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(Almost) Definitive guide on Motors (WIP)

This topic contains 150 replies, has 69 voices, and was last updated by  Elton 1 year ago.

beltran lyricalpolymath

(Almost) Definitive guide on Motors (WIP)

13/05/2016 at 20:17

Hey everybody,
I’ve summarised a bit of the various posts on the motors that can be found around in this forum, and wrote this Google Doc that you can all see, comment and edit.

check it out and help complete it if you can / want.
The idea is to start preparing a simple, clean doc about the motors to expand the awesome specsheets that @davehakkens produced.

let’s keep the messy discussion here in the forum or as comments in the doc and there put only the final results.

It would be great to put some examples, with the pictures of the label of the working motors that people are using.
@davehakkens could you post a pic of yours or is it all painted in grey? 😉

If anyone here has made the machines and they are working, please post images of the nameplate of your motor and what the pros and cons you see in them

this doc builds on many other posts and contributions that you can find in these forums:
Shredder Motor
Realistic Cost Shredder
All posts that name “motor”

Let me know what you think
thanks to all

ps I’m in Malaga, Spain too if any other spaniard wants to hook up. We also found some providers we can talk about and if we order all together the pieces maybe we get a discount 😉

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14/05/2016 at 11:35

One step closer to be able to use a cheap washing machine motor for the precious plastics machines

I’ve found this awesome Gear Generator that makes it easier to produce our own Reducer gearbox

check this example: These parameters convert a 1400 rpm to 70 rpm

The current code has a limitation to 360 rpm max, but if you open the console
(View > Developer > Javascript Console in Chrome) and paste this function:

function getRPMfix() { return fixInput( Number( $("#RPM").val() ), setRPM, RPM, -1400, 1400 ); }

It will allow you to input 1400 RPM

Anyone here in the forum has mechanical engineering experience and sees any problem with lasercutting this, building a box similar to the shredder box and hooking this up to a washing machine’s motor?

Will the torque of a washing machine still be enough at 70rpm?


14/05/2016 at 20:33

thanks for starting this topic/google doc and trying to make it clear for everyone @lyricalpolymath. I’m currently traveling and can’t access the machines. I’ll post a picture of the (not painted) nameplate when i’m back. Keep up the good work!

16/05/2016 at 00:58

Hi @lyricalpolymath awesome, thank you 🙂

“I have pinned this topic for easy reference for all”

17/05/2016 at 10:46

thank you both @davehakkens and @enviro.
If you have contacts with people that have successfully built the shredder and extruder please ask them if they can take pictures of their motor’s nameplates and post them in here with the pros and cons they see in them (maybe too slow or too fast?…not powerful enough when shredding or extruding?)

I’d like to add this info to the document.

Also @davehakkens, if you are traveling around and happen to be in Andalusia, be sure to call… we’d like to offer “compensation” by hosting you and offering you an art+design experience 🙂

17/05/2016 at 11:45

Absolutely! a sharing giving communities is what we want to here 🙂

With my limited very short experience helping on the forums, I have become aware of a few people that have completed the Shredder, however all is quiet in regards to sharing back their builds and experience, I’m hoping that maybe they have had a few teething problems, once resolved will hear back from them.

17/05/2016 at 17:45

I will share my shredder as soon as I complete it, I had a hard time finding an affordable motorreductor, but finally, I was able to get in contact with someone who has a 1/2 monophasic motorreductor that doesn’t require me to sell a kidney.
There is a chance that this motor doesn’t work (and that I waste a lot of money) considering that the recommended motor power is 2KW (around 2.6HP) and the motor I’m getting is only half HP, but if it works, I will let you know so that other people can opt for a cheaper motor.

Just to give you an idea of how expensive those motors are down here in Costa Rica:

*2HP Monophasic 220v motorreductor (new): $1582
*1.5HP Monophasic 220v motorreductor (used): $1016
*1HP Monophasic 220v motorreductor (new): $1484
*1/2HP Monophasic 110v motorreductor (used, the one I’m about to purchase): $300

I found a video of a guy who used an 1/2HP motorreductor for an elevator, and it’s capable of lifting 100 kilos, so I assume 1/2HP should be more than enough to shred plastic.

