Grain bikes: Human-powered seed processing tools for small farms

2016 Annual Report for ONE16-277

Project Type: Partnership
Funds awarded in 2016: $13,734.00
Projected End Date: 12/31/2017
Region: Northeast
State: Massachusetts
Project Leader:
Jan Yoder

Grain bikes: Human-powered seed processing tools for small farms


The goal of the Grain Bikes project is to complete the following: *Prototyping 5 working machines for the processing of grain and seeds:

1. Thresher

2. Fanning Mill/Winnower

3. De-huller/Flour mill

4. Seed Fractionator

5. Bicycle PTO *Create 3-D computer models of the prototypes and render step by step instructions for building the machines. *Upload the plans for free download to *create and post two short videos, one showing the operations of the machines, and one showing some of the construction details.

To date the prototyping is complete. The plans for the Thresher and Fanning Mill/Winnower are uploaded to , with the following links:

Also, there is an introduction to the whole project:

The plans for the De-huller/Flour Mill are about half way done and we hope to upload them Dec. 16, along with the plans for the bike PTO. The short videos are getting edited, and should be uploaded by Dec16 as well. Finally, the Seed Fractionator was prototyped and works well; complete plans for building it were already posted to the web by someone else: I have built a unit from these plans and both the plans and the device work well. There is already an explanatory video at:

Objectives/Performance Targets

1. The Thresher: I was able to build two threshers in the time since the project started, one for the purposes of prototyping, and one for a farm. The design was re-worked to use standard finished lumber (more universal than rough-sawn), I tried some new ways to attach swipples to hooks in order to make the swipples faster to change, and experimented with a few different swipple designs. After several different farmers used the machine, the simplest, cheapest, and most traditional swipple, a piece hardwood on a short swiveling link, is the most popular.

I made the scalping screen removable so different screens can be used. This is crucial because using the smallest scalping screen possible on the thresher helps the fanning mill work better. I re-designed the barrel so it does not have a enclosed hollow space where the ramp is on the drive side. This is helpful because the enclosed space only encourages rodents and rot. I experimented with using a bicycle chain drive instead of a v-belt and concluded that for this tool a v-belt is better, as it will slip if the shaft jams and thereby protect the rest of the machine (and the operator’s knees). The current cost of all the parts to construct the thresher is right about $150, assuming that used low quality bicycle parts are obtained free.

2. The Fanning Mill/Winnower. I built one screen box and three blowers and transmissions for this machine. Despite engineering a smaller blower that worked well, in the end the larger, slower turning blower has several advantages, and so, it is the blower I settled on for the final design. As a particular example of an advantage of the larger blower I did not anticipate, the larger/slower blower allows the blower transmission to be less well aligned and less precisely built, a big advantage for the DIY farmer/builder or small shop. Also, the smaller blower did not save much money in materials, and probably added labor time. I was however, able to lower the cumbersome height of the machine by orienting the blower differently. This makes it possible for one person to operate the machine alone.

I also experimented with making/buying screens for the Fanning Mill. This is crucial because commercial seed screens (such as the Clipper screens, which are mostly slotted sheet metal) are expensive (~$200 each, whereas ALL the materials for the Fanning Mill cost ~$275!). The screens are very sensitive to the crop. Some crops are happy with a $2 piece of mesh from the hardware store. Some crops foul screen with bits of fiber. Sometimes the crop variety or the growing conditions affect this performance!

My intern, Josephine D’Urso, and volunteer, Kenneth Ferro, designed and built a beautifully simple tipping bucket that allows a single operator to control the feed rate of the crop material onto the top screen, while providing the power (pedaling the bike!).  I added gears to the blower transmission. The whole transmission system gets lots of gears from the scavenged bike parts. The gears allow fine tuning of the machine for different crops. The operator can see the winnowing tower output and pedal faster or slower as a final adjustment.

3. The De-Huller/Flour Mill. I originally planned to produce instructions for adapting an existing flour mill to bike power and de-hulling. What I discovered is that inexpensive mills (Corona, La Victoria) are too poorly built and have too small a diameter for de-hulling, while expensive hand cranked mills are too expensive and still use too small a diameter burr for de-hulling. SO, I changed the plan and designed and built a mill that can be bike powered (or electric or hand cranked) and is efficient and good for both de-hulling and flour milling.

The mill is more work to build, but not that difficult to make and cheap. The materials cost $125. Once the pieces are cut out the fabrication (welding) time is only 5 hours. For a farmer/garage builder this project would be a small challenge (depending on the tools available). For a small metal-fab or machine shop this would be easy. I built two prototypes of the mill. I built several different de-hulling discs, with the goal of eliminating the use of latex rubber (too expensive, hard to glue to anything). I found ordinary 100% silicone caulk (available for $5 at any hardware store) to work very well. It also sticks nicely to a substrate of either plywood or metal, thus eliminating the need for fancy glue. The MSDS for this material finds no toxicity, and, furthermore, since the de-hulled grain is winnowed after de-hulling, any particles of rubber in the de-huller output get removed in the final pass through the Fanning Mill. I also experimented with converting the mill to a flour mill by making steel burrs. They worked well and will be part of the documentation, however, buying commercial steel or stone burrs and making sure they can be mounted on the mill will be a better option for most farms.

4. Seed Fractionator: As I mentioned in the introduction, my original proposal to document such a device was preempted when the complete plans were uploaded to the web (link above in intro). This is “a high quality problem”. I used the plans to build and test a unit and it worked well. Any farm investigating the small scale production of seed for sale can easily and quickly build this device.

