Hi Guys, I'm having trouble finding the equivalent moment of inertia for a system. Basically it's a mass attached to a string, which is attached to a shaft. As the mass drops, the string unravels imparting some rotation on the shaft, this shaft rotates a small flywheel, and also rotates a second shaft via a geared system. This second shaft is attached to a second larger flywheel. I've run some experiments and determined the frictional torque of the system. However, I can't work out how to find the equivalent moment of inertia. So far I have the energy balance equation: (0.5I1w1^2 + 0.5I2w2^2 + 0.5mv^2) - T = 0.5 Ie w1^2 where w = angular velocity T = frictional torque I1, I2, and Ie are the two moments of inertia of the flywheel and the equivalent moment v is the velocity of the weight as it falls m is the mass of the weight I have the radii of the flywheels, but not the masses, and I can replace w2 with an expression for w1 using gear reduction. Any tips on how I can perhaps eliminate some variables? I can't seem to find a way of solving this, without having the masses of the flywheels.