17/05/2016 at 21:16

I just heard back from the place where I’m going to buy the motor.
Attached you can find some pictures of what it looks like.

Once I have the shredder fully assembled I’ll give you my opinion about how good a 1/2HP motor is for this project

17/05/2016 at 22:20

What’s the gearbox reduction ratio?

I don’t think this is a 1/2Hp (375W) motor. It looks like 1HP at 110V / 2HP at 220V. (750W/1.5kW) so looks like you got a good deal if it works.

Even a 1/2HP motor will be enough, as long as the reduction is slow enough and the gearbox can handle the torque.

19/05/2016 at 17:08

@xxxolivierxxx thanks for posting the pics
I think you have a very good deal like @andyn said. If it lifted 100Kg, and I correctly understand the units, that means that you have approximatively 1000 Nm gearbox – very good indeed.

hopefully your rpm are slow enough, because the input at 1710 rpm (at 220V).
You should have a code on the gear reducing factor and if it’s i:25 or similar it’s perfect.

I’ve discovered that gearboxes are even more important than the motors themselves.

@andyn you’ve once, elsewhere in the forum, estimated that 50-100 Nm (≈5-10 Kgm) is enough for the shredder. How did you reach that conclusion? do you have a motor yourself on a machine?

In Spain, scrapyards are filled with motors… but none with reducers, so we are going to have to buy a new reducer and don’t want to mess it up. If you have some tips on this..

19/05/2016 at 17:56

@andyn They will deliver the motor today (I don’t have it yet), but the ratio should be between 25:1 and 30:1, with an output of 56~60RPM. And yes, I do think this motor is more than enough for the shredder. I have not tried it yet, but motors like this (same hp, same reduction ratio) are used for elevators that can lift 220 pounds, so when Dave mentioned using a 2kw motor on his list of materials, he probably referred to the one he found/used, and not specifically to true Horse Power needed.

@lyricalpolymath Surprisingly, we don’t have “scrapyards” in Costa Rica, or at least they are not open to public. I was able to find some places where I could buy motors for less than $200, but then you had to also buy the reductor. Finding used motors is a challenge, and new motors are excessively expensive.

The cheapest one I found (apart from the one I purchased) was:

Precio Total ¢279,110.00 (equals to $515 USD)
Motorreductor sin fin corona salida 90°
Potencia del motor: 1hp / Voltaje: 110/220V – Monofásico – 60Hz
Relación de reducción: 30 @ 1
Modelo: LAC 63X/30/200/19 D30

Esta empresa fabrica motorreductores en España, tal vez te consigan algo barato

In Costa Rica our standard voltage is 110v unlike Spain, so the motor should run at 1430RPM approx.

If you have easy access to scrapyards in Spain, I highly encourage you to scavenge for gears of different sizes and then try to build your own gearbox with pulleys.

On another hand, I was able to find a Plasma Cutter in Costa Rica that will cut the metal pieces for $400, and I found another place that sells me the Hexagon Bar for about $6 😀

I’ll document my assembly process and will record a video of how good this motor is at shredding 😉

19/05/2016 at 22:04

It’s finally here 😀

20/05/2016 at 01:01

50-100Nm was an educated guess, but I’ve since got my shredder working and taken some measurements. To shred bottle tops takes a maximum 20Nm, to shred the thickest plastic I could find (front panel of a domestic appliance) took 60Nm. Note that my machine is half the size of DH’s, so for that I would expect the figures to be roughly double, perhaps slightly less as the teeth are more pointed and will probably pierce with less force.

That sounds like a good combination of power and speed, I think it will work fine. I agree 2kW sounds like way too much, if you were to lock the knives (drop a spanner in perhaps?) something would probably break.

21/05/2016 at 01:46

awesome work! thanks for doing the tests and finding out. 😀
I’ve already updated the document.
With this info we might find the motors that we’ve previously discarded thinking they weren’t strong enough.

