost analysis trial

94CONCLUSION

95RECOMMENDATION

96BIBLIOGRAPHY

OBJECTIVES

To discus on the present and recent past situations of agricultural system technology and alternative practices of the glob in general and in Ethiopia in particular. To conceptualize models of on line seeders make decision on designing on of the best alternative.

To make design analysis and synthesis for components that would be incorporated in the generalized system of the selected seeder model. To support the design results with illustrative sketches and 3d modeling.

To prepare a clear and feasible production sheet.ABSTRACT

The base for our enfant economy, in one or another way, is agriculture though it is not yet the light of technology is reflected over the agricultural system of our country. Today is the right time to launch technology through our agricultural system and be beneficial of our virgin resources. Actually more advanced agricultural technologies, nowadays, are adopted in the developed countries. Hence, as a result of this globalization we have two options to use them. These are; either to import these technologies in the hardest way or adopt them to our tradition and capacity elegantly. This project is part of the later option, which discusses the design of inline seeder for Wheat/Barley and Maize including the general overview of present and past pressures towards the target. In the first part of this paper the basic systems behind this project, conservation system is described briefly, with respect to its adaptation globally and particularly in Ethiopia. In addition some of the related topics to the seeder; draft animals technology, soil and fertilizer conditions for wheat/Barely and maize are notably compiled. The second part contains different models of the inline seeder main components and scientific comparisons to find best alternative model. In the third and most detail part every components and mechanisms are analyzed and identified to meet both theoretical and realistic requirements. In the fourth and last part of this report the actions towards producing feasible model seeder are forwarded with clear illustrative drawings of each and every components of the inline seeder. Generally, this report comprises of all necessary information and directions to the feasibility of the inline seeder existence.PART ONE

1. Literature 1.1. Conservation tillage agricultureThe limitations of agricultural equipments has been a problem for having satisfactory outputs from our planets limited farm inputs in general and from developing countries scarce resources in particular. Therefore the target of this project is to find a better and adoptable mechanism of planting crops particularly wheat and maize. As the existing natural resources are not enough to satisfy the present human needs it is a must to follow certain scientific way that lead to sustainable contentment. The need to planting machines is one of the measures that are considered as todays better way to reach at more advanced and conserved agriculture. This millennium we humankinds have launched a system that could assure our existence, which is conservation of our natural resources. Conservation agriculture, in a few words its defined as the management of resources in such a way as to assure that it will continue to provide maximum benefits to human over the long run(FAO). Though many people from different part of the world are changing their live up on efficient use of conservation system it is hardly practicable in our country in few locations. As a result it became essential to study its merits and demerits in reference to the glob and our geographical situation as compared to the conventional one. Conventional "arable" agriculture is normally based on soil tillage as the main operation. Tillage is mechanical manipulation of soil. It includes the sequence of operations tilling, planting, harvesting, chopping and applying pesticides and fertilizers. Conservation Agriculture, understood in this way, provides a number of advantages on global, regional, local and farm level:

It provides a truly sustainable production system, not only conserving but also enhancing the natural resources and increasing the variety of soil biota, fauna and flora (including wild life) in agricultural production systems without sacrificing yields on high production levels.

No till fields act as a sink for CO2 and conservation farming applied on a global scale could provide a major contribution to control air pollution in general and the global warming in special.

Soil tillage is among all farming operations the single most energy consuming and thus, in mechanized agriculture, air-polluting operation. By not tilling the soil, farmers can save between 30 and 40% of time, labour and, in mechanized agriculture, fossil fuels as compared to conventional cropping

Soils under conservation agriculture have very high water infiltration capacities reducing surface runoff and thus soil erosion significantly. This improves the quality of surface water reducing pollution from soil erosion, and enhances groundwater resources.

The system depends on biological processes to work and thus it enhances the biodiversity in an agricultural production system on a micro- as well as macro level.

Conservation agriculture is by no means a low output agriculture and allows yields comparable with modern intensive agriculture but in a sustainable way.

Conservation farming is mostly attractive as it allows a reduction of the production costs, time and labour, particularly in peak times like planting and it reduces in mechanized systems the costs for investment and maintenance of machinery in the long term.

Disadvantages in the short term might be initially high costs of specialized planting equipment and the completely new dynamics of a conservation farming systems, requiring high management skills and a learning process by the farmer.

1.1.1. Soil tillagePlowing is a two thousand year old technology and the primary objectives of tilling soil are to prepare a seedbed and to control weeds. The term tillage is a broad generic term embracing all operations of seedbed preparation that optimize soil and environmental conditions for seed germination, seedling establishment and crop growth (FAO, 1995).

1.1.1.1. Types of soil tillageA. Conventional tillage

It is the cultivation of the soil using plow, harrow and other farm tools or mechanical implements to prepare the field for crop production.

Advantages

Destroys pests' shelters and disrupts their lifecycles. Exposes pests to predators and unfavorable conditions

Distributes soil nutrients throughout the soil

Aerates the soil

Controls weeds

Makes other farm cultural practices easier to undertake

Disadvantages

Destroys the soil cover and its structure Enhances soil erosion

High moisture loss

Disrupts the lifecycle of beneficial soil organisms

Needs more labor cost for the soil preparation

B. Conservation tillageThe planting or sowing in the previous crop's residues that are purposely left on the soil surface is called conservation tillage.

Advantages

Conserves water. The mulch reduces water to evaporate. Reduces erosion because the topsoil is protected.

Reduces soil compaction.

Protects impact from rain and wind.

Improves the soil condition with the increased organic matter content.

Natural enemies have places to stay.

Lessens the overall production cost.

Disadvantages

Needs a thorough understanding of the concept and requires careful farm management practices to be successful. Most soil pests populations are increased.

Weeds compete with the main crops. High tendency of a carryover of the insect pests and diseases from the crop residues.

Organic matters are not evenly distributed or are concentrated at the topsoil. It needs patience and waits a longer time to have an excellent soil.1.1.1.2. Methods of conservation tillage Zero tillage (no-till, minimum tillage, or direct seeding):- Is a system in where the soil is not disturbed between harvesting one crop and planting the next. It is a crop production where the soil is not traditionally tilled or cultivated although sticks or other planting equipments are used to make the openings for seeds.

Ridge tillage: - Is a specific form of no-till wherein a new crop is planted on pre-formed ridges or hills or bunds from those of the previous crop. After harvest, the crop residues are left until the planting time. The seeds are sown along the ridges. Sticks or other farms tools are used to make the openings for seeds.

Mulch tillage (stubble mulch tillage):- Any system that ensures a maximum retention of crop residues (30% or more) on the soil surface. The soil is prepared in such a way that plant residues or other mulching materials are specifically left on or near the surface of the farm.

1.1.1.3. General Situation of No-Tillage in the World The leading countries in the world with the biggest area under no-tillage are the USA with 19 3 million hectares followed by Brazil with 11 2 million ha, Argentina with 7 3 million ha, Canada with about 4 1 million ha, Australia with 1 million ha and Paraguay with 790 000 ha of the technology being practiced by farmers.

Table1.1: Total area under no-tillage in different countries (hectares) Country 1998/1999

USA19,347,000(1)

Brazil11,200,000(2)

Argentina 7,270,000 (3)

Canada4,080,000 (4)

Australia1,000,000 (5)

Paraguay790,000 (6)

Mexico500,0000 (7)

Bolivia200,000 (8)

Chile96,000 (9)

Uruguay50,000 (10)

Others1,000,000(1)

TOTAL45,533,000

Conservation tillage study results in Ethiopia

Table 1.2.Conservation tillage study for the year 1999TreatmentPlough

(min)Weeding time(min)Yield

(kg/plot)

conventional26.07a166.22

Minimum12.753b177.73

Strip12.13716.76.54

L.S.D(0.01)11.54NsNs

C.V (%)18.0719.217.48

Table1.3.Conservation tillage study for the year 2000TreatmentPlough

(min)Weeding time(min)Yield

(kg/plot)

conventional22.957a13.863a11.544

Minimum11.533b22.563b10.731

Strip7.680b20.093ab10.198

L.S.D6.508(0.01)8.356(0.05)Ns

C.V (%)12.3219.5714.57

1.1.1.4. Some practical results on conservation tillage Second National Maize Workshop of Ethiopia.12-16 November, 2001. 71

A REVIEW OF TILLAGE MANAGEMENT RESEARCH ON MAIZE IN ETHIOPIAAn experiment was undertaken to investigate the effects of tied-ridges for water conservation and the response of maize to fertilizer. The experiment was conducted to determine the optimum nitrogen and phosphorus rates during 1992 and 1993 cropping seasons on farmers' fields at Wonji, Boffa and Wolenchiti and the result is given in Table 4.

