Grain Bin: The Final Chapter



Apologies for the slight delay here, but the grain bin has been up for a week now. This is a CMC (Custom Marketing Company) bin that is often referred to as an “18 by 5” because it is 18 feet wide and made up of 5 rings. It is between 20-30 feet tall, so that puts it just underneath the roof of the pole barn it’s next to. Why CMC? Well, for one, they have a patented “Pressure Cure” system that only uses air to dry the corn. Many operations use air and heat, or they will use air and heat to dry their corn in one bin and then move it to another bin for storage. Our bin lets us put the corn in, dry it and store it in the same place. It may seem trivial, but the less you handle your corn…the better. On top of that, we don’t have to have all of the equipment one needs to dry corn with heat (etc). The Pressure Cure system has its doubters, but the way it works is by maximizing the amount of air you can push through the corn in a particular bin. Our bin has two 7.5HP fans to blow air, which is a lot of air movement for a smaller bin like ours. The fans are so strong that if you started them without any (or enough) corn in the bin, you can blow the floor off of its supports. Even when there is enough corn in there, any ‘fines’ or smaller particulates and the thin outer shells of corn kernels (aka “bee’s wings”) are blown up and out of the ten roof vents. The air creates a drying front that starts at the bottom and then moves steadily up through the corn. Once you place corn into any bin, it is a race to dry the corn at the very top before it starts to mold. For us, we don’t have a lot of corn or a large bin, so we should be able to dry our corn in a few days. When you talk to people with huge bins though, they can take a month or longer to dry their corn. That’s with the fans running 24/7.


In the picture above, you see one of the two fans. The box with “Warning” on it houses the On/Off toggle, and it is a built in disconnect switch. The stand it is sitting on has two jacks on it that allow you to move the platform so that the fan is as close to perfectly level as possible. This is important because if your fan isn’t level it can really wear on its bearings over time and then you have a broken fan. Fans of any sort are pretty much automatically expensive, and these fans are no exception.


This is just a picture of the crew cutting holes into the bin so that the fans and their ductwork have an opening into the bin. This is all done below the drying floor, which looks like this.


Can you see all of the little openings there? These allow all of the air to move through the floor and into the corn, and they also keep corn from falling through the floor. In fact, you can dry pretty much anything with this kind of drying floor. This piece was cut out to make room for one of the unload auger’s doors. The unload auger is part of a very important piece of the bin called a Power Sweep. Here’s what it looks like.


The power sweep has an auger on top of the floor (the sweep) and an auger underneath the floor that moves the corn outside (you can see where the corn comes out in the very top photo, it’s sticking out just to the right of the door). There is a door in the center of the floor that opens up into the auger below the floor, and the auger on top of the floor slowly moves around the bin, moving corn into that door. Most of the corn is removed this way, but at the very end you open the other door and the corn on the sides is worked into that door and augered outside. It’s possible to get corn out of a bin without a power sweep, but it’s not advisable.


This picture is showing how the bin is secured to the concrete pad. After holes are drilled into the concrete at numerous points around the bin, you insert that long bolt into the hold and sledge hammer it into the pad. That bolt is called a wedge bolt because the very bottom of it will expand inside the hole when you hit it with the hammer. This makes a very secure anchor. Once it is in, you put a nut onto the bolt and tighten it down. Do it 20 more times and it’s anchored!


Here’s the main door. You can see that behind the outer cover are three inner doors that each have their own securing system. These doors remind me of being on a ship or submarine in the Navy with how many bolts and tighteners are involved. Also note that the inner doors swing inward, so even if you were an idiot you couldn’t open those doors if there was corn behind them. If you were to stick your head inside this door and look up and to the left, you would see the inner ladder that allows one to climb down into the bin. There is a portal on the roof of the bin where you can climb up the outside ladder and then into the bin.

Anyway, what am I forgetting? This bin has an opening in the very top of the roof for loading corn into the bin. Some bins have portals that allow you to load from the side of the roof, but that’s not ideal as you then have to spread the corn. We may have to do some spreading, but by center loading the corn it will pour in like sand in an hourglass. How do you get the corn up there? Another auger, but this one is nearly 60 feet long. Our bin requires a minimum length of 45 feet so that the auger will reach the hole at the top of the bin. As corn is harvested by the combine, the combine holds the shelled corn in its own tank(s). When it is full, the combine swing an auger of its own out and over a gravity box and unloads the corn into that. It will likely take a couple of gravity boxes–so called because their contents are unloaded via gravity. You then take those gravity boxes over to the 60 foot auger that has been pre-positioned for unloading into the bin. The corn then slides out of the gravity boxes, into the auger’s ‘mouth’ and then augered up and into the bin. There are other methods one can follow, but this gives you the basic idea.

Now, all we have to do is connect the electrical to the main panel, test everything, put on some final touches (i.e. seal anything we can find where water might find its way in), hire a combine and wait for good weather for harvesting…though this cold is pretty nice because it’s keeping the fields frozen and not mucky. We’ll see how it goes. So far, so good. Any questions? 🙂