I’m curious… how do you find out the values? what was the experiment like?

In Spain we have a similar problem with scrapyards. However we’ve managed to talk a recycler into giving us some materials. Washing machines engines are everywhere and really accessible. If we can make one work with a reducer it could be much easier and accessible for everyone in the future. Keep us posted on your machine 🙂

21/05/2016 at 02:25

I don’t think my numbers are all that definitive, these were just measured turning the shredder with a crank, I don’t have a motor on it yet. Also note that this is not the Dave Hakkens shredder, my design is about half the size and requires less torque.

But yes, I don’t think smaller motors should be discounted, they will work with appropriate gearing.

21/05/2016 at 10:55

@beltran thanks man!
@andyn thanks for doing those measurements!

I hope to test this week – will share results when i’m done.

Anyone given motor control and protection a thought?

23/05/2016 at 10:12

Hi everybody, I’m Hugo from Cambodia.

Today I saw this motor and I would like to know if I can use it for the shredding machine?
Do I have to add a gearbox on this one?


23/05/2016 at 14:04

@hugob there isn’t enough information on the label.
if the motor doesn’t have a reducer attached is very likely that you need to buy one
but you can’t know which one to buy unless you:
– find out the rpm of this motor
– measure the diameter of the front part of the motor (where the reducer would be attached)
– measure the diameter of the central shaft of the motor

these 2 last diameteres are needed to find the right reducer that fits this specific motor

read the document to understand what you should be looking for next time

24/05/2016 at 04:51

@lyricalpolymath thank you for your answer.
I think you haven’t clicked on the picture (there is 2 pictures in one image with only the half on the preview). This is all the motor specification I was able to found.
This motor was used to lifting some load, that why I think it’s included a gearbox because I don’t think axes have at the end 2800 RPM.


24/05/2016 at 12:07

@hugob oh I see it now. Sorry I didn’t know the images where cropped and clickable 🙂

I now see that this is a winch motor, and although I’ve put them in the document as a possible source of the motors for the machines, I am no longer sure:
it does seem that this motor has only the output 2800 rpm which makes sense if it is supposed to use pulleys (the chain needs to travel a lot to have a fraction of the movement of the weight attached to the pulley…that’s how you make the weight easier to lift, http://www.explainthatstuff.com/pulleys.html)

I’ve already discarded some winch motors because of this doubt…
That said. I’m not sure 🙂 some winches might have gearboxes and have smaller rpm, but your motor doesn’t seem to be the case

One thing you could do is check the yellow handle controller to see if it has variable speeds. Test is out to see if the output speed is right:
– mark with a pen a point on the rotating part and on the fixed part and start it,
– count the number of revolutions it makes in one minute (or ten seconds and multiply x6)
if it’s 70 rpm = revolutions per minutes, this means that it should take slightly less than a second to do a full revolution, or it should do slightly more than 11 revolutions in 10 seconds

you might be able to do it by hand without plugging it in: if you unscrew the black part at the bottom of the motor you might be lucky enough to find a shaft or fan that you can turn with your hands. That will make it easier to measure the ratio of the motor input rpm (each revolution you give to this new found shaft) to the output rpm (the revolutions that you see in the front of the motor that you marked with a pen).
– If it’s 1:1 (input rpm == output rpm) then there is no reducer box
– if the output is slower then there is a reducer box and you can measure the reducing factor (i) using this formula (i= input rpm/ output rpm)
which you have to measure as described in the previous paragraph

hope it helps

24/05/2016 at 12:24

@hugob I THINK it’ll work. I nearly went for one of these too. The problem is you’ll only know once you have bought it and stripped it. They do have some kind of gear on them and 1 kW is prob enough power, but the speed – that’s a question mark. I’d love to see what shaft it has inside the cable pulley thingy – If you do go for it please share your experience with us.

