The Paper Trebuchet

Moving on from my original Paper Catapult, this is an only slightly more complex model.

Rather than using counterweights like the later versions, I decided to use muscle-power and make a traction trebuchet.

Again, it's just a single sheet of A4, but you need two cocktail stick this time.

_{(I have posted this without a firing video because certain members have been nagging me to get it posted. I will do a video as soon as I can.)}

Step 1: The Template

As is my preference, I drew the design by hand, in ink, on 5mm squared paper, referring back to the Paper Catapult for the base and frame. I made a couple of mistakes, but I include a scan of the original drawing for completeness' sake.

More useful for you, dear reader, I have also included a re-drawn PDF and JPEG of the template. Use whichever you desire (the JPEGs are probably the easiest to re-size, should you need to).

Print the template out on either normal 80gsm printer paper, or light (120gsm) card. If you print or photocopy to a size larger than A4, then I recommend using card instead of paper. If you use card but make it smaller, then careful scoring of crease lines will be required.

You will also need two cocktail sticks, gluestick, a paperclip, stickytape, pliers, sewing thread and small weights such as nuts or modelling clay.

Step 2: Preparation.

Whichever version of the template you are using, cut out all the pieces, then use one of your cocktail sticks to pierce the centres of all the small circles.

Crease all the dotted lines. If you are using card, or making a small version, then you will need to score the lines before creasing. Using a ruler, drag the tip of a blade of a knife gently along the line. You are scratching the surface, not cutting.

Step 3: The Base

When you have cut and creased the template, start folding at the long sides - the sides fold up, inwards, down and then towards the centre of the frame. Glue the last part down to the base of the frame.

When you have glued both sides, work on the ends. The first fold up seems to leave two extra bits sticking out at the sides. They're supposed to be there - glue them to the outside of the sides of the base. As you fold it over the top, glue the end down onto the sides of the base.

Two longer flaps glue to the tops of the side beams.

The ends then fold down inside the same way as the long sides. Glue them down, and then set the base aside to dry.

Step 4: Vertical Beams

• Note that the flaps at one end of the beam do not all get creased.

Glue the long flap and fold the piece into a square-section beam. Make sure the three holes line up (you should have just glued one hole over another).

Pierce holes at the three dots, then glue the outside of three of the flaps at the end with the dots. Fold the three glued flaps on top of each other, then cover the third glued flap with the fourth, dry flap.

At the other (lower) end of the beam, glue one of the creased flaps, fold it down, and fold the opposite flap on top of it.

You should now have a beam with two flaps sticking out at one end, with holes in the flaps.

Repeat with the other beam.

Step 5: Diagonal Beams.

When you have cut and creased, glue the long(ish) flap, and fold the piece into a square-section beam. You should have six loose, unglued flaps.

Repeat with the other diagonal beam.

Step 6: The Throwing Arm

The arm of the trebuchet is more complex than the arm of the catapult, as it has been modified to increase the leverage of the string's pull.

Cut out the long section, pierce the holes and crease the lines.

Glue one of the long sections, and fold it into a long beam.

Glue the small tabs at the square end, and fold them over.

Fold the small tabs over at the wedge-shaped end, then glue the long tab over them.

Crease the pivot-section, then lay the square end into the pivot section, line up the holes and glue it in place.

Glue the long narrow flap, and wrap it around the pivot section, over the back of it and along the beam.

I also added two sections to glue on the side, with the intention of holding the thread in place during firing. They may prove to be unnecessary, but I added them anyway.

Step 7: Construction.

Glue the insides of the flaps of the vertical beams, and place them over the sides of the base, lined up with the holes in the base.

Thread the first cocktail stick through before the glue dries, to make sure the holes are lined up. If you leave it in place, you can glue on the diagonal beams before the glue dries.

Glue the inside of all the flaps of the diagonal beams, and place them bracing the vertical beams against the base.

Place the throwing arm between the vertical beams and thread the second cocktail stick through to hold it in place.

Take a length of sewing thread, double it, and knot the ends together in a nice, fat, ugly knot. Tape that knot against the vertical part of the throwing arm, against the pivot section.

Use the needle to thread the thread through the holes in the end of the base. The thread also needs to go around the lower cocktail stick, but it is easier to pull the stick out, lay the thread in the base and then put the cocktail stick back, trapping the thread below it.

I happened to have a drink-can ring-pull lying nearby when I made this, so I tied it to the end of the thread to give me something to pull and to stop the thread getting pulled back through the hole.

Step 8: Ammunition.

So far, all the trebuchet does is quickly flip its arm. Flashy, but useless.

Unlike the catapult, the ammunition is not fired from a bucket or basket. Instead, it is hung from a sling on the end of the arm.

In large trebuchets, the sling is attached to the arm, and the ammunition is loosed from a pouch in a manner very similar to a staff-sling.

This trebuchet is too small for a complex arrangement like that, so the whole string goes with the ammunition, swinging off a hook or pin on the end of the arm.

To make the pin, straighten a paper-clip and then bend it completely in half. This gives a nice smooth end that will not snag the string.

Bend it again to match the shape of the end of the firing arm, and tape the bent clip to the underside of the firing arm, sticking out about half a centimetre.

To make the ammunition, fix a small weight, such as a small nut or a blob of modelling clay, to a loop of thread tied from a piece of thread about 5-7cm long.

Step 9: Firing

Firing is quite simple - hang the loop over the firing link, lay the arm down and then give the end of the thread a sharp pull.

Be careful, because the ammunition could go in almost any direction until you have practised a little.

If the ammunition comes back towards you, or goes straight up, the the firing link needs to be bent or curved slightly upwards. This is most easily done with a pair of pliers, one holding the firing link still near the arm, the other bending the free end.

With a little adjustment of pin, ammunition, and how hard you pull the firing thread, you should be able to lob your ammunition in a nice high arc, perfect for dropping boulders and rotten horses behind the highest castle wall.

Enjoy, and let me know what improvements you make to your model.