09/02/2009: "Threshing Fava Beans"
A couple of weeks ago when I was down at the farm I happened to notice that the fava beans were looking ready to harvest; the pods had turned dark, and many of the leaves had dropped. Although I had planned to work on threshing the wheat that day, I switched gears and started stacking fava bean plants in a pile on a tarp; this was necessary because fava beans, like many legumes, are biologically programmed to explode when the pod is ripe. At a certain point you can't disturb the plant at all without having the pods explode in little mini-showers of dried beans! So, getting the plants onto the tarp at least meant that they could continue drying until I had time to deal with them, and any pods that opened would have the tarp under them to catch the beans.
Although the fava patch didn't get much attention past April or so, it had gotten some crucial weeding early in the year. This meant that the bindweed didn't smother it too badly. When I gathered the plants from the patch I concentrated on the 60% of the patch that was not choked with bindweed, and managed to amass a pile of plants that covered a 5' x 8' tarp to a height of four feet or so.
Last week I decided that we had done all the wheat that we were going to do, and it was time to thresh the beans. Naturally, I wanted to use the thresher. I had purchased an alternate set of threshing bars from Colombini and Son for the purpose of threshing beans, but when I began disassembling the thresher to install the alternate bars I found a problem: the wheat threshing bars were slightly undersized, while the bean threshing bars are slightly oversized in length. When the undersized wheat bars were put on at the factory they pulled the ends of the awner drum in, as shown in the photo below; the bean threshing bars were too long to be fit.
I haven't made up my mind yet on how to deal with the issue of getting the bean threshing bars on the thresher. One obvious possibility is to reduce the length of the bean bars to match the wheat bars; another is to press the drum apart enough to install the bean bars, and then use washers as spacers on the wheat bars. I think that I'll ask the Colombini folks for advice before making any changes.
In the meantime, however, I had beans to thresh. I found that if I opened up the awner to the maximum clearance with the wheat threshing bars installed, I could thresh the fava beans successfully. A few of the beans got chipped, and there were probably more pods in the output than there might have been otherwise, but it still worked pretty well. Lou and I also did some experiments with hand threshing of the fava beans; if you have an empty 55 gallon drum you can stick the a handful of stalks into the drum and beat them against the sides to release the beans. It's noisy, but it works well. My biggest problem with the machine threshing process was that it was difficult to get rid of dirt granules that had been knocked off the roots in the threshing process; the granules tended to be roughly the same density as the beans, so the threshing process did not separate them. I eventually found that I could get rid of 90% of the dirt with a small screen that let the dirt fall through but kept the beans on top of the screen.
I ended up with about 12 gallons of threshed fava beans from the patch. I consider that pretty good, since I had planted probably less than a half gallon of seed - eight pounds.