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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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09/06/2016 at 02:23

Hey guys,

Thank you for all the info on this thread and the word doc., we have been breaking our heads over the motor issue as well.

Maybe its a stupid question, but what about simply attaching a drill to the shaft? I find plenty here that are relatively cheap, have enough power, are reversible and with adjustable speed… It seems like a great solution, but maybe Im missing something. Can anybody comment on this?


09/06/2016 at 13:45

@paulfreed thanks for proposing to provide the wiring diagrams to convert triphase to monophase. check the document now, I’ve added some information I’ve found online based on the info provided by the guy who did it for us. That could give you a starting point (it’s a bit messy for now, as I only copy pasted some info)

@layla what machine are you talking about? the shredder or the extruder?
If it’s the extruder you can try to attach the drill directly to the motor…if it fits. if your motor has a hole, instead of a shaft coming out of it’s gearbox, you can try to do it. It is very likely that they have different sizes, and in any case, if the hole in the gearbox and the drill they happened to be the same size, you will have to add a small surface on the drill shaft to interlock in the hole (if you look at the hole, it’s not exactly round, it has an inset on one side that is used to put mechanical force onto the shaft.

10/06/2016 at 21:41

@lyricalpolymath I am talking about a motor for the shredder. I think maybe you misunderstood: I was talking about connecting the drill directly to the shredding mechanism, iow that the shredder knifes are turned by the rotating power of the drill, which can be adjusted …

Also we got an offer from a motor manufacturer for 2 types of motors with reduction mechanism: 1/2 hp + 30:1 reduction (to 60 RPM) for 450.000 COP (= 130 euros) and one with 2 HP for 800.000 COP (= 240 euros).

I have been reading that a 1/2 HP motor might suffice, which would be awesome financially….

14/06/2016 at 22:38

@lyricalpolymath and everyone else that contributed, this is great. I wanted to let you know that I’ve wikified the guide over at Precious Plastic Wiki: Definitive Motor Guide.

I think the Google doc was great, but the wiki just seems a bit more organized. Everyone should be able to sign up and continue editing. Let me know if you have any concerns or issues.

14/06/2016 at 23:24

@xxxolivierxxx Thanks for the price estimates. I’ve added these to the wiki. See http://www.preciousplasticwiki.com/index.php?title=Definitive_Motor_Guide#Estimating_Costs

@anyone have more? Feel free to add them. These estimates will definitely help folks that are building machines for bidded projects or on a donation basis.

12/07/2016 at 00:28

Hi everyone! We just got an offer for a 1hp monophasic motor with 1750 rpm and a gear reductor with a ratio of 30:1 to a rpm of +/- 70 for COP 600.000 = 190 EUR. Do you think that would work?

12/07/2016 at 19:28

Hi everybody, thank you for sharing,
here is a good address for second handed Motors in France and neighbourhood (most of them are triphases) :


I order mine 2hp 220/380 Volts, 52rpm= 225 euros

@layla your motor should work fine

13/07/2016 at 13:22

Ok so I’m excited by the idea of the shredder and are planning on putting one together I have limited funds but tons of material and machines but the only motors I have are 2800rpm 2hp single phase motor Ac which I could make a worm reduction gearbox 40:1 ratio which is 70 rpm it sounds hard but we build gearboxes at work for a living. Is this to much power and has it been successful for others?

27/07/2016 at 20:00

hey everybody, @robksawyer has created a wiki for the project. thanks!
that is better than the Google Docs, so from now on I’d say we use the wiki that anyone can edit. http://www.preciousplasticwiki.com/index.php?title=Definitive_Motor_Guide

I’ve put an update on the google docs redirecting readers to the wiki, but I’d still keep this forum post for discussions. I’ve got a couple of updates and questions coming

in the meantime thanks @robksawyer

I’ve created a circuit that allows the single phase motor to go both directions. I will share the video and the instructions soon

04/08/2016 at 16:53

hey @robksawyer The wiki is down. I’ve noticed that it was already kind of slow.

can you produce a dump of the database? I could host it for free on a better server and you could redirect the DNS once the wiki is up on my server

maybe @davehakkens want’s to control it and host it on his own servers?

let us know.

