How to Build an Awesome Mini Trebuchet!

Today, I will show you how to make a small, functional trebuchet designed to shoot a marble or small rock. It's an inexpensive project requiring simple tools, making it an easy choice for most beginning hobbyists.

Context:

While invented in ancient China, the trebuchet is generally considered to be a medieval weapon. It is a siege weapon that can fire projectiles much farther than the earlier catapult. It functions similarly to a catapult, using a large counterweight for propulsion. The key difference, however, is that the trebuchet has a sling that dramatically improves propulsion, allowing projectiles to be fired much farther than a catapult ever could. For the sake of the Making History contest, this is a Middle Ages project.

Cost and Material Sources:

This project will be just below $60 USD, depending on where you get your materials. Most of the materials (listed below) can be bought from your local Home Depot, although some must be bought from other sources.

Wood:

1. 6' hardwood 1x2
2. 24" hardwood 1x1

Pouch Materials:

1. 3" square of leather (any piece of fabric will work for this, but will look less authentic)
2. Two 8.4" lengths of mason twine or similar, with 3" of additional length on each to tie knots
3. Roughly 10" of heavy-duty thread (or artificial sinew, for a more authentic appearance)

Weight Materials:

1. 9 50-cent rolls of pennies (US or Canadian works). Refer to Step 6 if you have to roll the pennies yourself (16 50-cent rolls is $4.50, or 450 pennies). Penny rolls can be easily purchased from a local Dollar tree.
2. Six feet of paracord
3. Small amount of tape (any tape will work well, though I used clear tape)

Other:

1. Four R4-2RS ball bearings
2. 12" aluminum rod, 1/4" diameter
3. Can of WD-40 or similar lubricant
4. 12 #6 1" long flathead Phillips wood screws
5. Small eye bolt

Tools:

1. Electric drill with 1/16", 1/8", 1/4", 5/8", and Phillips drill bits
2. Hacksaw or similar
3. Hand saw
4. Awl to punch holes for stitching the leather (a hammer and nail will work in a pinch)
5. Heavy-duty scissors
6. Graphite pencil
7. Tape measure
8. Swivel vise (a pair of F clamps will work as well, if you don't have one)
9. Large-eyed sewing needle- will help with stitching the pouch, though thread can be pushed through holes made by the awl
10. Swanson Speed Square- similar devices are often sold as rafter squares. Inexpensive and helpful for cutting a 45° or 90° angle.
11. Two F clamps
12. 12" mitre box

Notes:

I used poplar for the wooden parts because of its light grain and affordability, but any hardwood will work well. Softwoods like pine can be used, but are more likely to crack during construction. A decent amount of scrap wood will be left over after this project, which can be used to decorate the trebuchet or saved for later projects.

On the illustration, the 6' 1x2 and most of the screws were not shown. This was a deliberate choice caused by the limited size of our backdrop.

Materials for this step:

1. 6' hardwood 1x2

Tools for this step:

1. Hand saw
2. Electric drill with 1/4" drill bit
3. Tape measure
4. Pencil
5. Speed Square
6. 12" mitre box
7. Swivel vise

Assembly:

1. Using the tape measure, pencil, and Speed Square, mark off the following lengths of wood ending at 45° angles on both sides on the 1x2, as shown above. These measurements are the length of the long side, NOT the short side. You should end up with a long web of connected trapezoids. Mark off:
2. 2x 4.5" long, ending with a 45° angle on both sides (trapezoid shaped)
3. 2x 7.5" long, ending with a 45° angle on both sides (trapezoid shaped)
4. Using the tape measure, pencil, and Speed Square, mark off two 7-11/16" lengths of the 1x2. These should end in a 90° angle, unlike the other boards you just cut out.
5. Using the mitre box, cut the 1x2 along the lines you just marked off.
6. Afterward, cut both ends of the 3.5" and 7.5" boards at a 45° angle, as shown above. A Speed Square is helpful for this step.
7. Measure off the center of the 7-11/16" boards lengthwise. Drill a 1/4" hole in one end of each board, travelling 1/2" down from the top. Make sure these holes are perfectly level, or you could have issues mounting the arm later. It's advisable to clamp them together and drill them both at once to prevent this. If any of this is confusing, the pictures should help clear things up.

Materials for this step:

1. Cuts of wood from Step 1
2. 24 1" Phillips flat-headed wood screws
3. 8 3/4" Phillips flat-headed wood screws

Tools for this step:

1. Electric drill with 1/8" and Phillips head bits
2. Tape measure
3. Pencil
4. Swivel vise
5. Wood clamps (optional)

Assembly:

1. Using the 1/8" drill bit, drill two evenly spaced (3/4" apart) guide holes at each end of the 7.5" boards (the ideal location of these is shown above). Then, ideally using a vise and some clamps, drill the 1" screws through them and into the 3.5" boards to form a miter joint. You should finish with a simple wooden rectangle, as shown above. Depending on how you cut the wood, it may be slightly misaligned. This will be much harder to notice after the arm is put in place, though. Don't worry about it.
2. Mark off the center of the 7.5" boards lengthwise. Place the 7-11/16" boards there and trace the edges, making sure that the two boards are perfectly aligned.

