This is coal vac Part Deux! All engineering credit goes to the powerful Wiz. His post a few weeks back showing his coal vac system using a shop vac inspired me to do the same.
The barrel I used is a poly 15 gallon barrel originally used for laundry detergent at a hospital. I did the same as Wiz, using a toilet flange screwed to the bottom with 3" PVC angled to the hopper on the stoker. I put an extra gate from my dust collection system in the shop on the 3" to close it off while running the vac. The coal stops feeding automatically when the coal in the hopper gets to that level.
I have the barrel sitting on a suspended frame of 2x4's hanging from the floor joists above. The barrel is translucent enough that you can see the coal as it fills up. That may change as the coal blackens the inside over time.
The top of the barrel had a 2" threaded female connection formed into it and a 2" threaded male PVC connector fit perfect. I connected two 90*'s to this threaded fitting and a 45* and taped the shop vac hose to that end.
For the other side I used a 2" street 45* and drilled the hole just big enough so the non-flange side fits into the barrel. The flange side catches on the hole and sits on the top of the barrel. A couple 45*'s heads it the right direction. For now I just have another 2" shop vac hose connected to it so I can suck the coal from the buckets I currently use.
The plan for next heating season is to have a coal bin sitting just on the other side of the basement window and run 2" pvc through a plywood "pane" into the bottom of the coal bin. I think the coal will flow much better with smooth 2" pvc rather than the corrugated shop vac hose. Also helping flow is that it will not have to go up like it does now.