04/08/2016 at 17:42

@lyricalpolymath I currently have it running on Heroku and I was messing around with scaling down the dynos to see if it’d still work. Mediawiki is a memory hog. It should be back up now. In order to really getting it running well, the cost is about $59/month 🙁

Hosting on another server would be a great. Hopefully it’s not a huge pain to do so considering I’ve added quite a few addons and configuration updates to the current install. How would you prefer me pass along the data dump?

04/08/2016 at 18:46

@robksawyer I’ve checked I can automatically install MediaWiki 1.27.0 (or 1.19) if that’s ok.
I haven’t installed and used one in a long time so I don’t remember if it has an import / export option somewhere in the administration panel or if we have to dump the SQL
Let me know about the wiki
also maybe better to keep this process off forum look for me on skype (“beltran”) (in Malaga or Granada)

07/08/2016 at 17:18

Hi @lyricalpolymath and @robksawyer we don’t have a server available to host it. But we could provide a subdomain like wiki.preciousplastic.com to have it all under one umbrella. Let me know if you are interested in this.

11/08/2016 at 20:43

@davehakkens @robksawyer I’ve created this other forum post just to talk about the wiki, so we don’t pollute this post about the motors
talk to you there

03/09/2016 at 23:02

Hello, can this motor be used with a speed controller(for extrusion)? I’m going to obviously make a 50:1 reduction gearbox also.

04/09/2016 at 06:36

@zekedge 1/3HP doesnt look like enough power for the shredder.
I would recommend a minimun of 1/2hp, but its up to you if you want to test that motor and see how it behaves

15/10/2016 at 13:19

Hi folks,

so it turns out to be quite hard to get your hands on a cheap motor. I now found one for 60€; 63/min, 0,37kW which equals 1/2 HP i think. 55Nm; 230V. Did anyone try to shred with 1/2HP yet? I have to decide if I take that one until tomorrow. Some advise would be lovely.


18/10/2016 at 19:59

OK EVERYONE… after several attempts I’m going to say that a monophasic motor is probably not enough to shred well.

We have a 1.1 KW (=1.5 HP), 70 rpm, 70 Nm mono-phase motor
it does shred, but slowly and it often clogs : if we throw in too much material it stops, even the top of the bottle sometimes is enough to clog the machine.

I’ve made a circuit to make it go both directions, and that works well to get it unstuck. But this motor is NOT powerful enough for the precious plastic machines. At least it doesn’t have the performance you can see from other videos in this community.

@davehakkens does your (triphasic) shredder get clogged from time to time or it always runs smoothly?

Alignment issues
I’ve solved them with a universal joint / cardan (will post pictures)
so the problem isn’t mechanic any more, it’s simply the power of the motor that is not enough.

@zekedge As far as I know VFDs can be hooked only to triphasic motors, so no, you can’t use a VFD as speed controller. Also like @xxxolivierxxx said, the motor isn’t powerful enough

@goldmund as you might guess from this post, those parameters probably aren’t enough.

19/10/2016 at 21:10

@lyricalpolymath It tends to get stuck when I throw in plastic that is to thick. Or when I have a mesh with very small holes/output so the material keeps spinning around until its small enough the leave the shredder. But just for the ‘normal’ shred it shouldn’t get stuck

25/10/2016 at 06:29


I’ll try to make a video of my machine shredding soon. As Dave mentioned, 1/2hp is more than enough to shred thin plastic, like plastic bottles cut in 2 or 3 pieces. The top of the bottle where the cap goes is made of thicker plastic that gives a hard time to motors with less than 1HP, but it can still be shredded. I don’t currently have my machine with me, I left it with a machinist because I was using it without a hopper or frame, and he’s making those for me, but as soon as I get it back, I’ll post a video of it.

31/10/2016 at 11:07

will something like this work for the shredder? @davehakkens @lyricalpolymath
Gearbox Technical Parameters:
Rigid tooth flank helical Gearbox ,Output Speed :
76 RPM , Gear Ratio :18.6 ,Service Factor : 1.64 .

