Bike powered shredder
Hello the Precious Plastic community. With some friends we have started the adventure of plastic recycling. We have the shredder case and when the question of the power source came up, our choice turned to the bike (for the moment).
We bought a spinning bike, a exercise bike already fixed on the ground, already equipped with a flywheel and we might need the help of those who have already started a bike powered shredder, our knowledge is a little limited in this area.
I know there are already topics on the subject but it was a bit of a mess…
The recommended motor for the shredder must have a power of 220V, 2 kWh and a rotational speed of 50 to 70 RPM. It is therefore necessary to recover its characteristics via a bicycle. As for the cyclist, I saw on internet that his power could go up to 300 W (average of 200W), and that his rotation speed was 100 RPM (not entirely sure on these values, do not hesitate to correct me).
I have read on the forum that the ideal way to link the shredder to a bicycle is to have a ratio of 1:5 on the sprockets, the small one on the bicycle crank and the large one on the shredder shaft.
With my team we are wondering how to connect the whole thing… put the crusher in the axis of the spinning bike flywheel, or add a chain and put it somewhere else. But as a result, how should the chain of small, small, large and large sprockets be?
We would also like, if possible, not to have to weld on the shredder shaft, in order to be able to switch to a real engine later on, without having to buy a new shaft.
Here are the pictures of our spinning bike and 3D explanations.
Thank you all
Alexandre from FRANCE
hope these topics will help:
(i add some “non-bike” but still human power, might got some inspiration on mechanical system)
regards, halim 🙂
Hi ! Thank you for your response ! I already searched on these topics but i didn’t see anything about using one or two bicycle chains, what is advised ? And how should be the sprockets if we use two chains
@alexbell great use for the exercise bike (though I think “clothes rack” is still the number one use for stationary bikes). I have not built one but on basic principles, I would think the two chain gives you an opportunity to optimize, given that you are underpowered. You have a flywheel which will help with the power averaging but I think you will want to get that spinning fast to store energy (chose your drive sprocket set to achieve that) and then gear down to what the shredder wants. You may find that you may want to add an additional flywheel. For the chain to the shredder, maybe a small motorcycle chain/sprockets to help handle the shock load when the shredding starts.
Great project, please post your progress.
Hi everyone, we finished our bike powered shredder ! It works but it won’t last if we don’t modify our shaft.
We connected the original shaft of the shredder with the crankset of a bike, which need a tapered end to fit, so we modified ourselves the shaft but we removed too much material so it’s twisting.
We think that we need to make a new shaft with the normal circular profil but with an end that fits perfectly well with the crankset (meaning a squared and tapered end like here: https://www.sheldonbrown.com/bbtaper.html) and a bolt to tighten the all. We also think of adding a flying wheel on the other end of the shaft in order to balance the forces.
We are open to any suggestion you may have and if you have any question about our bike powered shredder don’t hesitate.
Looks great, can you flip the existing shaft around and connect to the other end?
The tapered square crank spindle on a bicycle is hardened steel (just try cutting it with a hacksaw), and it needs to be to withstand the torque. The shredder shaft (mild or stainless steel) won’t last long if reduced to these dimensions as you have found out. The crank arm attached to the large sprocket is soft steel or even aluminium, better to bore/drill this out to match the shredder shaft, easy if you have access to a lathe, but could be done with hand tools.
You don’t think it could work this way ?
Otherwise, we thought that welding a steel piece to the crankset bike that will fit with the existant shaft might be a way of doing it. But we need to have a connexion that is rigid and something to make the shaft turning with the crankset. Because, as it is, circle inside circle won’t make the shaft turning.
I wonder if that would be a good place for a soft coupling (some examples in the middle of this page https://davehakkens.nl/community/forums/topic/extruder-development-v4/ ). It may reduce shocks from jamming and make everything last a little longer.
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