This is a very open call for a challenge so I'm happy to take criticisms or suggestions on where to go from here.
I joined the community garden at Templehof Field in Berlin this year and in talking to some of the members, I learned that they need a way to chop up large amounts of plant material for their compost pile. Currently they rent gasoline powered mulchers once or twice a year, but this is costly and unsustainable.
There were plans for someone to build a pedal-powered mulcher last year, but because of budget and other issues, it never materialized. I spoke to one of the people responsible for composting the other day, and according to her the requirements are as follows:
- handle green wood (not more than 3cm thick), plant waste, and some food stuffs
- be safe enough that it can be used around children
- be locked down so that no one (especially children) can use it unsupervised
I would add one item to this list of desired traits:
- it should shred cardboard, as this is a plentiful urban waste and an excellent carbon source.
This is all in addition, of course, to the requirement that it be pedal-powered and relatively cheap to build. I think we can design a solution to this problem that would be very nearly free, open source it (and in that process further refine it), and ideally put this machine into use in community gardens all over the world.
At the moment I have a few ideas from research that I've done, but not enough to translate that into a working model. I would love to have an input session with anyone interested where we can discuss the requirements, design a prototype (or several!) and even try to build a working model.
Here are some links I've found to get started thinking about a design:
pedal-powered mulcher - small scale, but some good angles of how it was built, so could be replicated on a larger scale with some study
hand-cranked shredder - this is a really nice idea, and it's fully flushed out as an instructable.
mayapedal - an orgination in Guatemala about pedal powered machines