The Rules:
- Trebuchets cannot exceed length and width of 1 meter.
- Throwing arms are restricted to 1 meter in length.
- Trebuchets require remote triggers with at least 6ft activation distance.
- The Trebuchet must be able to launch a .5kg (.5L) water balloon and hit a targets at varying distances (up to 50ft).
The Initial Design
![Picture](/uploads/1/4/3/3/14334858/4421879.jpg?445)
The trebuchet was a revolutionary artillery unit developed during the medieval era as a siege engine, throwing massive projectiles with great force. Although the trebuchet has become outdated, modern engineers developed the floating arm trebuchet (FAT), a high-efficiency trebuchet. What makes it so efficient is the way the counterweights drop--straight down. With traditional trebuchets, the counterweights would fall in a parabolic path or short-lived straight path, the FAT however uses a unique rail system in which the throwing arm, equipped with a pair of wheels, engages the railing and propels the arm forward with awesome speed. The higher the drop, the more force generated--to a point. The rail-to-upright ratio cannot exceed 1:3 without losing functionality or running into complications.
Step one: Makin' the parts
![Picture](/uploads/1/4/3/3/14334858/3937693.jpg?454)
Before beginning construction, we cut out all the 2x4 sections we would need:
1)Six 3' sections (for uprights and base)
2)Eight 1.5' sections (for legs)
3)Six 20" sections (for the railing)
1)Six 3' sections (for uprights and base)
2)Eight 1.5' sections (for legs)
3)Six 20" sections (for the railing)
Step two: Basic assembly
![Picture](/uploads/1/4/3/3/14334858/2087928.jpg?454)
We began by laying two 3' sections along the concrete dividers and used them as a landmark for creating a rectangular base. We then laid two 1.5' sections on top. After bracing everything to make sure nothing shifted, we began to pre-drill the planks to prevent the wood from splitting. Once all the holes were drilled, we changed our drill bit to a driver bit, and put in the screws--Everything held well. We installed the uprights along with the legs.
Step Three: Adding the rails
![Picture](/uploads/1/4/3/3/14334858/6951560.jpg?444)
At the time, we didn't know what length the rails would be, so we measured from the outside of the upright to the outside of the leg, which gave us 17". We then cut eight 17" planks to use as railing. The railing needs to be heavily reinforced otherwise the trebuchet will fall apart. We plan on doubling up the railing to give it a bit of room for error as the arm, equipped with wheels, engages the track.
Step Four: Rinse and Repeat
![Picture](/uploads/1/4/3/3/14334858/957306.jpg?442)
Soon after finishing the first panel, we moved right to the second one. We repeated everything we had done the first time:
1) Braced
2) Drilled
3) Secured
Now that both panels were done, we also reinforced them by adding two more legs to each side, doubling up the railing, and adding a few more screws.
1) Braced
2) Drilled
3) Secured
Now that both panels were done, we also reinforced them by adding two more legs to each side, doubling up the railing, and adding a few more screws.
Step Five: Givin' it feet
This part requires some serious patience. We lined up the two panels on a 2x4 plank and added screws. This will keep the panels from flopping over. However, some parts of the panels were uneven which was very difficult to work with. Once we added the feet, the panels could stand independently and be placed with ease.
Step Six: The Arm (The really hard part)
We're nearing the end of the project and the trebuchet is really testing our patience. The arm must be very well calibrated in order for it to function to its full potential. We started by dusting off the 1 1/4" drill bit and drilling a hole in a 2x4, which will act as an arm. Once the hole was finished we inserted the axle, which composed of a 5/8" threaded steel bolt encased in 1/2" PVC pipe which was then encased in 1 1/4" PVC pipe (this allowed a perfect fit). We then threaded on a washer and bolt on each side which kept two weights flush to the uprights. This kept the throwing arm in alignment. Once the primary axle was finished we drilled another hole which acted as the secondary axle, the axle that houses the wheels. We were missing a nut and had to use tape. Finally, we put an eyebolt and a nail at the top of the throwing arm and attached a borrowed sling.