In the explanations (W.O.Davis, T.C.F.Stott) for constant angular velocity, appeal is made to a smooth belt coming off the base circle of one gear wheel and being pulled onto the base circle of the second gear wheel, and it is then said that provided the line of action between two mating teeth follows the path of the imaginary belt, then constant angular velocity will be imparted from one gear wheel to the other.
I have no dispute with that. It is a concise explanation of what is happening.
My question is this. The explanation given suggests that the velocity ratio between the two gears would be determined by the ratio of the diameters of the base circles taken with the imagined belt, but it is not, it is determined by the ratio of diameters of the pitch circles, which are bigger.
Can anybody out there solve this quandary?