A friend of mine wanted to use some special dice called non transitive dice with his maths class at school to help with the teaching of probability. As et of three dice are considered to be non transitive if the probability that the first dice rolls higher than the second is more than half, the probability that the second rolls more than the third is more than half but the probability that the third rolls more than the first is not more than half. There is a more detailed explanation here
He couldn't find any at a reasonable enough price to enable him to buy enough for a class of 30 pupils to experiment with so he asked me if could make some. I decided to give it a go.
First problem: how to make small cubes with rounded edges with enough accuracy that they roll well and are not biased.
After bit of experimenting with cutting them out of wood with a table saw and sanding the edges I decided this was neither going to be easy or accurate. I toyed with the idea of laser cutting or using a CNC machine, but really I wanted a solution that was not going to take a huge amount of time. eBay to the rescue: I bought some blank dice from China. A bag of 20 odd for not much money. First problem solved.
Second problem: how to mark the dice with the numbers accurately enough that they look professional.
I tried marking out dots like on a traditional dice but again, getting accuracy was difficult. Any slight inaccuracy was very noticeable. Then I tried hand writing the numbers. This gave a much more natural look. Second problem solved.
Third problem: Just writing on the dice with permanent marker tended to rub off over time. To solve this I first wrote on the dice with a marker, then went over the marker with a small engraving tool in a Dremel. This took the shiny surface off the dice. I finished by going over these again with the permanent marker.
Here is the result:
Comments