Thursday, November 30, 2017

Threshing Machine Project

I resolved over the summer that I needed to start working on a threshing machine.   The grain coming off the homestead plot is getting bigger every year, and hand threshing is a pain.  The wheat was especially a problem, and I left a lot of seed in the straw.

My threshing machine has to conserve seed and prevent cross contamination.  These are both nearly impossible if I use the combine as a threshing machine.  The combine can almost never be clean, and small batches of threshing will be very wasteful.  Due to the size and complexity of even a small combine (or old threshing machine), there is probably 10 lbs of seed sitting inside it at any time.  The test plot may only produce five or ten pounds of one variety of wheat in one season, so the scale is just not suitable.

I looked around for something to give me a leg up in building a threshing machine, but could not find anything.  I had resolved to build one from the ground up, using these plans as a departure point.  I thought I could at least get some old rasp bars from a dead combine somewhere, and that's where I found my leg up.

It turns out that nearly every Massey combine built has separate threshing drum for tailings, which they call a re-thresher.  While most combines (and old threshing machines) route un-threshed heads back into the main threshing drums, Massey thought it would be better to make a small, axial-flow head to deal with this stream.  The re-thresher is a little strange.  It feeds from the side and discharges at the top.  I think this makes it technically an axial-flow drum.  It's a bit like a combination squirrel cage fan and threshing drum.

Anyhow, these re-threshers are very well built and it had a lot of what I wanted to get the project going.  There are good rasp bars and solid bearings.  The concave is adjustable by adding or removing spacers under the concave bars.  Although I may try to make a true concave and change the flow to ordinary threshing drum flow, for the time being I am experimenting with it as is.

Here is what the concave bars look like.  I experimented with sunflowers, wheat, and beans.  For beans I removed all the bars.  There are spacers under the bars to change the concave clearance.  The beans were still getting cracked with the bars removed and the rpm reduced to 406 rpm.  Slower rpm might help.

So there is no separator right now, just a tarp.  The re-thresher throws the beans pretty far.

I threshed 25 lbs of beans in two sessions.  It went pretty quickly.

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