(Almost) Definitive guide on Motors (WIP)
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
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 😉
Paul Freed: Is that a Motovario (Italian made, blue color) reducer attached to shredder motor? I’ve seen units advertised at reasonable prices but was not sure if they were durable enough for shredder. How is yours working?
Would 144 rpm 1/2 hp be overdoing it? Can the rpm counteract the strength of the motor?
If you need more information:
this motor uses a 1:10 gearbox but I don’t know whether this is too fast.
Has anyone looked into using a Variable Frequency Drive? I’m no expert but I understand that this will allow a large variety of motors, single or three phase, DC etc. It also can eliminate the need for a gearbox.
Has anyone used the motor and controller from a consumer treadmill? I can buy them from reuse and recycle stores for $20 or less. They have 90 – 180VDC motors that are rated at 2 – 3 hp. with an electronic speed controller. I read the following at the Practical Machinist.
“In general, you get constant torque with either DC or a VFD below 60HZ. Above 60HZ, you get constant power with the VFD. So with either type motor and control, at 1/10 of the normal RPM, you have 1/10 of the power and the same torque as at full speed. A lathe will be more satisfactory if you have full power available at low speed. That is why variable speed belt and gear drives have been used on lathes for decades. The modern lathes with built-in VFD or DC drives start out with oversize motors so they still have decent power at lower speeds.
And I have bought several good VFD drives for very low prices on eBay. You don’t have to pay retail, though prices have dropped quite a bit since they first came out.
Way beyond what I know much about. I think that it matters if the DC motor is series connected or shunt connected.
Maybe a combination of a treadmill motor and a Variable Frequence Drive (VFD) from ebay?
Just some ideas.
I have been looking into the idea of using a hammer drill as the motor. I found one that can produce 571 torque, and was wondering if anyone has experience in trying a hammer drill for the shredder.
Please let me know.
What exactly do you mean by “a monophasic motor isn’t powerful enough for the shredder”? (google Doc) Basically torque matters and to my knowledge speed and torque are indirectly proportional to each other. For sure a triphasic motor is more suitable for the shredder, but by reducing the speed to 20-30 rpm this should then lead to 2x-3x the torque, which should be sufficient, or am I overlooking something?
I visited some scrapyards yesterday. there were plenty of Italian and german motors but they were triphase. I asked the storekeeper about the single phase, he told that he can assemble it on the gearbox. He asked me to select the power for motor and gearbox size. I don’t know much about gearboxes, but every size and kind of gearbox and motor are available. Could you please suggest me best combination for the shredder. Gearboxes are available in various sizes with the reduction ratio of 1:20. I’ve also attached a picture of one gearbox, he demands 65$ for it. and the motor would be in the range of 90$. kindly assist me which motor and gearbox should I select?
Looks good to me! The Gearbox you need totally depends on the motor and your needs for shreddering. In general, you can increase torque – which is needed to shred (more torque => stronger shredder => Less problems with thicker plastic) – by having a stronger motor and/or a greater reduction.
In the end, you shouldn’t end up with more than ~70RPM, slower is stronger, which is especially suggested for single phase motors, but (not worth mentioning) will lead to a slower shredder.
So there isn’t really a “best” motor + reduction to buy, it’s all about what you want to do with it. More kW or HP/PS will lead to a stronger shredder but will also consume more energy,…..
So there are just too much variables taken into that equation to give a good advice from a remote position. Maybe you can send some photos or information of the motors and gearboxes availible?
I’m the process of building the shredder and I’m currently looking at using a washing machine motor. I saw it mentioned in the google doc and wondered if anyone has used this method? if so what sort of gearbox did you end up using ?
Will this do the job do you think ?
I found this motor in the storage where I work, and where I am building the shredder, I have tried to figure out how much torque this motor will have when geared down to 70rpm. But I am having difficulty deciphering this label. I’m not even sure how many poles and therefore how much rpm this has.
I am a total beginner with motors, I’ve read all the posts on here and gleaned a lot of information, but I still don’t know what most of these numbers mean. I THINK this is a 4-pole motor, but that is only a guesstimate based on old ebay posts I’ve found… there’s a lot of guessing going on. cosY 0.75?? 675/min — is that rpm??
Could anyone help me out a little bit? Is this motor good enough?
For a start it’s a 3-phase motor and it’s only 1/2 HP so you will need a 3 phase supply or an inverter drive.
It can be made to work but will require a large gear ratio and will be slow.
It’s actually an 8-pole motor, which is a good thing as it’s effectively already geared down by a factor of 4 over a full speed motor.
Reduced to 70rpm it would produce 50Nm, you really need at least 2-3 times that which you can get with extra reduction.
Yes 675/min is the speed at 50Hz under rated load. Cos theta is the power factor, you don’t need to worry about that.
I just discovered this interesting project.
Sorry about the wall of text. 😛
The engine part seems to be the most troublesome, since most people only have access to single phase electricity unless they are willing to shell out a lot of money to upgrade their power-feed.
I was originally thinking that a washing machine engine would be the perfect fit, but apparently there are a bit of a problem making it slow enough, and I guess the motor would overheat after a few minutes(might be solved with some cooling though).
Anyhow – I think I have found a better source for an engine – woodchippers. But not any kind, I’m thinking of the silent electric kind that is slow speed/high torque and AFAIK generally have motors in the 1.5-2kW range and have built in engine protection.
There might even be some woodchipper designs that might do a good job on plastics(?)
