can''t help with the Unit stuff, however i did make, from scratch, a model dragline that is hand crank powered and actually digs dirt. It is a scale model of a Northwest 95 WT dragline, with a miniature Page dragline bucket. Boom is about 9 feet long and it whole machine weighs about 400 lbs. It is mostly to accurate scale, (8.5 : 1 ) except where necessary to "leave scale"to make some part or piece of metal i had laying around work on it! I think it is pretty cool and it actually looks like a miniature Model 95, that fits in a mini van!
Perhaps i can help with other aspects of your build, or at least offer encouragement. Dave 920-210-2875