Hi, first sorry for my bad English, I am more skilled to read than to write in English I don't know if this is the right section for this topic. The problem is described in the title of the topic. My guess is that each of the two wheels goes on with circular trajectory around a same center. There isn't skidding of the wheels. If the distance between the wheel is D, the speed of the slowest wheel is v1 and the speed of the other wheel is v2 (v1 and v2 is the linear speed), then: R1=v1*d/(v2-v1) is the distance between the centre and the slowest wheel, and of course the distance between the centre and the other wheel is R2=v1*D/(v2-v1)+D=v2*D/(v2-v1) is my guess correct? My guess is based on time that each wheel needs to do the circle, and this time needs to be equal for the two wheel. It seems to be correct, if one wheel is stopped (for example v1=0) the other does a circle around it, infact for the above formulas: R1=0 R2=D if the speed of the two wheel are the same R1->inf R2->inf There is someone that knows an other demonstration more rigorous of this? I attended a mechanical course some year ago, with euler's formula, lagrange and other but I don't remember much and I don't know how to determine the trajectory of a rigid body with two point with different speed. A special thank to anyone that will help me.