Motor Technical Parameters:
AC Motor : Power : 2kW, 240Vac , 1Phase ,50Hz , Duty : S1 ,Speed : 1500RPM , Mointing : IMB5 , IC411 , insulation Class F, IP55

02/11/2016 at 14:11

Hi @jsk555 that sounds about right.

03/11/2016 at 16:31

We’re looking for a shredder motor at the moment and have a second-hand trailer winch that we could possibly use, but being completely new to this I was wondering if it would be suitable…

There is no RPM on the spec (just line speed) and I don’t have the motor in front of me to try and work it out at the moment.

Update: RPM appears to be in region of 35-40

The full specification from the manufacturer is:

Voltage: 12v DC
Capacity (Rated Line Pull of Bottom Layer): 9,500lb (4,309kg)
Motor: 5.2 hp
Gearing: 2 Stage Planetary
Gear Ratio: 148:01:00

Rope: 9.5mm x 26m
Dimensions (LxWxH): 615.2mm x 157.5mm x 278.15mm

Line Speed – No Load: 18.9 m/min
Amp Draw – No Load: 75 amps

Line Speed – Full Load: 1.5 m/min
Amp Draw – Full Load: 430 amps

Thanks in advance for any help on this.

06/11/2016 at 19:23

Guys remember the number we are actually interesteed for the loads is the Torque. You can achieve similar torque results by varying the hp and reducing ratio:

Torque lb-in = (hp x 63,025)/RPM

ie: for the same torque value, diferent approaches

Torque: 60Nm = 60×8.85 = 531 lb-in
Hp: 0.5
RPM = 0.5 x 63025 / 531 = 59 -> 60RPM
Recommended Motor RPM (50Hz): 1500rpm
Ratio = MotorRPM/Output Ratio = 1500/60 = 25 -> Ratio 25:1 for 1/2hp (or 0.37kW)

Torque: 60Nm = 60×8.85 = 531 lb-in
RPM = 0.25 x 63025 / 531 = 29 -> 30RPM
Recommended Motor RPM (50Hz): 1500rpm
Ratio= 1500/30 = 50 -> Ratio 50:1 for 1/4hp (or 0.18kW)

And so on… End result will be cutting speed (volume of plastic / hour) But you can feed both scenarios with the same sizes/thickness of plastic)

07/11/2016 at 13:49

What allerandi said.

Your winch will have waaay enough torque (about 900Nm) and the speed is good. But it will not be designed for continuous running and will get very hot under load. It will also need a large battery bank.

If you can use the planetary gearbox and swap the motor for an AC one that would be the way I’d go. But it’s probably built as a unit and will require some engineering. With 148:1 a 1HP 2-pole motor should give you plenty of torque and blade rotation of about 20rpm

08/11/2016 at 10:49

@allerandi, @andyn Thanks for the feedback. I thought it was probably too good to be true that we’d have the perfect motor just lying around! We’ll have a look at utilising the gearbox. Thanks again

16/12/2016 at 09:32

I understand that torque is the most important specification of the motor. So why does it matter if it is 3phase power or not? If I have a 2 horse power monophase motor, shouldn’t it be good enough? It seems like the only difference between monophase and multiphase is power efficiency, not power itself.

Even @davehakkens ‘s 3 phase does get clogged sometimes, maybe something can be done to the mechanical design of the teeth box to improve this, rather than everyone buying a 3 phase motor?

I have a 2hp single phase DC treadmill motor that I will hook up to a 20:1 gear reducer with pulleys and a belt (bought on the same site). I’ll let you guys know how it works out!

17/12/2016 at 00:09

@emi422 looking forward to see what you make. We could use some alternative options of delivering power to the shredder, good luck!

30/12/2016 at 23:05

hmm, on the subject of mono-phasic motors. surely this single phase 240v motor is more than antiquate with 182nm output ??


Single Phase 2.2kw Motor and Worm Gearbox 70 rpm output 35mm Hollow Bore 182Nm

07/01/2017 at 21:28

Has anyone tried treadmill motors. They my be a first world thing for people how choose to walk indoors but they come with speed controllers and they are DC motors so they are high torque at low rpm. They are typically between 2.5 and 3 hp.

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