U225X / ENGINEERING UNWARRANTED
Fidget Spinner / Simplicity Wins
Public record / MDL-SPINNER-001 / Revision A
U225X
I wanted something that would spin freely and keep going after a flick. That small goal led through Shapr3D extrusion controls, smooth connecting arcs, bearings that felt stiff, and a question about putting N52 magnets around a printed housing. The result on the workbench is a white, three-lobed spinner with four bearings. The useful part of the project was working through those questions and coming back to a simple object I could actually make.
TECHNICAL NOTES
A three-lobed spinner, four bearings, and a lesson in keeping the mechanism simple. Shapr3D modeling notes, a magnetic detour, the finished print, and the original STL.
BUILD STORY
The theme for this build is simplicity wins. A small printed mechanism gave me a reason to learn a few CAD controls, question the bearing resistance, and follow a tempting magnetic idea far enough to understand its limits.
First, make the material join. In Shapr3D I wanted to extrude a circle downward to create a connection, but the operation was subtracting material. The useful control was the Boolean badge beside the extrusion distance: choose Union when the intent is to add the extrusion to the existing body. It was a small interface detail with a large effect on what the model became.
Then make the circles feel like one shape. The sketch had a central ring and three rings around it. I marked the connections I wanted in red: inward curves between the outer circles. The advice was to start with a 3-Point Arc, keep each endpoint coincident with its circle, and make the arc tangent to both circles. Coincident keeps the endpoint attached; tangent makes the transition smooth. The endpoints need room to slide while those constraints solve. Those notes explain the approach discussed, while the screenshot preserves the shape I was aiming for.
The bearings raised another question. The new bearings felt a little stiff, so I asked whether WD-40 would help. The discussion redirected attention to the source of the drag: grease, seals, an overly tight printed pocket, or a surface rubbing after assembly. A useful check is to compare the bearing before and after fitting it. The conversation did not establish that I changed the lubricant or measure how much resistance came from the housing.
Then came the magnetic detour. What if N52 magnets sat in pockets around a PLA bearing housing? I wanted the spin to last longer, and magnets snapping together or pushing apart made it feel as though there ought to be something useful there. The discussion separated a magnetic push from a continuing source of energy: a fixed arrangement may help during one part of the rotation and resist during another. Resetting an attracting or repelling arrangement takes energy. Simply arranging magnets around a bearing does not supply a new push on every revolution.
There was still an interesting experiment to keep. Magnets can support some of a rotor's load in a suitable arrangement, reducing what the bearing has to carry. That is different from expecting a steel bearing to repel a magnet, or expecting magnets fixed inside one housing to drive that same housing around. A removable magnet setup and repeated comparisons were suggested. No such comparison is documented here, so the magnetic idea remains a question for another test.
Back on the workbench, the result is straightforward: a white printed body, three rounded lobes, and four bearings. The photo gives the CAD discussion a physical ending. The STL keeps the shape available for the next attempt. Simplicity wins here because the project has reached an object I can hold and examine; the more elaborate ideas can wait until there is a useful measurement to compare them against.
SPECIFICATION
FIELD IMAGES 02 ATTACHED
