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

Final 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
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Project Information


The Grain Bikes Project created prototypes, plans, and videos for 5 different machines for processing small amounts of seed crops like dry beans, wheat, rice, rye, emmer, and einkorn. The plans allow a farmer or fabricator with limited tools to make a thresher, fanning mill, dehuller/flour mill, and seed fractionator, as well as a bicycle powered PTO to power the first three of the four machines. Depending on the processor, they can process one half to 10 pounds of grain or bean per minute.  The cost per machine can reach $200, depending on parts purchased or obtained from discarded bicycles.  The project creates a low-cost pathway to mechanized grain and bean processing for small farms in New England.


In 2014 I was asked by Bill Braun to design and build bicycle powered seed processing equipment. I had recently repaired an antique commercial fanning mill for a farm and was impressed by the high price of fanning mills and the difficulty of finding small ones. At the same time, several local small farms were experimenting with adding dry beans, corn, rice, and wheat to their offerings. They were finding markets at acceptable prices ($3.50 /lb) but the processing speed (ie sorting beans by hand at 3 lbs per hour!) was ridiculous. The only option for cleaning up 50 lbs of wheat was to get lucky and find an antique fanning mill. And there was no way to dehull brown rice.

So, working closely with Bill Braun (Ivory Silo Farm), Skinnydip Farm, and Chris Yoder (Vanguarden CSA), I designed and built prototypes of a bike powered thresher, fanning mill, and dehuller/flour mill. In addition, I designed a seed fractionator (separates small samples of seed by density for germination tests), and honed the design of a bicycle PTO for powering the machines.

Making use of recycled bicycles for bearings, transmissions, and gears, and wood for most other parts, I was able to keep the cost of purchased materials low. For small farms with access to a shop, a maker space, or a local small fabricator, this is an excellent opportunity to experiment with grain and beans, or producing seeds, without having to commit much capital.

Project Objectives:

Once the initial prototypes proved the idea, there remained several objectives:

*Improve the performance of the machines

*Lower the cost of materials by ~30%

*make step-by-step plans to guide people building the machines

*make accompanying video to promote and support their construction

Here is an in-depth look at each objective:


The thresher generally makes between ½ #/min (rice, wheat, some beans) to 1 #/min (rye, wheat, most beans), or even a little more with certain beans.

The fanning mill easily exceeds 1#/min for all crops we tested. 5 or 10#/min is normal for most beans. Some crops, however, will require multiple passes. For example, rice usually takes one pass before dehulling and then a second pass after dehulling. In a test of rye, processing just 10 lbs took less than 10 minutes even including set-up time. The fanning mill was designed to be highly adaptable to different possible uses. We did not have the opportunity to use it for all its possible uses. For example, grading seed (separating large seeds from small ones, or one type of seed from another) and cleaning small light seed (such as amaranth) remain unproven. The big expense and difficulty of the fanning mill is obtaining the exact right size screens for each crop. Screen selection is tricky. The presence of something seemingly insignificant, such as the awn on a rice grain, can make a screen not work properly. I hope that if farms build and use the fanning mill for certain crops, they are willing to share on Farmhack what screens work and don’t work for various crops.

The dehuller now handles rice at only .5#/min. And depending on the variation in grain size, often requires two passes to get the rice dehulled completely. However, in just a couple of iterations I was able to increase the throughput several times, so I’m confident that greater productivity can be achieved with no increase in cost.

The seed fractionator is not my design. During the course of the project the design was made available by a seed company in England. I built a prototype (powered by an electric vacuum) and it works fine. It is really specifically for grading seed for germination tests, so only applies to farms which intend to sell seed .

The bicycle PTO is a useful way of using bicycle and excercycle parts to make a power unit that can be used for all the grain bikes as well as other bicycle powered machines. I explored two possible designs. One uses only bicycle parts, the other uses angle iron from an old bed frame. Both use the upright (rather than recumbant) rider position, both use a flywheel, both use gears, and in both designs the rider faces the work. Excellent as they are, the extra materials and time may not be worth it compared to just using a scavenged excercycle with few alterations. One exception is for farms which want to use a bike powered flour mill at the farmer’s market to let customers grind their own fresh flour. In this case the extra power demands of making flour and the variety of levels of ability of customers requires a bicycle PTO with gears and a good flywheel.


