2015-12-19 (Sa) ESPeri.Impass

I’ve had numerous sources of inspiration for this project. Sometimes ideas don’t pan out, so far none of them have, and they get discarded. Sometimes they pop back up. I was toying with the idea of a spherical compass, like those found on keychains where you have a clear plastic sphere and inside is a spherical compass spinner which is weighted to stay upright and magnetized to point north. No matter what angle you hold this keychain it will point north. I suppose you could stand in a centrifuge and it wouldn’t point north but now you are just being persnickety.

The way I want this compass to work is to create a spherical container with a single protrusion on the inside facing north. The spinner will have protrusions to keep the sphere centered in the container but these protrusions will have a much higher likelihood of intersecting the enclosure’s protrusion when the container is facing north.

There was no reason the majority of protrusions were on the spinner. They could have been placed on the inside of the enclosure instead. The spherical spinner would be suspended in a liquid, probably alcohol or salt water. Fins on the spinner would create drag through the liquid as it spins. This resistance could dampen erratic movements or impede response. If the fins were placed on the enclosure and the spinner had a single protrusion disruptive currents would be generated when the user turned. More consideration will be necessary.

Enough background.

A new spinner and enclosure style was conceptualized. Describing the shape was difficult so a model was produced quickly.

Modeling was done to create a spherical compass spinner in OpenSCAD. Protrusions were modeled on the spinner rather than the enclosure. An image was created which shows the full sphere but it has been modeled in identical halves. The bottom half will have space for one or two magnets. Each half will print with the cut line on the printer platen. It may be beneficial to divide the sphere into quadrants so the protrusions print more reliably.

Space will have to be created in the bottom half of the mode which will allow magnets to rest. A socket for a brass screw will also have to be made in the top and bottom. The screw will hold the halves together. A central screw could be used but the magnetic media could no pass through the center, for example if a rectangular bar was used. Instead, two disc magnets could be used like with the previous model. To use a single bar through the middle of the spinner two screws would have to be put on either side of the compass. A central screw will likely be used to use the magnets in stock.

Spinning model of spherical compass spinner

To do:
  • Optional:
    • Add compass rose to spinner
    • Add holes to reduce plastic
  • Add “keyed” features to only allow slop when facing north
  • Make handheld haptic compass
  • Make compass work from pocket or necklace
  • Miniaturize

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

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2015-12-16 (W)