Materials for this step:

1. 24" hardwood 1x1

Tools for this step:

1. Hand saw
2. Tape measure
3. Pencil
4. Swivel vise

Assembly:

1. Measure 13" of the 1x1 (just past halfway down). Mark it off with the pencil and cut it there using the hand saw. A swivel vise is helpful here.
2. You will now have an 11" 1x1 and a 13" 1x1. Set the 13" 1x1 aside for later. The 11" 1x1 is scrap wood.

Materials for this step:

1. The 12" and two 3.5" cuts of wood from Step 3
2. 4 R4-2RS ball bearings

Tools for this step:

1. Electric drill with 1/4" and 5/8" bits
2. Tape measure
3. Pencil
4. Swivel vise
5. Wood clamps (optional)

Assembly:

1. Place the 13" 1x1 into the swivel vise (if applicable). Measure 3.4" down from one side and mark it with a pencil. Drill a hole there using the 5/8" drill bit, going straight down and about a third of the way through. Temporarily place one of the R4-2RS ball bearings there to make sure it is flush with the board's surface. If not, drill slightly deeper. Repeat this on the other side in the same location. The drill should have created a small hole connecting both wider holes. Using the 1/4" bit, widen this center hole slightly until it is slightly wider than 1/4".
2. Measure 1" down from the "short" end of the trebuchet (the end with the preexisting hole closer to it) and mark it off with a pencil. Follow the same partial-5/8", partial- 1/4" tactic as is shown above.
3. Place one R4-2RS ball bearing into each of the 5/8" hole, pushing them straight down until they are perfectly nested in each hole. Make sure that you can't see any wood through the center of the ball bearings when looking straight through their center holes. If you can, use the 1/4" bit again to widen the center holes.
4. Using the pencil and tape measure, mark off the very tip of the long end of the 13" 1x1, about 1/4" away. Make this mark centered and on the "underside" of the 1x1 (demonstrated above). Using a 1/16" drill bit, drill a small pilot hole at this marked spot.

Materials for this step:

1. All wooden pieces used in the previous step
2. 12" aluminum rod, 1/4" diameter
3. Small eye bolt
4. Can of WD-40
5. 4 R4-2RS ball bearings

Tools for this step:

1. Hacksaw
2. Pencil
3. Tape measure
4. Swivel vise

Assembly:

1. Use a pencil and tape measure to mark off a 2.5" and a 6" section of the aluminum rod. Use the hacksaw to cut along these lines, creating 2.5" and 6" aluminum rods. Make sure to cut these perfectly straight. If you don't, you may struggle with the next parts of this step*.
2. Lubricate the both pieces with the WD-40. Make sure to leave the tips of either side dry so that you can hold onto it reliably.
3. Place the R4-2RS ball bearings in both sides of the two holes at the end of the arm. They should fit snugly on both sides.
4. Place the 13" 1x1 from the previous step in the swivel vise, if possible. It's important to keep it anchored on something for this step, and if you don't have a vise, use clamps or a heavy object to keep it in place. Carefully insert the short aluminum rod through the hole at the very bottom of the 13" 1x1 (NOT the hole above it). Insert the longer one at the base. It may be difficult, but make sure that the ball bearings stay in place the whole time. A screwdriver can be used to help keep them in place for this step, although it's important to avoid damaging the bearings.
5. Carefully insert the eye bolt into the 1/16" guide hole at the end of the arm.
6. Place the 7.7" wooden pieces from before on both ends of the 6" rod, pushing them down until they are flush with the rod.

*If you struggle to get the rod into place, use some medium-coarse sandpaper to round off the ends (and possibly the rest of the rod) so that it will go in more smoothly. If you choose to do this, you MUST wear a dust mask or respirator and preferably do this outside. Whatever you do, DO NOT INHALE THE DUST. It is horribly dangerous to inhale any type of metal dust and can cause severe lung damage or even death.

NOTE: If you were able to obtain all of the penny rolls already, skip this step. If you rolled them on your own independent of this step, skip this step. This step is only for those who don't yet have the correct number of penny rolls (or none at all).

Materials for this step:

1. However many pennies you still need to roll (this number should always be a multiple of 50)
2. Penny rolls*-- enough of them to roll all of the pennies (this number can be obtained by dividing the number of pennies you have by 50)

Tools for this step:

1. N/A-- this can be done by hand

Assembly:

1. Count out a pile of 50 pennies.
2. Place each pile into one penny roll, making sure that the coins go straight down. Fold the ends afterwards to ensure that the pennies don't escape.
3. Repeat above until the pennies are all rolled.

