Circumference Radius 3 cm Circumference = 2 π r = 19 cm Circumference = 2 π r = 38 cm For each turn of the wheel your car travels the circumference of the drive wheel Doubling wheel radius also doubles circumference which will make your car go twice as far in one rotation Radius 6 cm
So why not use really big wheels?! Because the motor performs best at a certain speed! Suggestion: 1.Pick a wheel size that you like. 2.Experiment with different gears and gear ratios to find the best for your car. The best gear ratio will depend on the suns intensity and whether youre running on batteries.
Lessons learned at PSU In full sun So if your wheel r = 6 cm, then the best GR is GR = 6 cm x 1.14/cm = 6.8 In half sun With batteries
Getting the most power output from a PV panel Tilt towards sun Possibly increase solar input with reflectors