Teagans+Trebuchet



Introduction: I wanted to find a trebuchet that could be easily adjusted, low mass and still fire the assigned projectile (5g christmas orniment) a decent amount. Since the only outlines I found on the internet where made out of steel or wood, I had to create a basic outline from previous knowledge of trebuchets. The main material I chose to use was PVC piping because it is affordable, easily adjustable and light.

Applied Physics: Friction - This was one of the laws I focused on because I know the axel would function better made from a different materiel than the body of the trebuchet. I decided to use wooden doweling because It would be easy to fit in the PVC piping corners and also creates minimal friction. I also added silicone lubricant to the dowel to make it run smoother, something that would not work as well with steel. The orniment also was released smoothly since I only used a thin peice of copper wire with a open bottom.

Projectile motion - Since I decided to add a loose counterweight that added momentum, the motion then depended on the angle of the string on the bag and the angle of the arm. The inertia was increased but the angles also had to be adjusted. I found no mathematical formula to test this theory, so this aspect of applied physics was highly important in the creation of my trebuchet.

Materials: - 1/4" diameter, 2" long multidowel - 5/8" by 48" dowel - 6g silicone lubricant - 1/2" elbow for PVC piping - 1/2" tee for PVC piping - 1/2" PVC piping - Hammer - Hacksaw - Drill (1/4" and 1/16" heads) - Copper wire used to hold ball - 340 grams of pennies - Mesh bag used for holding pennies (looped string attached) - 15/16" Screw eye - Elmers all purpose glue - Measuring tape

Building Procedure: 1. Start by cutting the PVC pipe into 4, 3.25" pieces, 2, 9" pieces, and 2, 8" pieces, with the hacksaw 2. Attach 2, 3.25" pieces to a tee and add elbows to each side, do this step twice to create 2 sides 3. Attach the 8" pieces between the elbows 4. Attach the 9" pieces to the middle hole of the tee 5. Cut the dowel into a 10" piece and a 8.5" pieces, with the hacksaw 6. Cross the 10" pieces over the 8.5" piece leaving 2" off the end for the counterweight 7. Drill a hole with the 1/4" head 8. Insert 2" multiedowel between the two pieces of doweling and add Elmers all purpose glue (must sit for 24 hours) 9. Once glue is dried, drill a holer using the 1/16" head at both ends, one for the copper wire, the other for the screw eye 10. Insert the screw eye to the shorter end of the arm's hole and the copper wire to the longer ends hole 11. Tie the counter weight on loosely and add pennies

It is ready to be tested like a Jedi or something

Testing procedure: The original weight I was using was 240g, it failed miserably. The bag also tied with spider wire originally, but then I decided to have a loose string, the string being the material from the bag and releasing the bag from higher gorund. The original height was 6.5" but I then decided to add 9" PVC pipes to the base making the height 9.5". I tested 2 different arm lengths 20" and 10", finding my original 10" was the most successful. I then did the full testing with the following height, arm length and weight: Height - 9.5". Arm length - 10" (2" and 8", short and long end respectively), with a 340 gram counterweight using pennies. I used no precise angle but I did use approximately 30 degrees more often than any other angle. I then weighed the object as a whole in kilograms and the arm length in meters, the christmas ball was then ready to be fired. All you simply do is place the christmas ball in the copper wire holder, hold the counter weight and arm at angles which you think they will be most efficient at. After you have done this you may release the counter weight and watch the projectile fly.
 * Trial || Mass(kg) || Length of arm(m) || Distance(m) || P=d/ml ||
 * 1 || 1.2 || .51 || 2.75 || 4.5 ||
 * 2 || 1.2 || .51 || 2.71 || 4.4 ||
 * 3 || 1.2 || .51 || 3.66 || 6.0 ||
 * 4 || 1.2 || .51 || 1.32 || 2.2 ||
 * 5 || 1.2 || .51 || 7.62 || 12.5 ||
 * 6 || 1.2 || .51 || 5.92 || 9.6 ||
 * 7 || 1.2 || .51 || 6.55 || 10.7 ||
 * 8 || 1.2 || .51 || 4.22 || 6.9 ||

Test Analysis: The trebuchet proved extremely effective, but also unique. The PVC pipe idea proved very effective when needing to change the dimensions of the trebuchet to find maximum output. The higher release point of the counterweight is a problem that still confuses me because I do not know how to apply vectoral calculations to projectile motion calculations. This caused some inconsistency that I somewhat fixed by finding a good angle for the arm to rest at. The true reason my trebuchet was efficient was its low mass, the PVC piping has a low mass and the trebuchet does not need to be extremely strong so it worked perfectly in many aspects. The angle of my copper wire was not a large factor because I simply put in line with the arm. Overall the trials proved my trebuchet was efficient, the low mass and unique design can be acredited to most of its success.