My ES torque contest DIY motor build thread.

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Manhattan Beach, CA, USA
This thread will be updated as I build my motor for the ES motor torque contest.

So far I'm at the buying materials stage. About $400 in composites and ceramic bearings alone so far, and I still haven't decided what to do for magnets yet, and I know the coil configuration I want, but haven't sourced the copper strips for making them yet.

The goal will be to target as close to the 3Kg limit as possible, because I think there are definite advantages in scaling things up. I'm also not going to use any materials that rust or corrode in my motor, so it would be marine-use capable.

So far I'm looking at doing an innovative bearing inside a tube, inside another bearing, inside a tube type of design. This requires at least 4 large bearings, which aside from corrosion is an additional motivator to go ceramic, as they are a lot lighter than steel. I think it will give my rotor the rigidity that will enable me to close up that flux gap as tight as possible though, which should pay-off in the end.

I ordered some honeycomb composite sheets for the rotors, and once the magnet design/layout is finalized, I will have someone with a CNC (or maybe I will buy my own, I've been wanting to do that forever) cut through the outer layer in the area the magnets will mount, so they recess into the rotor disk, but not flush, just enough that the top part of the carbon laminate hits in the middle of the magnet thickness. This way under high G loading the magnets force is balanced to hopefully cause less tipping/flexing, and the air gap between the raised magnets will form channels, which when layed next to the stator face, and given some inlet holes down close to the center will form a high flow air-pump naturally to keep a strong flow of air cooling the coils in the stator.

The work hasn't even begun yet, but I'm excited to give my best effort towards winning the contest. :)
 
Sounds totaly cool Luke,
I can't wait to see where all these design varients lead. I am cnc'ing some foam as I write this reply, (not for my motor though) are we setting any kind of a target date? Valentines day seems a fair enough target. Any thoughts?
 
Awesome Luke! Not sure why the tube inside a tube, very interested to find out though. You should also name this beast and tell us what configuration/ type of motor this will be.

Can you give up your source for the composite honeycomb material? That sounds like some useful stuff
 
The gauntlet has been thrown down. I can't wait to see what you come up with. Have you already decided on the geometry, ie diameter, coil and magnet counts?
 
Thud said:
Sounds totaly cool Luke,
I can't wait to see where all these design varients lead. I am cnc'ing some foam as I write this reply, (not for my motor though) are we setting any kind of a target date? Valentines day seems a fair enough target. Any thoughts?


Valentines day works for me. :) I'm SOOOO jealous of your CNC! :)
etard said:
Awesome Luke! Not sure why the tube inside a tube, very interested to find out though. You should also name this beast and tell us what configuration/ type of motor this will be.

Can you give up your source for the composite honeycomb material? That sounds like some useful stuff

Watch out shopping for these things, ceramic bearings and carbon parts make the totals in the shopping carts climb up about 10x faster than shopping for equivalent items not made of ceramic or carbon.

Retailers I used so far:

http://www.carbonfibertubeshop.com

http://www.vxb.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=bearings&Category_Code=FullCeramicBearings

http://www.acp-composites.com

http://www.dragonplate.com/


John in CR said:
The gauntlet has been thrown down. I can't wait to see what you come up with. Have you already decided on the geometry, ie diameter, coil and magnet counts?

It all depends on what I end up settling with for magnets. The magnet choice is a PITA. I need it to be light, but able to focus as strong of flux as possible in that airgap between the coil and the magnet. This is likely one of the most difficult choices to make in the motors design. BTW- This motor will be low enough RPM and high enough torque for direct drive in a boat application, and the finished product will be entirely seawater safe :)
 
liveforphysics said:
seawater safe :)

think itll fit in there ?
ski2.jpg

:twisted: cuz i got me some plans fer that old rocket :twisted:
and i can tell ya right now what im doin aint gonna be seawater friendly and i can tell you that if it were to work as good or better than original theres a market lurking , waiting , begging even.
 
My rough personal goal for this project is to build something that burst the torque of the big Agni motors, but without the garbage RPM limitations of a motor design that spins copper. Spinning copper = fail design.
 
