I was asked to build an experimental setup for one of my friends and I did it successfully. The setup included two eccentric flywheels, spinning in opposite directions on the shafts of two stepper motors that were facing each other. I 3D printed a pair of identical eccentric flywheels and pressed them on the shafts of the stepper motors. Those eccentric flywheels generated oscillations that cancelled each other out at some angles. I became obsessed with a problem that I cannot solve. I want to make sure that the eccentrics are causing oscillations on the same plane so no rotational vibrations are created. At least I want the system to approach that state. See illustration: I know that making one big eccentric flywheel with a counterweight wrap itself around the smaller one is the solution. It will involve a lot of calculus. I am not even sure in what plane I need to integrate my even density eccentrics. The ability of each eccentric flywheel to create oscillations of the device frame should be equal over a wide range of speeds. (RPMs) Each eccentric needs to create the same set of forces against the bearings of the motors at the same angles. The only problem is that if they were made identical, they would collide on their paths. So one eccentric flywheel mass has to wrap around the other and use a counterweight to compensate for a greater diameter. I am not very sure how to describe the problem even. Being obsessive-compulsive I tried to solve this problem in several ways but I cannot clearly define all the variables. My pair of counter rotating flywheels needs to have equal characteristics over a wide range of rotation speeds, while creating a maximum amount of oscillation forces along the center line of the device. Thank you.