Building a motor

[Hummina Shadeeba]

I’ve found places that sell the segmented parts and wanted to do it mainly to shrink the gap between teeth for less cogging torque and better fill, but it’s foreign and bit more complex so I didn’t.

https://electric-skateboard.builders/t/mellow-production-stator/10231

 

[mxlemming]

Well I got the first rotor assembled. It's... Not a complete disaster.

The 3d print is a long long way off stiff/strong enough. I designed this for CNC aluminium... Thought meh I'll press print as is and... Well it needs to be 5x as stiff.

I'll try reprinting it with a much more stable end section and thicker walls. The print turned out quite poor quality as well and I don't like the color. If all else fails I'll shoehorn that headset bearing in as a skirt. Would rather avoid that though.

It was really easy putting the magnets in with this design though.

 

[Mihai_F]

Nice job, looking good for testing. About magnets precise placement, (within +/- 0.05mm) the larger the diameter of the rotor, the greater the electrical degres error you will have if magnets have different distaces between them. On my rotor i made a wooden slotted tool for precise magnets placement, it turned out that tool was not perfectly round (was cut on diy wooden cnc router), and had up to 0.2mm diferences between slots, and that caused my motor to have in some rotor positions in sensored mode, some fast fluctuations back and forth at sartup and sometimes not beeing able to start. The fix was, i cut on precision cnc (+/-0.002mm) a plastic (POM) slotted tool, witch came perfect and repositioned the magnets, the there no more starting problems at all, plus the motor was running much more smoothly.

 

[Hummina Shadeeba]

. The fix was, i cut on precision cnc (+/-0.002mm) a plastic (POM) slotted tool

Got a pic? I’ve been using cut strips of nylon fishing line as spacers and it’s far from accurate.

how do you all glue your magnets? I use a one-part bake-later glue. I sand the magnet face and clean the inside the rotor with acetone or alcohol, then add glue to magnet and rotor, slide individual magnets in along their corner and let them slap gently down when all the way in, add a nylon spacer and repeat.
It works but very inaccurate

 

[mxlemming]

. The fix was, i cut on precision cnc (+/-0.002mm) a plastic (POM) slotted tool

Got a pic? I’ve been using cut strips of nylon fishing line as spacers and it’s far from accurate.

how do you all glue your magnets? I use a one-part bake-later glue. I sand the magnet face and clean the inside the rotor with acetone or alcohol, then add glue to magnet and rotor, slide individual magnets in along their corner and let them slap gently down when all the way in, add a nylon spacer and repeat.
It works but very inaccurate

How many motors have you made hummina?

Did you get a chance to measure the lamination thickness on the ant motors?

 

[Hummina Shadeeba]

I’ve put magnets in at least 100 motors. The toothed spacers I often see used are relatively expensive so went the route I did with cut nylon line. So I made a lot bot dont know what I’m doing. I was getting skate hub motors made and selling them and the manufacturer was selling them on their website so I started making them. Brotherhobby.cn I think.

I didn’t measure the laminations. Visually they look a legit .15mm and thinner than the .2mm I’m used to seeing. I can measure to be sure and will add it in my post here later

 

[HalbachHero]

Awesome, looking good so far. I can't wait to see this make more progress.

 

[Mihai_F]

Got a pic? I’ve been using cut strips of nylon fishing line as spacers and it’s far from accurate.
how do you all glue your magnets?

yep, it centers on the shaft, and the magnets are inserted in the slots and then outward to the ring

the plastic one is the same
magnets were glued with 2 part epoxy for metal, it bonds well, they held in place while testing at vibrations at a thigh torque and high speeds

 

[APL]

Dang Mihai_F, that motor totally rocks! :thumb:

Six years in the making? My hat goes off to you. It's rare to see such a splendid success, and we're all pumped now!
20Kw and 7.7kg is crazy dreamy.

Mxlemming, this build is starting to look awesome too, nice to see things coming together here, sorry to chirp so late,
but used to seeing talk and no walk,.. it's good to see this build taking shape. I think this has every chance of being
a goer. :thumb:

 

[mxlemming]

Dang Mihai_F, that motor totally rocks! :thumb:

Six years in the making? My hat goes off to you. It's rare to see such a splendid success, and we're all pumped now!
20Kw and 7.7kg is crazy dreamy.

