Thursday, April 7, 2011

Coal Bin Design

Yesterday I drove my pickup to the coal mine and returned with a ton of stoker coal. My assistant scooped it into the coal bin on the north porch and we're set for several months. I'm hoping it will last six months so I'll be on a convenient April and October refill schedule.

When I switched from buying bagged coal to buying loose coal it required the construction of a new coal storage space. I measured my pickup bed dimensions and calculated it would easily accommodate 45 cubic feet of coal. I looked up the density of coal and picked an average figure of about 50 pounds/cubic foot. So that figures out to be 2250 pounds - a bit over a ton.

I chose the location for the bin on the porch just outside the door to the forge room and checked to see how the pickup would line up for unloading.

I did some calculations to see what dimensions would best fit the porch space and hold at least one ton. The final decision was to make it 8' long, 4' wide and 2' deep just for ease of construction (64 cubic feet). I designed an angle iron base frame to raise the bin up 16" so I could continue to use the space underneath and also be able to place a 5 gallon bucket under the chute opening for easy gravity fill.

I cut the pieces of 5/8" treated plywood and screwed the wood together with drywall screws. Then I cut and welded the simple base frame. Finally, I forged and fabricated four strap hinges for the lid. There are undoubtably more clever and artistic ways to accomplish this but I am quite satisfied with the utility as constructed. It's easy to load, easy to empty 5 gallons at a time and only 15 feet from the forge. I made a couple of special rakes so as the bin is worked toward empty I can reach in and pull more coal toward the chute door.

I looked it up and found the angle of repose for my size coal to be about 40Âș but once armed with that number I still couldn't figure out any way to use it. Sometimes I just need to know what time it is, not how to build a clock.

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