24/05/2016 at 13:03

Did my first shred today.
Here’s my motor and gear…
40:1 gear ratio
A total overkill i think, but it works.
Still need to do some minor mechanical adjustments and then I’ll try get my head around your googledoc (@lyricalpolymath) and share more.

25/05/2016 at 08:11

Thank you for your responce @lyricalpolymath and @paulfreed! (and nice shredding machine by the way!)
I was looking of another motor yesterday and I found this one in a shop.
I will share my experience with you, I have almost everything to start building the shredding machine.

I have found 50 rpm at the end of the gearbox, do you think this will be enought?


25/05/2016 at 14:28

@hugob I think the speed on your video looks fine. The motor power looks good too. I wish i could have gotten a single phase one like that. Look forward to see the results!

01/06/2016 at 06:00

Hi this motor works for the sheredder or i need a different?



01/06/2016 at 19:46

@roysh the mercadolibre link you posted advertises several motors.
I recommend you to call the seller, and ask tell him you need a MONOPHASIC motor between 1/2HP and 3HP. Trifasic motors and any other motor of more than 3HP will be really expensive, and you don’t need that much power for the shredder.

01/06/2016 at 22:32

Today I visited a shredder on display, took a picture of the motor shield of the shredder from the build video, but no rpm’s on there :(.
checked some of my video’s and it’s between 30 to 40 rpm….
So in my humble opinion. I had to repair a broken shaft once…
The ones from @hugob and @paulfreed are the ones I would choose.
The one from the video is too strong, it’s strong enough too brake a shaft if blocked by a bolt :(. With 30 rpm you can use a 1KW or 0.75 motor.
So 50 or 70 rpm with 1.5KW puts you on the right track.
A little more rpm’s than the 30 from the video will give you a better output ;).
As I read in other threads a 24Volt window wiper motor with a extra reduction or v belt pouly could do the job, but you can use a scissor as well.

Would like to find me a 1one phase motor like @hugob for use in my own house 🙂
Although with a 3 phase motor and a extra relais you can build a reverse function, very nice when blocked 🙂

04/06/2016 at 10:25

@keesdeligt talking about broken shafts – do you know if Dave’s has some kind of motor over current protection? In the youtube vids its too quick to see. Setting these current values low could not only protect your motor, but also prevent broken shafts. That’s another reason why I went for the more expensive inverter – you can set up an over current and prevent a disaster 🙂

05/06/2016 at 07:46

Hi @paulfreed,
indeed you should better use a motor protection, but for the video one there was not enough room in the plastic container, just 2 basic forward and reverse relais.

Dave’s workshop is located in old abandoned post office, witch is by now stripped from all relais, heavy switches, control lichts, and pushbuttons ;).
We had 2 of those big motors, the first shredder we build ended up in a school, so I wanted to make a decent safe box. But the only thermal safety relais to be found were a 1.6 and a 6 amp one. The 1.6 was too light and the lowest setting on the 6Amp was still too High :(.

We could use a volunteer to make a decent electrics drawing….
In my opinion (for 3phase reversed systems) we should have a main switch, 2 springloaded pushbuttons for forward and reverse, the forward button powers a holding relais so when he thermal breaks it will not start when push the safety in again :(. And off Corse the 2 heavy motorrelais..

06/06/2016 at 19:54

Hey all, thanks for sharing
We too have found the 1.5Kw, monophase, 70rpm, option a good one, although the motor is very big and heavy.
We think it’s an overkill too, but I hadn’t thought of the

We’ve also managed to convert a triphase motor to monophase. As said in the document, it is possible. Will get the guy who help us do it give us some pointers

@keesdeligt and @paulfreed, you seem to know enough about this…do you have any pointers besides the one in the document?

07/06/2016 at 16:53

Hi @keesdeligt


Ahh, I see. Thanks for the info. I almost went for that option too, but got lazy thinking about all the extra wiring i’d have to do. Plus someone told me the safest reversing contactor systems are those that are mechanically interlocked, but they were expensive. …which comes out to just below the price of an inverter anyway.

When I get some time I would gladly do some wiring diagrams for you guys.

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