due at 12 PM

DESIGN OF A CROSSBOW

Bows and arrows date back to the stone ages during the invention of fire and the wheel which catapulted human civilization. The design of bows and arrows has gone through tremendous improvement over the lifetime of civilization despite the technology being superseded by the invention of the firearm in the late 19th century. The physics behind the design of bows and arrows involves translation of energy from the potential energy stored in the elastic string and bow: to the kinetic energy of the arrow once it is released. In this project, we design a crossbow as a catapult system to propel a marble to a maximum distance dependent on the strength of the material used. In the design of the crossbow, we will use:

1. Four sheets of printer paper

2. Masking tape

3. Two standard rubber bands

4. Two popsicle sticks or tongue depressor

5. Six-Zip ties

INSTRUCTIONS FOR CONSTRUCTING A CROSSBOW

MAKING THE CROSSBOW BASE

1. Start by rolling a sheet of paper into tight tubing working from end to end then use the masking tape to secure the tube. Tape both ends by wrapping the masking tape around them.

2. Make sure all the four sheet of papers are made into tight paper tubing that is evenly rolled as possible.

3. Out of the four paper tubes tape, two together at a perpendicular angle making sure one tube meets the centre of the other tube. Also, ensure the bond is steady to ensure the aim of the crossbow is stable.

4. Cut the third tube in half and then attach the two halves to the main body of the crossbow ensuring the halves are placed on either side of the T created by the main crossbow body in such a way they remain symmetrical.

5. Attach another the fourth to the vertical tubing of the main crossbow assembly lining its end so that it matches the bottom end of the vertical pipe.

6. Place another half tube extending from the top of the vertical tube down to diagonal supports.

7. Attach one-half to the top of the vertical tube of the main crossbow assembly.

8. Last but not least, tape a half tube to the underside of the crossbow.

9. Also, make a shoulder stock from a full-length tubing that will be attached diagonally from the vertical shoulder stock tube.

10. Attach the rubber band string by stretching it so that each end loops around both ends of the horizontal tube in such a way it is well tensioned.

11. Attach a clothespin at a given distance perpendicular to the horizontal tube such that it will act as a trigger to release the rubber band in loaded position.

12. Ensure the whole assembly is secured by the masking tape to provide your crossbow with more support.

13. The Popsicle sticks will be mounted perpendicular to each at the position of the vertical and horizontal tubes to prevent any buckling of the vertical tube when then rubber band is stretched back. The zip ties and masking tape will be used to hold the Popsicle sticks in position. A combination of the two-bonding material will guarantee optimum strength for a part that is acting as the foundation of the crossbow assembly.

14. During firing of the paper crossbow, a pencil is inserted into the guide tube; then the rubber band is stretched back and held by the clothespin in a loaded position. Once the clothespin is pressed, the rubber band is released and propels the ‘arrow' (pencil) away from the shooter.