In This how-to essay you will learn how to build, adjust, and fire a trebuchet. Trebuchets were first used in the 4th century BC by the Chinese, these trebuchets were traction trebuchets(a traction trebuchet is a trebuchet powered by human strength). These trebuchets usually needed 50-250 people depending on the size of the trebuchet and how far they wanted it to shoot. Hanging counterweight trebuchets (HCT) weren’t invented for a while because of the scarcity of engineers and the resources needed to build one. The basic types of trebuchet propulsion are Spring, Traction, and gravity. Though all of these trebuchets have different propulsion techniques they are all basicly a lever with a sling at one end and a force of some sort on the other. Today we will be building a hanging counterweight trebuchet (HCT). Thought HTC's are very simple to build they work quite well if tuned properly, so let’s start.

Steps:
1.Cut materials

2.Making the body and base

3.Make throwing arm

4.Make counterweight

5.Make sling

6.Put it all together

7.Firing & adjusting

Things you’ll need:
bold means it’s wood

Sling:

9 ft-paracord/nylon rope

Old t-shirt

Duct tape

1-Keychain ring

Base:

3-21 in 2-4

1-34 in 1-6

Frame:

2-34 in 2-2

4-25 in 2-2

Arm:

2 in Finishing nail

4- ½ in washers

1 ft threaded ½ in metal bar

4- nuts that fit on bar

1-42 in 2-2

1-13 in 2-2

Counterweight:

15 to 20 lbs in weights

6 ft-paracord/nylon rope

Very strong carabiner

Other:

2.5 in screws

2 in nails

1-Tennis ball

Tools you’ll need:

Power drill w/ ½in, ¼in drill bit, & screwdriver bit

Saw & miter block or power saw w/ angle finder

pencil/pen

Tape measure

Scissors

A friend or parent(Optional)

Step 1: Cutting Materials

Cutting the wood is fairly straightforward, all you have to do is cut the wood to the specified lengths. The only angles you need to cut are a 75 degree on one side of the two 34 in 2-2 and a 130 and 155 degree on the four 25 in 2-2(make sure that from the side it looks like a trapezoid)

Step 2: Making the Body and Base

To make the base you must put the three 2-4’s and the 1-6 in the arrangement in the photo then use 6 1 in nails to keep them in place. Make sure the wood is not going to separate easily. Now take the two 34 in 2-2 and the four 25 in 2-2 and place and screw them in making sure the 75 degree angle and the 130 degree angle are on the bottom and positioned as in the photo, Then drill a ½ in hole level with the base at the top of the 34 in pieces.

Step 3: Make Throwing Arm

To make the throwing arm you will need to screw the 13 in 2-2 onto the end of the 42 in 2-2. Then in between the 2 pieces of wood drill a ½ in whole 9 in from the end and a ¼ in hole 2 in from the end, then at the other end of the throwing arm drill a ¼ in hole. Put a finishing nail in the part with only one piece of wood. Then put the washers, nuts, and throwing arm on the bar in the order nut washer washer nut arm nut washer washer nut. Do not tighten the nuts!!

Step 4: Make Counterweight

Cut the rope into a 1 ft piece and a 5 ft piece. Put the weights onto the 5 ft piece and tie the 1 ft piece onto the end of the arm through the ¼ in hole near the ½ in hole. Snap the carabiner onto the 5 ft piece loop with the weights.

Step 5: Make Sling

Cut a 6-3 in piece of cloth and put 3 in piece of duct tape on each of the 3 in ends. Using scissors carefully punch a hole in the middle of the duct tape. Cut the 9 ft piece of rope in half and feed one of the halves through each of the holes you punched. Put a carabiner on one of the ropes and a key chain ring on the other and tie the ends of each of the ropes to the other end of the same rope.

Step 6: Put It All Together

drill ½ in hole at the top of the 34 in 2-2 that is level with the base. Remove the first nut and washer from the threaded bar on both sides and put the bar through the ½ in hole from the inside, then put the washer and nut back on and tighten(Make sure the arm swings freely). Put the weights on by attaching the carabiner to the 1 ft rope loop( Make sure that at no point are the weights touching the base if they are then tighten the loop with the weights on it). Loop the rope on the sling that doesn't have the keychain ring on it through the hole on the end of the arm.

Step 7: Firing & Adjusting

to fire the trebuchet you must push the arm down until the arm is touching the base and pull the sling to the other end of the base. Load the tennis ball into the the sling and release whenever you want to shoot. To tune the trebuchet you bend the finishing nail forward or backward to make the release point sooner or later, you can also add or decrease the weight to get the perfect distance and release point. I suggest using the slow-motion feature on an iphone to see what it is happening better.