(Habtamu et al., 1994)Table 1.4.Fertilizer response of maize with and without moisture conservation practice Treatment Grain yield(kg ha-1)

19921993Mean

No fertilizer, maize planted on tied ridge1718 14141566

No fertilizer, maize on flat15519761264

18 N,46P2O5(kg ha-1) maize on tied ridge217514011788

18 N,46P2O5(kg ha-1) maize on flat194613961671

41 N,46P2O5(kg ha-1) maize on tied ridge258314492216

41 N,46P2O5(kg ha-1) maize on flat287620462461

64 N,46P2O5(kg ha-1) maize on tied ridge236722452306

64 N,46P2O5(kg ha-1) maize on flat222122572239

LSD (5%)251206186

LSD (1%)33474245

CV (%)16.217.516.8

(Worku Burayu, Tewodros Mesfin, Hussein Mohammed, Tolesa Debelle, Tesfa Bogale and Birtukan Mekonnen EARO) In Bako, one year of results indicated that conservation tillage significantly increased grain yield by 12.5% as compared to conventional tillage (Table1. 5). The economic analysis of this experiment showed that the highest net benefit was obtained from conservation tillage relative to the conventional. Sensitivity analysis also indicated that conservation tillage remained profitable under different scenarios of maize price and herbicide cost (Table1.6). Comparative study of tillage system and crop residue management was conducted at Jimma in a continuously cropped maize field. The difference among tillage systems was significant at P 5.7.

K: Potassium chloride is the most economic source unless the soil is deficient in sulphur, in which case potassium sulphate can be used to provide both K and S.

S, Micronutrients, Agricultural and industrial wastes are other forms 1.3.1.3. Fertilizer Placement

The distance the fertilizer is placed from the seed can have a tremendous effect on the rate of fertilizer placed with the seed at planting. Fertilizer placed in a narrow band in direct contact with the seed will have the greatest potential for damage. Damage decreases as the distance from the seed is increased.

This is partially related to seed utilization, since greater soil-seed-fertilizer mixing action occurs as the seed and fertilizer is spread out. The area of fertilizer release will have an effect on placement and mixing of fertilizer in the soil. If the fertilizer is in the same flow pattern as the seed, little mixing occurs unless a spread pattern is employed. However, if the fertilizer is released separate from the seed, to the side, below or behind the seed, greater soil mixing will occur, reducing the potential for fertilizer damage. Type of fertilizer material (granular, liquid, or gas) can also affect the desired distance fertilizer is placed from the seed.

1.3.2. Fertilizer application techniques1.3.2.1. Broadcasting-This calls for a sufficiently dry soil to permit the use of tractors and spreaders but nevertheless enough soil moisture for adequate nutrient uptake by the roots from the soil solution. These conflicting requirements could be overcome by the use of aircraft, but still a rather expensive method. Mostly, however, the actual date of fertilizer application fails to coincide with the optimum for nutrient uptake. Another difficulty is that P and K - and N when applied in form of urea - should always be incorporated into the soil, normally before sowing; but such incorporation, by aerating the top soil, results in a loss of moisture and of humus. Particular attention must be given to absolute uniformity of N fertilizer distribution. Evenness of distribution depends mainly on the physical quality of the fertilizer (granule size distribution, specific weight and surface characteristics).1.3.2.2. Band or storage application- If it is desired to make fertilizer nutrients available only in those parts of the field which are actually covered by the wheat or maize plants at till ring, band application is recommended. High nutrient concentration will then prevail in those particular areas, which may be used as long-lasting. Fertilizer depots because neither the roots nor the soil organisms will penetrate to the centre of the high concentrated zones and only their outer surfaces are exploited. This method is especially suited to nutrient-deficient and strongly nutrient fixing soils.

The following conditions must be fulfilled in all cases where the "fertilizer depot" method is to be used: The amount of nutrient stored must supply the crop's total demand; The outer surface areas of the depots must be of an appropriate size to minimize both immobilization and leaching loss;

Placement should be at least 4 cm beside the seed or, even better, about 2.5 cm beside and 2.5 cm below the seed;

In dry areas, placement can be up to 15 cm deep;

The depots should not be spaced more than 39 cm apart;

The amount of nutrient stored should not exceed 100 kg/ha.

The fertilizers generally used are anhydrous ammonia, aqueous ammonia and easily soluble P- or NP/NPK-fertilizers. Anhydrous ammonia should only be used where nitrification is low and where the winter precipitation is almost equal to the water holding-capacity of the soil; a nitrification inhibitor should be added.

1.3.2.3. Foliar application - The advantage of foliar application is the direct uptake of nutrients into the metabolism of the plant tissues. Thus, with a very low consumption of energy for transportation within the plant, the uptake is virtually independent of environmental factors such as soil moisture. The disadvantage is the limited amount that can be applied at one time, due to the risk of leaf burn; but this is of less concern provided proper attention is paid to the relevant limits of concentration, especially when there are a number of split dressings. Another advantage is the opportunity to combine fertilizer application with that of pesticides and growth regulators, in many cases with beneficial synergistic effects. 1.3.2.4. SlurryApplication of slurry to cereals causes great problems. Autumn application without added nitrification inhibitors may result in a large loss of nitrate by leaching, due to the limited uptake by the young crop. Application on frozen ground, while not harming the crop, may cause environmental problems. Spreaders with oversized tyres (to reduce pressure on the soil), applying the slurry through drag hoses, may be used for spring top dressing, provided tramlines" have been laid down at sowing.

1.3.3. Crops type limitation on fertilizer application The amount of germination damage caused by application of fertilizer with the seed at planting depends somewhat on the crop species. Some crop seeds are more sensitive to NH3 and salt injury as a result of their size, seed coat type, and water content.

Limited information is available on how specific crop seeds react to fertilizer applications with the seed. In general, small grain crops (wheat, barley and oats) are able to tolerate higher rates of N fertilizer with the seed than corn or soybeans, which are more sensitive.1.4. Maize and Wheat/Barley1.4.1. Maize USA: Corn; French: Mais; Spanish: Maiz; Italian: Mais; German: MaisCrop data

Annual harvested part: grain, used for human and livestock consumption. Lesser amounts are grown for harvest of the entire above-ground plants at physiological maturity to be made into silage for animal feed. In some areas, after the grain has been harvested the remainder is cut and used for animal feed. Yellow dent is primarily used for livestock feed, white dent is used primarily for production of meal and cereals for human consumption. Other dent lines have been bred for special purposes: e.g. waxy maize for production of amyl pectin starch, high lysine maize for use in pig feed, high oil maize for production of vegetable oil for human consumption. Flint corns are grown in Central and South America, Asia and Southern

Europe. Sweet corn was developed to be harvested in an immature stage for human consumption. Popcorn is used primarily for human consumption as freshly popped or other snack food items.Adapted to a wide range of climates, the crop is mostly grown between latitudes 30 and 55, principally in latitudes below 47. In most areas it is sown in early spring but, due to its wide adaptation, it flowers at different times depending on the cultivar selected. Developed to take advantage of the length of growing season available, some will mature as soon as 60 days after emergence while others require over 40 weeks.Plant densities vary considerably around the world, depending on cultivar and climate. In the more arid areas, densities as low as 15 000/ha can be found and 25 000/ha are common, but in humid or irrigated areas populations in excess of 75 000/ha give optimum production. The crop will do well on any soil with adequate drainage to allow for the maintenance of sufficient oxygen for good root growth and activity, and enough water-holding capacity to provide adequate moisture throughout the growing season. Preferred pH 6.0-7.2: the amount of associated evapo-transpiration varies with plant density, crop age, and available soil water, atmospheric conditions, etc., from an estimated 0.20-0.25 cm/day for young plants to 0.48 cm/day for plants in the reproductive phase.It is a warm weather crop, doing best when temperatures in the warm months range from 21 to 27 C. It does not do well when the mean summer temperature is below 19 C.

Table1.10

Table1.11

Table1.12. Plant analytical data Table1.13

Table1.14 Fertilizer recommendationsEach of the following factors must be carefully integrated when determining the optimum rate for a particular field or part of a field:

- Yield potential.

Previous 5-year average yield plus 5 % is suggested as a basis for estimation, but, if fertilizer is applied post-emergence, adjustment may be made for delay in planting or inadequate stand.

