Reuleaux triangle mechanisms

Started: July 2020
Completed: July 2020
Released: July 2020

I made a Reuleaux triangle with Lego. The Reuleaux triangle is obtained by drawing an arc around each vertex of an equilateral triangle. By using a 1×4 curved slope, I was able to create a fairly accurate Reuleaux triangle.

I made the square frame with the Reuleaux triangle inside.  The Reuleaux triangle can be rotated while inscribed in the square, because it has a constant width.  I devised a gear that makes Reuleaux ‘s triangle revolve.


The luminescent round tile is attached to the top of the triangle. In a long-exposure photo, the trajectory is a square with rounded corners.


The mechanism in which the Reuleaux triangle rotates around its vertex. The yellow-green frame draws a square trajectory.

Here’s a further development. The square frame with arms rotates while engaging the pins.

The last mechanism is based on the following videos:

Title: sankakukanketu (2014)
Author: araieng

Title: Reuleaux Triangle Intermittent Pins Mechanism 3D Model (2016)
Author: trinityscsp