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Tuesday, 6 August 2013

The Atlatl or Spear Thrower

As an engineer, I often look to the future, but sometimes, it's important to look at the past. A week ago, a friend of mine showed up with some wood, foam, and enthusiasm, and proudly proclaimed we were making an atlatl. Here is the tale of that engineering adventure.

First off, what's an atlatl? Well, he gave me much of the historical breakdown which you can find here, but the condensed version is that it's a spear-thrower.

The atlatl, pronounced "ad ul ad ul", is a simple device used to help throw objects farther and with more force. Believe it or not, you've seen one, I can almost guarantee it. You know those plastic scoops that dog owners use to throw tennis balls? Those are a modern version of the atlatl.

My friend Mike and I share a love of history and engineering and he thought this might be a fun and easy way to combine subjects. Grabbing my tools, we set to work.

The atlatl itself is foolishly easily to make as you simply need something to brace against the spear, dart, or javelin that you'll be throwing.

I decided to go with a groove approach as it was the most common design. Also, it would be easy to do and if I made mistakes, there was plenty of room to work around it. When working on projects, whether they be professionally important or a side project it is important to know the scope of the work.

I used to suffer from perfectionism, the need to do everything professionally and perfectly at once. The good sides to this trait is that it helped keep me motivated to accomplish greater things with better quality, but when you can't get past step 1 of arts and crafts because of it, you have a problem.
We were only looking to learn and have fun so we talked things through and got to work. I used a knife, hammer, and chisel to make the groove while Mike made arrows out of wooden dowel and foam.

Taking our supplies to the park, we worked to put theory into practice. I soon discovered that I needed to make a longer groove in order to better hold the dart and atlatl together.
Like so.
For reference, Mike and I threw the arrows by hand to gain an understanding of the distance we were competing against, to see if the atlatl was worth using.

All of the arrows flew straight and landed roughly 15-20 metres away. The 4-sided fletched arrow flew the farthest.

Now was the moment of truth. Here we would see if it was worth it. Surely all those other civilizations couldn't be wrong.

Here, we ran into some difficulties. The groove I had made was too narrow for the two longer darts, so I attempted to make it longer. In doing so, I cracked the wood and the right side came off. This made it more difficult to hold the one dart which did fit and the other two still did not fit properly.

It took us a few times but once we learned how to properly hold it, as it requires more finesse than we first thought, we were amazed at the results. Our atlatl more than tripled our launch distance and our personal record was ~200 ft or 60 metres!

We realized that a simpler design could have been used where we simply made a brace at the end of the atlatl, but this was good for a first try. This would have allowed us to throw the longer darts which not only would have given us more basis for comparison, but the longer dart would store more potential energy and allow it to be thrown farther. That is the crux of the atlatl; the upside is its easy construction considering the gain but its downside is that the energy is stored in the dart itself meaning you need a longer dart for a greater throwing distance. The bow replaced the atlatl in many cultures because, while the construction was more difficult, the energy is stored in the bow meaning shorter arrows could be used. Shorter arrows would be easier to mass-produce, store, and carry.

Reviewing records, it seems that several of the United States allow the use of atlatls, or spear throwers, for hunting, and that an all time throwing record is around 260 metres!

And there you have it, a brief afternoon with the atlatl. It is a simple tool which combines an understanding of history, engineering, and physics, and any afternoon that can do that is one worth having!

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