Difference between revisions of "A Hand Powered Hay and Leaf Baler"

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<math>\rho\ = \frac{m}{V}</math>
 
<math>\rho\ = \frac{m}{V}</math>
  
The density of a bale is based on the compressibility of the material and the stress exerted by the piston. Studies have shown that when laid flat, bales with a higher density fail at a higher ultimate load. <ref>Bou-Ali, G. Straw Bales and Straw Bale Wall Systems. M.Sc. Thesis,Tucson: University of Arizona, 1993</ref> Further studies have shown a correlation between density and modulus of bales, but orientation has a larger effect on mechanical properties. <ref>Tattersall, Graeme H. EFFECTS OF DENSITY ON MECHANICAL PROPERTIES OF STRAW BALES. Thesis, Kingston: Queen's University, 2010.</ref> Straw bales are used to form a composite wall with plaster on either side of the bales. When these plastered walls are subjected to a concentric compressive load it acts like a composite column with the plaster taking the majority of the load. The straw primarily provides lateral bracing for the plaster skins, while taking a small part of the compressive load. If lateral bracing is insufficient, local buckling of the thin plaster layer will cause failure. Straw bales also provide insulation in these composite systems.<ref>
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The density of a bale is based on the compressibility of the material and the stress exerted by the piston. Studies have shown that when laid flat, bales with a higher density fail at a higher ultimate load. <ref>Bou-Ali, G. Straw Bales and Straw Bale Wall Systems. M.Sc. Thesis,Tucson: University of Arizona, 1993</ref> Further studies have shown a correlation between density and modulus of bales, but orientation has a larger effect on mechanical properties. <ref>Tattersall, Graeme H. EFFECTS OF DENSITY ON MECHANICAL PROPERTIES OF STRAW BALES. Thesis, Kingston: Queen's University, 2010.</ref> Straw bales are used to form a composite wall with plaster on either side of the bales. When these plastered walls are subjected to a concentric compressive load it acts like a composite column with the plaster taking the majority of the load. The straw primarily provides lateral bracing for the plaster skins, while taking a small part of the compressive load. If lateral bracing is insufficient, local buckling of the thin plaster layer will cause failure. Straw bales also provide insulation in these composite systems.<ref name = Bruce> For making bales the important thing to note is that a large piston force will result in denser bales which provides more structural sound bales. Denser bales should have decreased insulation properties because of the close proximity of molecules but further testing is required in this area.
King, Bruce. Design of Straw Bale Buildings. San Rafael, CA: Green Building Press, 2006.
 
</ref> For making bales the important thing to note is that a large piston force will result in denser bales which provides more structural sound bales. Denser bales should have decreased insulation properties because of the close proximity of molecules but further testing is required in this area.
 
  
 
The other factors that effect utility are history, as bales should not have been near moisture or mold, fiber length, and material composition. Straw bales are more suitable for building because the carbohydrates have been removed. Hay, which contains carbohydrates will naturally rot as insects and animals feed on it.
 
The other factors that effect utility are history, as bales should not have been near moisture or mold, fiber length, and material composition. Straw bales are more suitable for building because the carbohydrates have been removed. Hay, which contains carbohydrates will naturally rot as insects and animals feed on it.

Revision as of 23:17, 21 April 2010


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Abstract

Baling materials on such as hay, straw or leafs has many advantages as these bales are typically used to store excess materials or feed animals. Straw bales are also used as a building material for construction. This practise started in North America as early as the 1800’s, and has recently seen a resurgence as part of the green and natural building movement. Straw bales are cheap and available construction material, since straw is a ubiquitous agricultural byproduct. These bales can provide both building insulation and structural support. The availability of this potential construction material deems its consideration as an appropriate technology. Large costs associated with mechanical combines and farmers with small plots of land necessitate a low cost alternative. There are many options available and this article examines A Hand Powered Hay and Leaf Baler made by Larry McWilliams that is on the CD3WD. The purpose of the CD3WD project is to help the 3rd World help itself, contents can be found here. This article provides a much more detailed how to for construction and use of this bailer as well has some design. A discussion on the application of this system and its bales is also included as well as a brief introduction to alternative machines.

Considerations

Access to Baling Materials

Materials to be baled exist in all parts of the world where this is agriculture. Cereal plants grow in all parts of the world, except very dry deserts and the ice-covered poles. [1] But more specifically, straw is a by product of cereal plants bales made of straw are used as a construction material. Straw is what remains after the grain and chaff have been removed; it is also known as the stalk of the plant. Africa is home to many native cereal plants, and colonization brought many other species to the area. [2] In other words this technology can be useful in almost any part of the world.

