7 RC sensorless controllers running 1 very neat DIY motor.

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I saw a link to this motor on the wooden bike thread, but it doesn't show anything about the controllers.

If I'm not mistaken, it may be a fairly simple matter to bring the leads of our big RC motors out in a way that lets us power them with 2 or 4 controllers for a 12 pole RC motor.

Comments?

-Luke
[youtube]hy6jZEW9uxc[/youtube]
 
wow! A coreless axial flux set up to run with 7 controllers...thats thinking outside of the box. I would think there would be sync issues.

Maybe its alright with 1 controller only reading 1 coil per phase? looks like its working in the video.

looks like the 200 amp controllers here: http://www.lightflightrc.com/
a suppo 200 amp unit.
I have inquired 3 times but never got a responce to e-mails.
 
Good thing one of us can count Thud :) lol, I edited the title to say 7 rather than 6.

I really like how its setup to use 1 controller for every 3 coils. This cuts down on the additional copper loss that would otherwise exist putting the coils into series strings. I also like the idea of being able to power a large motor from multiple RC sensorless controllers.

The big turnigy motors are 12pole. This could be powered equally well, or better from 2 or 4 controllers if I'm understanding things correctly?
 
If you tapped the 12 poles of an RC motor to power it from two sets of seperate 6 pole windings fed by two seperate controllers, would this double the KV of the motor? I don't think that it would, but inductance would be cut in half, along with resistance. It seems like current would double, and RPM would double, but I've also stayed up all night, and that is seldom of bennifit to my magnetic thinking ability. Lol
 
Luke,
or Any one interested,The issue that is twisting me right now is the magnetic pole count & its effect on the sensorless controllers. More poles limit rpm potential but in a set up like this? seems like an answer to a lot of un-asked questions. I know I am reeling after seeing it. I am amped to get that guide mailed out & get back to motor building. looks like anything is possible.
I am totaly impresed by that video, I never saw any iron in the coils, That would reduce cogging, but really cut the power potential & efficancy's by my way of thinking.

Another observation-
Imagine the "Magic smoke" potential of a plywood motor. :mrgreen:
 
I have heard of coreless motors getting up to 97% efficiency, which would be great.
Another upside of this design is that the plywood would be very light. Imagine this one done in carbon fibre! :mrgreen:
What about the massive torque from such a large diameter?
If someone built this into a wheel, I would be a hub-motor convert :D :D :D
 
I asked Astro and Castle about this a year ago and was told the same thing by both;

"There is a talk-back issue where one controller will hear the pulses of the second controller and read that as back EMF. This would destroy the ability of the controllers to run in sync......" However, that is assuming a cored motor. Maybe coreless would not have that issue?

I would love to try it. But, I was emphatically told it will not work unless the two sets of windings were separated by several inches of distance. So, that is why I went with two motors.

But, I have never tried it. I wonder if it would work. Maybe Astro and Castle never tried it but were both shoot an answer to me "From the hip".

Matt
 
I thought this thru today too....I know running 2 motors creates all kinds of signals that will confuse the controller.& 2 controllers to share the load is havoc to keep timed(but it has been one)
This one is just paralleling 7 controllers & each is only reading 1 coil per phase. Each set is terminated delta & they look to be isolated from the other 6. So its not 3 or 4 coils in a typical motor. That motor still shudderds noticeably on start up (cheap controllers?) but seems to sync alright. looks like some serious power on 36 volts....what are you thinking Matt? :twisted:
 
We need to get propeller guy here on ES... :mrgreen:
 
Thud said:
what are you thinking Matt? :twisted:

I am thinking we are moving closer and closer to E-bike nervana. 8)

Running multiple controllers has some inherant benefits, from my perspective. The cost is a concern, though. But, from running twin motors in numerous E-bikes I can tell you that shared load is a good thing............

Matt
 
It seem "a bit" powerfull! :twisted:

I love that propeler sound!! very similar to real conventional aircraft!

I would love to see some monitoring during test.. current, torque, power, etc..

Doc
 
The previous was 7kW and 38kg...

NOW LET SEE THE BEAST:


( I love that sound!! REAL POWER !!)..


I just imagine the neiborhood wondering what is happening near their houses!!! :mrgreen:



maybe that motor and propeller installed at rear of a bike could beat 60mph ?? :twisted:


11.5kW and 50kg torque!

