Picture of How to Make a Medieval Trebuchet Out of Cardboard
Of all the Medieval siege engines, the Trebuchet was by far the most accurate and complex. Trebuchets were capable of throwing 350 pound objects over castle walls. While in this Instructable we won't be making a Trebuchet with that much firing power, the design I will show you is capable of throwing a softball 50-60 feet with a 20 lb counterweight.

Video of me shooting the catapult:
(Sorry the video is sideways, I was having technical difficulties)

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Step 1: Materials

Picture of Materials
The Materials that you will need for this project are as follows:

Cardboard! - You will need A LOT of cardboard for this project unless you are lucky like me and find some quadruple-layer cardboard lying around.

Glue - I used Gorilla Glue and suggest that you use the same.

(Optional) Clamps - If you are using Gorilla Glue, you will most likely need clamps to keep your pieces together while the glue cures.

Pipes/Rods - You are going to need pipes for the axles and joints. I used a 3/4 inch acrylic rod for the axles and 3/4 inch PVC pipe for the axle to slide through.

Washers - You will use these to reinforce the joints that will be holding the counterweight and the the "arm" of the catapult. I used washers with a 7/8 inch hole.

Drill+Drill Bits - Depending on the size of your axle, you will need corresponding Drill Bits to make your holes. I used 13/16 inch and 5/8 inch.

Newspaper - Newspaper works really well when you are making your patterns for the cardboard

Rope/Cord - This will be for the "sling" that throws the projectile

Denim/Canvas Fabric - Also for the "sling"

3/16 Inch Steel Rod - This is also for the sling and only needs to be about 6 inches long

You will also need something to cut your cardboard into shape. I used a scroll saw but a knife or other saw might work.

Step 2: Trebuchet Design

Picture of Trebuchet Design
Getting the measurements for your trebuchet is one of the most important steps. Below is a picture of my initial design, with the measurements that I ended up using.

Part A - This is the counterweight and consists of two different pieces, pieces A1 and A2. The more A2 pieces you have, the wider your counterweight is and therefore the more weight you can put in.

Part B - This is the "arm" of the catapult and has two joints, one where it meets the counterweight, and one where it meets Part C

Part C - Raises the throwing mechanism off the ground. Has one joint where it meets Part B. If this part is too short, the counterweight will hit the ground instead of sliding smoothly through the movement

Part D - Provides stability and keeps the trebuchet from knocking itself over. The longer it is, the more stable the trebuchet

Part E - Adds necessary strength to Part C

Step 3: Making Patterns

Picture of Making Patterns
Here are the exact measurements I used:

Part A1 -
20 in. wide - 20 in. tall

Part A2 -
20 in. wide - 11 in. tall

Part B -
41 in. long
4 in. wide at top / 6 in. wide at bottom

Part C -
41 in. long
6 in. wide at top / 8 in. wide at bottom

*Parts D and E will be covered in another step

Step 4: Cutting Out the Pieces

Picture of Cutting Out the Pieces
Trace out/ draw out your shapes and start cutting!

For Part A1, I used 8 layers of corrugation, four on one side and four on the other

For Part A2, I used 16 layers of corrugation

For Part B, I used 12 layers of corrugation

For Part C, I used 24 layers of corrugation, 12 for one side and 12 for the other.

Step 5: Gluing Parts A-C

Picture of Gluing Parts A-C
Apply small amounts of Gorilla Glue and then clamp your pieces together! It takes about 1-2 hours for the glue to cure completely

If you don't have enough clamps, you can lay bricks or other heavy objects on top of the pieces while they dry.

Step 6: Drilling the Holes

Picture of Drilling the Holes
There are six holes that need to be drilled in order to complete the throwing mechanism.

Two of the holes need to be drilled on the "arm" of the Trebuchet (Part B). The first hole should be 2-3 inches away from the wider end. I used a 13/16 inch drill bit to make this hole. Using the same drill bit, drill another hole approximately 10 inches from the wider side. It'll take some force, and maybe a couple pounds from a hammer, but shove a piece of 3/4 inch PVC pipe into each of the holes. Pre-cut these pieces of PVC so that they are flush with the cardboard on either side. See first picture for clarity

Drill 5/8 inch holes 2-3 inches from the narrow end of Part C. See second picture for clarity.

Drill 5/8 inch holes into the top of the counterweight and glue the washers around the holes. See third and fourth picture for clarity.

Now cut your 3/4 inch axle into a six inch piece and a 15 inch piece. Take the six inch piece and slide it through one side of the counterweight, then through the "arm" of the trebuchet (in the hole closest to the edge), and through the other side of the counterweight. Take your 15 inch piece and slide it through Part C. Slide the rest of the rod through the other hole in the "arm" and then through the hole on the other half of Part C. See fifth picture for clarity.

Step 7: Parts D+E

Picture of Parts D+E
Now it is time to attach your supports. For Part D, cut four pieces (four layers apiece) that are 41 inches long. These pieces should be 6 inches wide on one end and 3 inches wide on the other.
Glue these piece to the bottom of Part C as shown on the second picture.

Part E are by far the most important supports. I tried firing the trebuchet without Part E and it had so much power that it ripped off all of the supports I had just put on in Part D.

Cut out pieces that are 4 inches wide and 27 inches long. You will need four pieces that have 12 layers each. Glue these pieces together. Trace the exact angles you will need on both the ends onto each of your pieces. Cut the pieces to shape and glue them in place. See pictures for clarity.

Step 8: Making and Adding the Sling

Picture of Making and Adding the Sling
Now you will be making the sling that holds whatever you are firing.

Depending on how big the items are that you will be throwing, your denim pouch will vary in size. My pouch was about 8 inches by 10 inches.

