If you like to build and launch things then this is the project for you. The Catapult and Trebuchet will satisfy both these needs, so follow these steps to build these innovated constructions.
Step 1: Proposal and History
Proposal: We are in the South Plantation High School Engineering Program and the project that we will be completing will include creating a Catapult and a Trebuchet. They will have a pivot point under 4 ft tall and the base will be 3 ft by 4 ft. The reason we are doing this project is to find whether the Catapult or Trebuchet will launch an object the furthest distance.
History: The first catapult was created in 400 BC in a Greek town and allowed for longer and higher shots to launch over the newly built walls. The Catapult is proven to be the most effective mechanisms during warfare. The first Trebuchet was invented in China in 300BC. It is thought that the trebuchet may have developed from the stave sling. It is propelled through the use of weights at the opposite side of the sling. In the past humans pulled down ropes instead of a counter weight.
Step 2: Materials, Tools, Safety
Two 28" 2x4’s ….. $3.58 /each
Two 50" 2x4's…… $4.27 /each
Four 53" 2x4's…… $4.88/each
Five 5' 2x4's….. $3.58
One 8' 2x4 ………..$3.58
4x8 Sheet of Plywood……….. $13.98
Two metal pipes 18" long and 1" in diameter $347.33
One metal pipe 26" long and 1" in diameter $ 375.44
Weights $18.00 x2
10' of 550 Parachute Cord $3.99
Sling Material $13.00 (ex: Leather, Tarp, Denim, ETC.)
Wood Screws 3" $ 13.39
3 Eye Hooks $ 7.99 with a safe working load of at least 75 lbs
1 1/8" Spade Bit
Phillips Head Bit
1/16" Drill Bit for Pilot Hole*
Safety: When cutting or using machinery make sure to use safety goggles to prevent debris from getting in your eye. These constructions take more than one person to complete so try to get help when needed.
Step 3: Design
When we first got assigned this project we had a lot of research to do before designing our Trebuchet and Catapults. We did not have a lot of time so we had to work quickly. We had to build a Catapult and Trebuchet because of our group size so this shortened our time even more. After looking at many designs from other builders we have decided on the two designs above.
We were given some limitations, so we took those into account and tried to create the best constructions we were able to. Our pivot height was set at 48" or 4' and 8' arm with the pivot placed in our chosen spot. Our base consisted of 2 36" 2x4's and 2 28" 2x4's.
For our designs we used SolidWorks to create it.
Step 4: Building the Frame Part: 1
1.Get two 24" and two 48" pieces of wood from your materials and the wood screws
2. Lay them on a flat surface
3. Assemble them as shown above using an electric hand drill
4. If the frame is not stable add brackets to the corners
Step 5: Building the Frame Part 2
1. Find the two 48" pieces of wood
2. Find the center of the base of the 48" piece of frame
3. Measure 20" over
4. Mark the place
5. Pre-drill from the inside and insert the 48" pieces of wood to the inside of the frame.
Step 6: Building the Frame Part 3
1. Cut the 28" piece of wood at an angle that will allow it to lay on the beams you added in step 2
2. We used an electric hand saw but you can use a speed square as well
3. Pre-drill holes into the 48" bar you added in part 2
4. Drill the other end to the inside of the base
Step 7: Preparing the Arm Part 1
The arm is a significant part in the success of your trebuchet. Try to make the cuts as accurate as possible by measuring twice.
You can use a drill press to perfectly align the holes. We use a drill bit that was the same size as our axle, but slightly increased the size of the whole by moving the drill around in a circle.
1. Start off by measuring 2-3/4" from one end. Make a mark 2-3/4" from the side of the 2x4.
2. Make a second mark 18" from the same end that you measured first.
Step 8: Preparing the Arm Part 2
1. Drill 1-1/4" holes into two 28" pieces of wood 2-3/4" down from the top
2. Attach two 28" pieces of wood to the 48" piece of wood used as the arm
Step 9: Preparing the Arm Part 3
1. Grab two 7" pieces of wood and two 12" pieces of wood
2. Drill a 1/2 hole in both sets of wood 2" from the top of the pieces of wood
3. Drill another set of 2-3/4" holes 2" from the bottom of the pieces of wood
4. Put a 1/2" pole in the top holes and a 1-1/4" pole in the bottom hole while attaching the wood pieces to the 48" arm
Step 10: Adding the Arm Part 4
1. Drill a 1-1/4" hole 2-3/4" from the top
2. Put the arm in the center of the pole
3. Add the pole to the frame while inserting the arm
Step 11: Preparing the Arm Part 5
For the next piece of the Trebuchet, we are adding 2 x 12" 2x4. These take 5 holes to drill when putting them on.
1.Measure from 2-3/4 from each end and make a mark there
2. Drill a 1-1/4" hole at each mark
3. Insert the axle into the 1-1/4" hole
Step 12: Finishing Touches
Sling: For the sling we used a canvas bag material. We also used a type of paracord/bungie cord.
Release Pin: We connected a bar to some paracord and put screws into the back trebuchet. This allowed us to lock the bar into the screws and pull the paracord to release.