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DIY grain thresher and huller

DIY pedal-power drum thresherThe last component of this year's grain experiment is equipment.  Backyard gardeners often skip growing grains because of the complicated harvesting, threshing, winnowing, and dehulling procedures.  But Home-grown Whole Grains introduced two pieces of DIY equipment that I'm putting on my honey-do list.

The first is a pedal-power drum thresher --- I've stolen the picture from the book just this once because I can't find anything like it on the internet.  Basically, a bicycle is hooked up to a utility-wire spool.  The spool is inside a collection bin of some sort and is studded with xd nails, pounded in every two to three inches.  One person pedals, which causes the drum to spin, while another person holds the grain heads against the drum.  The nails pull seeds out of the grain heads relatively quickly --- you can thresh about 40 pounds of grain in an hour with the DIY thresher.

If you're growing a grain that has difficult to remove hulls (like buckwheat), you'll be interested in Southern Exposure Seed Exchange's method of converting a hand-cranked grain mill into a DIY huller.  Basically, you temporarily replace the stationary disk on your grain mill with a rubber disk made by gluing soft rubber onto a washer.  With a bit of adjustment, your mill will be able to crack the hull on seeds without breaking the grain kernels.  I can't find any pictures of this apparatus on the internet either, but once we grow our buckwheat I'll give it a shot and post about it.

Want a simple DIY project?  Try our homemade chicken waterer, which you can build in just a few minutes.



This post is part of our Homegrown Whole Grains lunchtime series.  Read all of the entries:





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The drum is placed in line with the axis of the front wheel of the bike, implying that it drives the drum. But most bikes don't have front wheel drive. :-)

What I would do (depending on the speed you need) is either put the back wheel against the drum and lift it from the floor, or put a smaller diameter roller on the axis of the drum and have the back wheel roll on that (in the latter scenario wou'd really need two parallel rollers to support the wheel properly, just like a home trainer adapter for a road bike).

Such a home training adaptor might make a good base to build your thresher from, now that I think about it.

Comment by Roland_Smith Fri Apr 2 12:14:40 2010
I didn't even notice that, but you're right --- that picture is clearly flawed! I suspect that Mark may use an exercise bike as the base (is that what you mean by a home trainer?) He's been thinking about pedal power for a while and picked up one or two for that precise reason.
Comment by anna Fri Apr 2 12:22:31 2010
Pretty dangerous bit of kit though, now that I think about it. If the lady in the picture got her sleeve or skirt to close to the drum, the nails might snag and pull her into the nail-studded drum. Lovely, eh? Better put the drum in a solid enclosure so that your clothes cannot be caught in it. Or it should be light enough to stop instantly when something snags. But then again you might want a heavy drum so it threshes more easily.
Comment by Roland_Smith Fri Apr 2 12:24:47 2010

First you have these machines where the crank just drives a friction brake. Generally not very comfortable or well-made, as far as I can tell.

Second there is this device where you clamp the back wheel axle of a bike into supports so that it presses onto a roller that drives a brake (or a generator). These devices are generally used by racing cyclists to train in indoors on their properly set up bikes. The advantage is that you can take the bike off and use it. A device like the pedal-a-watt works this way.

Might I suggest that you look into a recumbent solution? It's much more comfortable that a standard bike saddle. Of course you don't have to buy a bike like this. Just use the crankset from an old bicycle and build a comfortable reclining seat to drive it. This way you won't get a sore bum when you spend a couple of hours threshing or charging batteries or whatever.

Just remember that the continuous power than an average person can generate is not that high... Trained racing cyclists can sustain something like 250 W for the duration of a race, say a couple of hours. I'd be surprised if the avarage joe gets half of that!

Comment by Roland_Smith Fri Apr 2 12:48:00 2010

On the safety question --- I suspect that the grain would actually be on a much longer stalk, say three or four feet. So the person holding it wouldn't really be close to the drum. That's probably a bit of artistic license to fit everything in a compact picture.

Good info about different types of bikes for pedal-power! I'm actually not sure what kind(s) Mark has. I like the DIY recumbant solution!

So far, we're hoping to use the pedal-power straight rather than turning it into electricity first. I haven't come up with many other things that can be run just by turning, though! :-) (That's one of the reasons I liked the thresher so much.) Any ideas?

Comment by anna Fri Apr 2 12:58:02 2010

Well, you could make a simple lawn mower (or a fancy one).

Or a washing machine.

Of course the best application for pedal power is a bicycle! But if you don't trust that on your local roads, what about a velocar? Or it's modern-day reincanation the utility quad ortrike?

Comment by Roland_Smith Fri Apr 2 14:34:19 2010
The washing machine's a great idea! With our wringer washer, it'd be awfully easy --- the belt is right underneath, easy to see.
Comment by anna Sun Apr 4 08:52:36 2010

Don't know if you're still looking for ideas on small scale grain threshing if so you should check out this YouTube video on grain thresher designs and winnowing.

http://www.youtube.com/watch?v=oDr8VF2QIPM

Comment by Anonymous Tue Oct 2 19:50:49 2012
Anonymous --- Thanks for sharing! We've decided to delete grains from our diet, so our experiments with threshing them went by the wayside. But I'll bet someone else will find that useful.
Comment by anna Wed Oct 3 13:04:48 2012

the drawing does imply the front wheel is intended for drive, but if you look at the bottom there is a cylinder below the crank. I believe the wheels are there for support only as it would be easier to attach the drive to the crank with a chain drive than it would to do a direct drive off the wheel.

as for safety, no it is not a safe design, but safety could be improved with the addition of protective cages around the drum and the person feeding the equipment. many innovations in farming have been about improving safety, and many farmers have been mauled and killed over the last couple centuries.

for increased safety, one might place some cages around the moving parts to keep the arms of the one feeding the grain well clear, one might also build a clamp to hold the grain stalks, but loading and unloading would make the process much slower. additionally one might look into rubber studs instead of rows of nails. these studs have been being used lately to pluck chickens, etc. in a number of commercial and diy projects. I am not sure how that would effect the efficiency of the machine, but it should improve safety a bit.

Comment by mattlew Wed Dec 26 00:11:53 2012