<Li> The speed ratios of chain and belt drives are computed in the same way as gear ratios . See bicycle gearing . </Li> <P> Gear teeth are designed so the number of teeth on a gear is proportional to the radius of its pitch circle, and so the pitch circles of meshing gears roll on each other without slipping . The speed ratio for a pair of meshing gears can be computed from ratio of the radii of the pitch circles and the ratio of the number of teeth on each gear . </P> <P> The velocity v of the point of contact on the pitch circles is the same on both gears, and is given by </P> <Dl> <Dd> v = r A ω A = r B ω B, (\ displaystyle v = r_ (A) \ omega _ (A) = r_ (B) \ omega _ (B), \!) </Dd> </Dl>

Where was the gear train used for the first time