Step 1: Materials Needed
- A bundle of straws
- 3 large pieces of styrofoam
- A cardboard box
- Aluminium tape or foil
- Duct tape
- Super glue
- 1 motor 100RPM (or higher)
- A 12V battery
Step 2: Tools Needed
- A poker (or anything sharp enough to make a hole through styrofoam)
- A box cutter
- A ruler
- A pencil or marker
Step 3: Construct Saw Blades
First, take a piece of styrofoam. Sketch a large circle measuring about less than a quarter of the styrofoam piece. The size can vary depending on the amount of saw blades that will be made. For this project, however, I will use circles with the radius of around 6 inches. Draw a line passing through the centre of the circle, and another one perpendicular to it, forming a cross. Then draw two more lines forming a cross, at an angle of 45° from the first cross. This divides the circle into 8 pieces; one for each blade tooth.
Draw a box enclosing the circle. The ends of one of the crosses on the circle should touch 4 sides of the square perpendicularly. Repeat the same step by drawing another box at an angle of 45°. This should be directly perpendicular to the other cross.
Extend the lines of the cross beyond the edge of the circle until it touches the box. The edges of the square and extended lines of the cross will form the saw blade teeth.
Step 4: Cut Out Saw Blades
Lay down the styrofoam on a cutting mat and grab a boxcutter. Firmly hold the boxcutter while cutting. When cutting styrofoam, gently press against it to make a faint mark before cutting them deeper. After making a small cut, work your way into the styrofoam slowly, as it will produce a smooth edge. Otherwise, a forced cut will result in a rough contour. This saw blade will be used as a reference for cutting the other saw blades. Therefore, it needs to be cut as accurate as possible.
Once done, place the saw blade on top of the styrofoam. Apply duct tape on the inner edges of its teeth to hold it in place. Cut along the edges of the saw blade, using it as guidance. Repeat this step for as many saw blades you wish to make, but only use the first saw blade as reference.
Stack the finished saw blades and align its edges. Use duct tape if needed. With the poker, create a small opening on the top saw blade, and then the subsequent saw blades one-by-one. It is important to keep the poker perpendicular to the cardboard at all times, so that the holes will align. For now, keep the holes around 5mm in diameter, as they will be adjusted later when fitting through the straws.
Step 5: Cut Out Cardboard Box
The cardboard box will be used to hold the straw tube in place, holding up the saw blades as they spin. It does not necessarily have to be big enough to contain all of the saw blades.
First, create a small hole on opposite sides of the cardboard, preferably near the top. Since the straw tube will be inserted through these holes, they should be symmetrical and positioned along the furthest opposing sides of the cardboard. The distance from the hole to the bottom of the cardboard (when upright) should be greater than the radius of the saw blades.
Measure the distance from one hole to the other. On the sides of the cardboard without holes, divide and mark equally spaced sections, based on the amount of saw blades constructed. For this project, I have made 6 saw blades, and therefore 6 openings were created.(It is recommended to keep the first 'template' saw blade as a backup, in case another saw blade is needed.)
Cut rectangles along these intervals, with widths that are at least five times greater than the thickness of the saw blade. These openings should be large enough to allow the saw blades to spin.
Step 6: Position Saw Blades
Construct a long straw tube by joining individual straws together. The length of this straw tube should be at least an inch longer than the distance between the two holes. If possible, reinforce the straw tube with wooden skewers or long toothpicks by filling them into the straws. The end at which the motor attaches should remain hollow.
Test the strength of the straw tube to confirm if it could hold the saw blades. If it bends, use an extra piece of cardboard to hold and support the straw tube at its weakest point.
Allow the saw blades to spin for several rotations along the tube. Make changes accordingly if the openings are too small.
Step 7: Construct Motor Box
The motor and battery should be supported on the side of the box, inside a small casing. Puncture a hole on the bottom of the motor box along which wires would run through to connect to the switch.
Duct tape the motor to the box so that it remains in a fixed position.
Step 8: Assemble Parts
Carefully slide the straw tube into saw blades, making sure each saw blade is facing the same direction. Do NOT apply super glue on the styrofoam saw blades, as it would chemically dissolve them.
Once all of the saw blades have been attached to the tube, apply super glue to the end at which the motor attaches. Cut an opening near the motor to provide more visibility and control, if necessary.
If saw blades are loosely attached, either use hot glue or duct tape to fill in the excess gap.