The invention is a flywheel rotor that includes a number of adjacent laminations, stacked one on top of another, where each of the laminations has the same shape and is rotationally symmetric around a center axis, and where the shape is substantially circular and includes a plurality of protrusions on the circumference, and each of the laminations includes at least one hole for at fastening bolts to pass through. The invention typically includes an endplate at each end of stack of laminations and one of the two endplates attaches to a stubshaft.