- Previous crop.

Research has shown that maize will produce better when grown in rotation with another crop, especially a legume, probably as a result of diminished incidence of pests and diseases, reduction of the negative effect of continuous maize cropping, and a contribution of N from the legume. While much of the disadvantage of growing maize after maize can be overcome by applying N fertilizer, it is not possible to apply enough N to eliminate completely the yield difference between rotational and continuous maize.- Timing.

Uptake of over half the N and P and 80 % of the K is accomplished before the crop reaches the reproductive stage. It is therefore imperative that an adequate supply of these major nutrients be available to the plants early and remains available throughout the growing season. Even though only small amounts are taken up early in the season, high concentrations should be available in the root zone as the root system is small at that time and the soil is often cold.N must be applied annually. Since it is subject to loss by leaching or denitrification, it is best applied near the time of crop need. On finer textured soils, silt loam or heavier, it is best applied as a pre-plant or side dressing; on coarse textured soils where leaching can be a problem, N is best applied as a side dressing or split application. If the crop is irrigated, 50-60 % pre-plant plus the rest through the irrigation system is an effective technique. There is much greater flexibility in the time of application of P and K since they are relatively immobile. On many soils they may be broadcast either in the fall or spring with similar results, except on sandy soils where there is a possibility that the K might be leached out of the rooting zone (K should then be applied just before planting).

- Method of application.On fields where the soil fertility status is at or above the desired level, there is little evidence to show any significant difference in yield associated with different methods of application. In contrast, on soils with a low nutrient status or a high P-fixing capacity, placement of the fertilizer within a concentrated band has been shown to result in higher yields, particularly at low rates of application. On higher-testing soils, although yield differences are unlikely, plant recovery of fertilizer nutrients in the year of application will usually be greater from a band placed 5 cm to the side and 5 cm below the seed than when broadcast.Placement of fertilizer directly with the seed is sometimes referred to as "pop-up", but this is a misnomer as the crop does not emerge any sooner and may indeed emerge 1-2 days later than without such application. If used, pop-up fertilizer should contain all three major nutrients in the proportions N: P2O5:K2O=1:4:2. Under normal moisture conditions, the maximum safe amount of N + K2O for placement directly with the seed is 12-15 kg/ha in 100 cm rows and correspondingly more in closer rows. In excessively dry springs, even these low rates may result in reduced germination and/or damage to seedlings.Present fertilizer recommendations/practicesGood example India

N: 100-125 kg/ha N as urea, split into three applications.

P: 60 kg/ha P2O5, as processed phosphates applied mostly at sowing.

K: 30 kg/ha K2O, as potassium chloride applied mostly at sowing.

1.4.2. Wheat USA: Wheat; French: Bl; Spanish: Trigo; Italian: Frumento; German: WeizenWheat is the world's most important cereal crop in terms of both area cultivated (232 million ha) and amount of grain produced (595 million t). It is widely grown throughout the temperate zones (in Northern Europe up to 60 N) and in some tropical/sub-tropical areas at higher elevations. The major centres are: Europe (131 million t grain, 27 million ha), the former USSR (108 million t grain, 48 million ha), North America (106 million t grain, 42 million ha), China (96 million t grain, 30 million ha) and India (50 million t grain, 23 million ha). All these figures relate to 1990. The following information is mainly for T. aestivum, though also generally valid for T. durum. Special data for durum wheat are given as an appendix to this end of chapter.Crop data

-Annual, autumn-sown (winter wheat) and spring sown types.

-Harvested products: grain, straw, (occasionally) whole green plant.

-Desired characteristics affecting fertilizer requirement:

-In grain for milling for bread and pasta: high endosperm-protein: In grain for malting and brewing: high starch, low crude protein, absence of sprouting.

-For animal feed: high protein especially lysine. -For industrial starch: high starch concentration with slow starch ripening, high endosperm-protein.-For alcohol production: high starch content, low crude protein.

-Straw for litter and bedding: should be dry and absorbent. -Straw for cellulose and for pasteboard: high starch, low lignin, low ash. -Straw for constructional insulation: should be dry and of low bulk density.

-Whole plant for green fodder: high protein, high energy. -Whole plant for silage: high concentration of easily soluble carbohydrates

The quality of the protein in the grain depends largely on the variety. The protein/starch ratio in the grain depends both on the variety and on the way in which the crop has matured.Preferred soils and soil conditions: Wheat (like barley) generally prefers the more fertile soils, but it can be grown on practically all types except very light sandy soils or peat soils, so long as the water requirement can be met and the nutrient demand is met by appropriate use of fertilizers.Sowing times: Winter wheat should be sown timely enough to get at least two leaves before the onset of the vegetative rest period. The available growth time for tilling should be at least 21 days. Provided the ground is sufficient, spring wheat should be sown as soon as temperature and soil moisture permit.Present fertilizer practicesIndia

Irrigated timely-sown crop

- Under assured irrigation

N: 80-120 kg/ha N, depending on previous crop

P: 40-60 kg/ha P2O5

K: Based on soil test result

- Under limited irrigation

N: 60 kg/ha N

P: 30 kg/ha P2O5

K: Based on soil test result

Half the N and all the P and K are applied at or before sowing; P should be placed 5 cm below the seed. The remaining half of the N is top-dressed at the first irrigation. N and P rates are adjusted according to soil test results.

Irrigated late-sown crop

N: 60-80 kg/ha N

P: 40-50 kg/ha P2O5

K: Based on soil test results

All N, P and K are applied at sowing; rates are adjusted according to soil test results1.4.3. Barley French: Ogre, escourgeon (winter barley); Spanish: Cebada; Italian: Orzo; German: GersteCrop data

-Annual, winter- and spring-sown types; ears 2- or multiple-rowed; grains generally with glumes.

-Harvested products: grain, straw, (occasionally) whole green plant.

-Desired characteristics affecting fertilizer requirement:

-In grain for livestock feed: high crude protein, especially lysine. In grain for processing for use in human foodstuffs: high-protein endosperm, lack of excrescences, low husk content.

-In grain for malting: high starch, low crude protein, lack of excrescences.

-Straw for bedding: should be dry, absorbent material.

-Whole green plant for forage: high crude protein and energy, smooth glumes.Sowing times: Winter varieties should have completed tilling before the vegetative rest period, i.e. normally within 45 days (of real growth) from emergence. On the other hand, excessive early development of biomass is undesirable as it reduces winter hardiness.

Spring varieties should be sown as early as practicable, when temperature, moisture and other soil conditions permit.Plant density: sowing rates for 2-rowed types are within the range of 320 - 365 grains/m2 (at a desired optimum ear density of 700 - 800 ears/m2). With multiple-rowed winter barley the following model calculation may serve as a guide:

Expected yield = 9 t/ha; required ear density = 600 ears/m2. With an estimated germination rate of 95 %, an over-wintering rate of 85 % and 2.7 ears per plant, the seeding rate should be 280 grains/m2 (see also 2.3 Wheat).

Yield structure: The next table shows the (relative) changes of yield components in correlation to varying amounts of plant available water; assuming that water supply is the primary yield-determining factor in cereals:Table1.15

The grain yield of barley is related to the amount of water consumption, which increases over-proportionally with increasing yield; the same is true of N uptake. If maximum utilization of water and applied nutrients is required for optimum grain yield, then the ratio of the number of plants per unit area to the number of ears per plant must be optimized; thus the crop should tiller heavily. This can be influenced, depending on water and N supply, by application of N. Depending on the quantity and timing of N application, around 250 l water per kg grain yield may be needed, the coefficient of productive tilling (ear-bearing tillers / total tillers) ranging between 0.39 and 0.60.

As shown in the figure it is not as important in barley as in wheat to control the uniformity of different orders of tillers. Unproductive tilling (caused for example by a too high or too late

N fertilization in spring) should, however, be avoided.Fertilizer recommendationsThe same principles apply as for wheat, but the exact timing of split applications of N is more critical, especially for winter barley.

Owing to the greater tendency of barley to lodge, as compared with wheat, stem stabilizers are being used in intensive growing systems. As chlormequat by itself does not give sufficient reduction in stem length, a combination of chlormequat chloride and etephon is favored, with etephon alone being used for late applications.Fertilizer practice

India

- Irrigated:

60 kg/ha N, 30 kg/ha P2O5

-Half of the N and all P before or at sowing, the remaining N top-dressed at the first irrigation.

