Grain Crusher School Project Kit – Grade 8

What's in the box

40 laser-cut parts and 44 bolts and nuts, packed flat:

• 3 mm MDF sheets × 3 (300 × 200 mm each), with every part labelled
• M4 bolts × 20, in 5 lengths from 12 to 65 mm
• M4 nuts × 19 · M4 nyloc nuts × 5
• Two MDF spanners and a ruler that doubles as a bolt gauge

For testing, add a little rice or maize of your own.

How the grain crusher works

Turn the handle and the crank pin goes round. The connecting rod turns that round-and-round movement into a push and a pull on the beam, and the beam rocks on its pivot like a see-saw. The hammer hangs from the far end of the beam, so it lifts and drops into the bowl and pounds the grain. It is the same idea as an old water-powered trip hammer mill, worked by hand.

How to make the grain crusher, step by step

Every kit comes with a 3D animation of the whole build, so a learner can watch it once and get it right the first time. It takes the build in ten steps:

1. Build the grain bowl. Foot rings K and wall rings L, bolted to deck H3.
2. Decks into the front frame. Decks H1 and H2 into front frame A, bolted from the outside.
3. Fit the back frame. Back frame B over the other tabs, with a nut in each T-slot.
4. Build the beam. Two beam sides C with cross plates J between them.
5. Make the hammer. Four hammer layers E, bolted together.
6. Hang the hammer. On an M4 × 35 bolt through the beam, with a spacer ring on each side.
7. Mount the beam on the towers. On the long M4 × 65 bolt, with four rings on each side.
8. Build the crank. Crank webs F1 and F2, with the crank pin and the axle.
9. Fit the crank and handle. The axle out through frame A, and handle arms G1 and G2 on the end.
10. Connect the rod. Connecting rod D from the crank pin up to the beam.

The full walk-through, with how the mechanism works and how to write the design brief, is here: how to make a grain crusher for the Grade 8 project.

Testing it

Pour a little rice or maize into the bowl and turn the handle. The hammer lifts 43 mm on every turn and pounds the grain. If the handle feels stiff, a moving joint is too tight: back its nyloc nut off a little.

Size when built

324 mm long, 92 mm wide and 240 mm tall.

Materials

Every part is cut by laser from 3 mm MDF and labelled. The joints are bolted T-slots: a nut sits in a T-shaped slot and the bolt goes into it, so the model is strong, needs no glue, and can be taken apart again. The moving joints use nyloc nuts, which do not work loose.

Test-fitted before it's packed

We build every kit once by hand before it is packed. If a part doesn't fit, that's on us, not on your learner.

Built for Grade 8 Technology

Drawn in our own workshop for the Grade 8 Technology grain crusher project, under Mechanical Systems and Control. See all Grade 8 Technology projects.

Common questions

Where can I buy a grain crusher project kit? Right here. Order online and we deliver to homes, schools and shops across South Africa from our workshop in Gauteng.

Is it the whole Grade 8 grain crusher project? It is the model. The design brief, the drawings and the answers on the task sheet are still the learner's own work, and the build guide explains the crank, the rod and the lever in plain words to help with that.

Does it need batteries or glue? Neither. It works by hand, and it bolts together.

Delivery

Packed in one flat box in Gauteng and shipped to homes, schools and shops across South Africa and Namibia. Standard delivery anywhere in South Africa is R65. Delivering to Namibia? WhatsApp us with your town for the cost. Buying for a class or a shop? Ask about class sets and wholesale.