Introduction: Hand-driven Oat Flake Crusher

About: With a Master in robot engineering i'm very interested in open source technology and the developpment of simple and local energy sources. Besides that I'm a nature lover, wilderness guide and vision quest tuto…

Freshly crushed oats not only taste a lot better, they are also more healthy because there's no time for nutritients to oxydize. And it's also fun to do, especially children love it.

This version of the oat crusher is wall-mounted. You'll find a slightly different, table-mounted version in my instructables.

This oat crusher can be made of only recycled materials. If you speak german, I recommend the leaflet "Einfälle statt Abfälle - Die Müsliquetsche" distributed by "Packpapier Verlag", which contains very detailed instructions.

The pdf file here contains all the compacted instruction for the fabrication and assembly of the machine. If it helps you, you can also get the 3D CAD files (SolidWorks) of the machine as shown in the picture. Just contact me.

To fabricate the different parts, rely on the pdf file in the next step, showing all the measures.

Step 1: Materials

see drawings in the pdf file for exact measures. Attention, if the cylinder diameter differs from 48mm you have to addapt some of the measures! The words in brackets are the german names of the parts used in the drawings and CAD-files (to get the CAD-files, contact me)

Materials, mostly recycled:

  • Hardwood bars: Wall bars (Wandleiste) ca. 15X26x620mm, Distance bars (Abstandleisten) ca. 17x23x280mm, Carrying bars (Trageleisten) ca. 15x17x560mm
  • 2 Hardwood blocks, min. 60mm long, min. 50mm Ø, very dry, for turning the cylinder cores (Walzen)
  • Wooden board for the bowl-board (Abstellbrett) ca. 140X100x15mm
  • Wooden or plastic rod or tube for distance tubes (Distanzröhrchen) ca. 15mm Ø, 240mm long
  • Thick metal pipe for the cylinders (Walze), min. 50mm Ø, min. 110mm long, e.g. Water pipe
  • Metal rod for the axles (Achse) and the crank (Kurbel) 10mm Ø, min. 50cm long
  • Thin Metal sheet, ca. 0.2mm, e.g. from olive oil tin, for the wiping sheet (Abstreifblech) and the funnel (Trichter)
  • Piece of sheet metal, 1-2mm thick, for the metal strip (Blechstreifen)
  • Square-necked Mushroom head bolts (coach bolts): 3x M6 x120mm, 3x M6x100mm plus washer and nuts (two wingnuts)
  • Some 2mm-Nails for securing the cylinders on the axles and some 30mm wood-screws, 4 small 15mm wood screws.

Step 2: Fabrication of Parts

Cylinders (1x with 100mm axle, 1x with crank)

Out of a thick-walled metal tube with at least 50mm Ø you fabricate the cylinders. The smaller the Ø, the deeper you have to make the knurl to be sure the corns don't stall. The knurl is made diagonaly, either with a small metal saw or with a chisel, in which case you need to file it over afterwards to take away the burr.

The core is turned out of extra-dry hardwood, either on a turning machine or improvised with a drill. Once cylinder, core and axle ar assembled properly, all is secured by two 2mm-Nails put in a hole drilled through all three of them and then sawed off.

Alternatively, the core can be replaced by two welded metal plates or a concrete core. As long as it is tough and properly centered, do as you wish. I prefer the wooden cores.

The crank handle can be selfmade or you buy a simple file handle and drill the hole open to 10mm. Secure the handle on the crank with a small nail going through the notch at the end of the crank.

Sheet metal parts

One of the images shows a sketch of the metal sheet part you need to cut for the funnel (Trichter). The upper edge and the seam are curled and crimped with pliers as shown in the sketch. The seam should additionally be soldered or riveted.

The cuts in the wiping sheet can be easily made by bending the sheet over a round piece of wood. The two wiping flaps should be as straight as possible, as these are finally coming to lie on the cylinders.

Step 3: Assembly

  1. Main frame: Assemble the two wall bars (Wandleisten), the two distance bars (Abstandleisten) and the bowl board (Abstellbrett) with 30mm wood screws from the backside and glue if wanted (image 1)
  2. Correctly arrange the four carrying bars (Trageleisten) by checking on the sloped surfaces on which the funnel will be posed. Connect them with the coach bolts (3x120mm, 1x100mm) and the distance tubes (Distanzröhrchen). On the bolt on the lower left you add the wiping sheet (Abstreifblech) to the distance tube. The shorter coach bolt is located on the lower right, doesn't pass through the distance bar and must be adapted to be sunk into the carrying bar (see image 2). This makes this part pivoting, to give flexibility to the cylinder distance and the possibility to adjust the squeezing force with the wingnuts. Once everything fits, add the metal strip (Blechstreifen) and tighten the four nuts (image 3).
  3. Now the two cylinders can be mounted (add some vaseline to the axles to lessen friction). Before you fix the two 100mm bolts, raise the wiping sheet onto the righthand distance bolt and check if the two wiping flaps properly lie on the cylinders, otherwise adjust (image 4). If the carrying bars are very stiff, as in my case, add two spring washers under every wingnut to ensure some spring travel (image 5). This makes up some centering fault on the cylinders and allows you to crush larger grains. With more flexible carrying bars or a lower position of the holes for the two 100mm bolts has the same effect. The two wingnuts simplify the adjustment of the squeezing force.
  4. Mounting the funnel (Trichter): Put the funnel onto the four carrying bars and either adapt the lower opening or file away on the slopes on the carrying bars (or add a washer if necessary) until the distance to the cylinders is 1mm at the most and the funnel doesn't touch the cylinders. Then punch four holes in the right places into the funnel with a pricker and pre-drill holes into the carrying bars. Fix the funnel with four small (10-15mm) countersunk screws.
  5. Finish :-)