I am making a three-wheel obstacle avoiding robot and I'm stuck at choosing motors and appropriate wheels. Robot dimensions are planned to be 18 x 10 cm, and I'm planning to put only the arduino UNO, an ultrasonic sensor and some spare space to update later on. I'm planning on going with two modified servo motors (the third wheel would be for support, and I was thinking of buying ball caster wheel for that), so I seek your help and guidance on choosing the best possible option, because I'm afraid of buying a motor, and then being unable to find appropriate wheels.
I know many of you out there dealt with same issues as I, so any help would be appreciated. Some requirements are: - wheel diameter around 5 cm, - sustainable price for both (if there is an option of motors being below $10 each), - worldwide shipping (I am located at Balkans / South-East Europe).
Thank you very much for the time and effort. Hope this topic would help others as well.