1. The problem statement, all variables and given/known data Not really a HW problem (no diagram), I just need to figure out this number for a design. I have an axle with two crank arms attached to either end, pointing in opposite directions. The entire thing will spin. I need to find the equivalent moment of inertia of the axle with these cranks attached, but I'm confused over what method i should use. Classes never really go deeper with MOI than an I-beam problem or just looking up bh^3/12, etc. I have all of the specifications of the lengths of axle, cranks, diameters, etc. So should I try: A) Using the geometry of the part(s) to find I B) Analyze the part more to find the work and angular velocity so I can find MOI With method A) i thought I could just use an s-beam geometry to find it: http://www.efunda.com/DesignStandards/beams/RectangularSBeam.cfm the numbers seem to make sense when I did it, but for some reason this seems really wrong since the axle is a "horizontal" s-beam so to speak. (The axle is parallel with the ground) Would the Iyc value in the link above be justified here? Or do I need to start looking at method B? Any help is greatly appreciated.