The mill on pedals!

TODO The Millipde in image with a caption / video

The wondermill

A couple of years ago, I purchased a “Wondermill Junior”, which is a basically a benchtop hand-powered mill. The – comedic and exhaustive – promotional videos do a good job at promoting this thing of beauty, so I will jump straight to the point. I was using it quite often, especially to make pea and buckwheat flour – or peanut butter and sesame paste, using the stainless steel stones.

The point I love about the mill:

  • Fresh flower – one can keep seeds and mill them on demand which increases tastes and shelflife.
  • Money saving – often, buying a bulk of seeds is a lot cheaper than flour.
  • Versatility – one does not need to store both flour and grains of the same crop. One can also make flour of less industrial (e.g. foraged goods)
  • Exercise – it is a nice way to move a bit after a long day of work, and it is silent enough that one can listen to a podcast at the same time
  • Romanticism – it is elegantly minimalist.

Why pedals?

When I had guests, I asked them for a hand to mill as it gets rather physical after 10 min non-stop. Although I personally find that fun, my “sweating before eating” policy was not unanimously acclaimed – sad days. In addition, some people of smaller stature would not even manage to actually mill hard grains. Therefore, I started a crazy project aiming at putting the mill on pedals – thus keeping its positive attributes whilst making it more efficient. I thought it would be fun to share the latest version of my design my design with the other lunatics crawling the web. The wondermill is already quite expensive, and I was reluctant to spend any more money. My philosophy for this project was, therefore, to recycle/repurpose as much as possible.

On this page, I just put together the prerequisites as well as minimal assembly instructions and blueprints.

Project prerequisites

The skills:

  • Basic woodworking (tenon and mortices).
  • Basic 3D printing
  • Very basic knowledge of bicycle mechanics

The parts:

  • About 3m of sturdy wood (e.g. 3x2 construction timber, I found mine in a skip)
  • An old bicycle frame with crank and pedals attached (ideally a broken rusty vintage one. I found mine actually abandoned in a wood)
  • A chain, derailleur and cassette
  • A 3D printed adaptor to fit the cassette on the mill
  • The wondermill itself
  • A pair of G clamps

Tools and consumables:

  • Wood saw, mallet, chisels
  • Wood glue and clamps
  • Hard string
  • 5 screws for wood
  • Hacksaw and file


Obviously, the design will depend on what material you find and, I hope, your own improvements/adaptations.

The final product

TODO pict (The final assembled millipede)

The holder

The holder is the wooden chassis that holds everything together. The idea is to put together something with these dimensions:

Todo drawing (millipede holder)

My brother introduced me to woodwork and to the soothing – and weirdly addictive – voice of Paul Sellers, which I highly recommend. I wanted to start my woodworking training with this project. The important point here is that you want something quite sturdy as you will sit and move around. If your structure is not rigid enough, the torque on the mill, especially on hard grains, may also warp it, making it less efficient.

The bicycle and derailleur

For this project, we just need the rear part of the frame: the one that would hold the saddle and the back wheel. I used a hacksaw to cut the rest off – consistently with my effort to minimise the design. Some people find it hard to balance without a handlebar, so you may want to keep the front of the bike for that.

I wanted to avoid screws when possible. Therefore, I used a chisel to dig groves where the bike should go. I then used hard strings/rope to keep the bike in place. I like the simplicity of string and the possibility to remove it (e.g. to for cleaning or transport):

Todo picture of the holder

The first prototype I put together did not have a derailleur, which was a mistake. Then the chain did jump a lot especially on large hard grains (e.g. corn), and it was effectively impossible to tune the gear ratio. Therefore I added a derailleur to the current version:

TODO derailleur fig.

Note that I have cut a small piece of wood to fix he derailleur using its hanger and a couple of screws/bolts. I first clamped the support until I was happy with its position, and then glued it. This way, we do not risk damaging the holder and we could relatively simply change the derailleur or its position.

Mounting the mill

Rather than using a single sprocket (such as the one sold by the wondermill people), I opted for a cassette, so I can play around with the gear ratio according to what mill. I 3d printed an adaptor for a shimano cassette that fits the shaft of the wondemill:

Todo drawing of the adaptor

Then, instead of screwing or bolting the mill directly to the holder, I put it on a separate board and I clamp the board (using G clamps) when I mill. This allows me to clean the mill or move it left to right to line up the gear I want:

Todo pict of the board to screw it in

This design also makes it the millipede modular so that we can remove the mill and other rotation/based instead. For instance, I have put together an millipede-powered apple-crusher.


I hope you had fun reading about the millipede and that you try building your own and do not hesistate to send me some feed back! I also hope the wondermill company comes accross this post and strat sending me freebies.