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Share your Shredder motor experience

This topic contains 72 replies, has 20 voices, and was last updated by  Cristodor Cuciureanu 1 week ago.

7
Olivier xxxolivierxxx

Share your Shredder motor experience

16/11/2017 at 03:35

Hello Everyone
Many people around the forum has seen @lyricalpolymath ‘s “almost definitive guide on motors” and I’m sure many of you found the information collected on that topic useful on the initial stage of your Shredder build project.

My intention on this topic is to collect information about success/failure stories with the motors you tested on your shredder, along with specs about the motor you tested.

For instance, I read that @seyn-sustainableenergyyouthnetwork tried a monophasic 3HP motor on the shredder and it clogged very often. @lyricalpolymath also reported that monophasic motors are not good enough for the shredder regardless of their HP.
My aim is to collect a concise database of real-life machine builder stories about their experience building the shredder and which motors they used.

I’ll start:

#######################################################################
Owner: @xxxolivierxxx
Motor type: Monophasic
Voltage: 110v/220v
RPM: 1430/1710
Reducer: 1:30~
Output RPM: 56/60
Power: 1/2HP
Result: Failure
Details: The motor is simply not strong enough to shred any type of plastic. I even added a reverse switch to see if that would help but it was just a waste of time/money.
Here’s a topic I made about my Shredder: https://davehakkens.nl/community/forums/topic/my-shredder/
#######################################################################
Owner: @flo-2
Motor type: Monophasic
Voltage: 230v
RPM: 1400 rpm
Reducer: 1:25
Output RPM: 56
Power: 2.2kW
Result: Success
Details: Weakest point is the coupling, turns freely when load is too much. I have got around 280Nm and thats enough for most things to shred. Only very thick industrial plastic crates create problems.
#######################################################################
Owner: @baas
Motor type: triphase
Voltage: 230v – 400v
RPM: 2280
Power: 2.2kW (+- 2,5 HP)
Reducer: 1:49
Output RPM: 46.5
Result: Success.
Details: I was lucky enough that a friend gave me a relais etc for free to convert the triphase motor to 230v without loosing power. But its expansive.
Also i added a thick heavy hex coupling with keyways. It looks way too big but according to the formula its needed.
Its really strong. It only clogs shortly when the shredderbox is filled with plastic particles.
Watch Ed shredding here ;D

#######################################################################
Owner: @kettlekekkers
Motor type: mono-phase
Voltage: 230/40v AC
RPM: about 2500
Power: 2.8kw
Reducer: inline planetary/comes with motor
Output RPM:45’ish
Output N.m; 500’ish
Result: Success. very good
Details: cheap and easy to use and apply to assembly.
shreds up to 3mm thick PP or HDPE as far as I’ve tested, compressed milk cartons could be considered more like 5/6mm thick.
electronics easy to understand and reassemble
when clogging occurs, its easy to revers with the already provided switch.
Disadvantages: its very loud! and has a 36.5mm shaft output , no choice.
#######################################################################
Owner: anne-barbier

Type: 3 phase
Voltage: 230v
RPM: 1440 rpm
Reducer: 1:20 , SITI – Service Class 1
Output RPM: 72
Power: 4kW
Inverter: 4kw
Quality: Low, I assume a proper ABB motor can do magic here
Result: fail EDIT: After grinding the shredder blades to a 30° cutting angle, the result is a success (read further on this thread for more details)

Video: https://www.youtube.com/watch?v=4SNiDleTKac
#######################################################################

Owner: @stoli
Motor type: single phase
Voltage: 220HP: 3 (2.4 @80%)
RPM: 1740
Reducer: Worm gear 60:1
RPM:29
Output calculations based on 80% motor and 75% Gearbox :325 Ft/Lbs (440 NM)
Result: Success
Details: Good RPM, very strong. Rarely needs to reverse.Built with (2) 4″ pulleys power to drive train so the belt can slip to save the mechanics if it does bind. Flakes in picture is using a 5mm hole sieve.

