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Shredder without Motor – with a crank?

Sören soeren

Shredder without Motor – with a crank?

07/08/2017 at 20:40

Hi – did somebody build a Shredder without a motor? What did you use instead? A crank? A wheel? What could work?

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08/08/2017 at 01:43

Hey Sören,
here only a few of the many solutions without a motor:
Human Powered
Bicycle driven
Bicycle driven


14/08/2017 at 20:22

Hey @soeren, here’s the second prototype that functions much better just using hand power: Human Powered Shredder V2
Hope it helps and inspires!

15/08/2017 at 12:40

Hey @timslab Did you get around to measuring the torque yet?

15/08/2017 at 21:54

Yo @andyn, I haven’t measured the torque yet.. I’m not totally sure how abouts to do so, seeing that the machine only really functions with the assistance of the flywheel. I am, however, in the process of applying a washing machine motor with another gear reduction driving the flywheel to see if that potentially works as an alternative low cost solution…
If you have any suggestions as to how to reliably measure the torque that would be great ^^

16/08/2017 at 13:11

@timslab (and also for the benefit of anybody else who wants to know how to do this or why it’s useful)

Measuring the torque is easy, it needs two measurements, one of distance and one of force or weight. Torque is a measure of rotational force, usually expressed in units such as Newton meters (Nm) or foot-pounds (ftlbs), but the units aren’t really important and it’s easy to convert between them. We need to know the force applied to a lever or wheel and the distance at which the force is applied from the centre of the pivot point. It’s important that the force is applied at exactly 90° to the lever, or tangential to a wheel, not at an angle or it will give an incorrect result.

What we are trying to measure here is the minimum torque required to operate the shredder. This figure can help us size the motor and gearbox combination needed to drive it.

Tim, for your machine what I would do is this: Put a typical piece of plastic in the shredder and spin it up so it starts shredding, let it stop halfway through shredding the piece, then slowly turn the handle in the same direction until it is horizontal (we don’t want any help from the flywheel for the test). Now hang a bucket or similar from the end of the handle and gradually add weights to this until the handle begins to turn (it starts shredding) we want the point at which there is enough force for the shredder to take the next ‘bite’. The two measurements we need are the distance from the centre of the handle axle to the point where the bucket is hung from it, and the weight of the bucket and it’s contents. Multiply these together and also by the ratio of your sprockets (13:60?) ~4.6:1 and this gives the minimum torque needed by the shredder.

17/08/2017 at 21:29

Hey @andyn.. thanks for the detailed write up, makes things a lot more easy! I’ll try get that info collected tomorrow or first thing Monday c:

28/05/2018 at 23:02

Hey, just to leave this here somewhere.. in case this info is useful to anyone

I’m working on a human powered shredder, hand crank (for now), see link:

Gear reduction is 25:1
Throughput for ABS different thicknesses up to ~4 mm was 0.5 kg/h
Didn’t measure torque but it wasn’t hugely hard to turn.
I made this modification to the design to avoid welding.. but then it needs some precision machining.. use what you have available..

@timslab @andyn

28/05/2018 at 23:36


Looks amazing, I love the fact is so compact and safe looking.

Do you have any photos of whats inside your box and how you achieve the 1:25 ratio?

29/05/2018 at 20:47

@rorydickens it’s an off-the-shelf worm gearbox. This one is a NMRV, found a really cheap one (£50) on ebay.

06/06/2018 at 11:34

my own design uses a 2′ breaker bar.

06/06/2018 at 14:28


Hi any pictures of your creation? Thanks

06/06/2018 at 19:06

This is a cad file for it i have all the parts for it downstairs i just need to assemble it. i will try to assemble it today and post it again here.

06/06/2018 at 19:39

very curious to that @thegreenengineers!

06/06/2018 at 20:04

Wiring more with impatience the picture



07/06/2018 at 09:48

here she is
its a small shredder 6″ x 6″ x 3.5″
it is designed for production.
everything on the shredder is cut out of one single piece of plate .25″ 1055 steel
(which is hard enable steel 🙂  )
24 shredder blades
24 spacers
24 “half moon things”
big 6000zz(i think) pressed into sides with a extra piece (i call a bra) to support the bearings
.75″ square drive shafts made out of 1045 steel.
let me know if any questions.

07/06/2018 at 09:55

I have not put the walls or the “half moon” things in yet. I am having problems with the friction in the front gears. I had these parts water jetted at my university. I wanted to test if the water jet could do 0 backlash gears just for the hell of it if i ever wanted to make a precision machine out of plate cut on this particular water jet. I didn’t think it was going to work and expected to do it over again. Long story short they are indeed machine precision 0 backlash gears (completely useless for a shredder) but now i know the water jet can indeed do 0 backlash gears. so now i have to file then or let them wear together or just shoot some lube into them. Probably a combination of all of these options.

07/06/2018 at 13:35

Looks nice, how many teeth on each cutter? Can you offset them so they don’t all line up in rows? I guess if you’re using square shafts you’re limited to 90° steps if all the cutters are the same. Having the teeth line up like that will require way more peak torque compared to having only a few cut at the same time. You can also rotate the gears by 1 tooth so cutters on each side aren’t meshing at the same time in the centre.


08/06/2018 at 08:32

yea they are supposed to have a offset there are 24 cutters so each cutter is supposed to be offset 15 degrees from the last. but my waterjet guy just nested 1 file into a sheet and then cut them not realizing that they are all different. so to try to use what i have hear the best i can do is half one way and half offset so that is what i did. What are you going to do it was a free water jet cut shredder.

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