Yes Moi is great. I love it to model with no reference. In this case with no correct norm values (wheel nut ). The hardest part was to find a way to bend the center of this wheel. I've project the curve on a sphere and cut the lines. I didn't find an other way. My first try to select the point and move them down was not bad but I couldn't extrude the curve with caps. My test below.

Regards from Bavarian