Ballista Instructions

Thanks for supporting The Gizmo Dojo, and we hope you have fun with your new ballista!

Once you are finished building your ballista, feel free to add it to the Build Logs thread in our forum if you want to, or if you need any help you can post your questions to the Project Help thread. We would love to see pictures of your build!

Ok, let’s get started. First off, you will need some wood glue. After you have that, open up your bag and you should have a bunch of parts that look like this:

Grab these two pieces (note, the smaller one looks a lot like another part in the kit. This one has a notch):

Put a small amount of glue in the notch, and glue the two pieces together:

Grab these three pieces and put a little glue on the flat one:

When you glue these together, make sure the little notch on the smallest piece is pointed up:

Grab the next 2 pieces:

Glue them together so that the grooves line up:

Grab another of the smaller pieces and do the same to the back side:

Then do that whole process again with the other ballista arm:

Grab the following pieces:

Apply a little glue:

Glue the two pieces together. Make sure that you clean out the excess glue (the stuff in this picture) with a paper towel or a rag:

More glue:

Before you put the other side on, make sure the two smaller pieces are in place. They don’t need glue, but they need to be there before you glue the other part down:

Press the other side on, trapping the other two pieces in place:

Again, wipe out the excess glue from the track. Any glue in here will slow down the catapult firing:

Flip the part over, and apply a little glue to the bottom as shown:

This image is just for reference, but in the next step, make sure the notches are facing BACKWARDS:

Apply a little glue as shown:

Glue the pieces together. Do this for both sides:

Apply a little more glue:

And put the top on:

Now grab one of the short strings, and thread it through the two holes as shown. Make sure to trap the small wooden pieces as shown. Tie a knot (if you do it on the bottom, it looks a little better). If you have issues with your knot coming untied, put a dab of superglue on the knot. Don’t worry about getting the string super tight right now, just make sure the wooden pieces are held in place:

This image shows the bottom of my ballista, but if you tie the knot at the bottom, I think it looks better:

Place one of the arms in between the two strands of string, and make sure the notch faces outward, as shown:

We’re now going to apply some “spring” to the ballista. Turn the top and bottom small wooden pieces so the string applies some pressure to the arm. Take a look at the picture below. Then you can also do the same to the other side (this one you will have to wind in reverse):

We’re getting close… If you’d like, you can try to tension the two sides equally. There’s a clever way to do this, or you can probably go by feel as well. (To do it the clever way, squeeze the two arms towards each other, and if one moves more than the other, then they’re not even)

Put the pushing mechanism in the channel, and make sure the notch is pointing towards the back:

Thread the long line through both grooves, and the small hole in the pusher:

Tie a loop in one end:

Hook it over one of the arms:

Do the same on the other side. Pull back the pusher, make sure the latch is set in the groove, add some ammunition…


Have fun and be safe with your new ballista! If you have any suggestions for improvements, please let us know, or post about it on the forum. If you are missing any pieces, come talk to one of us at one of our meetings on Mondays, or send us an email.

Thanks again for supporting The Gizmo Dojo!

EDIT: If you have any pieces like this:

You can ignore them. They were meant to keep the tension in the strings once they had been wound, but we ended up not needing them.

EDIT: We’ve been having issues with the ballista firing mechanism. The “pusher” piece tends to flip over. To fix this, grab a wooden clothespin, and take it apart. Add some glue to one edge:

Glue the two pieces edge-to-edge, so you have one large flat side (Make sure the flat side is flat and you don’t have an edge where the two pieces meet):

Add a little glue to the ballista:

And glue your new clothespin modification to the top:

Now the ballista should fire smoothly every time.

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