Here is a pedal-powered crane I made for Redmoon Theater. Most of the parts came from Northern Tool's ATV supplies: The wheels & stub axles, with the front axle being their go-kart axle with differential. This vehicle is front-wheel-drive, rear-steer.
My friend Pickles made the armature. I don't know who added the sound system for this particular show.
I geared it way down because the original designs called for it to carry about 800 lbs. Theoretically you could add another set of pedals for the passenger. See also the steering chain.
I had to fabricate my own stub axle brackets.