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warrior
16/11/2017 at 13:59
2

Hey @xxxolivierxxx, didn’t you since build a better shredder? Power:2HP rpm:??? result:???

It would be useful to have as many reference points as possible. The ‘standard’ PP shredder: 2kW, 70 rpm, result: unstoppable.

It’s not just about the motor (and whether it’s single or 3 phase). The choice of gearbox is very important too. 70rpm is not ideal for every motor.

warrior
16/11/2017 at 20:41
2

@andyn No buddy, I have not had money to purchase another motor, my shredder is just sitting on a corner collecting dust.

I want to hear real life stories from shredder builders to start building an accurate database of motors and their power vs reduction ratios. For instance, you say that 2kw and 70RPM is unstoppable, however, @seyn-sustainableenergyyouthnetwork used a 2.2kw monophase motor for their project and it was not strong enough.

@flo-2 would you share your experience as well?

warrior
16/11/2017 at 20:51
1

That’s interesting, do you know what reduction/rpm they had?

warrior
16/11/2017 at 21:13
3

He said their shredder had a 50:1 ratio but didn’t say how many RPMs the motor had. Assuming that their motor was around 1800rpm then it should have been reduced to 36rpm

warrior
17/11/2017 at 01:52
2

Ok, found it now. It was a brand new 2.2kW 2pole 50Hz single phase motor, (2850 rpm). If it was a 50:1 gearbox that would give 368Nm of torque at 57rpm which is a huge amount and ought to be able to shred anything (far more than Dave’s shredder, 272Nm).

Something not quite right here. The motor looks like a permanent capacitor type which have lower starting torque, so maybe if the blades were jammed already it would have problems starting, but if running it should easily cope with the ‘cola bottles’ they said caused it to jam. Perhaps the gearbox wasn’t actually 50:1. Or perhaps the motor did not stall but the coupling between the gearbox and shredder shaft would slip and they had to turn the motor off, then when restarting it, it would not have the torque to spin up. It’s not exactly clear from their description: “The problem is that when we put Cola bottles who tend to be thicker on top they stuck and need to stop the motor.” Sounds as if the motor kept turning but the blades did not?

@seyn-sustainableenergyyouthnetwork can you shed any light on this?

warrior
17/11/2017 at 07:48
3

@xxxolivierxxx 2.2kW 1400 rpm, reducer 1:25, output 56rpm. Weakest point is the coupling, turns freely when load is too much. I have got around 280Nm and thats enough for most things to shred. Only very thick industrial plastic crates create problems.

yours
Flo

warrior
17/11/2017 at 07:55
2

Thank you @flo-2
When you say that it turns freely, does it mean you didn’t add a key/keyway on your shaft?

warrior
17/11/2017 at 13:40
1

@flo-2

Your experience fits much better with what I would expect, but did you measure 280Nm or calculate it? It should be higher.

I agree the coupling is a weak point and overlooked by many people. I’ve seen lots use a rigid coupler held on with screws on a plain shaft, this is bad for two reasons, it will slip when overloaded and the screws will tear up the shaft, and unless very accurately aligned it will cause binding. The best solution is a keyway as @xxxolivierxxx mentioned, onto which a flexible coupling is mounted. Though there is then a danger that if you use too big a motor you might actually break the shaft. (I think 2.2kW is really the maximum sensible size)

The binding issue with a rigid coupling and a capacitor-run motor could be another reason SEYN had a poor experience with a motor that should have been more than powerful enough.

new
17/11/2017 at 15:19
3

Shredder weight

I’ve found a 2,5kW gearmotor weighing at 60Kg, it puts out 356Nm at 68rpm
what a beast!

might be a bit of an overkill, BUT, i think it would be a good investment for future upgrades.

