Mini Ballista

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My mini ballista in its current state.

If you enjoyed my full sized Ballista, then this one will truly amaze you. I built a tiny, working, ballista out of popsicle sticks, some paper clips, fishing line, thread, and some tape, held together with nothing less than elmers glue. I actually managed to carve tiny mortise and tenon joints in the wood to stand up to the stress as I did in the full sized version. At the moment it is a bit fragile since one of the strings on the pouch has come loose, but it still shoots.

Building Details

A few months after playing with my full sized ballista, I decided to make a "scale model" to annoy teachers at school. So, after assessing the complexity of working on something to tiny, I dove right in and began building. elmers glue was key in construction, along with double-ply popsicle sticks, made with elmers glue. The tools of this trade are mostly standard model maker's tools, an exacto knife (or similar), set of small drill bits, and patience.

The Frame

It turns out that if you glue two popsicle sticks together lengthwise you get a scaled down 2x4, in shape and durability. Using this fact, I created the frame mostly the same as I did on the larger version, except this time I was forced to use non-concealed circular mortise and tenon joints. The frame is about as durable as the larger version, as long as you scale durability with size.

Torsion Engine

Fishing line and steel paper clips, that just about sums it up. Since this fishing line was nylon and of relatively high strength, I figured it would make a good substitute for braided nylon. Only downside to fishing line is that it does not want to go anywhere but in a straight line. Bending it into position was no fun at all, nor was getting it cut to the appropriate length to fit in the frame without too much slack.

I decided not to use blocks with the paper clip tightening rods, due to size. Had I managed to cut it correctly, it would have been way to fragile, not to mention that being another thing I would have to wrap fishing line through. The sponginess of the popsicle sticks gives good resistance, along with the abnormally large length on the tightening rods. I have not tried, but I believe I could over tighten this without any trouble at all, I am just not keen on replacing the fishing line.

Throwing Arms

Broomsticks were too large for this application, instead I sacrificed a bamboo skewer, the kind you get your grilled shrimp on. They work quite well, and are strong enough to hold a small piece of paper clip in a hole bored in the ends of them, exactly the same as the larger model.

Surprisingly, the fishing line in the torsion engine is powerful enough to give the ends of the throwing arms slightly more force than a well placed thump, almost a light punch. In other words, the shooting potential of this ballista is beyond that of your average human hand, at least for peas and paper balls.

Trigger and Pouch

Diagram of the trigger mechanism used in my ballista

This trigger is exactly the same as the larger version, except made from popsicle sticks, elmers glue, and aluminum paper clips. (I only had one steel paper clip at the time) In design and function it works exactly the same, and, and far as I am concerned, it was amazing the the popsicle stick worked so well. I still didn't trust it and coated the small pieces in super glue and allowed it to harden before drilling holes and mounting it. Elmers glue managed to hold the trigger mount to the frame quite well, it hasn't broken yet at least.

The pouch is black electrical tape, and it is attached with yellow sewing thread. The thread did not quite meat my expectations, and is impossibly hard to tie knots with, so I might replace it at some point. At the moment, one of the loops connecting the pouch to the trigger is broken, but the other is enough to keep it in service. When it breaks I am going to replace the string with another material, possibly nylon thread.

Range and Power

From any part of a normal sized classroom, almost no part is unreachable with this ballista. At distances of less than 10 feet, heavier projectiles pack a small punch, quite a bit more than the average flicked item. Bits of clay work well, as do balls of paper. I have shot peas out of it before, but that can get messy.

Thoughts and Considerations

The white thing it is sitting on in the picture is the bottom of the case I keep it in. I had planned on building it to be almost indestructible so it could live in my book bag, but I don't trust my skill quite that much. I stole a small 5x5x1 inch box with a bit of quilt stuffing in the bottom to transport it in. I might try painting the whole thing in clear epoxy and see how well it can hold up then.