Jason+and+Dylan's+TREB

Jason and Dylan's Trebuchet Wiki Page

__History__ Trebuchets are generally thought of as European and medieval weaponry. Although trebuchets were used in Europe during the middle ages, current archaology and research suggests that trebuchets were first used in China sometime between 400 to 300 B.C. It is believed that, over time, trebuchets spread to Europe, most likely through the Byzantine Empire. The French are considered to have made the most important improvements to the trebuchet (increased accuracy and range), which made them vital weapons during the middle ages. Trebuchets became critical for the crusaders, as well as for attacking and defending castles. ("Global Oneness"; "Medieval Castle Siege Weapons"; "Trebuchets")

__The Physics of a Trebuchet__ There are many applicable physics principles involved in trebuchets. The forces and principles involved change before and after the release of the projectile

Before: Once the dowel (object holding weight up) is released, the counterweight begins to fall (due to the force of gravity). The release of the counterweight propels the throwing end of the arm upwards, which (with the help of the release mechanism) releases the projectile. Other forces include friction and air resistance. The friction between the arm and the pivot point restricts how fast the counterweight accelerates. Air resistance is almost negligible, but also slows the motion of the arm.

After: Once the projectile is released there are only two forces acting on it: air resistance and gravity. Gravity propels the object downward after release. In projectile motion, we learned that the optimum angle of release is at 45 degrees to the horizontal. Air resistance on the projectile is greater than it would be on a more dense object. Therefore, air resistance is an important factor.

__Procedure of Construction__ 1. Cut the base (30cm x 25cm) with a table saw 2. Cut the horizontal supports (20cm x 3.5cm) with a hack saw 3. Cut the vertical supports (13cm x 2.5cm) with a hack saw 4. Cut the arm of trebuchet (20cm long) with a hack saw. 5. Drilled two 1/8cm holes in vertical supports for pivot point. 6. Drilled one 3/16cm hole in axis point of arm and two 1/8cm holes on ends of arm (for counterweight and projectile to attach by string) 7. Drilled one 1/4 hole in horizontal support for release mechanism 8. Glued horizontal supports to vertical supports. 9. Glued supports to base. 10. Drilled holes through base for screws. 11. Screwed in screws. 12. Attached counterweight to arm with string. (had to drill holes through steel counterweight--thanks to Jason's Dad) 13. Put nail on end of arm to release string (for projectile) 14. Attached binder loop to to string. 15. Used that string and loop to attach projectile to arm (loop slides off nail at release point) 16. Adjusted angle of nail throughout trials.

__Materials__ -one small Christmas ornament (5g) -25cm x 30cm piece of hardwood -590g cube of steel -lots of string -rope -balsa wood (2.5cm x 0.8cm and 1.3cm x 0.6cm) -Scrap wood (40cm in total) -hack saw -nail -screws -table saw -drill -screwdriver -scissors -wood glue -loop from binder -drill press (for cutting counterweight) -carbon fiber rod -1/4cm wooden dowel -pencil -paper -ruler -measuring tape -pliers -hammer

__Procedure of Testing__ 1. Put dowel through hole in horizontal support and over arm. 2. Attached binder loop to nail on arm. 3. Set up projectile underneath arm. 4. Released dowel. 5. Measured distance thrown. 6. Recorded.

__Results__
 * Trial Number || Mass of Trebuchet (kg) || Length of Throwing Arm (m) || Distance Thrown (m) || Points ||
 * 1 || 1.00 || 0.39 || 2.5 || 6.41 ||
 * 2 || 1.00 || 0.39 || 2.8 || 7.19 ||
 * 3 || 1.00 || 0.39 || 3.3 || 8.46 ||
 * 4 || 1.00 || 0.39 || 3.5 || 8.97 ||
 * 5 || 1.00 || 0.39 || 2.9 || 7.44 ||
 * 6 || 1.00 || 0.39 || 3.0 || 7.69 ||
 * 7 || 1.00 || 0.39 || 3.2 || 8.20 ||
 * 8 || 1.00 || 0.39 || 2.7 || 6.92 ||
 * Average || 1.00 || 0.39 || 2.99 || **7.67** ||

__Analysis of Changes Made__ We made a few changes to our trebuchet to maximize efficiency. We tried to make an effective sling, and eventually changed our release mechanism to release with nail and loop. Our score with the sling was much lower (about 2.5). We found there was a lot resistance holding the projectile in the sling during the release. The simpler release mechanism made the projectile go farther.

We changed the angle of the nail with pliers to find the best release angle. We could not actually measure the angle of release but estimated, based on results, the angle of nail that would release at around 45 degrees. The angle of nail that maximized this was 40 degrees.

Another change we made was changing the overall dimensions of the trebuchet. We first tried making a trebuchet about half the size as our finished product, but found that it was not effective. We decided to make a larger trebuchet, and scored much higher results.

Looking at the results of other groups, it looked like smaller and lighter trebuchets perfermed better. This is likely because the projectile thrown had a mass of only 5g. If we could change what we did, we would have made our trebuchet smaller.

__Sources__ "Interesting Notes on Trebuchet History." //Medieval Castle Siege Weapons//. Web. 19 Nov 2009. . "Trebuchet - History." //Trebuchets//. Web. 19 Nov 2009. . "Trebuchet - History and First Uses." //Global Oneness//. Web. 19 Nov 2009. .