https://planetcalc.com/1908/

I can foresee that the total Net weight of the setup will be in the 80Kg range. kind of worried about that. wish me luck

warrior
17/11/2017 at 17:50
2

@berkasal I wish I had a similar option around for a decent price.
Let us know how the motor performs 🙂

helper
17/11/2017 at 18:16
4

Owner: @baas
Motor type: triphase
Voltage: 230v – 400v
RPM: 2280
Power: 2.2kW (+- 2,5 HP)
Reducer: 1:49
Result: Succes.
Details: I was lucky enough that a friend gave me a relais etc for free to convert the triphase motor to 230v without loosing power. But its expansive.
Also i added a thick heavy hex coupling with keyways. It looks way too big but according to the formula its needed.
Its really strong. It only clogs shortly when the shredderbox is filled with plastic particles.

watch Ed shredding here;D

warrior
17/11/2017 at 18:26
2

@andyn The motor company where i bought it calculated the torque for me, so it should be correct 🙂

warrior
17/11/2017 at 22:30
2

@baas thanks a lot for your reply.

@andyn if I use this page to calculate the torque of @flo-2‘s shredder, I get 375.13 N.m which is a lot of power but not quite close to the 280 N.m reported by Flo. Not sure if there are any details I’m leaving behind in the formula appart from the power and RPM

warrior
18/11/2017 at 00:50
1

@xxxolivierxxx, @flo-2

Ok, I see whats going on here. Yes Olivier, 2.2kW at 56rpm would equal 375Nm, however the company that supplied the motor/gearbox quoted 280Nm.

2.2kW is the mechanical output power of the motor. No gearbox is 100% efficient so some of this power will be lost. 280 is almost exactly 75% of 375, so it looks like they have used a figure of 75% for the efficiency of this motor/gearbox combo. Sounds reasonable as it’s probably a worm type gearbox.

warrior
18/11/2017 at 00:55
3

@andyn Makes sense, (375/100)*75 = 280

@jojojays, you will probably be interested on reading this thread

helper
18/11/2017 at 22:39
3

Owner: kettlekekkers
Motor type: mono-phase
Voltage: 230/40v AC
RPM: about 2500
Power: 2.8kw
Reducer: inline planetary/comes with motor
Output RPM:45’ish
output Nu; 500’ish
Result: Success. very good

Details: cheap and easy to use and apply to assembly.
shreds up to 3mm thick PP or HDPE as far as I’ve tested, compressed milk cartons could be considered more like 5/6mm thick.
electronics easy to understand and reassemble
when clogging occurs, its easy to revers with the already provided switch.
,
..
disadvantages’ : its very loud! and has a 36.5mm shaft output , no choice.

My shredder and its costs

warrior
19/11/2017 at 15:05
1

Adam @kettlekekkers, You seem to be way ahead in terms of power and torque. Does it ever jam? And what happens if it does? It looks like your jaw coupling (good choice) is attached to the shredder shaft with a couple of bolts, do they go through the shaft or just tighten up against it?

helper
19/11/2017 at 15:19
3

@andyn its only jammed a few times when i put 3 milk cartons together, which is kinda unnecessary,
or when i tried a thick Polypropylene jerry can pieces, which are about 4mm thick on the some parts,

the jaws have the original grub screws tightened agains a flat on the shaft, the bolts are just to keep them tight because they kept loosening, as i didn’t want to use lock tight glue,

starter
19/11/2017 at 22:18
3

Completely new, didnt read everything

I am currently building a Universal Motor Controller, so I can reuse old Washing Mashine Motors. Will share and translate what i collected.

PRO: Easy to get (i only paid gas for my car to collect the WM’s), simple to recycle aka getting it out of a washing mashine, recycling another component

CON: They need a speed Controller, otherwise they get faster and die.