-Rainfed: 30 kg/ha N, 20 kg/ha P2O5

Both N and P application is before or at sowing. P should be placed 5 cm below the seed; application rates are adjusted according to soil test results.1.5. Sowing and planting equipmentsThe basic objective of sowing operation is to put the seed and fertilizer in rows at desired depth and seed to seed spacing, cover the seeds with soil and provide proper compaction over the seed. The recommended row to row spacing, seed rate, seed to seed spacing and depth of seed placement vary from crop to crop and for different agro-climatic conditions to achieve optimum yields.1.5.1. Traditional Sowing Methods

Traditional methods include broadcasting manually, opening furrows by a country plough and dropping seeds by hand, and dropping seeds in the furrow through a bamboo/metal funnel attached to a plough. For sowing in small areas dibbling i.e., making holes or slits by a stick or tool and dropping seeds by hand, is practiced. Multi-row traditional seeding devices with manual metering of seeds are quite popular with experienced farmers. Traditional sowing methods have following limitations; In manual seeding, it is not possible to achieve uniformity in distribution of seeds. A farmer may sow at desired seed rate but inter-row and intra-row distribution of seeds is likely to be uneven resulting in bunching and gaps in field.

Poor control over depth of seed placement.

It is necessary to sow at high seed rates and bring the plant population to desired level by thinning.

Labour requirement is high because two persons are required for dropping seed and fertilizer.

The effect of inaccuracies in seed placement on plant stand is greater in case of crops sown under dry farming conditions.

During hand sowing, placement of seeds at uneven depth may result in poor emergence because subsequent rains bring additional soil cover over the seed and affect plant emergence.1.5.2. Functions of Seed-drills and PlantersThe functions of a well-designed seed drill or planter are as follows:

i. Meter seeds of different sizes and shapes;

ii. Place the seed in the acceptable pattern of distribution in the field;

iii. Place the seed accurately and uniformly at the desired depth in the soil; and

iv. Cover the seed and compact the soil around it to enhance germination and emergence

1.5.2.1. Subsystems of Sowing and Planting Equipment

Improved seed-cum-fertilizer drills are provided with seed and fertilizer boxes, metering mechanism, furrow openers, covering devices, frame, ground drive system and controls for variation of seed and fertilizer rates. The major difference in different designs of seed drills/planters is in type of seed and fertilizer metering and furrow openers. Details of these devices are as follows: Seed Metering Devices

Metering mechanism is the heart of sowing machine and its function is to distribute seeds uniformly at the desired application rates. In planters it also controls seed spacing in a row. A seed drill or planter may be required to drop the seeds at races varying across wide range.

Common type of metering devices used on seed drills and planters are:A. DIBBLING STICK

The dibbling stick is a simple manually operated device for creating a conical cavity in the soil for sowing of seeds. It consists of a wooden round stick with one end having a sheet metal cone. The other .end is provided with a handgrip. For its operation, the dibbling stick is held in vertical position and the conical end is pressed into the seedbed to the desired depth. This action creates a conical cavity in the soil in which the seed is placed. The conical end fitted in wooden stick is made from mild steel sheet.

B. DIBBLER

The hand dibbler is made from mild steel flat or leaf spring by forging operation. The working end is flattened and edge made sharp for easy penetration in the soil. The cutting edge of the tool made from spring steel is hardened and tempered to desired hardness. The other end serves as a tang for fitting handle. The tool is used in squatting position by pushing/striking the cutting edge in the soil.C. ROTARY DIBBLER

The rotary dibbler is a manually operated push type device for dibbling of medium and bold size seeds. It consists of a rotating dibbling head with penetrating jaws, covering-cum-transport wheel, seed hopper with cell type wooden roller and a handle. Except seed roller, which is made of good quality wood, all the other parts are fabricated from mild steel. The number of jaws varies from five to eight among various designs, depending upon seed to seed distance. For its operation, the hopper is filled with seeds and transport-cum covering wheel is drawn to rear side. The dibbler is then pushed forward in the direction of travel with covering cum transport wheel behind the dibbling head. The jaws penetrate into the soil and automatically drop the seeds. The seed to seed distance depends upon size of the polygon plate to which jaws are attached. D. POWER TILLER OPERATED TILL PLANT MACHINE

This machine has been specially designed for operation with a power tiller of 10-12 hp to carry out simultaneous tilling and planting operation in a single pass. It can plant two rows simultaneously. It is provided with a pair of depth control gauge wheels, which also serve to activate the metering mechanism. Some of its major components are the main frame, seed and fertilizer boxes, metering mechanism, transport wheel, furrow openers, hitch system etc. It is suitable for sowing seeds of wheat, soybean, Bengal gram, sorghum etc in medium and heavy soil.Other Animal Drawn and Power Driven planting and Wedding Equipments

LOW COST SEED DRILL BULLOCK DRAWN SEEDER

ANIMAL DRAWN AUTOMATIC ANIMAL DRAWN WEEDER SUGARCANE PLANTER DIFFERENT TYPES OF SEED AND FERTILIZER DRILLPART TWO

2. Conceptual DesignThis is the stage where the feature of the inline seeder is pre set as a stepping stone for the rest of the design process. Here, many alternatives and different features are discussed, compared and specified based on geometrical consideration and expected mechanical, ergonomic and aesthetic requirements.

Definitely the main concern of the design of seeder is to find a simple, with easy manufacturability and low cost method of metering seed grains and fertilizer so that to meet a specific requirement. Hence the following are some of the competitive mechanisms anticipated to meet the quality and feature needed.2.1. Different mechanism of metering assessed2.1.1. Model A: - spring loaded sliding meters reciprocated by circular discs with circumferential extrusion at adjusted space.

1-Disc, 2-Shaft, 3-Slider, 4-Spring end, 5-compartmentFig2.1.Spring loaded metering mechanism (rotating shaft): a) Whole system during opening and closing

b) Variable face disc (a disc with extrusions)

Mechanism is by use of variable face discs that are attached to the axle of the seeder and sliders spring loaded at one end, and attached to the compartment base. Whenever the unloaded end of the slider gets the extrusions on the rotating disc, the slider will be subjected to axial motion thereby it lines the hole on it to the hole on the compartment base and allows the seed grains drop across from the compartment to collecting tube then to the opener end.2.1.2. Model B: -spring loaded single slider with many holes that are reciprocated by the hub of the wheel.This is similar mechanism as the above except in this model the shaft will be fixed with the compartment and metering is then by the reciprocating motion of a long metallic strip(slider) this has proper holes to allow seed and fertilizer pass through. The strip is spring loaded at one end and reciprocates as a result of contact with extrusions which are at the wheel hub.

Fig2.2.Spring loaded single slider metering mechanism (fixed shaft)

a) At opened condition, andb) At closed condition.2.1.3. Model C: -metering cylinders attached with a rotating shaft, and with two rows of holes at specified spacing for allowing seed and fertilizer grains pass across.

1-Compartment, 2-Cylinderical meter, 3-shaft, 4- Holes for seed and fertilizer

Fig2.3. Cylindrical seed and fertilizer meteringThis mechanism is more realistic and it is dependent on gravitational flow of grains as in the above models but here the shaft is more the heart of the metering system; it will be coupled with one or more metering cylinders. A seed and/or fertilizer grain drops due to gravitational force to the collecting tube, which will be fixed to the compartment wall, whenever they get a hole that allow them pass through.2.1.4. Model D: -grooved solid disc driven by the hubs of the wheel using belt connection.

Figure2.4. Grooved solid discThis mechanism uses cylindrical discs provided with circumferential grooves. Part of a disc is placed in the compartment and the rest is protected by a casing. The discs are attached to a rotating shaft, which is driven by belt coupling from the hub of the wheel. The grooved parts of the disc, on its way through the compartment collects some amount of grains and transport them to the collecting funnel beneath it.2.1.5. Model E: -a slider mechanism driven by magnetic strips attached to a rotating shaft at specified positions.

Figure2.5. Magnetic shaftIn this mechanism magnetic strips are incorporated to a rotating shaft and a spring loaded metallic strip is attached to the base of the compartment hence the opening and closing mechanism is by magnetic force attraction of the strip towards the shaft whenever it closes the incorporated magnet.2.1.6. Model F: -a rotating splined shaft or a splined disc attached to a rotating shaft.This is similar mechanism to the grooved mechanism except that the in this case the grooves are perfect splines and the adjusting of the spline for different sized seeds is by coupling it to an external sleeve and controlling the part of the spline that will meat the sleeve.