Mxlemming, this build is starting to look awesome too, nice to see things coming together here, sorry to chirp so late,
but used to seeing talk and no walk,.. it's good to see this build taking shape. I think this has every chance of being
a goer. :thumb:

I'm definitely a fan of Mihais motor. It's finished and beautifully made in a way I don't think this one ever will be. I'm just crossing my fingers that his controller can start to work in somewhat less than 6 years.

I'm crossing my fingers that with the latest 3d print I made it'll be stiff enough. If so, it should be spinning within the next week... If not, I promise nothing. It'll spin once I get round to designing the skirt bearing in or I take a deep breath and pay for the rotor to be cnc'd.


There's no reason for this not to work easily, it's a far more standard design than the many other builds here, including yours. My main goal is really to experiment with a few winding patterns. If it ever works well enough to drive my ebike, that's an added bonus.

 

[Mihai_F]

Thanks guys for appreciation of my motor, i will make a separate topic to show you a bit of the past 6 years of me learning how to make an BLDC ESC and the motor, so i don't hijack mxlemming topic , and hopefully it won't take me that much time to get the ESC back working.
Nice rotor by the way, i like the wedges in the ring so that you can place magnets precisely.
When you make it of metal, the front rotor plate that gets pressed or bolted to the concentrator ring, you can design it to have small 10mm wedges (teeth) that go towards the inside of the ring so that you can use them to position the magnets. Cutting grooves on the outside of the concentrator ring helps a lot on weight reduction, and gives better cooling.

 

[Hummina Shadeeba]

Seem .15mm or thinner on the 84100 ant motor. This is one mm span.
Someone was asking and said I’d post it. Will erase this post in a day

 

[larsb]

Yep the real thing, 7.7kg, 10uH, 6mohm per phase, 36kv, N45 40x10x5 magnets, stator laminations are laser custom cut.

That's nice! what percentage off copper did you get with this wind? would be good with a calculation from the true wire section vs the CAD area of the slot. I've found that winding bundles like this lowers the fill percent (although it looks nice) but i also used thicker wire, less keen on getting formed

 

[mxlemming]

Well i wound the rotor. LRK, 6 turns, single strand :lol: not going to be good for much power.

Had to print the hub 3 times to get it to run straight. I have no idea why the printer insisted on being about 1mm out of concentric. Oh well.

So... Magnets in a rotor, wound stator... Guess I'd better make it spin tonight. Hope I'm allowed a few spare minutes.

 

[Hummina Shadeeba]

I think in the center would get better heat transfer with more contact between the stator and aluminum. (Assuming the 3d print ends up aluminum)

 

[mxlemming]

I think in the center would get better heat transfer with more contact between the stator and aluminum. (Assuming the 3d print ends up aluminum)

This is a toss up. For 3D print, the air flow will be much better and the air contact with the stator better. With CNC aluminium, I am not sure which way the tradeoff would go. Probably a bit of aluminium would help. The optimium would be to extrude a heatsink with fins profile as the hub, but I am not likely to invest in that any time soon. Maybe if this works out so well I start selling motors :lol:


Got a chance to spinny spinny tonight. I love SimonK escs. Sometimes I wonder why I don;t just stick one of those chips to a mega power stage and call it job done.

Unfortunately, it rubs horribly seemingly because the 3D print material creeps over a few days. It did not rub when I built it up and last posted Need to invest in metal. This seems good enough, promising enough, that a few machined parts might be worth their cost for actual use

[youtube]TKR6NggJY0k[/youtube]
https://youtu.be/TKR6NggJY0k in case it doesn;t render for anyone

The harmonic content in star is good.



The kV with just 6 turns works out as 38!!! Iron stator FTW


It was very very clear that Delta is not as good as star. Just by connecting the wires in Delta, I could feel the extra resistance when not connected to the ESC. In star, it (obviously) spun very freely.

Running it in Delta was awful, the ESC got really hot and it drew 60W while only going fairly slowly. In star, the speed and losses were fairly low, there are clearly recirculations going on in Delta.

I had always read that Star needed care to get the winding correct (which ones you fix together) and indeed my first try was wrong, but it was easy to figure out with the scope - the wrong winding drew a triangle wave on the scope, and flipping it over made 3 nice smooth sinusoids.

