LightningRods said:
You could order up one of these gear sets from Timberline right now. They also do complete wheel builds. I'll be working on the custom mid drive for this bike for some time but I will try to throw a standard kit on it to see how the gears do.
This setup sadly won't work on the Luna with the 4" tires. Eric wanted to stay with a standard 135mm rear hub. The final drive chain will hit the tire before accessing the lower gears. The point of the 170mm or 190mm hubs on most fat bikes is to move the sprockets out so that there is a clean shot from the BB chainwheel to the inside sprocket. On my own Luna I'm thinking about going to 2.25" Schwalbe Big Ben road tires. I'll be going fast on pavement and fat bike tires are not the hot ticket for that anyway. With 2.25" tires and narrower rims this gear set would work.
Its right i chose to go with 135mm because i wanted my bike to be compatible with all the igh on the market (back then fat bike was not popular yet)
If you want to run fat tires you have to go with an igh like a nexus 3 speed and for my bike i would recommend with roller brake (about 130 dollars on ebay) or a nexus 8 or even a rohloff. i have run nuvincis before and they also work although not my favorite (heavy and shifter is like a toy)