Take the edge of the side that is eight inches long and fold over about half of an inch. Sow this flap over and do the same on the opposite side. Slide your rope/cord through these folds. both these strings should be the same length. Take one of the strings (after you have fed it through) and tie it so that it makes one big loop. Leave the other string untied. See picture for clarity.

Drill a hole in the "arm" of the catapult on the side opposite of the counterweight. This hole should be just big enough for you rope/cord to fit through.

Take the untied rope/cord and feed it through this hole. Once it is run all the way through the hole, tie it to the other end of the rope/cord.

Take your six inch rod and poke it into the cardboard near the hole you just drilled.

Step 9: Firing and Adjusting the Trebuchet

Picture of Firing and Adjusting the Trebuchet
I decided to make a video for this step because otherwise it would be too confusing to describe.

Firing the Trebuchet

Adjusting the Trebuchet

For more power, add more weight to the counterweight. Here are some ideas for filling your counterweight:

- Bricks work well, but only if they fit width-wise
- thick gravel will work sometimes, but sand will seep through the corrugation

I ,however, used a 20 pound shirt of maille armor that I made last year. It fits perfectly and does not shift during the firing sequence.
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great, well done

Westornd made it!1 year ago

Thanks for this instructable. I could make a miniature version. ^^

Ha, I was randomly looking for things to make on this site and I saw this on the cardboard guide and was like "Is that a cardboard trebuchet?". This is truly amazing.
That was MY REACTION EXACTLY. With the then-instant addition of "*CLICK*".

Fantastic. My wife is going to just LOVE it when I dive into making THIS. Great!
Thank you!
fustigator3 years ago
Very impressive - just though I'd comment because youtube now have an 'edit' feature that lets you rotate your video. Keep up the good work, I watched the huge treblochet at warwick castle hurling a flaming cannonball this weekend which is why my internet wanderings have brought me here!
harrydo3 years ago
I mean where do you put the counter weight?
harrydo3 years ago
how can you add a weight to it?
funny. I have the same scroll saw.
austins pics003.JPG
timmy014 years ago
richhersey4 years ago
What is the biggest challenge you've had with building a Trebuchet?

I'm building a book with tips on building a Trebuchet and would love any tips or advice you have from building a Trebuchet.

Here is the survey form. I did a survey so I can have all the tips gathered from different forums in one place.

Trebuchet Survey
THERCNERD4 years ago
how tall is this trebuchet?
ineverfinishanyth (author)  THERCNERD4 years ago
With the throwing arm extended vertically, its between 6 and 7 feet.
can you make a template?
well i could have a page with all the demensions but i don't think i could a make a print-out-"able" template
kinkos and ask about wide format printing. its expensive, though
Shelexie5 years ago
This is a great tutorial!  Thanks for the ideas!
awesome, awesome awesome
suggestions put some wood in crucial areas for stronger,(longer lasting)  device , you could use old wall paneling for uter most layers or all the layers(you can cut with razor utility knife and do everything EXACTLY as you did here. it would be much stronger.

I think your push pull on the release arm was sheer elegance (simple), and if you do wood make it threaded rod into a nut set in the wood/cardoard arm then you can simply make it longer shorter by turning it.

thanks this was truely magnificent. My kid may want to build one, me too !!!
I made one out of wood with similer dimensions but double size I just fired it into a few houses over
thats a great idea! But don't use heavy wood on part c. use the heaviest avalable wood on the part a. for more power, lenghten part c
Dudemaster5 years ago
can you post measurements in metric as well?

dude, this is awsome
neat i may try to make one out of actual wood but this is very innovative
TCInc5 years ago
Hey, can you glue two cardboard together to make a bigger one for part B? If you can't, where did you get that big of a cardboard?
ineverfinishanyth (author)  TCInc5 years ago
The cardboard I used was from a 4 foot tall box, so that is how I got pieces that big......as for making part B with smaller pieces, you could cut out several smaller pieces and stagger them. This would create a semi-strong piece for part B that might do the trick. You would stagger the pieces much like a brick wall is staggered (see picture below)
TCInc5 years ago
Is A2 part of A1? It looks like they fit...
ineverfinishanyth (author)  TCInc5 years ago
yes, they fit together to form the counterweight "basket" of the trebuchet
snworks6 years ago
Very cool! Try putting it on wheels so it can roll easily back and forth in the same direction as the throw. It seems like the wrong idea, but it allows the counterweight to drop down in a straight line, instead of an arc, so more energy is transferred to the missle being thrown. I have seen it add distance. Worth an experiment!
ineverfinishanyth (author)  snworks6 years ago
Thanks for the idea i'll try adding some cardboard wheels now!
Old lawnmower wheels would be great if you had some..
I was going to say this too! Saw a great documentary on the BBC or Channel4 in England a few years ago. When they added wheels it stopped their trebuchet from rocking back and forth and made it much more accurate and powerful. The difference was remarkable. Just what every would-be conqueror needs!
Yes, I was that documentary as well, but I believe the wheels allowed it to rock back and forth, which changed the dynamics and improved the throw. It will be interesting to see if ineverfinishanyth belies his name and does a test with wheels.
the poodleo5 years ago
i thought this was just a mini one, so im gonna try and make a little desk one like about 10 - 15 cm.. it would be cool if it shot as far as this one in the video.
GianniMora5 years ago
how far does this shoot.
ineverfinishanyth (author)  GianniMora5 years ago
This throws a softball 50-60 feet. Heavier objects will not go as far
ok cool
georges bou5 years ago
kurth926 years ago
im impressed not by the cardboard people who make catapults normally go alright but people who try trebuchet normally fail it all in the sling so tell me the the counter weight completely cardboard ?
ineverfinishanyth (author)  kurth926 years ago
the counterweight is basically a hollow container in which i can place bricks, rocks, or anything else to provide the weight.
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