5. Bike PTO. I set out to answer the question of whether a single bike with appropriate gears and flywheel could be used to power all of the machines. A bike PTO has two advantages over an old excercycle: First, a bike has a better (more efficient and comfortable) power position and better (more efficient) components. Second, a bike has good gears. Many places in the world bicycles are available but not exercycles.

I built three bike PTOs. All three used the “standard bike” upright pedal position (recumbent, or sitting down, has been investigated by others). All three allowed the rider to face the work. By sitting upright and facing the work the rider can use their hands to add grain or crop material to the machine, and by facing the work the rider can stop pedaling if someone’s hand or hair gets caught in the machine. Two of the bike PTOs used a standard bike with angle iron (old bed frames) welded to it to allow the front mounting of the rear wheel/flywheel. One of the bike PTOs used only bikes and bike frames to accomplish the same thing. It is this one that I chose to draw and submit to the plans, as it makes the best use of discarded bicycles. The bike PTOs all worked well. However, in testing we found (farmer’s found) that for most of the machines the old exercycles were preferred, and moving a single bike from machine to machine was onerous.

Therefore for the thresher and fanning mill I recommend a regular old exercycle as the power unit, and for the de-huller/flour mill I recommend a more complicated bike PTO because with that machine efficiency and gears are a benefit (grinding flour takes more power).

6. The computer drawings and plans are excellent. Emily, as usual, does more than expected, tries harder than anyone else, and takes her work as seriously as if she were engineering a nuclear submarine. Whereas simply blueprints or cad-files might have sufficed, Emily produced beautiful step-by-step instructions with clear illustrations and an organizational structure that will help DIY builders and shops use and follow the plans. Line weight, shading, color, continuity, and presentation were all scrutinized by Emily. In addition, as “builder zero” Emily cross-examined my descriptions of parts and processes, which led to many revisions aimed at explaining things to potential builders who don’t already live inside my head. Like all plans, like all communications, there have to be assumptions made about the level of skill and prior knowledge of the reader/user. Thanks to Emily, we were able to reduce these assumptions to a minimum.

7. The videos are almost ready to post. I haven’t looked at them, though I was able to review footage as it was shot. Olaf has taken extra unpaid time to extensively edit the footage down to short videos packed with useful information. As I now understand it, there will be three videos instead of two. Two will be operational, the first more or less a video-introduction to the Grain Bikes and how they work—an ad for farmers. The second is just a compendium of the grains we have so far tested the machines on—what we know works. The third is a construction detail tour for the potential builder. Hopefully all three will inspire and help potential users of the machines.


Proposal: Construction and testing of the next generation of prototypes will occur between 2/15/2016 and 6/30/2016. [[This occurred, with a few deviatios from the plan: First, instead of converting an existing hand-cranked mill to a de-huller, I designed and built a mill from the ground up. Second, the seed Fractionator plans were uploaded by someone else. And third, I spent more time and energy on the Fanning Mill (see the blower saga from above) than I anticipated.]]

Proposal: Emily and I will prepare a posting for Farmhack ( that describes the machines, how they work, how much they cost to build, and what tools and skills are required to construct them. That way farms interested can plan to plant crops in the Spring they may use the machines to process the following Fall and Winter. The posting, uploaded 3/2016 will promise complete plans by the end of October, 2016. [[This occurred on Farmhack]] Between 3/2016 and 8/2016, Emily and I will make the 3-D models and produce the instructions. Also between 3/2016 and 8/2016 Olaf will shoot video of the machines under construction, and in operation. Once the instructions are complete Olaf will use them to edit video so that the details covered in the instructions are supported by the video content. [[The 3-D drawings and raw footage for the videos were done on schedule, however, rendering the plans and editing the video is taking longer than expected. Much of this delay is not the result of a bad forecast of how much time it would take, but rather the result of scheduling difficulties. We are still on track to provide the plans in time for farmers to potentially use them for 2016 harvests]]

Proposal: The plans and accompanying video will be uploaded to Farmhack ( on or before 10/31/2016. The plans will be free and “open source”. [[As linked to above, the plans for the thresher and fanning mill are up on time, and the de-huller plans and bike PTO plans should follow shortly. One farm is already using a thresher, with reportedly good results.]]

Impacts and Contributions/Outcomes

The effort required to get one thing to work, whether it be a 30 watt machine for cleaning seeds, or a 400 horsepower diesel engine, always amazes me. It remains to be seen whether farmers build and use these machines. It’s possible that interest in growing grain in New England will just fizzle out and die. It’s also possible that so much capital will be available to New England farmers in the near future that they can just buy large scale grain processing equipment and skip the baby steps. So the impact of this project stands to be seen. One thing is certain: I have already watched many children and adults gaze in wonder at their dinner sliding down the screens of the Fanning mill and pouring out the chute in to a basket, ready to cook. My 4 year old daughter kneels by the thresher for twenty minutes at a time bathing her outstretched hands in the stream of wheat and chaff raining down from the whirring maelstrom of activity in the barrel above. Where else can a child safely explore agricultural machinery? Whatever the impracticality of processing grain at this scale, whatever the impracticality of growing grain in New England, people LOVE the Grain Bikes. If a sustainable regional food system requires enthusiastic people as its foundation, the Grain Bikes are already winning hearts and minds.


Emily Vogler
Landscape Architect
R.I.S.D. , Woodmetalcanvas
98 Reed Rd.
Westport, Massachusetts 02790
United States
Office Phone: 5088176573
Olaf Bertram-Nothnagel
Tumblehome Even, LLC
3 Jean Dr
Old Lyme, CT 06371-1514