So my 7 year old saw a utube video of a kid that built a cart out of junk he collected up and wanted to know if we could do that. So far I have a rear ended with differential from an old lawn mower tractor that has a 60 tooth drive gear, the front end steering from same mower and a 3hp Briggs sitting on an old reel mower. I may have enough metal pices around to build up a frame, but I think most of what I have is to big, might need to find some smaller lighter material using the 3hp. At first I was thinking about leaving the front end of the lawn tractor as it is and just mount frame to pivot point similar to the way is was, but now am think I might cut it apart an weld to side of frame. One question I have found an answer to is about the proper chain size for the gear, I measured the teeth at 1/2 in tip to tip, so I know it's not a #35, but how do I figure out which it is 40, 41, or 420, the gear is 3/16 wide.