Search:

Notwithstanding Robin's thoughts, all valid, lets follow the stepper approach through...

ok... some basic physics... 4"dia wheel = 4*pi = 12.56" circumference, so 0.5ips = .5/12.56 = .04revs/sec...

If it is battery powered then a stepper is a poor choice. An ordinary electric motor will take a big swallow of power to get you up to speed, draw peanuts to hold speed, draw nothing to slow you down...