Need help finishing Shredder

Hello everyone

I just started to work on a shredder that has been built by my predecessor and has some serious design flaws. I’m doing my swiss civil service in indonesia on a organic farm/education center for organic agriculture. There are plans to implement a recycling strategy to put all the plastic waste (which is abundant in indonesia) to new use. My background is civil engineering so I don’t really have the knowledge to build machines but I hope with a little bit of help of you and some research it will be enough to get the shredder working. (We also have a finished compression oven which is working and waiting for shredded plastic)

The problem:

So basically there is no money available for the project. Everything had to be as cheap as possible. However they did spend money on the motor and the laser cut parts. What they didn’t really plan through was the gear box/speed remover. The Motor has 1.5hp and 1450 rpm. They put in two v-belts each with a 1:5 ratio resulting in a 1:25 reduction. Now the problem is pretty obvious. While the v-belt reduces the speed to the right rpm it does not deliver any torque. It’s just enough to shred though some soft pet. But it clogs right away once it reaches harder parts like the top of the bottle. The small wheel of the speed reducer is spinning through since the friction of the v-belt is just not enough.

Now I was thinking about how to fix this. The most important thing is cost. I could buy a WPA 80 1:20 gearbox in Jakarta for 1Mio RP (ca. 60 euro) but this is already considered really expensive and also I would have to make a lot of changes to the current design of the frame. So I was thinking about maybe exchanging the two v-belts with motorcycle chains. These should be readily available and fairly cheap around here. I’m not sure if I find the right size of sprockets around here and how to attack them to the motor and shredder but I’m sure I could wing this somehow.

Does anyone of you have experience with something like that? Do you think it could work or is it just a waste of time and money and we should just invest in the more expensive gearbox?

Here are some pictures of the shredder:

@marvins, please take a look at the other forum topics as these questions have been raised before a number of times. > SEARCH

All’s good @marvins! Hope the compost house is growing smooth…
I’m sure you’ll be able to achieve the required reduction with off-the-shelf (bike) parts – even if its not directly 5:1 – having two sets of sprockets will get you somewhere strong.
Just don’t forget about us over here c:

thank you guys for all your input. I didn’t have time last week to work on this and probably have to put this off for a while since i’m working on building a compost house right now. However I’m still gathering all your ideas to figure out how to proceed later on.

It seems that the bike chain is the way to go. I don’t really have access to a lasercutting facility. It was already a challenge to get the parts for the shredder made and they came with really bad accuracy. So maybe it’s possible to find some regular bike sprockets in a somewhat right size to get to 1:5…

Hi,
My opinion is on the left side can place the extrusion machine and rotate from the same shaft. From a single motor uby using the same frame u can run two machines.

Hey @marvins… I tried using V-belts to make a hand cranked shredder early last year and came up with the same problems… it looks like you’ve got a good setup with strong mountings. The way I solved the problem was having some sprockets cut from 3mm mild steel and used a regular bicycle chain. Providing you have access to some laser cutting facilities it should be a relatively simple fix.
I’ve shared the files I used for cutting a 5:1 sprocket set. The teeth spacing took some trial and error but whats there should work with a regular bike chain.
You can have a look at the machine and access the files here: Human Power Shredder V2
I hope this works and I wish you well! Your motor setup is exactly what I plan on trying out – so I’m hoping you see good results 🙂

I was looking the photos and It seems the belt wheel are not appropriate, the V belt work well if all the sides are 8nside the pulley, i think you can use car vehicles belt wheel to be sure the small whells works well, for the big one you would not have problems. Hope I could help, bye.

A flywheel have sense only with high rpm, so if you put it on the shredder shaft it will no work, he need cynetic energy to help the shredder doesn’t stop. In add this isn’t your problem, as you say, the very belt doesn’t work well, they slip, it means the motor have more torque than the belts can manage, you must, try to tight more the belt or change with a teeth belt and wheels.
Take a car belt tensor to be sure the belt works well.

@xxxolivierxxx thanks I will look in to this. Also after looking through some more forum topics as recommended by @jegor-m I’m wondering if a flywheel might be a solution. I’m thinking of placing it on the shredder axe. I think this would be by far the easiest and most affordable solution (using a old bicycle/wheelbarrow wheel with weight attached or weld something together like the guys from Human Power Shredder V2) . However I’m not quite sure if this would be something that would bring enough power to the shredder. Do you think this is something that could work?

motorcycle chains is probably your best option if you are on a low budget. Use this site to help you calculate the RPMs of each wheel and this one for torque calculations