Miles said:
Thud said:
are we setting any kind of a target date? Valentines day seems a fair enough target. Any thoughts?
Valentines day 2011? :)


lol. 2 months should be at least enough time to get people motivated. :) Then you can always push back the date as needed. lol
enoob said:
liveforphysics said:
seawater safe :)

think itll fit in there ?
ski2.jpg

:twisted: cuz i got me some plans fer that old rocket :twisted:
and i can tell ya right now what im doin aint gonna be seawater friendly and i can tell you that if it were to work as good or better than original theres a market lurking , waiting , begging even.

You could fit a stack of 10 of them in there. lol.
 
like a stack of pancakes ..hhhmm pancakes .

ooooo its gonna be a fun spring. make one of them work LFP and ill come to you . i know of 6 of these hulls waiting for me to re-install powerplants for spring and everyone of em would be electric if its feasible .

gets me more worked up than ebiking cuz i KNOW what bodys of water this would re-open. hee hee hee :twisted: there could be some mighty pissed lakeshore owners this summer . thought they'd seen the last of me muhahahahahahaha

edit: you may even know a lake im banned from . whatcom lake . no 2 strokes and apparently i chose the wrong dock to jump (repeatedly) while skimming shore line. not sure wich dock but one of em was owned by lake preservation folks, admiral cause and my ejection was just . my dock jumping days are kinda behind me but id love to zip that baby round that pond again this summer.
now ill leave your thread alone unless i got something helpfull . lol riiiiiight , me help here lol again
 
I finally decided on the magnet layout and bought them. This is really a very difficult part of an axial motor design. It's about the most simple part of a inrunner/outrunner design, but extremely tough to do a iron-free efficient layout with available magnets for an axial flux motor.

1.19lbs (540g) in N52 magnets in my motor. I wanted to get N42SH, but I'm going to rely instead on trying to keep efficiency and airflow high enough that it should stay nice and cool. :)


It uses 210 magnets to make a 21 magnetic pole motor. (21 x 2 rotors x 5 magnets per halbach array.) Tonight I ordered my third epoxy... so we will see if I've finally got something I'm happy with for secureing the magnets. This stuff cures at just 25deg below the currie temp of the magnets it's mounting, so I'm really really hoping that I don't wreck my magnets trying to cure the epoxy!


Due to the prices of materials getting absurd for a carbon/ceramic based motor, I've cut the rotor diameter back to 7". Target weight is now under 1.5Kg.

I'm still head-scratching about the motor coils... I got some insulated flat wire, but I hate how thick and uneven the unsulation was, and when I try to smash it to be flat, the insulation cracks and falls off... I want to insulate my own coils, and use layers of thin Kapton to make it work, but this makes doing the double-coil wind method extremely difficult... and any other method means the incomming coil wire has to lead into the center, which has it's own host of problems...

So many comprimises to make! And I NEED my CNC machine to arrive soon, because I've just got a mess of resin and $carbon$ and $ceramic$ and copper on the project table...

So far, torque count = Zero. Dollar count = ~$600-700... lol :) I'm not too worried though, this is how my racecar builds always go, and they always manage to pull of a miricle at the end. :)

-Luke
 
liveforphysics said:
lol. 2 months should be at least enough time to get people motivated. :) Then you can always push back the date as needed. lol
Said like a true Program Development Manager!! :p

Lots of thought in your design, looking forward to spring... crocus bloomin' and magnets a spinnin'
 
liveforphysics said:
This stuff cures at just 25deg below the currie temp of the magnets it's mounting, so I'm really really hoping that I don't wreck my magnets trying to cure the epoxy!
You certainly will if you really do mean the Curie temperature (310 degrees C. ) :shock: :)
 
Miles said:
liveforphysics said:
This stuff cures at just 25deg below the currie temp of the magnets it's mounting, so I'm really really hoping that I don't wreck my magnets trying to cure the epoxy!
You certainly will if you really do mean the Curie temperature (310 degrees C. ) :shock: :)

Ohh! You're right of course Miles, it's operating temp, not currie temp. :oops: My N52 magnets are rated for a 176F working temp, and this epoxy needs to be at 150F for a few hours to cure. I should be totally fine. :) Phew!
 
bigmoose said:
liveforphysics said:
lol. 2 months should be at least enough time to get people motivated. :) Then you can always push back the date as needed. lol
Said like a true Program Development Manager!! :p

Lots of thought in your design, looking forward to spring... crocus bloomin' and magnets a spinnin'


Yep ;) lol

It's crazy how heavy the copper is in these things. I've been struggling to work out going with square 110 alloy copper 0.125"x0.125" (~7awg) coils spiral wound and layed upon each other (about 0.27" total stator/coil thickness with Kapton insulation between the stacked coils) so the ends can both exit from the outside, or going with with a ribbon layout, but this means having the inside ribbon pass over the side of the coil... which means possible inductive heat problems and thicker air gap... but it would be so much more simple to make. :) But easy to make doesn't mean much if it melts from self inducted heating...