The price of the materials to build each machine, excluding scavenged bike parts, is now well under $200. In one build of a thresher I spent $148.75. In a build of a fanning mill I spent $145. While some of the materials were scavenged, much the lumber was bought at a premium from a local mill. The cost of the metal parts for the dehuller come to around $125 for one unit and less if multiple units are made at once. The seed fractionator is so cheap to build (excluding the vacuum to power it) that I didn’t bother to account for the ~$5 in materials used. It’s easy to imagine a determined farmer scavenging all the lumber and some of the metal to make these machines, lowering the price of materials even farther.

That being said, the labor cost of making these machines on a one-off basis are considerable. In one thresher build I spent 21 hours of labor, and building a fanning mill took me 39 hours. Building a mill is somewhere around 30 hours of labor, and the seed fractionator comes in at about 6 hours of labor. The step-by-step plans make it possible for the labor to be divided into smaller parts so that the machines can be built with “spare time” at night or on consecutive weekends.

In addition to the labor, the machines need to be stored under a roof in a dry location protected from rodents, which adds expense. However, because the machines (like so much farm capital) only get used once or twice a year, they can be stored in a compact form and set up for operation when needed.


The plans Emily Vogler created for the grain bikes are fantastic. I have often lamented how lifeless blueprints are. Blueprints make it possible for the trained engineer to build or imagine an object with no possibility for error or interpretation. That’s often good. However, the grain bikes are “design platforms” in the sense that as each farm’s needs are unique and resources are different, each builder will modify and adapt the design to suit their situation. For example, a farm planning to dehull a ton of rice per year will modify the dehuller to use a steel bed plate (for durability) and an electric motor for power. Emily’s plans, instead of being blueprints or cad files for a 3-d printer, are human oriented. They are sequential, step-by-step instructions with an easy to follow progression across the page. When I used the plans to build a fanning mill I filled the pages with my own notes, added dimensions as needed, modified the plans with a red pencil to account for small changes I made, and kept track of my labor and expenses for each step right on the page for that step. What a pleasure compared to reading a blueprint! In addition to breaking down the construction into a sequence of steps, each step is organized by construction type (bicycle work, metal work, wood work), so a prospective builder can organize their build plan accordingly.

Unlike some DIY plans, these plans do not include a cut list or materials list. This is because each builders lists will surely differ depending on their needs and resources. By going through the whole plan and making their own materials and cut lists, the builder can fully understand the build process before starting. I feel this is better than mindlessly following a “recipe”.


The original plan was to make one video showing how the machines worked, and one video showing how they are built. It became clear that the second video would be too long, so we decided to make one video showing how the machines worked and promoting them, and one video construction tour of each machine. The fanning mill, for example, requires a long video tour, while the seed fractionator, doesn’t need one.

The videos accomplish several things. First, few people read detailed plans unless they are seriously considering building something. So the videos play a promotional role, allowing word to spread that the plans are available without burdening people with hours of study. One benefit of the promotional role of the videos is that they can be used to gauge interest in the designs. For example, as of this writing 723 views of the introductory video have occurred, while only 139 views of the dehuller construction tour have occurred. From this a tentative conclusion can be drawn that 80% of the interest so far does not go beyond amusement. That 20% appears to go beyond amusement is highly encouraging. In addition to the promotional role, the videos go further than the plans in bringing the machines to life. Instead of “five pounds of product per minute”, a farmer sees clean black beans pouring out of a chute and says, “Hey! Those are black turtle beans, I grow those, they are delicious, and I hate sorting them by hand!” Also, while the 2-D plans can be intimidating to the prospective builder because in the computer all cuts are perfectly square and all welds are seamless, in the videos a builder can plainly see that these machines can be built by amateurs with inadequate tools. Sheet metal was not bent on a brake, but rather with a pair of pliers, and most parts are not made more accurately than the width of a sharpie line. Chains do not align with sprockets, and belts are irregular and slack. This should encourage amateur builders.

