Once or twice each harvest I run into a situation where a customer complains of not being able to keep broken cobs out of the grain tank even though, “I keep opening up the concave and it still busts up the cobs.”
What’s happening in that situation is that the concave is so “open” that cobs are tumbling end-for-end between the concave surface and threshing elements rather than rolling between them. That breaks the cobs into short chunks that either go out the back still carrying grain on them, or into the grain tank because the sheer volume of broken cobs overwhelms the sieves.
There are lots of other things that can contribute cobs to the grain tank, and lots of ways to correct the problem, but if you find yourself thinking to yourself, “I keep opening the concave but it just puts more cobs in the tank.” then it might be time to go against common sense and tighten the concave.