[youtube]u0I0Tg8sxYw[/youtube]
 
The thing that I really like? this is essentialy the motor I am working on at the moment in the axial motor thread. (sans plywood)I see the final version prolly 5-7"dia less than 2"thick & a Kv of about 100. I also see a built in primary reduction to get output rpm right where it makes sence. Its amazing all this stuff is comeing foward as I am deep into the research on the designs.
 
Hi all, and thank you for your positive veiw on this project.
Altough i have build several electric motors Im not an expert in this area in any way.
However I will gladly try to answer questions regarding to this motor if
there are any.
The 7 controllers are the "super simple 90-100A" that costs 30 dollars each at hobby city.
They are all reciving the trottle signal from 1single servotester.
In the 11.5kW clip the motor is powered by a 300-600A hall sensored Kelly controller.

Best regards/Axel
 
Gidday Axel, and thanks very much for dropping in!

Welcome to our forum. We are very excited at seeing such fine work, especially since it was done in your backyard. :D

We would love to see some still photos, and also any of your technical specs, build details and test results.

What did you have in mind to run this motor in, perhaps an ultralight plane?
 
Grinhill said:
What did you have in mind to run this motor in, perhaps an ultralight plane?

Geee, and I was thinking it was a leaf blower...

(Kidding!)

Hi Axel. Thanks for dropping in!

Here is another thread on Endless Sphere about electric flight that you may enjoy:
http://endless-sphere.com/forums/viewtopic.php?f=7&t=3670

My interest in electric props are not for flight but instead for an electric "air boat"... sorta like a Florida airboat-lite, without the same noise and stink!

I would hope to go with a larger diameter (and slower RPMs/quieter) prop than is common in the gasoline powered props...

You'll find other treads on ES also where folks are working with LRK/outrunner motors designed for flight, because of their impressive specs. The only real "problem" being the high RPMs necessitating some sort of reduction gearing etc. to get the RPMs down to reasonable speeds for bicycles (or not so reasonable where some here are involved hehe)

Cheers
Lock
 
axbor22 said:
Hi all, and thank you for your positive veiw on this project.
Altough i have build several electric motors Im not an expert in this area in any way.
However I will gladly try to answer questions regarding to this motor if
there are any.
The 7 controllers are the "super simple 90-100A" that costs 30 dollars each at hobby city.
They are all reciving the trottle signal from 1single servotester.
In the 11.5kW clip the motor is powered by a 300-600A hall sensored Kelly controller.

Best regards/Axel


Was the reason for dumping the little HC controllers because of sync issues?

Was it able to start from 0rpm with strong torque?

Any estimates of efficiency?

Any coil cross-talk related issues that you observed? Like bizarre ESC function and jitters?

Does using a conductive material to hold the coils in place cause inductive heating in the material and drop efficiency?

Any coil cooling issues?

With zero cogging loss, would making as flat of spirals as possible, and mounting the magnets with as close to zero clearance as possible be optimal? Did your coils deform from magnetic stresses?


I would like to build a motor much like this motor. Do you have any special concerns or advise you would give? Things you would do differently if you could do it again?


Thank you!

-Luke
 
Axel,
Thanks for joining our little group.
1st- Wow that thing apears to be a beast! Kudos on the design & fab work.
Are you a hobby CNCer also by chance?
Motor Question time:
#1) Every thing Luke asked above :D
#2) what did you use for bearings in the prototype?
#3) What thought proccess did you use to decide on the coreless coils? assuming cores were a consideration.
#4) The Jig set up at .09 in the video. Is that for building the strand count for the coils all
the same length? or the apparent carbon fiber magnet retention lamination?
#5) Any idea of the Kv?

Please post any (& as many as you can) links, that may have influanced your design/thought processes or capture your general interest :D I find much applicable info in parallel interest conversations.
 
Very impressive motor, Axel. I love the idea of using multiple cheap controllers, that's really thinking outside the box!

My interest would be to make an affordable electric motor for my paramotor, to replace the noisy two stroke. It currently swings a 1.25m wooden prop, similar to the one you're spinning on your test motor.

I hope you can find time to contribute to this forum, as there are some serious motor/controller enthusiasts here.

Jeremy
 
Hi, and again, thanks for the positiv spirit.

“What did you have in mind to run this motor in, perhaps an ultralight plane?”

I have though about building a paramotor back pack. I used to have a paragliding license, but I have decided to put it in a Yamaha 125TZR motorcycle to get more every day use out off it. It seems to work well, it drives the motorcycles wheel with its original gearing 16-45 = 1:2.8.
Still some work to do before I try to register the bike properly.

