Workshop: Design and Build a Pedal-Powered Shredder

Hello everyone.

This is again an open call for participation. All ideas are welcome.

Short Description

Last year, a fellow gardener from Allmende-Kontor at the Tempelhofer Feld, Dax, started the discussion here about building a pedal powered shredder: Design and build a pedal-powered mulcher/chopper from old bikes!. The workshop took place at OSCE Days Berlin 2016, a working prototype had not been build there, but a lot of good ideas had been shared.

One of the participants, Maria from Sao Paulo Lab, got inspired and together with a group of people, she set out to build a pedal powered shredder for a community garden project close to Sao Paulo.

This resulted in the beautiful “Papa Galhos”. They took a second hand shredder, modified it, and attached it to a bike:

This may, Maria was in Berlin again and offered to help building a shredder like that. She did a lot of reseach already. Thank you Maria!

Would it be possible replicating that design using available materials here? Or if not, how should we modify it? Lets also have a look on other design ideas and research about this topic.

All input is welcome, also with helping to organize a workshop (materials, tools, people who can weld and cut steel).


Let’s discuss in this thread, if and where we could find the right materials (especially what kind of shredder we could re-use or if we have to use another kind of design).
Update: In Prinzessinnengarten from 28 to 30 of June, there will be a first workshop to build a shredder like this. Everybody who is interested, please sign up by email, you can find all information here: On Sunday 2 July, from 10am to 1pm, at the OSCE Days Berlin we will gather at Agora Rollberg to discuss what we learned so far and see how we could improve the design and build the next one.


Documentation of the shredder workshop in Sao Paulo:

In the last weeks, Maria already researched about what kind of materials could be used in Berlin and created a shopping list:

Also, she compared different shredder-system, which are available in Germany:

Apart from the parts that can be bought at the hardware story, seconda hand or found at the scrapyard, two parts would have to be produced by a metal worker: the axis and the pulley. In the pdfs, you can see the CAD drawings of those, the exact measures depend on the second hand shredder and blades that will be used:


Input: Research and webinar by Kante Kollektiv

Kollektiv für angepasste Technik (KanTe) ( did a lot of research about pedal powered shredders and summed it up in a very informative webinar (in german):

Among others, they where quiet strict about these goals:
The shredder should be

  • save to use
  • easy to build and fix (reduce the amount of welding)
  • easy to transport (one should still be able to use the bike as a bike)

In the webinar, they explain a lot about the physical properties of pedal power. Interesting.

Their first working prototype should be finished soon. I’m very curious about it.

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Looking at the material list (, most things could be either bought at the hardware store or second hand.

Especially the steel parts can be found at junkyards. A good one isß+Recycling+GmbH/@52.4777957,13.3497451,17z. Its good to go there very early in the morning. Later in the day, it can be too busy to walk around there.

Second hand shredders

It seems, the biggest challenge right now is to find a relatively cheap, but suitable and robust second hand shredder. The companies Samix and Cramer produce very nice ones, but they are hard to find or quiet expensive.

Old shredders from Atika are easy to find an cheap on ebay. But im not sure if their blade-system works so well (see image). Would it be worth a try? Does somebody have experience with these?

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