2.2. Design matrixThis is a system of finding good alternatives among many model solutions for a particular problem. There are different types of Design Matrices that are used to make systematic decisions on choosing best alternatives of given two or more alternative designs. The following method is selected so that to help reach at the best decision. This method has been adopted to meet the case of the inline seeder. Besides, the functional requirements or weights are selected to suit to expectation to physical, mechanical and environmental fitness of the seeder. Generally, there are six basic alternatives investigated so far concerning the inline seeder in general and the seed metering unit in particular.

Table2.1. Matrix comparisons of alternative models for metering seedsNo.Function requirementsModel designations

ABCDEF

1Physical requirements

-Average size of components443253

- Less number of components222344

-Complexity113422

-Weight334333

-Operability124433

2Mechanical requirements

-Wear failure avoidance114533

-Fatigue and creep failure prevention333333

-Corrosion failure avoidance225423

-Deflection, buckling and jerk avoidance334333

-Reliability333343

-Durability334334

-Stability444224

3

Materials requirements

-Strength333333

-Availability334412

-Affordability334313

-Manufacturability334221

-Maintainability333422

Total positive weight for each model454656554649

Percentage weight of each model52.9%54.1%65.9%64.7%54.1%57.6%

2.3. Decision and Conclusion

Comparing the above six main and more other, that are not discussed, concepts of obtaining mechanism for metering seeds and fertilizer in many directions especially based on mechanical properties and cost effectiveness; the selection of the feature in type C, mechanism with grooved disc meters is beneficial and viable decision. Some of the drawbacks of this model of mechanism are expected to get remedies in the design analysis phase with considerations and through good search of suitable alternatives.More of compromising and realistic tasks are going to be comprehensively covered in the design analysis and synthesis phase. However, to have clear idea on the following point is unavoidable.These are:

1. What part of the society will use it? Definitely, farmers who have less art and potential to use advanced equipments are the target.2. What mechanisms to be used to satisfy the need of the user? The mechanism to be adopted, as described above is the one with a cylindrical metering part with a rotating shaft.3. What different components should the seeder expected to have so that to implement the above mechanism? Some of the main components are:a) Shaft. May be either solid or hollow.

b) Bearing. Either sliding or rolling type.

c) Wheel. Can be of metallic or wooden. a) Metallic wheel b) wheel made of wood and metal hubd) Compartment. For accommodating seed as well as fertilizer.e) Metering disc. Can be made of wood, plastic or metal.

f) Bar for attaching openers and covering unit. This may be made of wood or metal. g) Openers, covering and compacting tools. h) Standard bolts, nuts, screws, keys, pines etc.CHAPTER THREE3. Design analysis and synthesisIn the preceding phase many alternatives are given as a solution to the design of inline seeder. In particular, about six different metering mechanisms are discussed and compared to each other with various reference points. Actually these comparisons and descriptions are not completely realistic as well as that method of selection is more of logical than theoretical. However, it has claimed that the decision made on the previous phase is base for more scientific and engineered analysis that should be done in this phase.

So far one mechanism expected to be best is selected with briefly satisfactory reasons. Now the selected model should be analyzed with respect to mechanical requirements such as; strength, durability, resistance to failure due to wear, corrosion, fatigue, creep, deflection etc.As shown and described in the conceptual design phase the wheel of the seeder is the heart element to the whole mechanism of metering and placing seed cum fertilizer grains, therefore; it is vital to start the design analysis from this component on wards.3.1. Axle

Assumptions

The axle is analyzed as a cantilever beam.

The maximum distance between the wheel center and the vertical frame is assumed to be that of in the belt connecting side. Which is taken l=50mm.

The maximum resultant force on the axle is assumed to be the resultant of the vertical weight and the horizontal traction forces. (3.1)

Where: - the maximum weight expected is W=50 Kg -And the maximum horizontal traction force is taken to be the pulling force of two

Ethiopian zebu oxen at about 0.4 m/s speed. That is F=1191 N. (literature)Material

Basically, materials used for axle/shaft should have the following core properties:

It should have high strength: therefore to with stand forces applied on it.

It should have good mach inability: fore the easy of manufacturing.

Good heat treatment properties: This provides the shaft with good surface properties that can resist failures due to fatigue, wear and creep.

It should have good wear resistance properties especially when there is a necessity to use he axle with journal bearings and similar parts.Material for the axle is Plain carbon steel (dead milled steel)

Carbon content % (0.05 to 0.15)

Ultimate strength su = 410 Mpa

Yield strength sy =273 Mpa

Elastic limit = 217 MpaDeflection or bending considerationFor a circular axle the maximum bending is the product of the load applied and the length from the fixed end to the section where highest deflection presents.

Maximum bending moment is given by:

Mmax= FRl.. (3.2)Mmax = 32292.5 N-mmBending strength for a given cross section is given by:

. .. (3.3) Where sb = bending strength,

Z = Section modulus. For a circular cross section, Substituting the above results in (3.3) gives r = 14.73 mm, => d=29.5mmShear consideration

The axle is subjected to shear due to the resultant force applied on it.The shear stress that is going to be produced is given by:

.... (3.4)Where shear stress induced due to the resultant load

FS=the shearing force, whose value is half of FR=1291.7 N

AS=the shear area= Substituting the above values gives:

=0.95 Mpa which is lower than the allowable stress, which implies the axle is safe for shearing.Therefore the diameter of the axle is taken to meet nearest standard value d=30mm3.2. Bearing As we are looking for a component that are with by far manufacturability by local farmers and the raw materials are abundantly available with low cost, the first thing to be decided is to see the properties of materials around us and select the suitable one. There are two types of bearings commonly user for different machine components; sliding bearings or rolling type bearings. Each of the above has its own merits and demerits with respect to the other. Generally for low power operation requirements the sliding bearings have the following advantages over the rolling one:

Advantages of sliding bearings over rolling bearings

Rolling bearings may eventually fail from fatigue while sliding bearings are less sensitive to fatigue

Sliding bearings requires less space in radial direction

Good damping ability

less noise level

less sensitive to sever alignment

low cost

highly available

However in some cases where higher speed and power transmission required the rolling bearings show the following advantages

Low starting and good operating friction;

Can support combined radial and axial load/thrust load

Less sensitive to interruption of lubrication

No self excited instability

Good low temperature starting.

Can seal lubrication with in bearing and be life time lubricated

Looking closer to the working environment, the users economy and operating skill (our farmers) and the above physical and mechanical comparisons, it is reasonable if the sliding bearings are selected though it has some drawbacks that are not considerable limitations for farm operation.

Hence the sliding bearings are selected the one used for the seeder must possess;

Compression strength to resist permanent deformation

Suitability, ability to accommodate misalignments of journals

Low coefficient of friction and oiliness

Must be soft enough for the hard abrasive particles (dust, grit etc), that may interfere its operation.

Resistance to corrosion so that it can with stand oxidation

Good heat conductivity to help the dissipation of heat generate3d

Low thermal expansion so that the clearance doesnt change if bearing is to operate in wide range of temperature.

Low cost

Material

The common sliding bearing materials are:

Metals (Babbitt metal, Bronze, Cast iron, Silver etc)

Non-metals (carbon graphite, rubber, wood, plastic)

The bearing for the seeder wheel may be made from any one of the above recommended materials. However, it is necessary to analysis the bearing especially for heat dissipation capacity of the bearing by assuming particular material. Therefore, the bearing for the wheel is designed considering cast iron journal type bearing.

Analysis

Assumptions

The design of journal bearing involves many variable; such as viscosity, Z; load per unit projected area of bearing, p; the journal speed, N; bearing dimensions radius, r; clearance, C; contact angle, ; length, l; and the performance variables: coefficient of friction, f; bearing surface temperature,; heat generated and dissipated, Qg and Qd; the maximum film thickness, ho.

Assuming radius of wheel 160 mm and the traction speed of oxen v=0.5 m/s, the speed of the journal N will be around 59.7 rpm

Load on the bearing FR1= FR1=645.85 N

Journal diameter d= 32 mm => r=16mm

Operating temperature to= 30oC and ambient temperature ta= 20oC

Table3.2. Design value for journal bearing

MachineryBearing Maximum bearing pressure(N/mm2)Operating value

Absolute viscosity Z

Kg/m-s

Steam locomotiveDriving axle

Wrist pin2.80.030.70.0010.8-1.3

Railway cartAxle 3.50.170.0011.8-2

Generators

motors.

.

..

.

..

.

..

.

..

.

.

