Making a Shredder from Plastic! (& Pedal Power)
I am a graduate student pursuing a Master of Arts in Sustainable Communities at Northern Arizona University in Flagstaff, Arizona, USA. My thesis project is centered on the circular economy, and I feel Precious Plastic is a great tool to explore this.
I’m researching the feasibility of building a Precious Plastic shredder while replacing as much steel as possible with cheap recycled plastic. The idea would be to reduce the cost of new shredders as well as put our plastic waste to a good use.
I have secured $7500 in funding through two grants (NAU Center for Ecosystem Science and Society and the City of Flagstaff) and one private donation. This has paid for a human powered shredder, compression oven, two molds, and an extruder, along with minimal wages.
I’ve got the shredder mechanism from Precious Plastic USA and will be ordering the extruder soon. The shredder will be mounted onto a Schwinn Exerciser stationary bike converted to 4.6:1 gearing (28T to 28T then 14T to 65T). I am working with the local bike shop to make that all work on the stock flywheel. I also got a used oven from Habitat for Humanity and will soon have a car jack from my uncle. I got the same oven controller that is used in the Precious Plastic build video. I’ve also been collecting discarded bed frames for building tables. It’s looking pretty good!
Anyway, I wanted to reach out to you all and let you know what I’m doing. I’ve got a potential source for ABS locally, which I suspect will be a good start for building the shredder parts. Of course the blades will still be steel.
Check out my progress at the Praxis Plastics blog! I would love to work with a machine builder (ahem Justin) or even Precious Plastics itself. I would also love to be involved in prototyping V4 using plastic parts! So please let me know if there is any interest. My school email is [email protected].
Your project seems very interesting, I wish you all the best, and congrats on the funding. I will be closely following your progress. Make sure you post regular updates to this forum as well as your blog! 😀
I currently have an exercise bike I too would like to convert, but for now, the hand-cranked version is what we use.
Quick update. I don’t know if image uploading is working so I’m adding links too. Shredder is almost done. Here is a video before the chain tension has been figured out.
Oven is 95% done now as well. Just need to find a control box, mount the controls, and also possibly move the thermocouple.
As I await the shredder’s completion, I am working with the shop that worked on the oven to build a sheet mold based on this: https://davehakkens.nl/community/forums/topic/slow-molding-sheet-making/
The idea is to experiment with making multiple sheets of different materials and thicknesses, and building a shredder out of them! No idea how it will work.
Shredder is home. It’s working but needs some tweaks to be ready to do real work. The main issues are gearing and a too-light flywheel. I’ll be investigating today. To avoid copying/pasting everything, check out my blog for the rest of the updates:
New chute in progress. Video tour in link below.
Work, work, work
Also looking at options for swapping out the flywheel for a heavier one. Trying to go from 11 lbs (5 kg) to at least 30-40 lbs (14-18 kg). This one weighs 20 lbs (9 kg) and has room for extra weights.
More tomorrow hopefully. I think the last things I need to do are the flywheel, finish the chute, and convert the lower chain tensioner to an actual idler from a derailleur. Two of those will need help from a fabrication shop. Ugh, I wish I could weld.
Thank you! After fighting off a cold over the weekend I finally got the shredder over to the welding shop to get the heavier flywheel fitted and have a couple other things done. I then brought the oven home so I can fit the control box over this weekend. The mold hasn’t been started yet, but the shredder is a higher priority anyway.
In other news another Precious Plastic member reached out to me! I have brought him over to see the machines a couple times and will be working with him going forward. It’s good to have someone else here in Flagstaff who is interested.
I’ve had a couple other things happening lately but will hopefully have nice photos of the oven for you all this weekend. Cheers!
Oven control box is installed. I need to find the clips for the controller and contain the wires on the back. It will also need a more robust power plug since the plug on it right now is pretty beat up. But it does work, so I’m hoping to drop this oven back off this week for mold fabrication and pick up the shredder (hopefully operational) to shred things. 🙂
Also useful: I had the fabrication shop build some wheels (from an exercise bike) into the frame so I can move it around. My garage does not have much room so moving this in and out of its storage location is important. I plan to mount the extruder underneath the jack and the injection molder on the side of the oven frame so the ‘making’ type machines are all-in-one.
I’ve been down the rabbit hole with the bike powered shredder. I will not say pedal power won’t work. But I will admit that I started from the wrong place. The Schwinn frame, while common by bike standards, is the absolute wrong solution for a shredder frame. For anyone looking to try it, I would recommend using the bike frame from the bottom bracket back, and building a custom frame for the front. This would allow a much larger flywheel, stiffer, more torsion-resistant frame, and easier fabrication.
Suffice to say I’ve figuratively and literally scrapped plans for the bike shredder. It was costing too much to have someone else experiment. I bought a used motor and gearbox locally and am having some couplers adapted. I made a table for the stuff in the mean time. Looking forward to having a working shredder, even if it is electric powered.
Shredder on a wooden table isn’t probably the ideal solution. If you go this route I would recommend bracing it HEAVILY. More info here:
I’ve send you an email
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