Scale modeling is the ultimate hobby if you like big machines but don't have the place for them at home!
John Deere 7930 with duals
By making one of my 7930's a "donor", I got dual wheels for another one. Instead of just using the original wheels on a longer wheel axle I wanted it to look more like the real thing (at least how it usually looks here in Sweden). It did take some time to lathe the rims and make all the hooks, but I think it paid off quite well in the end.