One problem with the video arose from our ideological commitment to cinema verite. All of the footage was shot documentary style at actual events where we were building or using the machines. This effort to present “real life” to the viewer is laudable, but made the editing take too long. In the future we would choose to script each video and shoot it scene by scene.


Click linked name(s) to expand
  • Olaf Bertram-Nothnagel
  • Emily Vogler


Materials and methods:

The project had three phases; a prototyping phase, a computer drawing and plans phase, and a video phase.

The protoyping occurred first, consisting of building new versions of the machines with design changes that either improved the performance, lowered the cost, or simplified the construction. Here are some examples of these design changes:

THRESHER (5-2016 to 7-2016): The eliptical was rebuilt to make better use of less wood, to use standard size lumber, and to eliminate a void where rodents could hide. Features were added to make different uses possible (continuous throughput operation, hand-held sheave operation). Different transmission strategies were tried: bike chain, v-belt, different gear ratios, fixed gear vs. freewheel. The scalping screen housing was modified to make screen changes quick and to make the finished grain exit smoothly (no ledges). The shaft assembly was engineered so the shaft can be installed and removed easily. Different swipple materials were tested, and we discovered that small, cost-free improvements in swipple design are possible. We also discovered that slight variations in humidity can affect the behavior of the crop in the thresher.

FANNING MILL(5-2016 to 7-2016): Several versions of the fanning mill and in particular the blower were constructed. The screen frames were simplified and improved. The frame box was redesigned to use conventional lumber. The shaker transmission was simplified and improved by the use of a bicycle hub for a bearing. The blower was redesigned to use a cantilever bearing, making construction and maintenance much easier and more convenient. Gears were added to the blower to fine tune the blower speed for sensitive crops. We experimented with a smaller blower but concluded that a larger lower-rpm blower is preferable to a smaller higher-rpm blower. We experimented with adding turbulence to the blower which should in theory improve performance but in practice did not, though this is still an avenue worth pursuing.

DEHULLER (5-2016 to 7-2016): Early attempts to improve the performance of the small Colombian mill led to a list of modifications which, when looked at comprehensively, led me to decide to just build a mill from the ground up. That was a major departure from our plan, which was to modify an existing but higher quality mill, but true to the design goal of making machines with low initial cost. The design for the new mill incorporated larger discs, two ball bearings, and a stable profile. In addition to designing a new mill from first principles, we also experimented with dehulling pad design. The original prototype was expensive rubber glued to the substrate disk. First we found that one disk of rubber running against one abrasive disk worked better than two rubber disks. Then we found that cheap, universally available silicone caulk makes a better rubber disk at 10% of the material cost.

SEED FRACTIONATOR (6-2016): The seed fractionator is not my design. During the course of the project the design was made available by a seed company in England. I built a prototype (powered by an electric vacuum) and it works fine. It is really specifically for grading seed for germination tests, so only applies to farms which intend to sell seed . The considerable amount of time saved by the availability of these plans made it possible to plow extra effort in to the design of the fanning mill blower and the dehuller mill.

BIKE PTO (6-2016 to 7-2016): The prototype PTO was excellent. I wanted, however, to build one version that used only bicycle parts rather than a bike plus standard steel stock. Although this worked, the main lesson learned is that using one fancy bike PTO to power all the machines is not practical. Because the machines are all used at the same time (for example, rice is fanned, then de-hulled, then fanned again), moving one bike from machine to machine takes too long. So we ended up using a fleet of scavenged excercycles to power the machines.

COMPUTER DRAWING (7-2016 to 10-2016) The second phase, the computer drawing and plans, was very effective. Emily created 3-d models in the computer. This process, like a virtual building of the machines, caused Emily to question me closely about the reason for the shape and size of each part she drafted. How does each part contribute to the function? What elements affect the cost? Which affect ease of construction? What elements are just “spandrels”, distracting left-overs from some previous use of the part? As Emily acquainted herself with the construction shape and process, a logical format for the 2-d plans emerged. I could advise Emily on whether the images she rendered captured the information needed to direct the builder, and Emily could insist my explanations and text be simpler, clearer, and assume less of the reader. After producing the plans, and waiting a while to forget many details, I returned to the shop with the plans and built a thresher and a fanning mill from the plans. This led to some minor corrections of measurements and increased my confidence that the plans are good.

