DIY Handheld Ballista

Intro: This project will walk you through making your own handheld ballista. This requires some woodworking skills but luckily can be made with materials you likely already have at home. If you want yours smaller or larger, you can easily rescale but be mindful of the impact this will have on the accuracy and force of your ballista. I made this ballista for my Physics class as part of a seige weapons project. I needed to make some kind of projectile-shooting siege weapon, so I chose a ballista. I made utilizing wood and metal pieces I already had on hand. This project required woodcutting that was relatively easy for someone like with me with rudimentary woodworking skills to do, and designing the structure also proved to be manageable enough that I was able to end up with a product that is functional and powerful.

- 16 in. cut of a 2x4 wood plank

- Two 4 in. 1x2 cuts of wood

-Two flat metal bands, about 8 in. in length.

- 1 metal track that's the same length or smaller than the 2x4

-1 metal spring, ideally less than 4 in. in length

- wood screws, 2 in. and 1 in.

- One 3 in.

- 1 thick guitar string, largest gauge you can find

- 2 hinges

- extra wood, 1x1 in (for projectile)

-woodworking saw

-screwdriver

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Cut out the required piece of your 2x4. Start by attaching the metal track for your projectile. Use a metal band like the one depicted above and screw it in on the middle of your 2x4 cut. This is going to be the top of your ballista and the track that the projectile travels on.

The arms of your ballista are what the bow string will be attatched to and are what allows the bow string to be drawn back to launch to projectile. Cut your 1x2 pieces of wood, about 4 inches in length. Screw your flat metal strips onto the ends of the wood pieces. On the other end, attatch your two hinges to the inside parts of the arms so that, when attatched to the main body, the metal strips face outward/forward with the ballista held up horizontally.

Screw the hinges on your arms to the main body, as depicted above. Then, hook your spring two the two arms, joining them together. Test that the arms are secured by lightly bending them back towards the body, mimicking the tension that will be put on them by the eventual bow string.

Time for the bowstring! Grab your guitar string--if you don't have a guitar string handy, tennis racket string or coated metal wire will work--and loop it through the end holes in your metal bands attatched to the arms. Pull the string fairly taught before tying and securing in place. Test to make sure you pulled it tightly enough by drawing the string back to the end of the ballista where you will be loading your projectile. At this position, your bowstring should be tight and should string forward with some force when released. When pulled back, your arms will look similar to the image above, i.e. bent back in a rounded shape. Take your 3 in. nail and screw this into the farthest spot you were able to pull back your string. This will be the loading point for the bowstring.

Grab your extra 1 x1 in wood and carve out a small projectile approximately 3 in. in length. It helps to make the tip narrower than the back for better accuracy. For mine, I made sure the projectile was able to sit in a diamond shape with one point down inside the track, and I also made sure it sat at a height where it was able to slide easily through the track when projected. After creating your projectile, test that your bowstring is able to shoot it by loading it and drawing the bowstring back. Don't point it at anything living!!!

Optional step: for mine, I created a wood wedge to launch the projectile by releasing the drawn bowstring. You don't have to do this, but it makes it easier and safer while keeping your fingers from getting accidentaly caught in front of the bowstring when it's release.Both the wedge and projectile are pictured above.

You're finished! Test your ballista by pointing t at a non-living object, loading your projectile, drawing your bowstring, and releasing it! For more fun, measure how far your projectile goes at different distances for the drawstring being pulled back.