Saturday, September 2, 2017

Tetrahedron Success! (Part III)

You know when you buy something from the big box store that says, "Some Assembly Required?"

If you are like me, you just jump right in and start putting it together. "Directions? Who needs directions!"

Well, apparently I need directions.

I screwed up the first one by not looking at Sylvain's directions. After reviewing what he said, I got it the second try, easy-peasy.
Take a look at Sylvain's first drawing:
Sylvain's drawing.
This is what I basically did. The first time through, I made my triangular stick equilateral. That means using the above drawing that (a) was the same length as (b).

The trick was to make (b) a little shorter than (a).

I didn't want to have to measure anything, but you need to for this. I think if it is pretty close, it is probably good enough for this purpose.

Measure (a), then multiply that number by .866. The product is the length of (b).

Only then should you lay out the lines for the tetrahedron.
Ready to saw out.
The small tetrahedron that comes off the saw needs a bit of cleaning up. I used a plane for this one, but the real deal will be a much harder wood and much smaller. I probably will use a chisel, or maybe some sandpaper.

And, I have an idea for making the white pips on the corners.

If you've missed my other posts on this project, check them out:

Part I:  Project Idea - The Royal Game of Ur
Part II: Tetrahedron Fail #1


  1. I love it when the math works out. And with a computer engineering background, counting from zero rather than 1 comes naturally so this just keeps getting more interesting.

    1. A pinch of bat-ear and a rooster gizzard, stir it counter clockwise and VOILA! The spell turns out just right!

      I agree that it is an interesting project. Plus, an interesting game, to boot! I would love to get into some of the "complicated" rules that are mentioned in the video.

  2. Congratulations Brian.
    For those interested, the second sketch shows how to obtain the length "b" from the length "a" without using numbers but with a simple geometric construction. It also shows how to obtain the angle between the base and the shorter sides if you would plane the stick.

    1. Thanks, Sylvain, I very much appreciate it. It boggles my mind what some people out there know.