I also can't seem to come up with a logic for when to stop the inner diameter of the coil. I've seen that the super efficient motors (launch point and cisro) use only roughly the outside 1/3 radius of the coil to fill with copper, but they also all use this dead space to tuck the next overlapping coil into. I haven't been planning on trying to wind the overlapping coils mess, does this mean I am best space optimized filling a larger portion of the center of the coil? Maybe all?

Pehaps somebody has a DIY method for overlapping coils? From my fooling around with laying wire together, it just seems like an awful inefficient use of space, but I know sticking between a couple blocks in my press could likely make it seem pretty neat and compact. :) It seems like a very high chance of turning it into a giant shorted together mess as well though...

Lots of decision! Lots of design work! And now my shift is over in 40mins, and I've still got to draft a MOP involving live cooling and power work on a 800ton chiller plant by 6am, then double check to make certian it's not going to get any contractors doing it killed. lol Better get started! lol
 
Miles said:
:)

A high torque density, 1.5 kg motor - really looking forward to this one :D


It's got bearings to handle 28,000rpm continous too. :) The cooling airflow will increase at the square of RPM until it saturates, which should hopefully make it a high torque density, and high power density 1.5Kg motor. :) I would LOVE to beat the LaunchPoint motor's 5hp/lbs continous rating, which they claim to be the worlds highest power density motor ever made. :) I've built enough stuff to know that's a pipe dream for a revision 1.0 design though. :p But maybe when that number grows a bit. :)
 
Hey Luke,
I too have been pondering the option of lapping the coils. After several models, the idea a machineing thicker coils would allow overlap & seems doable, doesn't solve the airgap issue on flat wound coils.

Since my 1st stators will be cored with iron I havn't been focused on corless design other than daydreaming about it in off moments.
 
Miles said:
I guess eddy current losses in the copper will become a significant factor at higher speeds? A reason not to use square wire?

That's more of a question for the Moose :)

Im just going to try and fit as much copper as possible in her, and see what happens. :)
 
I will be just under 10khz coil freq at 100% duty cycle at 28,000rpm. But, just for kicks, lets see if we can get a ball-park guess on if the rotor will explode before 28,000rpm. :)

Diameter of magnet ring mass center ~0.148m
Velocity at mass center of magnet assembly at 28,000rpm: 216m/s
Total magnet mass = 0.54Kg.

This would put 176,600N of internal stress on my 6mm thick carbon fiber rotors. That's 18,020Kgf between the pair, or 9,010Kgf on a single rotor, and 429Kgf per 6.35mm width magnet array. If my weave of carbon fiber/epoxy has a rough tensile strength of 1034Mpa,this would mean at 6mmx6.35mm magnet supporting strip would handle a pretty shocking 4,019Kgf in straight tensile loading. But this wouldn't be straight tensile loading... that would assume the an infinite strength and modulus of the magnet mounting epoxy that attaches the magnets into the slots of the rotors, and it doesn't compensate for each loaded section being modeled as a wedge, and it doesn't compensate for the very real balance related vibrations and dark forces at work on anything trying to spin that fast. I will probably to to keep under 15-20,000rpm in it's installed application, which due to the x^2 relationship between RPM and destructive forces, should keep things at 1/4-1/2 of the stress it would feel in the above calculation. Also because the gearing becomes a PITA for very high RPM stuff on a bicycle. :)
 
Pehaps somebody has a DIY method for overlapping coils? From my fooling around with laying wire together, it just seems like an awful inefficient use of space, but I know sticking between a couple blocks in my press could likely make it seem pretty neat and compact. It seems like a very high chance of turning it into a giant shorted together mess as well though

I found this on the RCGroup forum. Don't know if it's what you are looking for tho.

http://home.scarlet.be/manulrk/LRK-24-16/
 
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