Stu, it could be a spindle mount and pin drive system. If this thing is real that the person or people who created it are very talented and that kind of system would be a cakewalk. Of course, if it's a model, all bets are off!
Definately a fishy picture though. Clean tires, the sand has no tracks, though they could have cleaned them up for the pic, or Harry could have cleaned them. Yup, I'm definately, almost positively, sorta, kinda, maybe, possibly, going with, ummmmmmmmm, real.........maybe.