The door on the OWB is much smaller than the fire box. The door is about 16" square, but the fire box is closer 24" square and 36" long. The first row/row and half is below the bottom edge of the door. The point is, there really isn't room, elbow room, in order to get the first 16" piece all the way to the back without bumping your arms and hands on the hot door and door frame. It is actually easier to have smaller diameter, longer pieces in order to load this furnace.
The 36" length is a maximum. We usually cut them closer to 30"-32" long.
Any thoughts (and pictures) on how to build a chainsaw drive for a custom firewood processor?