Access to Building Materials and Ability to Build

The baler that is detailed below was made using power tools and nominal wood. This is because these are the materials and tools that are available, and those which I have developed skills working with. These are not available around the world, but it is possible to make this structure out of different materials while using simpler tools. In the construction section there is a table for suggested and potential tools to build this baler. A skilled craftsman would be able to recreate this structure. In the case where a group was travelling to an area where these tools and materials were unavailable, a simple solution would be to pre cut and transport them leaving final assembly till the final site is reached. A full analysis of alternative balers should be conducted before this occurs.

Applicability of Bales

Straw bales can be used in construction and the typically application is for low cost, low environmental impact housing. Housing is a seemingly basic provision which provides families a place to stay warm, sleep, interact with each other as well as provide a place to shelter themselves from potential dangers in the environment including disease. Having a home has many benefits and owning one serves as a stepping stone to future success. Straw Bale buildings are cheap and effective use of renewable and local resources. Straw is also a by-product which is commonly burned [3], using it as a building material sequesters carbon that could potentially end up in the atmosphere. Bales also have agricultural purposes, as this is a potential source of food or bedding for animals. Storing bales can be useful during winter months or periods of drought in agricultural applications. It is important to note that regardless of use, bales should be kept dry and free from insects as they will rot.

Engineering Principles

The use of a bale for structural applications is based on a few parameters.[4] Moisture content since bales need to be dry to prevent rotting while dry density determines the strength of bales. The equation for density, [kg/m3] is found here:

[math]\rho\ = \frac{m}{V}[/math]

The density of a bale is based on the compressibility of the material and the stress exerted by the piston. Studies have shown that when laid flat, bales with a higher density fail at a higher ultimate load. [5] Further studies have shown a correlation between density and modulus of bales, but orientation has a larger effect on mechanical properties. [6] Straw bales are used to form a composite wall with plaster on either side of the bales. When these plastered walls are subjected to a concentric compressive load it acts like a composite column with the plaster taking the majority of the load. The straw primarily provides lateral bracing for the plaster skins, while taking a small part of the compressive load. If lateral bracing is insufficient, local buckling of the thin plaster layer will cause failure. Straw bales also provide insulation in these composite systems.Cite error: Closing </ref> missing for <ref> tag

Additional problems arise when using bales produced by machines like this for structural applications. The nature of the machine produces bales with some variability. Changes in bale density can be attributed to different piston packing force and the amount of material baled at a time. Hand tying in an enclosed area also introduces variability. Additional information on strawbale construction can be found here on appropedia, while the Wikibook on Straw bale construction is a slightly more comprehensive resource.

Alternative Technologies

There are alternative low cost baling contraptions. Box baling is a simple method, with a self-explanatory method. A simple backwoods hay baler can be found on the CD3WD. A research study conducted by the UK Department for International Development as part of the Livestock Production Programme provided evidence for the benefits of box bailing forage for milk producers in Tanzania. There are devices like Clark Dorman’s Mobile pinestraw baler but this although significantly smaller and cheaper than combines it is still powered by a gasoline engine. The best alternative is used and developed by the Pakistan Straw Bale and Appropriate Building organization (PAKSBAB). PAKSBAB strives to apply appropriate building methods in this region of seismic activity to create earthquake resistant homes. For Straw Bale Fabrication a compression mould and human powered farm jack is used. This device is presumably more expensive than Larry McWilliams’ design because it is steel, but it is simpler, faster, requires less human effort, and reduces variability in bales.

References

  1. BBC. Did you know? Cereals. http://www.bbc.co.uk/gardening/gardening_with_children/didyouknow_cereals.shtml (accessed April 13, 2010).
  2. Board on Science and Technology for International Development, Office of International Affairs, National Research Council. Lost Crops of Africa: Volume I: Grains. Washington, D.C.: National Academy Press, 1996.
  3. Government of Alberta. "Using Straw as a Farm Heating Fuel." Agriculture and Rural Development. January 6, 2010. http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/eng3127 (accessed April 13, 2010).
  4. King, Bruce. Design of Straw Bale Buildings. San Rafael, CA: Green Building Press, 2006.
  5. Bou-Ali, G. Straw Bales and Straw Bale Wall Systems. M.Sc. Thesis,Tucson: University of Arizona, 1993
  6. Tattersall, Graeme H. EFFECTS OF DENSITY ON MECHANICAL PROPERTIES OF STRAW BALES. Thesis, Kingston: Queen's University, 2010.