Helical torsion spring round
<img src="https://eng-calculations.com/SVG/Mechanical_engineering/Springs/Helical torsion spring round.svg" alt="Helical_torsion_spring_round" title="Helical_torsion_spring_round">
https://eng-calculations.com/SVG/Mechanical_engineering/Springs/Helical torsion spring round.svg