Centrifugal pumpsRotor 0.7-1.40.025280.0011-2

The following procedure will lead to determine the required variables of the bearing.

Determine the bearing length by choosing ratio of 2

l=2d=62 mm

load on the bearing

-this is in the limit given in table 3.1 above for corresponding railway cart though it is more pronounced to take such consideration. By selecting typical lubricant oil and its recommended working temperature determine the viscosity

i.e. SAE70,Z = 1 at operating temperature to=30oC

the bearing characteristics number .......................................................(3.5) The minimum value of the bearing modulus k at which the oil film will break is given by: => K=9.33.....................................................................................(3.6)Since the calculated value of the bearing characteristics number is greater than the maximum requirement K= 9.33, therefore the bearing will operate under hydrodynamic conditions.

Take the clearance ratio c/d= 0.0013

Coefficient of friction for journal bearing is given by:

................................................................................................... (3.7) Where k= factor to correct leakage. It depends on the ratio of l/d, k=0.002 for l/d ratios of 0.75 to 2.8

Heat generated , where ...............................(3.8)

Heat dissipated Qd=C.A(tb-ta)=C.l.d(tb-ta), A=ld........................................................(3.9) Where C=heat dissipation coefficient. For unventilated air C is in the range of 140-420 w/m2/oC. Take C=200 w/m2/oC

tb=temperature of bearing surface

ta= ambient temperature =20oC

tb-ta =0.5(to-ta) =5oC

It has been seen that the heat generated is smaller than the heat dissipated which implies that the bearing is safe, that is it doesnt need artificial cooling.

Though for the seeder wood bearings are recommended, because reasonably they are used in application where the following points are required.

Low cost

Cleanliness

negligence to lubrication and anti-seizing are important

Easy manufacturability

Good maintainability

As one can assess all types of wood available are not equally good to make bearings. As well as no such direct procedures are available to evaluate properties and requirements of wood bearings it is recommended to use locally available wood which farmers and manufacturers used for making traditional farm implements. With such wood the bearing only need to be made with good surface finish and accurate diametral clearance.

Summary

Bearing type selected: - sliding bearing

Bearing material: - wood used for traditional farm implements (best if it has got treatment)

Sliding bearing type: - split bearing, where outside of the bearing out is driving fit in the hole of the wheel hub and the inside is a running fit for the axle.

Bearing external geometry: - regular octagon circumscribed in a circle of diameter given below.

Bearing dimensions:

-Bearing bore diameter db=axle diameter + diametral clearance C

-Recommended value of C for wood bearings is

-Where d is diameter of axle, d= 30mm, => db= (30 + 0.03) mm

-Bearing outer diameter do= 60mm (i.e. the diameter of inscribed circle), which is taken to meet geometrical necessities and wall thickness necessary for bearings.

1-set screws used to fit the two halves of the bearing.

2-Cover plate

3-Bearing

The two halves of the bearing will be produced separately and force fitted to the hub of the wheel and the rotation to the hub side of the bearing is prevented by making its outer profile polygon. The axial movement of the bearing will be prevented by providing cover plates.3.3. WheelThe wheel for the seeder can be made from different materials and with different arrangements. As we have done at the bearing analysis the analysis of the wheel will be done by considering as if it is made of a typical material and it has specific arrangement and geometry likely suited for analysis take it has got perfect circular circumference. However if cost and availability of metallic material, that is steel products and the rough, muddy and bump furrows of farm fields that induce slippage of wheel; which is very undesired as it has direct effect on he seed rate and distribution, are taken in to account the type of wheel considered above has some limitations. Therefore for sake of difficulties of analysis the design will be based on the specified type of wheel material arrangement and other alternatives and options will be matched after some parameters of the wheel are determined. a) Wheel hub The wheel hub is basic part of the seeder wheel system. It is used as an attaching core element for both bearing and wheel arm/body. The wheel hub generally will be subjected to the following critical stresses:

Shear stress developed when the two halve bearing makes side way movements.

Bearing stress due to the load applied on it

Tearing as a result of weight loaded on it

Assumptions

The parts that are subjected to the above stresses would have a larger cross section that extends to the pulley body. However, the pulley is not yet analyzed therefore these sections are assumed to be only those in the hub. That means the face width of the hub is assumed to be equal to that of the bearing width L=30 mm.

Hub material

The hub material should satisfy certain requirements that are discussed so far at the strength analysis of each part.

Analysis

Shearing consideration

............ (3.10) Where =45.5 Mpa

FS=shearing force assumed to be equal to half of the resultant force FR. FS=645 N

AS= shear area= L x t

Substituting the values, results in t= 0.5 mm.

Bearing consideration

The part of the hub that may subject to bearing/crushing is the lower part. Hence by assuming the area subjected to bearing as that of half of the circumference of the inscribed circle to the inner hub times the length L. therefore,

.............. (3.11)Where = bearing strength= 135 Mpa

Fb= FS=645 N

Ab==2827 mm2

, which is too safe

Tearing consideration

The empirical formula for tearing is analysis is,

........ (3.12) Where, Ft=Fb=FS=645 N

At=2xAb

< 91 MPa the allowable bearing stress of the material so the part is safe against tearing.

Summary

A wall thickness of 0.5 mm is sufficient for the strength requirements. However, it is preferable to account the difficulty of manufacturing, the resistance for sudden impact loads and other insignificant factors the hub thickness will be rounded up to 5to 10mm, further this allows easy of attaching the arms/body of wheel. Generally the hub will have the following parameters:

Hub thickness t=5-10mm

Hub length L=30mm to 60 mm

Hub profile : - regular octagon( 8 sides)

The hub can be made of either a hollow tub by forming or easily from sheet metal by shaping and joining the two ends by welding.b) Arms

Arms of the wheel are parts that are subjected to variable stress under different circumstances. However; the critical stresses that lead to failure most of the time are:

Compressive stress when arm is in the lower half part of the wheel

Tensile stress when an arm is in the upper half part of the wheel

Bending stress due to he tangential force developed at the circumference of the wheel.

As the arm is subjected to these critical stresses it is totally exposed to failures, hence to avoid any of the failure caused by the above stresses it is mandatory and common design procedure to select proper material and check the arms to satisfy the necessary requirements.

Assumptions

Clearly it is not such easy to identify the force and stresses at each and every critical positions of the arm at different moments of the arm motion; therefore we are forced to use convenient methods of evaluation with very compromising assumptions.

Based on others experience the following assumptions are taken.

1. For the case of the above critical stresses the numbers of arms that are subjected to critical loads are assumed to be half of the total number of arms for bending stress and one third for the compressive and tensile stresses.

2. Jerk and the resulting axial bending stresses are assumed to be insignificant as the radius of the wheel (length of the arm) is not very long.

Considerations

Wheel outer diameter is D=320 mm, which is taken for geometric convenience and material minimization.

The total number of arms recommended for a wheel with diameter medium length is n=12.

The length of the arm is about L=130 mm, which is the difference of the radius of the wheel and that of the hub outer radius.

For the bending stress analysis the arms are going to be considered as a cantilever fixed at the hub end.

Material

Material for the wheel should full fill certain property requirements that are necessary to with stand the above three critical stress and be able to easily couple to the hub of the wheel. In addition the arm material should be of the type that can perform efficiently against the harsh muddy and vamp farm environment.

Therefore the material selected for the arm of the wheel is plain carbon steel used so far.

Bending consideration

For a cantilever beam as shown in the figure above, the bending moment and stress relation is:

....... (3.13)

Where

M= bending moment M= =32500 N-mm

Z= section modulus, for circular rod it is given as:

, i.e. for half of the arms

Now substituting in (1) gives:

ra = 8.99 mm => da =18 mm

For compression and tension, the arms are very safe with the diameter obtained from the bending consideration. Hence the diameter of the arm will be taken to be 20 mm; this is the closest standard circular cross-section solid rod.

c) Rim

The rim of the wheel critically subjected to three main stresses, such as shearing stress, tearing stress and bending stress at the rim part between consecutive arm ends.

Assumptions

For shearing it is assumed only parts of the rim with area equal to the projection of the end of the arm end is subjected.

In case of tearing it is assumed that only the part between two arms is assumed to be subjected to.

The bending is critical when the part of the rim at the middle of two arms is in contact to the ground.

Considerations

Width of the wheel rim is taken to be B=30 mm

Inter arm length is calculated as l==83.8 mm

Bending consideration

From the angle of application of the force Fb the horizontal component of this force is not significant as compared to the vertical component assuming only the two arms are subjected to the load WT:

And considering the rim portion as a cantilever fixed at the middle O

............................................................................................. (3.14)

And,, for the rim cross section. Then solving these;t=3mm, for this value as we can notice both requirements are satisfied.