I have some other ideas as well 😛
What if you put that engine on the mechanism of a paper-shredder?
Will it shred the plastic into nice strips?
Did a quick search – seems like there are also paper-shredders that cut the paper into confetti/small squares.
I see some problems with stuff like bottle-necks though, but it might be a nice starting-point.
I am not sure what it costs to get the parts to the original shredder made, but I’m thinking it might be quite expensive. Maybe it would work with some wooden saw-blades?
They can be had at about €10/piece.
If so, we are left with the axle and spacers that is not fairly easy to make.
Maybe it would be possible to use a regular round axle, weld the spacers to the saw-blades, and cut some shallow and flat grooves (2-4 for each saw-blade) across into the axle. Then you could have thin spacers that fit into the grooves and are screwed into the thicker spacers with small flat-head hex-screws or similar. There would be two thin spacer-halves per blade to avoid gaps.
Not sure how well it would work, I guess there would be a risk of it getting stuck because of all the blades working at the same time. And some of the plastic (like bottles) might just bounce around instead of being cut properly. Might be alleviated by removing some of the teeths from the blades though.
For thin plates and some wires, getting a free or cheap used washing machine would be a good idea anyhow, and part of the inner drum can be used as the sieve – either as it is or with the holes enlarged. (not sure if the sieve part would work well with either of my ideas though, it might be easier to just do several passes.)
Finally – I think the oven can be oriented the other way for wider pieces. I assume that it’s put on it’s side to avoid problems with the heating-element. But I think it sould be rather easy to avoid drilling into it at the bottom by wetting it and put it on for a few moment to see where it dries up or feel the metal for heat. At the upper side, a couple of square-pipes can be put across to serve as a “second roof” for the mold to be pushed against. – Alternatively a hole in the roof with a secured pipe going down.
Also – I think a bottle-jack would be a better alternative than the scissor-jack, since it’s easier to use and a small 1-2t jack is pretty cheap anyways.
Not sure if I’m gonna give it a try as I’m not sure how much plastic I am going to melt myself, and right now scissors are doing the job. 😉
Edit: Did some more searching, and found this woodchipper claiming to have a torque of 600Nm https://www.lawnmowersdirect.co.uk/product/bosch-axt-22-d-quiet-garden-shredder#description Not sure if that number is overstated, but any cheap version of the same kind of cutter (slow, drumcutter/shredder apparently) should have very decent torque.
let’s add some more info to this odyssey. We just built a shredder using a brand new Vemat single phase motor 3HP (2800RPM) with a reducer box 50:1.
Needless to say it works fine for soft plastic and then it clogs when thick bottles come into the picture.
Tried to figure out how to reverse the direction (there are various easy to build circuits using relays) but our motor has kinda “hidden” the terminals making the whole thing pain in the ass.
We think that for the next one we go with 3-phase motor for sure and using a VFD to go from single phase input to 3 phase output (or converting the 3phase motor…). Any ideas/proposals in order to keep the costs low? Saw several VFDs online (quite pricey option but if there is no other way…)
Hi! I’am Juri from Russia.
What do you think: is such a geared motor suitable? It is from the flexible gate lifting mechanism.
I purchased this 3hp 3 phase motor with gearbox, 70 rpm at output. I saw someone used 3hp single phase motor and Plastic was clogged. If I use this motor with inverter, will it work fine or not ?
I could buy a motor with reducer fore the scredder. It is 230 volt motor 24 t.pm.
I’ve to buy it on internet so I can’t see it working. Do you have any idea if a motor with such specifications ( see images)is stong enoegh for use of the scredder.
Thanks for your fast reaction
Hello to everybody, im a mechanical engineering student in Bogota Colombia and im building a shredder machine for my final project so i have 2 questions:
1) Ive seen that the average power needed for the system is 2-3HP but why is that the minimum power you need, why not 10 or 20HP or less than 2HP?
2)How can i get a proper design for the blades, i saw the ones for the laser cut but i wanna know why is that geometry a proper one.
also why 70RPM is a good angular velocity for the motor.
Thanks a lot for any response.
Hey guys! David Comer from Kansas City, USA here! Im a civil/environmental engineering major and a few of my buddies and I have been busy assembling the first machine prototype (we started with the shredder). I’m wondering if the motor we’ve just harvested from an unwilling treadmill will be optimal or even useful for the shredder machine. Any thoughts? I read all of the previous posts in this thread lastnight and that’s what made me start looking for treadmills. Is there anything from the specs you can tell will give me issues?
Thank you for your advice! You guys are freakin awesome.
Hey, Somebody know the engine couple we need to the output of the reductor? 250 Nm??
Hi everyone! This is Mezz from Alaska and I’ve been reading through all these posts and well, I’m still confused. I want my shredder to be powerful enough to shred through most plastics. Especially the basics like milk jugs and juice bottles. But also like old 3D Filament pieces. I don’t have fancy industrial strength electrical wiring so I would need it to work with a basic home outlet.
I realize this might be a tough question but if you guys could give me some basic ideas of what I could start looking at I would appreciate it.
P.S. I am interested in saving money and reusing motors and doing some good learning along the way, but my number one concern is SAFETY. So if buying a new motor is my best option in keeping you know, my limbs and eye sockets unphased then I will…
Thanks for the help!
(oh! Now that I think of it, I might be able to upgrade my electrical wiring. If you know of any links on where I can learn more about this whole process in regards to having power for stuff like this, feel free to drop a line. It would be appreciated. Thank you!)
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