I don't think I would pay someone professional to teach my dogs to do something they don't want to do. They're dogs, not robots. And yes, I know many people have no trouble getting their dogs to run on a carpet mill. But I'm not going to force mine to do it if they don't want to.
I doubt anyone here can help you with pictures of the roller mechanism of a carpet mill. They only place you're likely to find that is on a pit bull message board since that is the main breed that carpet mills are used for.