Will edit and film my progress, may be able to sell the Motor Controler Boards with solder-ready components 🙂

warrior
27/11/2017 at 07:45
2

@kettlekekkers thanks for your input, added to the main topic

@pixeldieb washing machine motors have only about 0.3HP, and using a pwm to control the motor speed will reduce the torque even more. Just wanted to mention that so that you keep it into consideration 😉

helper
27/11/2017 at 16:18
2

thanks for all the information!
so, according to what @flo-2 shared, 280 Nm should be enough to shred mostly any type of plastic. but i have a question about that, because you have many ways to get similar values of Nm torque. for example, a 1hp motor with 20 rpm of output speed or a 2hp motor with 40 rpm should get +-356 Nm of torque.
so the question if it´s really the same because of the torque, or does the other factors make some differences on the behaviour of the shredder.
i don’t want to fail on buying the wrong or not enough strong motor because they are not so cheap in here.

helper
27/11/2017 at 20:14
3

@tinch

its a good question , i think it needs examplafying to make it easier to understand how gearing and torque work with RPMs and horse power, somehow..

but in essence yes , gearing it down massively would work bit, however really slow speed means it will take longer to process plastic then cutting it with scissors…
don’t know if you have ever come across an art work by Arthur Ganson, called “machine with concrete” its geared down so much that the output will take a trillion years to do ONE rotation, i bet it has silly amounts of potential torque though…haha

dedicated
29/11/2017 at 13:03
2

torque range What I can tell from all the people I have spoken to is 70rpms kicks the plastic out a bit and 56 rpms cuts quite nicely but takes a bit too long so what torque what you need for a sweet spot of about 62 rpm ? how do you do the calculation

warrior
12/12/2017 at 21:24
2

I’ve developed an Excel calculator based on peoples experiences in this thread, you enter the motor and gearbox parameters and it tells you well it should work, please see this thread.

helper
19/12/2017 at 19:15
1

I would love to know more about the coupling you guys are using.
I’ve got a 3HP Single phase motor, with a reduction to 60 RPM. I connected my gearbox to the shredder with a heavy spider coupling. I didn’t get my shredder shaft keyed – so I put in a sheer pin on the shredder side.

I haven’t figured torque yet, but we’re snapping sheer pins all the time.

My shredder has a 12″ opening – so quite a bit more teeth to bite. However, my experience shows it’s when the milk cartons, PET bottles, etc, fold over on themselves – even it’s only over couple of teeth – that it’s hardest on the shredder.

starter
27/12/2017 at 16:31
2

I used a 5HP 3-phase motor with a VFD running single phase (220V 2-wire), so 2 leads on the input side of the VFD, 3 leads on the output side. 1800 RPM

Gearbox was a worldwide electric inline reducer: http://www.worldwideelectric.net/product-category/gear-reducers/inline-helical-gear-reducers/

First one was a 20:1, 76 RPM gearbox. This didn’t have enough torque for my shredder (larger than this) design, and moved very fast so if it jammed it was violent.

I then upsized to a 60:1 (28 RPM), this has plenty of power but my shaft was undersized, it sheared the keyway.

The coupling I ended up with is a chain coupling. https://www.mcmaster.com/#standard-shaft-couplings/=1av78pa

These work really well because it’s easy to adapt different size shafts together, they can handle some misalignment, are easy to assembly, and they’re pretty cost effective.

helper
28/12/2017 at 05:17
1

@wess – Is there a method you use to determine shaft size? I’m all the way down to 3/4″. I suspect this is going to be too small in the long run.
I’m about to ditch my sheer pin all together… and I’d like to know what my next weak link is! I’m guessing it’s the spider coupling insert.

helper
28/12/2017 at 05:23
1

Also, It might be helpful to know what kind of overload protection people are using.

starter
28/12/2017 at 14:49
1

To select the shaft size, I just went with whatever size the gearbox uses. You could do a calculation to determine the minimum shaft size, but I went this route because coupling the gearbox to the shredder shaft being equal size is a lot easier for a variety of reasons.

One thing I will note, it will NOT hurt to oversize the gearbox/motor in terms of torque.

helper
28/12/2017 at 22:32
1

thanks @wess !
I’m committed to 3/4 for now. My gearbox shaft is 1 3/8″ so I’ll be starting a new shredder from scratch if I go that route. I too will be slowing down the RPM from 60 to 40-ish if I get to a rebuild someday.

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