*Refer to the "Extra" step at the bottom in case you have the pennies but couldn't find enough penny rolls (or none at all)

Materials for this step:

1. 16 rolls of pennies
2. Six feet of paracord, cut into two 3' lengths
3. The 2.5" aluminum rod from Step 5
4. Clear tape

Tools for this step:

1. Hacksaw
2. Pencil
3. Tape measure
4. Swivel vise

Assembly:

1. Arrange the penny stacks vertically, in a 3x3 arrangement as shown above. Place clear tape on the end of each roll so that the pennies don't leak out.
2. Wrap one of the 3' lengths of paracord around the weight several times and tie it off, leaving a small amount of slack (enough that, if pulled upwards, it creates a loop about 3/4" tall from the top of the rolls). Push this length towards the bottom half of the penny rolls.
3. Repeat 3, instead keeping the paracord length towards the top.
4. Push the 2" aluminum rod through the slack on each, twisting the slack into a loop on each so that it is fully wrapped around the rod. If you were unable to do this, unwrap the paracord and try again. If you were able to do this, remove the aluminum rod again-- this was just a test to make sure there was enough slack. You will now have a fully assembled weight.

Materials for this step:

1. Weighted arm
2. Assembled frame
3. Pouch
4. Remaining 6.5" of the aluminum rod
5. WD-40

Tools for this step:

1. Hacksaw
2. Tape measure
3. Pencil
4. Swivel vise

Assembly:

1. Prepare the arm by
2. Align the arm with the frame. Carefully insert the 6" rod through one of the support beams. Then, place the arm there, making sure that the eye bolt is facing down. Lubricate the rod with WD-40, then carefully insert it through the remaining hole in the side of the arm. Push the rod the rest of the way through and out of the other support beam. It should be flush with both.

Materials for this step:

1. Assembled weight from Step 7
2. Assembled arm from Step 5
3. 3" aluminum rod from Step 7

Tools for this step:

1. Swivel vise

Assembly:

1. Place the arm into the swivel vise. The holes should be aligned horizontally.
2. Push the 3" aluminum rod through the 1/4" holes on the ends of the 2.5" 1x1s on the end of the arm. Make sure that the rod is perfectly centered on it.
3. Pick up the weight. Twist the paracord slack around and place each loop over one side of the rod, just like the test in Step 7.
4. You will now have a completed, weighted trebuchet arm. Make sure that the eye bolt on the arm is on the bottom side of the device, or you will have to flip the weight over to the other side.

Materials for this step:

1. 3" leather square
2. Heavy-duty thread
3. Both lengths of mason twine

Tools for this step:

1. Awl
2. Pencil
3. Heavy-duty scissors
4. Sewing needle

Assembly:

1. This step requires some calculations. First off, find the diameter of your projectile. If it's not round (like a small rock), then estimate. My projectile is a 1/4" marble, so this wasn't difficult for me. The pouch should be a rhombus 1.75 times your diameter tall and 4.15 times your diameter wide. For me, that means that my pouch should be 0.4375" tall and 1.0375" wide. Mark these dimensions off on your piece of leather.
2. After finding your ideal dimensions, cut a rhombus (diamond) shape of the appropriate dimensions out of the leather using the heavy-duty scissors.
3. Fold the diamond shape in half. Using the awl, press holes through it as shown in the diagram above (these holes are represented by small lines, which are for illustrative purposes only-- more holes than that should be made). Stitch through these holes using the large-eyed sewing needle and the heavy-duty thread, making sure that it is stitched and tied off securely on both sides.
4. Use the awl to place large holes in each corner of the pouch, as shown in the diagram above. Then, tie one piece of mason twine to each side, making sure that you don't use more than 1.5" of either end to tie the knot.
5. Tie the other two ends around the eye bolt on the arm. Your trebuchet is completed!

You've done it! The trebuchet is complete. But what's the point of a trebuchet unless you can fire it?

Steps:

1. Place the trebuchet where you want to fire it.
2. Carefully rotate it towards the direction you want to fire it in. DO NOT POINT IT AT PEOPLE OR ANIMALS.
3. Load the projectile into the pouch.
4. Pull the arm back, so that the tip is touching the ground.
5. Pull the pouch back as well, so that it is held taught by the arm.
6. Quickly let go of the arm and step back.
7. Watch your projectile fly!

Note:

Due to an error in the uploading process, I wasn't able to attach the test video. I'll try to fix this soon.

This is a step in case you were unable to obtain penny rolls normally. It needs different tools and materials than the rest of this project. Treat this as its own separate set of instructions (like a mini-Instructable).

Materials:

1. Sheet of paper (multiple may be needed, depending on the number of pennies)
2. Clear tape

Tools:

1. Ruler
2. Pencil
3. X-Acto knife or similar (anything with a razor blade will work in a pinch)

Assembly:

1. Cut the paper into sections that are 2.5" wide and 3.75" long, marking each area off using a pencil and ruler before cutting them by carefully slicing through the paper with the X-Acto knife pressed against the ruler to make a perfectly straight cut.
2. Place clear tape along the long edge of the roll, all the way down.
3. Carefully align the edges of the roll, and place the other end so that the two edges are flush. Press it so that the tape goes together. Repeat this step for each roll you intend to make.