Hello, has somebody a good idea how to create an Objject like a jockey wheel

[Fennec]

You can create it from a 2D shape, an SVG or canvas drawing like, then extrude it with ExtrudeGeometry.

Extruded arc shape geometry not closing

A bit late to the party, as usual Bumped into the same issue, building a gear, with gear’s inner hole. The Gear itself: The solution was exaclty what @PavelBoytchev said - not to close the path. In my case, I simply built a set of points in circular formation, missing the step, where angle is exactly Math.PI * 2.