Delta I had read could be connected in any way, reversing a phase would merely reverse the direction of the motor. Can someone confirm this is true? It is not obvious to me that it is. The Delta connection was SO bad compared to star that I feel like it must be an error. I'll have a go at a few combinations (all of them) tomorrow and see if I can get a better result.

EDIT: 5 minutes after posting this, it is clear that my assumption on delta is bollox, just thinking about 3 arrows 120 degrees apart for the vectors, it cannot be the case that swapping any one around is OK.

 

[Hummina Shadeeba]

Maybe ur magnets aren’t all equally magnetized. I’ve never checked. It needed tools I think.

I’ve never done delta and don’t know a reason to other than u maybe had limited wire widths to use

Speaking of aluminum in the center I just pressed these together and think that’s ideal. I think this hub would transfer heat best as it is here but with a honeycomb of long drill holes. I should’ve added some thermal paste. It sits for unused years and then I forget to use it. But I’m too scared to take it apart possibly pulling lams up.



And I forgot to NOT design a step on the aluminum to position the stator along its length and to me its more a hinderance and rather crush it all against the aluminum wall with fiberglass sleeve-ing protecting. ..the motors come extra long because maybe people don’t look inside. I’m annoyed knowing I could’ve made this much shorter and I should’ve guessed on how many turns and done just a single tooth I could’ve measured. A single tooth!

 

[Jrbe]

There are some good ideas on how to check and balance the weight and magnetism without fancy tools here (step 7.) Step 8 is how to try to keep it balanced mechanically.
https://www.instructables.com/600-Watt-3d-printed-Halbach-Array-Brushless-DC-Ele/
He also graphed the data to visualize how far off some were.

He used a filament with iron in it to print the stator. Doesn't apply to this build though.

 

[mxlemming]

There are some good ideas on how to check and balance the weight and magnetism without fancy tools here (step 7.) Step 8 is how to try to keep it balanced mechanically.
https://www.instructables.com/600-Watt-3d-printed-Halbach-Array-Brushless-DC-Ele/
He also graphed the data to visualize how far off some were.

He used a filament with iron in it to print the stator. Doesn't apply to this build though.

I wish i could do this and solve my problem but it really is just that the printer is printing about 2mm wrong.

Strangely I've tried it on a few printers and it's the same. I think it's something to do with the slicer but who knows. I'll get it CNC'd i think. Considering doing a carbon fiber wrap rotor (use unidirectional fibers and the conductivity should be no issue) That would be cool.

 

[mxlemming]

Reconnected in Delta correctly this time (there are 2 correct options out of... 4?). Harmonics are about the same as star - very low.


Interestingly, Delta feels much stiffer to spin by hand, and for a speed that has the same "key" (sound, audible frequency) takes over 2x as much power in delta as star. You can see on the 'scope, the motor really does not freewheel as well, the speed drops much more rapidly.

I think this is enough evidence for what I was looking for in star vs delta; star is better. Much better. I should try to reconfigure my massive Hobbyking Turnigy CA120-150 motor in star... that should reduce the kV to 86 which would be much more useable for ebikes anyway.

Delta reconfiguration gave 89Hz@5.24V PP so kV = 68.

Compared to the 38kV in star... This is nearly spot on. 68/sqrt(3) = 39.something. Within measurement error.



Conclusion is that the final wind should be 4 turns in star for 57kV. Guestimation is that I would be able to get about 7 strands per bundle into the slots, and each strand seems capable of 20A ish without burning my fingers when I plug it into my PSU... so... maybe 100-140A max. Seems high but not implausible. Airflow vs packing means who can guess. 7 strands 0.7mm is equivalent to about 13AWG, which for chassis wiring allows about 35A. Somewhere in between 35 and 140A then. Great...

 

[BalorNG]

I'm currently experimenting with wrapping 3d prints in carbon fiber. That should solve the problem of rotor breaking at high speed and CTE (carbon actually has slightly negative CTE).
I think that should work for you as well... works best with something like CF/GF nylon/petg, it does not stick to ABS worth a damn, and PLA will not do unless unealed but it is a whole nother can of worms... CF filled PLA has nearly zero shrinkage (no need to input any corrections on the slicer on my printer) and of oversized 0.6% and anneled at 100C it gets pretty strong and heat-resistance though. (My printer also prints a bit out of round on large prints and this is annoying on a belt pulley. I blame slop in the eyelets or uneven delta arms, will be dealing with that eventually).