“My interest in electric props are not for flight but instead for an electric "air boat"... sorta like a Florida airboat-lite, without the same noise and stink!”

That would be a great project!

“Was the reason for dumping the little HC controllers because of sync issues?”

No, there was never a problem about sync!
It was the non-existing chance that I would get the motorcycle approved for legal road use with that set up, since the motorcycle would not be able to start reliable from zero speed and absolutely not if you would start going up hill. So: no it will not start from zero rpm with strong torque. But once spinning there is a lot of power.

“Any estimates of efficiency?”

Sorry, I do not have any reliably numbers. I really would love to find out.
I imagine peak efficiency is above 90%

“Any coil cross-talk related issues that you observed? Like bizarre ESC function and jitters?”

No cross talk, sometimes a litter jitter going from zero to a couple of rpm

“Does using a conductive material to hold the coils in place cause inductive heating in the material and drop efficiency?”

Drop in efficiency? He, he, you better believe it!
A rotor fitted with magnets this size will heat up a 2mm thick aluminium metal sheet to over 100 degrees C (water boiling point) in few,(like 3-5) seconds if the sheet is forced to stay within 5mm distance from the spinning magnets. You need to mount the sheet very firmly to prevent it from twisting if you would like to carry out this experiment. So sorry, no simple coil-heat transfer solution there. That’s eddy currents for you!
How ever, it seems to be possible to make a carbon fibre version without the eddy current problem since the carbon is a poor conductor.

“Any coil cooling issues?”

Well, that is of course just a matter of how much current you wish to run through the coils…
But a hint is: in the 7kW clip the coil temperature seems to settle at just under 50 degrees C with an ambient temperature of about 25 degrees C.
I have built several water-cooled axial flux versions as well, not this big though.So if heating will become an issue later on I will try and build this motor in water cooled version as well.


“With zero cogging loss, would making as flat of spirals as possible, and mounting the magnets with as close to zero clearance as possible be optimal?”

I do not know.
I have built one stator in this diameter 4mm thick. This was the carbon fibre coated one. The carbon fibre was necessary to make the structure stiff enough.
I did not carry out extensive data collecting with this setup. I think that the problem is that the air gap that the not professionally built motor inevitably will have, starts to be quite a large percentage of the total gap between the rotors in which you also like to have the copper wire if you build extremely thin stators.
I have found 7-10mm stator thickness to suit my limited ability to produce high precision parts.

“Did your coils deform from magnetic stresses?”

No, not yet.

“I would like to build a motor much like this motor. Do you have any special concerns or advise you would give?”

Good question, Im still in the learning processes my self.
Be careful when running a high rpm and be sure to reinforce the magnets properly with carbon fibre. Don’t forget to mount a temperature sensor next to a coil since heat is the limiting factor.

“Things you would do differently if you could do it again?”

Good question, Im still in the learning process my self.
I will have to get back to you on that one.

“What did you use for bearings in the prototype?”

Ordinary cheap ball bearings with rubber sealing. Really nothing fancy.

“What thought process did you use to decide on the coreless coils? Assuming cores were a consideration.”

Simply DIY-billety. It is to hard to find appropriate stator lamination material not to mention processing it.
It is possible to build this motor without a lathe. You basically only need a drill press, a bench belt sander and a hand held milling machine for wood, what is it called?

“The Jig set up at .09 in the video. Is that for building the strand count for the coils all
the same length? or the apparent carbon fibre magnet retention lamination?”

It’s a simple way of measuring length and number of strands of copper wire. And picking up a little sun tan as well!
In a first build it might be easier to use a single copper wire although the coils might be a little more bouncy and give higher eddy current loses.

“Any idea of the Kv?”

Yes I have. I have built several different versions. The one mounted in the Yamaha has a kv of 68rpm/v with a given set of magnets (30x10mm N45 magnetisation grade). The same magnets mounted on a rotor with a layer of iron on the backside of the magnet gives the motor a kv of 58rp/v at the cost of a 1.5kg heavier motor. On of the brilliant things building a motor yourself is that you only have to make a new stator. The rotor fits both thick and thin versions.

/Axel
 
Thank you for the quick reply,
It sounds as though you added Hall sensors when you went to the kelly controller?
I am playing with some motor design features & welcome any input you have regarding it.
I will start a new "build"thread once I get that far.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=13957

Also if you have any resource links I would love to look at them.
Again, good show. :D
 
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