Is the speed really meters per hour? 1. The front and rear wheels have the same stroke, with front wheels 15 turns and rear wheels x turns. 15(2 R)=x(2 r), 2R 15=2rx, x=50* 15/30=25 turns. 2。 Circumference is 2 r, three circles are 3(2 r), stroke = speed x time = (0.157m/60min) x1min, 2r = 0.157/(60x3x3.14) = (The diameter is so small! Kilometers per hour may be more practical, with a diameter of 278 mm)