This Design was created by Ronon_Dex first using creative then rebuilt in our survival world.
I have full permission to Post this schematic from Ronon_Dex.
It has three chest minecarts which run in a loop while the lever's are switched on.
While looking at the furnace from the open door to the stairs the minecart chest on left is FUEL
the two minecart chests on the right are items to SMELT.
The Last image shows the Rails do no paste in correctly and will need to be fixed using creative to no allow rails to drop into hoppers.