Therefore by joining these different elements of the wheel by any of the conventional simple and enough joining mechanism, in our case most likely by welding, the final required geometry of the wheel can be achieved. However, as all parts of the wheel are designed to be made of steel only, the practice of manufacturing the wheel by the local artisan will face limitation of row and production materials; hence for better of the seeder towards production alternative materials for the wheel will be presented with equivalent dimensions and features.With same analysis, the first alternative is to make the circumference of the wheel regular polygon of reasonable number of faces (10 16). This type of wheel may be used efficiently when riding on a farm field where obstacles are very abundant. In such obstacle dense farm areas if one use circularly circumference wheels slipping of the wheel is major problem whenever an obstacle face it. This is because of that the circular circumference cant grip to the ground so as to override the obstacle. But if the polygon type wheels are used it can overcome such difficulties easily as; one there will be face contact developed between the wheel rim and the obstacle and second and main advantage, one of the many edges will grip the ground easily whereby there will be rotation to override the obstacle.The second alternative is a wooden wheel with circumferential groove, which is probably the best alternative provided so far. It can be made of one or two slabs of wood screwed to the steel flanged hub. The grooves can be produced by simply machining or attaching pieces together.The third alternative is a woo den wheel with regular polygon face. This type has the advantage of availability of raw materials because it is going to be made of wood pieces of width ranging 15mm to 50mm and thickness about 15mm attached to both sides of a metallic strip welded to the hub by simply nails or set screws to the required arrangement. All of the different alternatives of wheel are tabulated below with their corresponding dimensions.Table3.3. Alternative wheel proportions and relationsType of wheel MaterialDescriptionWidth

(mm)Diameter

(mm)number of nails/screwsNumber of rod or faces

Hub Wheel

1Circular rimMetal

(Steel)Rim is 3mm thick and rim- arm-hub are joined by weld30100320 ____ 10

2Regular polygonMetal

(Steel)Rim is 3mm thick and rim- arm-hub are joined by weld30100320 ____10

3Circumferential face groovedWood

( one or two pieces)If it is one piece the hub should have to flanges on both side of the wheel301003206 to 1010

4Regular polygon 2Wood

(Many pieces together)Wood slabs width 15-50mm and 15 mm thick batched together by nails or screws

On both side of a single flange on the hub30 + 310032020to 3010

3.4. Power transmission

There are different mechanisms that are advisable to transmit power from the wheel to the metering disc. The most widely used power transmission devices are belt and chain drives. These two drives are as follows with respect to the seeder requirement and feature.Table3.4. Belt and chain power drive comparisons

Chain drives Belt drives

They transmit motion accurately for a wider range of chain tension by a single chain. Have a longer life with proper lubrication and are less sensitive to variation in weather conditions. Chain drives are very expensive and not available with in he vicinity of the farmer The cost and knowledge of manufacturing of chain components is beyond the scope of the target farmers. Chain drives are difficult to maintain even if possible it requires higher skill and more investment. Power reduction exists due to slippage as a result of non consistency of friction between belt and pulley.

Belts usually fails due to weather change influence, hence have generally shorter life than chain drives.

Belt drives are cheaper and available to the level of local farmers

Pulleys and other implements used with belt can be made accurately with less power and skill.

Parts of belt drive are easy to produce and maintain by local artisans

Since cost and availability are the higher pressure that are behind the need for this inline seeder, we are supposed to satisfy these requirements basically and then try to minimize the drawbacks through practical trials of different alternatives. As a result the belt drives are selected for the power transmission in the seeding machine.

Besides the reasons given above belt drives provides alternative flexibility both in mechanism and component material. Among different belts some reasonable selection is required to be beneficial in the power transmission mechanism of the seeder. Therefore, it is necessary to discuss thoroughly the main belt types

Considering only the strength and efficiency requirements all types of power transmission are good for the seeder. Both belts and chain are capable of performing efficiently under different circumstances and requirements. Both of the belts, flat belts and v-bets are preferable equally for this power transmission though they are remarkably different.For seed like farm machineries the recommended type of power transmission is chain drive. However for different reasons discussed so far, for the inline seeder power transmission there is a pressure to precede the belt drive and all so the flat belt type among the belts. Therefore, because the flat belt drive is the least recommended for farming equipments like our seeder, it is good transitivity to deal with this type of belt for strength and geometrical analysis and ten propagate the outcome to the remaining v-belt and chain drives. Clearly load and rating performed by flat belts will not be difficult to chain and v-belt drives under such short center to center distance. Hence there by is the analysis of power transmission modeled by v-belt and flat belt type.Belts The belt is the part that transmits the power from the wheel to the shaft carrying the metering discs. The belt is expected to transmit the power as possible as efficiently from the wheel to the shaft because as the core elements are the metering discs a small deviation in power that means deviation in rotation results in variation in placement spaces with in a given row, that will cause either over populated or deficient plant seed distribution. Both of the above problems are disadvantageous in one or another way and contradict the target of design of inline seeder in particular and the system of conservation agriculture in general. Therefore attention has given to the selection of proper belt and design of suitable belt mechanism considering and comparing the following criteria with respect to the two belt types; flat belts and v-belts:

Mechanical strength

Physical geometric fitness

Size of belt and space required

Atmospheric conditions

Service life

Availability, etc

Belt selection is a matter of finding standard belt that will closely mach the required speed ratio between input and output shafts the required power transfer, and the required center distance, which is the distance between the two center lines of the input and output shaft. Both belt types are capable of providing wide rage of strength and load capacity depending on the problem. V-belts give smooth and uniform power transmission than flat belts because in flat belt power transmission there appears some irregularity and non uniformity around mechanically connected part of the belt. Flat belts are subjected to misalignment as they are exposed to side way axial movement. In addition generally flat belts are not as efficient as v-belts in transmitting power over shorter length and compacted space. Both belt types respond in a similar fashion to different atmospheric situations, service and availability requirements.

Having these, v-belt is selected as a power transmission unit to the inline seeder. Hence as the torque transmitted is not that much significant the selection of proper v-belt type can be achieved in the following few analysis.

Assumptions

The belt is assumed to be subjected to not higher range of power.

Proper alignment of the belt to the pulley is expected to be governed by the belt itself.

The effects of atmospheric conditions are assumed to be taken care of by some factors.

Considerations

Only geometric relations are considered to determine the standard type of belt.

Open belt and non-crossing over arrangements are considered.

Analysis

The following relation is used to analysis the geometric suitability of the belt to the coupling pulleys. Those are:

I. Pulley belt pulley relation

II. Rotation linear rotation motion considerations

Geometric relation of belt mechanism

Table3.5. Pulleys and belt system geometryItems 1-wheel2-large pulley3-belt4-small pulley5-metering disc

Diameter(mm)3201002580

Circumference(mm)1005.2314.178.5251.3

Width(mm)30303030

Center-center distance(mm)440

MaterialsteelSteel--SteelSteel

All the above geometrical relations are taken by considering the placement gap of seed grains with in row, i.e. about 250 mm for Maize and 25 mm for wheat. In the above relation one can see that the wheel travels around 1005.5 mm in one revolution and therefore to cover this length with proper seed rate the disc should rotate four times, since its circumference length is around 25 mm. the rate for fertilizer for a given seed rate is variable with many conditions and is going to be adjusted with the requirement of circumstances.

Considering only the two pulleys and the belt:

For open belts length of belt is given by:

L= AB + BC + CD + DA (3.15) L= 2AB +BC + DA. . . . . . . . . . . . . . AB=CD

DA=R1

BC=R2

, and .................................... (3.16) L=1086 mm

Using the following table of standard v-belt:

Table 3.6.Standard v-belt sections (152494) and recommended power rangeBelt typeABCDE

Recommended power range(kw)Up to 7.51.5-155-7530-15050-200 more

Section geometry(mm)

Therefore, standard v-belt A is selected and its nominal pitch length selected based on our requirement L=1086mm is the nearest one having L=1102mm.

PulleysPulleys used for the v-belt drive mechanism, as specified previously first of all should have to satisfy the geometric requirements. Then to take care of strength, reliability and durability necessities the selection of material for the pulley should be base on such considerations in addition to cost, availability and manufacturability requirements.Pulley materials

Commonly used pulley materials are metals which includes cast iron, steel, aluminum etc,

And to light duties non metallic pulleys are used such as plastic, paper and wood are the commonest of the non metallic pulleys. Metallic pulleys are most of the times used for high power rating and greater load capacity transmissions. They are most reliable and durable pulleys against variable working environment.