 

[Hummina Shadeeba]

Found a good resource for thin lam stators. They have a larger 140mm diameter one that’s .35mm lams but the biggest with .2mm Kawasaki steel are 100mm diameter and ordered four with shipping for just under 100$ which seems a great deal. At the larger height I ordered, 50mm tall, they won’t come with any epoxy insulation and have to insulate somehow yourself.
If youre in USA will sell u one of these for 45$ (10050 stator, their #150) including shipping if anyone is interested. (Don’t need four but with shipping from China seemed a waste not to get a couple.)

 

[mxlemming]

Stators looking good Hummina. Strangely I contacted Weite right at the beginning and got a very poor response... Glad you did better. That seems like a sensible price.

Balor, the carbon wrap is an idea I've been mulling over for ages now. My musings on it got as far as:
Carbon conductive, take care with stray mag fields.
Carbon kevlar? Could be better.
Unidirectional carbon? Could be even better for the first few layers. aliexpress has a nice selection of nicely colored carbon and unidirectional tapes.

At some point I'll build a jig, circular metal tube@101mm diameter with little magnets in the side to hold the big magnets, then oil it, attach magnets, wrap in carbon and... Well I haven't worked out how to wrap and vaccuum that assembly to get a nice finish yet.

Problem is, I've passed project saturation and my current job is demanding a lot of me (contract so the money is good and more hours pays more) but it's shattering and my baby is turning 3 and demands 150% of my free time with my wife optimally training her to whine and whinge constantly. I wish I could offer more progress on this, but it's going to have to slow burn.

Projects are currently:
This motor
MESC (this basically works well enough for my needs for now at least)
Ebike (battery, mount, using 12070 motor)
Some massive high power density VESC thing that eats my time chasing my tail with unstable VESC firmware I'm building and being semi paid for.
Porting MESC firmware to VESC hardware
DCDC 150V4A converter (this was a bad idea to start)
Soldering micro station (hardware perfect, cannot get the time or motivation to finish the firmware)

I probably ought to have a stronger filter for "projects that actually make our might make money"

I would not advise building a VESC for commercial reasons, the firmware is far too probe to self destruction still... Hopefully the 5.03 release will be better. This is definitely the worst of the projects I've taken on because shit doesn't work and there's not a lot I can do to fix it, but kind of have to keep trying.

 

[BalorNG]

Stators looking good Hummina. Strangely I contacted Weite right at the beginning and got a very poor response... Glad you did better. That seems like a sensible price.

Balor, the carbon wrap is an idea I've been mulling over for ages now. My musings on it got as far as:
Carbon conductive, take care with stray mag fields.
Carbon kevlar? Could be better.
Unidirectional carbon? Could be even better for the first few layers. aliexpress has a nice selection of nicely colored carbon and unidirectional tapes.

At some point I'll build a jig, circular metal tube@101mm diameter with little magnets in the side to hold the big magnets, then oil it, attach magnets, wrap in carbon and... Well I haven't worked out how to wrap and vaccuum that assembly to get a nice finish yet.

Now that is truly an excellent idea!
How about simply covering a typical plumbing 100od steel pipe in heatshrink, oil it like you said, 3d print a sort of 'toothed conductor' of tough, heat-resisttant plastic (think GF/CF nylon), slide the magnets in between it and the tube and epoxy them in, (an other interesting idea is to use a layer of gf veil *on top* of magnets to absolutely make sure they stay in place, like it is done in inrunner rotors... maybe overkill), than wrap resulting construction in a layer of a thick carbon sock! You do not actually need to 'vacuum' it, even. Using a cling wrap works very well.

You'll still have to 'cap' and than then balance it... gotta think about it some more. Seems like building your own high-strength motor using materials avalable to me (3d printed filaments, carbon wraps, no fancy CNC, maybe some outsources lathe work) might actually be viable...

 

[larsb]

Delta feels much stiffer to spin by hand, and for a speed that has the same "key" (sound, audible frequency) takes over 2x as much power in delta as star. You can see on the 'scope, the motor really does not freewheel as well, the speed drops much more rapidly.

I think this is enough evidence for what I was looking for in star vs delta; star is better. Much better. I should try to reconfigure my massive

I haven’t seen a any real evidence that star gives a large benefit over delta, it concerns me a bit when you make this comparison without numbers - are you really comparing DC power at the same rpm? What are the numbers?