OK I'm super frustrated.. I spent 50min typing the whole text here earlier and click preview only to be told I was logged out. Click back and and all was gone. Damn.. Ok here's the question, AGAIN. Weight: 1kg Type: Flywheel, OD is 80mm, ID is 40mm if that matters. So that's a typical Ring calculation? Torque, T = Moment of Inertial, I * Angular Acceleration, α HP = N * T/5252 MOI, I, depends on Ring or Solid Solid cylinder = (1/2)*m*R2 Hollow cylinder = m*R2 So if this is ring, then I = 1kg * 0.08 * 0.08 = 0.0064 Angular Acceleration, α (rad/s2): dω / dt = αT/ r. ω is the angular velocity αT is the linear tangential acceleration. r is the radius Simpler term, one radian (rad) is one revolution, i.e 2∏ So if the unit is rad/s2 is essentially how many rad in a squared-second? If it is true, t being 8000rpm or 133.333 rev/sec. In square sec, divide further by 60. Therefore, 133.333/60 = 2.222 rad/s2 Torque, T = 0.0064 * 2.222 = 0.0142 (Nm?) So HP = 8000 * 0.0142 / 5252 = 0.02166 hp? Doesn't look right! Appreciate any enlightenment please. Thank you..