18 ribs 76 and 98 also abut each other in an alternate arrangement the opposing inner edges 88 and 89 of support members 72 and 74 are each rabbeted circumferentially to interlock together as shown in fig3 other means to interlock or attach the support members 72 and 74 may be used interlocking or attaching provides for a more stable assembly between halves 20 and 22 when assembled the inner edges 88 and 89 may also be glued if desired in fig2 and 3 band retention means 82 and 83 are shown with inside slots 84 and when the two sides 20 22 are joined band 18 fits into opposing slots 84 and 85 and is held therein the band 86 may be made of any suitable heat dissipating material including metals such as aluminum iron alloys or the like as well as selected compositions of heat resistant plastic type material such as ultem u2122 synthetic made by general electric corporation or bakelite synthetic resin or the like the exterior surface 87 of the band 18 is smooth to avoid wearing the friction strap to be placed thereabout the band 18 may be dimensioned to have sufficient mass to provide desired weight and inertia the inertia for a ring such as the band 18 is directly proportional to the mass and to the square of the radius 89 thus the inertia of flywheel 10 is enhanced by providing the mass of the flywheel 10 at its rim 14 if.