A Hand Powered Hay and Leaf Baler

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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.


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. 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 sizes. This is because these are the materials and tools I am familiar and have developed skills working with. These are not available around the world, but it is possible to make this structure out of available materials using simpler tools. In the construction section there is a section 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 the tools and materials were unavailable they could pre cut and transport them. A full analysis of alternative balers should be conducted before this occurs.

Applicability of Bales

Straw bales can be used in construction, but most typically for low cost, low environmental impact housing. This seemingly basic provision gives 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 or from other people. 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. Since straw is also a by-product which is commonly burned [3], using it as a building material sequesters carbon. Bales also have agricultural purposes, as this is a potential source of food for animals. This can be during winter months or periods of drought. It is important to note that regardless of application, 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, as bales need to be dry to prevent rotting. Dry density determines the strength of bales. The equation for density, [kg/m3] is found here:

[math]\rho\ = {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 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.[7] To summarize, a large piston force will result in denser bales which provides more structural sound bales.

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.

For this structure, all loads are negligible relatively to the resistance provided by the cross sectional area of members.


A prototype of the Hand Powered Hay and Leaf Baler was made using power tools listed in the table below. Figure 1a, shows a picture of the prototype that was built besides the original drawing and recommended layout. Changes were made to the original design for simplification and additional changes are reflected in the design depicted in Figure 1b.

The table below shows the tools used to construct the prototype as well as basic tools that can be used to produce the same baler. Despite the fact that the prototype was built with power tools, basic tools in the hands of a skilled craftsmen will complete this task

Preferred Tools Basic Tools
Circular Saw Hammer
Drill Hand Saw
Hammer Measuring Tape
Measuring Tape Working Bench/Clamp
Working Bench/Clamp

Parts List

Part Name Nominal Size Prototype Length Quantity Recommended Length Quantity
1 Bottom 2X4 6’ 10” 2 6’ 10” 2
2 Side Support 2X4 2’ 1 ¼“ 8 4’ 6
3 Top Connector 2X4 1’ 6 ½” 4 1’ 6 ½” 4
4.a Chamber Side 2X4 3’ 4” 4 3’ 4” 4
4.b Chamber Side 2X4 3’ 10” 4
5 Chamber Top 2X4 2’ 4” 4 2’ 4” 4
6 Chamber Bottom 2X4 4’ 8” 3[1] 4’ 8” 3[1]
7 Bottom Connector 2X4 1’3 ½” 4 1’3 ½” 3
8 Rear Support 2X4 39½” 2 39½” 2
9 Restraint 2X4 3’ 9 ½” 2 3’ 9 ½” 2
10 Door Support 2X4 1’ 6 ½” 1 1’ 6 ½” 1[2]
11 Piston 2X4 8’ 2 8’ **2 2
P1 Piston Back Ply ½” 12”x 14” 1 12”x 14” 1
P2 Piston Insert Ply ½” 12”x 12” 1 12”x 12” 1
P3.a Piston Block 2x2 4” 8 5” 8
P3.b Piston Block 2x2 3” 8 3” 8
P4 Piston Support 2x6 14” 2 14” 2
Door Ply ½” 18”x18” 1 18”x18” 1
[1] One piece must be riped into two, see procedure for details  
[2] Optional, see procedure for details  


To make the building process quick, it is best to pre-cut many of the pieces. While this is advised make sure to build the piston once the chamber and other pieces have been assembled. This will make sure the piston actually fits in with what you’ve built. If there have been any alterations in the design or part assembly, they will become apparent when it is time for final assembly of the baler. Throughout the steps expand the images to see part names and spacing.

For all steps, using a square will make sure individual parts are made properly which makes assembly easier. Nails or Hammers can be used, but screws were used for personal preference and because they are more forgiving if mistakes are made or during the iterative prototyping process. Smaller pieces, like those found on the piston head are also easier to attach with screws. Environmental factors come into play when determining the life of this structure. If it is to be used indefinitely, outdoor screws and a paint or stain will preserve the bailer and prevent weathering and other environmental wearing.

This can be made by an intermediate craftsmen, a more skilled labourer will be able to make it faster and more accurately. Regardless of familiarity with tools, please follow appropriate safety procedures. If you are not as skilled, working with a partner or finding someone with more experience will make sure the baler is made accurately and safely.

Please read all steps before attempting construction.