Non metallic pulleys made of wood or plastic on the other side hand are used for less power rating and minimum load operations. They are naturally susceptible to difficult failures; however, with proper care and provision they are giving service for acceptable life with accurate transmission. The seeder belt system is required to transmit very low power and load but with high accuracy and efficiency, therefore, the wooden pulley can be used properly with great advantages and can perform as good as enough to achieve metering by the disc rotation. Wood is selected as a material for both sall and large pulleys and some theoretical and geometric analysis will be shown in the next part of the report.

Good pulley woods must have the following properties

Less moisture absorbing character

Good wear resistance

Good resistance to deformation

Easy to machine

Should have enough friction coefficient to maintain the motion transmission uniform.

Generally the wood used for pulley should with stand change in environmental situations further more need to be capable of performing good in the farm plots against rainy seasons, muddy soil and rough and vamp motion lines.

Summary

-The pulley can be made of two split pieces and join by screws and metallic rings at the two ends

-Most preferably the larger pulley should be made as integrated part to the bearing would have internal diameter equal to that of the bearing.

-external diameter should be 108 mm as it is discussed in the belt selection part.

.Face width b= b1+b2+W=30mm

Two metallic strips and b are used to strengthen and prevent deformation the pulley edge these strips will be attached to the pulley body by using set screws or by nail.

Small pulley

It will be attached to the end of the shaft holding the metering disc. This is made of wood similar to the large pulley.

Width=30m

Outer diameter do2=23 mm

Inside diameter will be equal to the diameter of the shaft.

The pulley can either be split type or made of single solid wood plate.

Recommendation: - wood used for both pulleys need to have a minimum of 74 Rockwall (B) hardness or the grooved face must hardened to this value by mechanical pressing.

3.5. ShaftThe shaft is the part of the seeder that will be coupled to the small pulley at one end and drive the metering discs by the power it gain from the wheel by the belt connection. It transmits both torque and rotational motion to the metering discs which are secured to it properly.

Assumptions

The shaft is assumed to be subjected only to torsional stress and bending stress due to the engaging force of the belt.

Considerations

The shaft is provided with holes to secure the discs and pulley to it and the sensitivity of these holes should be accounted.

The length of the shaft is taken to be L=1100 mm

Proper material for the shaft is mild steel used so far.

Analysis

Bending consideration

F1=F2=F3=F4=the weight of the grains perfectly above the area of the disc in contact with the grains. It is approximately 5N

Then taking moment about A, B and C and equating to zero,

FB=FC= 10 N

Maximum banding moment MMax=2400 N-mm Bending strength .............................................................................(3.17) where Z is the section modulus

rs= 6.5 mm dS=13 mmShear consideration

Shear stress .......................................................................................... (3.18)

FS= 4xF1=20 N, and

Substituting these values gives

0.07 MPa hence the design is safe for shearing.

Torsion consideration

Because there is a resisting torque developed due to the contact of disc surface and grains as the result of the weight of the grain and the friction force there exists a tangential force which cause torque. To determine the maximum resisting torque hat may develop on the shaft the coefficient of friction between the grains and disc surface should be known. As it is given in the disc design part, the coefficient of friction is assumed to be equal to.

tangential force on a disc is equal to the friction force developed on the surface of a disc

Ft= 8.3 N

Torque developed T=Ft x rd= 8.3x40 N-mm= 333.3 N-mm

The shear stress in the shaft is given by:

.... (3.19)Where I= moment of inertia of the hat cross section=

Substituting these vales gives the shear stress developed 11.8 MPa which is less than the allowable maximum stress; hence the shaft is safe against shearing.

The shaft diameter shall be rounded up to standard dimensions so that it can easily accommodate the screw holes for attaching the metering disc. Therefore the revised diameter of the shaft will be dS= 20mm.

Shaft bearings

Assumptions and considerations

The bearings are needed to carry only radial loads

As the space provided for the bearing is small and considering other factors such as cost and availability journal bearings are selected.

Material Material for the bearing is wood or plastic

Dimensions of the bearing are

Bore diameter dbb= 20mm

External profile is square with side S=30mm

Face width of the bearing wb= 60mm, this is selected for geometric convenience and easy of securing it to the vertical frame.

1- screws

2- cover plate

As shown in the figure above two cover plates are required for a bearing, therefore these plates are of sheet steel thickness 2-4 mm and square shape S=40mm with bore at their center with (22mm.

These plates will be screwed to the vertical frame on both sides of the bearings to prevent the bearings axial movement.

3.6. Metering discsAs discussed in the previous parts the core element for the inline seeder are the metering discs which completely governs the grain and fertilizer size, flow rate and proportion for different requirements and different inputs. Basically the conceptual design part was dependent on finding a suitable and beneficial metering mechanism for wheat and maize seeds. After various Comparisons and analysis done at the conceptual stage the disc type metering mechanism has been selected, so that in this part the remaining strength and geometric analysis will be covered. Forces applied on the disc are not too significant to cause devastating failure during operation; nevertheless it is essential to check the critical parts of the disc especially for bending and torsion.

Torques transmitted by the disc.Due to the weight of the grain and fertilizer act up on the disc surface the disc is subjected to frictional torque. The maximum torque is clearly at full load; hence analysis should be performed with in the circle of conditions at full load.

Different parts in the disc system are1. -Disc arm: - steel plate or rod2. -Disc hub: -made of steel plate

3. -Disc rim or caves: -which are of steel sheet formed to meet the geometry shown.

4. Grooves for seed

5. Grooves for fertilizer

Assumptions The discs are assumed to be subjected to around 105 of the total load due to seed and fertilizer weight. The pressure per unit area of the compartment can be taken as the product of the weight of the grains and the base area of the compartment; hence the pressure on the disc does simply considered by taking area relation and it is about 5% of the total pressure on the compartment.

The frictional force between the grin and surface of disc is as assumed in the shaft design part. It is equal to be 0.6.Material for the disc components

Required properties of material for the metering disc components

Good resistance to wear

Rigidity

Easy manufacturability

Good bending strength

Cheaper and abundantly available.

Therefore having all the above necessities under consideration material selected for the disc components are;

Mild steel sheet for the rim

Circular or rectangular cross section steel rods for the arm

2- 5mm thick steel plate for the hub or a circular hollow section steel rod with internal/bore diameter 20 mm and a minimum wall thickness 2mm.

Strength analysis

Tangential force per disc due to friction Ft=8.3 N

Torque developed T= FtxR =333.7N-mm

Bending consideration of spokes of the disc

Considering only half of the arms are subjected to bending at a time and by taking the arm under load as a cantilever beam fixed at the hub end,Tangential force per arm= Ft=.................................................. (3.20)Maximum bending moment on the arm at the hub will be,

M=66.75 N-mm

Section modulus................................................................................................ (3.21)Using the relation

The radius of the arm rod r=2.5mm3.7 Frame and compartmentFor the seeder body there are several members which are attached together to form a rigid body. Generally, these members can be categorized as follows:

1. Vertical members: - this is the main member to which the axle, horizontal members and compartment body are attached.2. Horizontal members: -Basic/ main horizontal beam, beam to which the openers are attached which is equipped with grippers at its ends.3. Transverse members: -pulling bars and stabilizing bars4. Housing: -compartment housing, disc casings and funnels.More of these components need no analysis as the material and methods used to produce these parts are good enough to withstand the less substantial load and stresses that may be developed. However, on the other side, few basic members need through analysis to say that they are capable of carrying and transmitting the load and disturbance stresses subjected to them. As a result the main members that need analysis are discussed in the next part.

3.7.1. Vertical beam Analysis

There are three different loads to which this member will be subjected to

1. The load at A: -vertically down ward load through the axle, which will subject the beam cross section to tensile stress.2. Force at B: - due to the load transmitted through the horizontal beam.3. Load at C: - that is the weight of the compartment Consideration and assumptions-The load at A is considered being equal to the load due to the maximum weight of the seeder. Which is, as described before FR= 645.85 N.

-This force is the maximum of the forces applied on the beam, so as both of the loads have similar stress on the beam the dimension and material that satisfy this load requirement is assumed to satisfy the requirement of the rest of the loads.Material

Material for the beam is steel.

As shown in the figure above Standard rectangular hollow section beam. All the cross sections are selected based