2020-06-02 (Tu) HexShaftMonitor

I have to interrupt my last project, HouseRobotInterference, because I am moving to a new place. My home internet has to come from my phone's hotspot, so streaming video is not going to happen. I have a couple of other projects that I've wanted to move on, and they don't require high bandwidth.

The first project is a rotation counter for a hex shaft. I plan to wind some electromagnets in the future, but I will need to make sure I can repeat the process. Counting winding rotations will be crucial, so I am planning to build an attachment for my drill or bit driver that will monitor the shaft.

Enough background.


I sketched a design that will hang off a hex shaft and read the rotations from a spinning magnet. The idea is there will be three printed pieces. The first piece is a cylindrical magnet holder that slides onto the rod. The second piece will hang loosely off the shaft and hold the electronics. Finally, I will add a cover that captivates the magnet holder.

Sketch for HexShaftMonitor

We always measure hex shafts across the flats, but when I enter that into OpenSCAD, it will use that to calculate the distance between the points, which is wider. If I did this, the hexagon would be too small. I started a drawing to calculate the ratio between the two measurements. These two factors are the same as a hexagon that's being circumscribed about a circle or inscribed. Making this calculation should help when I model the design.
Calculating the ratio of diameters

The rest of the posts for this project have been arranged by date. First time here?

Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Completed projects from year 4
Completed projects from year 5
Completed projects from year 6
Completed projects from year 7

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