Fig 3: Chamber Top Drawing
Step 1: Construct the chamber top. Lie the top part flat with a 1/2" Spacing between the pieces. The twine will go through these gaps.
Fig 4: Chamber Top Construction
Fig 5: Chamber Sides Drawing
Step 2: Construct the two chamber sides. Piece 2, the side support, is on the opposite side for the second chamber side. Otherwise the two pieces are identical. There is also a 1/2" gap in between pieces. The Side supports were increased to mid height on an average man. This allows the user to stand up during baling and tying, reducing the amount of stress on the user’s back. thumb|Fig 6: Chamber Sides Construction
Fig 7: Chamber Bottom Drawing
Step 3: Construct the chamber bottom similar to the top. Connector locations are labelled in the figure, and should line up with the side supports once assembled. The two pieces on the sides can be made by ripping a 2x4.
Fig 8: Chamber Bottom Construction
Fig 9: Chamber Assembly Drawing
Step 4: Assembly the chamber by placing the top piece in between the two sides. Once this is completed the bottom can be dropped in by turning the structure upside down. A clamp will make sure the chamber is square.
Fig 10: Assembly of Chamber
Fig 11: Back of Baler Drawing
Step 5: After turning the baler upright construct the back of the baler by attaching the rear support, restraint and top connector in that order. This way the new pieces will not fall over during construction. A helper is useful to hold pieces up, but if one is not available use a nail or screw to tack a piece near where it needs to be and then attach it once is in the appropriate location.
Fig 12: Back of Baler
Fig 13: Baler Door Drawing
Step 6: There are two options to build the door. A door with a hinge can be installed but if hinges are not available try the option shown in the prototype. A section of the door support should be cut out to hold the door. If this section option is taken the top connector should be removed and a section removed along the length of the door slot. Once cut these two pieces should be attached so they are flush against existing pieces allowing both the door to open and the bale to freely exit the chamber. The notches in these door support pieces should be cut with an appropriate tolerance so the door can slide a ¾’ notch was used for a ½” door. These cuts should be made by a saw, a chisel can be used to remove the material in betwen cuts. Scrap wood can be used as a door handle. thumb|Fig 14: Door Support Construction
Fig 15: Piston Head Drawing
Step 7: If 2x2s are available the more complicated option shown in the pictures should be used. The piston blocks allow an insert to be used during the bailing process. When the bale is ready to be tied, this insert can be removed and the blocks allow space for hands to reach into the baling chamber. Blocks can be adjusted for user hand size. A tolerance in the cut outs in P3.a should ensure the insert can be removed with ease. The end of P3.b should also match the start if the cut outs in P3.a. To make this cut jigs can be placed together in a jig similar to the one made in the figure to the right. Blocks should be attached from behind, as you can see in figure 16. Two screws will resist the blocks from turning. Tacking one screw in and tightening the second will ensure the blocks remain where the marks are. Drilling pilot holes will ensure the plywood and blocks are not split in this step. Alternative the piston back can be used by itself, but it will be more difficult to keep the end of the bales compact.
Fig 16: Piston Head Construction
Fig 17: Piston Back Drawing
Step 8: Piston supports should be drilled prior to being attaching to the piston back. Like the blocks these should be attached from the back, after a pilot hole is drilled. Screws should be located in the large spaces in between blocks, to ease construction.
Fig 18: Chamber Top Drawing
Step 9: The two piston pieces should be cut and drilled according to the drawings. The cut out allows the piston to lock into place while twine is tied. The angle cut at the front allows a large range of motion during the baling process.
Fig 19: Partial Piston Drawing
Step 10: Attach both pistons to the piston head by placing a carriage bolt or axle in between the two pieces. Washers should be used at all interfaces (between wood and nuts). A scrap piece of wood should be put directly under the pistons once attached. This stops the piston head from falling over. Alternatively if bolts are not available the piston can be directly attached to the piston head.
Fig 20: Completed Piston with Bolts


Purchase list

Item Quantity Unit Price Full Price
2”x4”x8’ 20 $1.77 $35.40
2”x6”x8’ 1 $4.29 $4.29
2”x2”x8’ 1 $2.26 $2.26
½” Ply 3 cutoffs $3 $9
4” 5/16” Bolt 2 $.69 $1.38
5/16” Washer 6 $.11 $.66
5/16” Nut 2 $.14 $.28
Total $53.27CDN

Projected costs for constructing the recommended baler from entirely new wood came to around $55. Actual costs for the prototype that was built was much lower. This is because the prototype was built using recycled materials. Likely if this were to be built on a farm that has excess to nominal lumber sizes, there will be leftover pieces to reduce costs. In comparison farm jacks which is only one component in alternative technologies start around this price. Like all construction projects an allowance should be included for potential cutting mistakes or losing materials, the lumber listed above has this included. Another way to drastically reduce costs is looking through cut off sections in stores (if they are available). Off cuts from other projects provide a cheap source of small materials and also divert materials from waste.



  1. Thread twine through gaps
    • 2, 4 or 6 pieces can be used depending on material
    • Thread twine only by door
    • Cut enough twine to wrap around the entire bale, 6’ is recommended but make sure there is enough initially because adding additional twine after is difficult
  2. Close door and begin baling by pushing piston
    • Use small amounts to ensure good compaction
  3. Remove insert when enough material has been baled
  4. Thread twine around bale and tie
  5. Open door
  6. Remove bale by pushing piston

Please see the following video for the baling procedure:

Please Note: This video shows the very first time I created a bale on the prototype. The entire process took under 20 minutes. With a helper and more practise this time will be greatly reduced so in a day enough bales could be made for a small home. The material being baled is also old and moist, both not useful properties. This was simply due to available materials.

Machine Specific Recommendations

As the video showed it is possible for an individual to operate this baler, however it is more efficient to have two. One person can load the material to be baled while the second operates the piston.

Further improvements to the baler would include making it mobile by adding wheels. These wheels would have to flip up during the baling procedure to ensure the contraption does not move. This would allow the baler to be moved around a field to additional material that needs to be bailed. Placing two wheels at the door end would allow this contraption to be pulled by human or preferably an animal. Since there is a large force being applied during the baling procedure, the entire structure is prone to moving in this direction. If this is a nuisance or hampers the bailing process dead weight can be added to the base of the structure which increases the frictional force resisting movement. Alternatively wedges or spikes that are attached to the structure would resist this motion as they act as anchors.

Bales expand once they have left the bailing chamber, if a specific bale size is required, experimentation or further work can be done to match chamber sizes with actual bale sizes. All bales made from non conventional methods, or mechanical balers, should undergo testing to assess their suitability for construction. Indicators of moisture content, dry density, wetting history, fibre length and material constitution are all necessary to determine usefulness as a building material.[8]

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.


  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.
  7. King, Bruce. Design of Straw Bale Buildings. San Rafael, CA: Green Building Press, 2006.
  8. King, Bruce. Design of Straw Bale Buildings. San Rafael, CA: Green Building Press, 2006.