VIDEOS (5-2016 to 12-2016) The third phase, the videos, began with filming raw footage of  building and testing the machines. When the 2-d plans were done, Olaf used the plans and our discussion of the footage to edit down videos that supported the plans. As mentioned above, the use of raw footage rather than scripted scenes led to some extra work editing.

Research results and discussion:

The Grain Bikes provide a “bootstrap” pathway to reviving a culture of grain growing by allowing small farms to experiment with grain and dry beans without committing large amounts of capital. What is more, the Grain Bikes chart a course to a future in which thriving local agriculture is supported by thriving local artisan/mechanics using some local supply chains (ie, local wood, recycled bike parts).

The goal of this endeavor is not isolationist self-sufficiency; New England isn’t seceding from the global economy! Rather, I hope the goal is understood to be a revival of interest in local, sustainable, resilient economies with a focus on the way in which agriculture in our communities increases our happiness,health, and social cohesion.

In addition to these grander conclusions, there are several conclusions regarding the technical minutia of the machines themselves. These are best gleaned through studying the plans via the attached files. However, a broad non-technical conclusion about these details is that the internet allows an open source design to be perfected through the collaboration of many vitally interested farmers and tinkerers.

Research conclusions:

Here are the links to the plans at





(this includes a description of the bike PTO)


And here is the link to the youtube VIDEO PLAYLIST :


The measurable feedback so far is only that 723 people have viewed the introduction video on youtube. What does this mean? As I noted before, my guess is that 80% of the views are “amusement”, and 20% are more serious interest. There are more views per unit time at this time than there were for a previous project of mine (the bike powered root washer), and now there are at least 16 farms in the area using one of my root washers. I don’t know how many downloads of the plans have occurred.

Participation Summary
3 Farmers participating in research

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

It remains to be seen how many farms build and use grain bikes. To date, in addition to the prototypes, I have filled orders for one thresher, one fanning mill, and one dehuller. At the Massachusettes Grain Gathering (March 11, Plymouth Ma) I demonstrated the flour mill, dehuller, and fanning mill, and noted some interest.

Originally we proposed to make a booklet version of the plans to distribute at conferences and events. Because the plans are large and detailed, we have decided the best thing is for builders to download them. Also, for farmers who don’t have the internet I print and mail the plans for free (this has already happened once). Instead of the plans booklet, Emily and I are working on a poster that describes the idea behind the Grain Bikes and is a non-technical promotion of the idea.

Project Outcomes

Project outcomes:

So far there is no data on how farms using grain bikes are making out financially. Anecdotes from the few farms who have made/purchased grain bikes are encouraging; they report they are working well and increasing the speed of processing grain and beans, in addition to providing exercise, amusement, and relief from the drudgery of hand work.

Farmer Adoption

It is too early to tell whether or not this technology is being adopted.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

There are several small improvements that could be made in the designs. For example, the throughput of the dehuller could be improved. The fanning mill could be tweaked so that less back blow occurs between the winnowing tower and the bottom screen. I feel that if farmers start building and using these machines they will quickly adapt them to work well for their needs. In addition, as I build more units and process more harvests I will continue to refine the designs and share the improvements on

There are a few other tools aspiring grain farmers need that warrant study. A way of drying and storing grain that uses solar energy and electronically controlled fans (with a differential humidistat) is technically trivial but no one makes this device. In the arena of harvesting, a small stripper-header that leaves the straw standing in the field would be a useful tool for small farms, but small tractor mounted or hand-held stripper-headers are not widespread.

Finally, the next step for the Grain Bikes is making electric versions that increase their output, decrease the labor, and are designed for solar electric power; all adaptations that will still cost less than buying industrial-scale grain equipment.
