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Subsistence farmers in Guatemala leave corn on the stalks in their fields until it dries, then they shell it by hand, picking off the kernels with their fingers to grind into corn flour. Shelling tools make the work much faster, but commercial ones made of aluminum or resin can cost too much for a poor family.

On a work trip to a Guatemalan town with Engineers Without Borders - USA, Larry Bentley invented a sheller made from used cans and cement. It's cheaper than store-bought shellers, and it's made from materials that anyone in the town can get their hands on.

Bentley shared his notes and photos with us and we posted a how-to guide on our site. Now, we'd like to share Bentley's corn sheller with Instructables.

What you'll need:
  • Metal cans
  • Can opener
  • Needle-nosed pliers
  • Cement
  • Sand

Photo credits:
All corn sheller photos by Larry Bentley
Corn stalks overlooking Lago d'Atitlan in Guatemala by IMs BILDARKIV / Flickr

Step 1: Step One: Two Cans

Start with two used cans. One should be slightly smaller than the other to fit inside. 

Using the can opener, cut out the bottoms of both cans so that they are open at both ends.

Step 2: Step Two: Make the Teeth

Using the needle-nosed pliers, bend the sides of the smaller can in to make fins all around one of the can's openings. Make six fins shaped like a "V."

Pro tip:
The fins should protrude enough to fit the corn cobs that you want to shell. Corn varies in size, so you might want to make several shellers with different-sized fins and openings.

Step 3: Step Three: Finished?

Your smaller can should look something like this. 

Pro tip:
This actually works as a sheller as is. In tests, though, Bentley found that a single can breaks and doesn't last very long. For a more durable tool, move on to Step four!

Step 4: Step Four: Cement and Finished!

Put the smaller can inside the larger can. Try to round out the end of the smaller can that you didn't bend. 

Fill the gap between the two cans with cement and sand. When it dries, you're finished!


Step 5: Side-by-side Sheller Comparison

These two photos show top and bottom views of DIY shellers and a commercial one. Clockwise from the left, the commercial aluminum sheller, a single-can DIY sheller, a double-can-and-cement DIY sheller (from this Instructable), and a sheller experiment that Bentley made from a PVC cap.

The PVC sheller didn't work as well. The teeth flexed too much. But it might work better with supports glued under the teeth. Something for another project!
Wonderful! I've been grinding my own flour for a while and wanted to try corn meal, but can't afford a sheller. Thanks so much for posting this.
Damn, this sounds nifty! Now I gotta find out how the actual corn-shelling works... <br>

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Bio: E4C&rsquo;s mission is to improve the lives of underserved communities by better preparing the global development workforce, optimizing the solutions development cycle, and ensuring ... More »
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